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+# Monthly Digest Feature - Implementation Plan
+
+## Overview
+Implement a monthly digest email feature similar to Google Timeline's monthly recaps. Users will receive an automated email on the 1st of each month summarizing their location data from the previous month.
+
+## Feature Scope
+
+### What We're Including (MVP)
+- ✅ Monthly overview with stats (countries, cities, places visited)
+- ✅ Distance statistics (total distance, daily breakdown)
+- ✅ Top visited cities (by point count)
+- ✅ Visited places (from visits/areas)
+- ✅ Trips taken during the month
+- ✅ All-time statistics
+- ✅ Lucide icons for visual enhancement (no external images)
+- ✅ Send to all active/trial users on 1st of month regardless of activity
+
+### What We're Skipping (For Now)
+- ❌ Walking vs driving distinction (no activity type data)
+- ❌ City/place images (complexity, API dependencies)
+- ❌ Static map image in email (to be implemented later with custom solution)
+- ❌ Activity-based sending (send regardless of previous month activity)
+
+## Technical Architecture
+
+### Design Principles for Extensibility
+This implementation is designed to support both **monthly** and **yearly** digests with minimal code duplication:
+
+1. **Abstract base service**: Core digest logic separated from time period specifics
+2. **Configurable time ranges**: Services accept flexible date ranges (month, year, custom)
+3. **Reusable query objects**: Data queries parameterized by date range, not hardcoded to months
+4. **Template partials**: Shared email card components that work for any time period
+5. **Polymorphic scheduling**: Job structure supports multiple digest frequencies
+
+### Available Data Sources
+- `stats` table: Monthly distance, daily_distance, toponyms, h3_hex_ids
+- `points` table: Coordinates, timestamps, city, country_name
+- `trips` table: User trips with dates, distance, visited_countries, photo_previews
+- `visits` table: Area visits with duration
+- `places` table: Named places user has visited
+- `countries` table: Country geometry data
+
+## Implementation Plan
+
+### 📋 Implementation Phases Overview
+
+The implementation is split into **5 sequential phases** that can be completed incrementally. Each phase has clear deliverables and can be tested independently.
+
+| Phase | Focus Area | Duration | Dependencies |
+|-------|-----------|----------|--------------|
+| **Phase 1** | Foundation & Settings | 0.5-1 day | None |
+| **Phase 2** | Data Aggregation | 2-3 days | Phase 1 |
+| **Phase 3** | Email Design | 3-4 days | Phase 2 |
+| **Phase 4** | Scheduling & Jobs | 1 day | Phase 3 |
+| **Phase 5** | Preview & Polish | 1-2 days | Phase 4 |
+
+**Total Estimate**: 8-12 days for complete MVP
+
+---
+
+### Phase 1: Foundation & Settings (0.5-1 day) ✅ COMPLETED
+
+**Goal**: Set up basic infrastructure for digest system
+
+#### Deliverables
+- [x] User settings structure for digest preferences
+- [x] Base mailer class created
+- [x] Route structure defined
+- [x] Basic specs for settings
+
+#### Tasks
+
+##### 1.1 User Settings Model
+**File**: `app/models/user.rb`
+
+Add helper methods for digest preferences:
+```ruby
+# app/models/user.rb
+class User < ApplicationRecord
+  # ... existing code ...
+
+  def digest_enabled?(period: :monthly)
+    settings.dig('digest_preferences', period.to_s, 'enabled') || false
+  end
+
+  def enable_digest!(period: :monthly)
+    prefs = settings['digest_preferences'] || {}
+    prefs[period.to_s] ||= {}
+    prefs[period.to_s]['enabled'] = true
+    update!(settings: settings.merge('digest_preferences' => prefs))
+  end
+
+  def disable_digest!(period: :monthly)
+    prefs = settings['digest_preferences'] || {}
+    prefs[period.to_s] ||= {}
+    prefs[period.to_s]['enabled'] = false
+    update!(settings: settings.merge('digest_preferences' => prefs))
+  end
+
+  def digest_last_sent_at(period: :monthly)
+    timestamp = settings.dig('digest_preferences', period.to_s, 'last_sent_at')
+    Time.zone.parse(timestamp) if timestamp.present?
+  rescue ArgumentError
+    nil
+  end
+end
+```
+
+**Default settings structure**:
+```ruby
+user.settings = {
+  'digest_preferences' => {
+    'monthly' => {
+      'enabled' => true,  # Enabled by default for new users
+      'last_sent_at' => nil
+    },
+    'yearly' => {
+      'enabled' => true,  # Future use
+      'last_sent_at' => nil
+    }
+  }
+}
+```
+
+##### 1.2 Mailer Skeleton
+**File**: `app/mailers/digest_mailer.rb`
+```ruby
+class DigestMailer < ApplicationMailer
+  default from: 'hi@dawarich.app'
+
+  def monthly_digest(user, year, month)
+    @user = user
+    @year = year
+    @month = month
+    @period_type = :monthly
+    @digest_data = {}  # Will be populated in Phase 2
+
+    mail(
+      to: user.email,
+      subject: "#{Date::MONTHNAMES[month]} #{year} - Your Location Recap"
+    )
+  end
+
+  # Future: yearly_digest method
+  # def yearly_digest(user, year)
+  #   @user = user
+  #   @year = year
+  #   @period_type = :yearly
+  #   @digest_data = Digests::Calculator.new(user, period: :yearly, year: year).call
+  #
+  #   mail(
+  #     to: user.email,
+  #     subject: "#{year} Year in Review - Your Memories Recap"
+  #   )
+  # end
+end
+```
+
+##### 1.3 Routes
+**File**: `config/routes.rb`
+```ruby
+namespace :digests do
+  get 'preview/:period/:year(/:month)', to: 'digests#preview', as: :preview
+  post 'send_test/:period', to: 'digests#send_test', as: :send_test
+end
+
+# Examples:
+# /digests/preview/monthly/2024/12
+# /digests/preview/yearly/2024
+```
+
+##### 1.4 Placeholder Template
+**File**: `app/views/digest_mailer/monthly_digest.html.erb`
+```erb
+<!DOCTYPE html>
+<html>
+  <head>
+    <meta charset="utf-8">
+    <meta name="viewport" content="width=device-width, initial-scale=1.0">
+  </head>
+  <body>
+    <h1>Monthly Digest Placeholder</h1>
+    <p>Hello <%= @user.email %></p>
+    <p>This is a placeholder for <%= Date::MONTHNAMES[@month] %> <%= @year %></p>
+    <!-- Real content will be added in Phase 3 -->
+  </body>
+</html>
+```
+
+#### Testing Phase 1
+- [x] Test user settings methods (`digest_enabled?`, `enable_digest!`, etc.)
+- [x] Test mailer can be called without errors
+- [x] Test routes are accessible
+- [x] Send test email with placeholder content
+
+#### Acceptance Criteria
+- ✅ Users can enable/disable digest preferences
+- ✅ Mailer sends placeholder email successfully
+- ✅ Routes are defined and accessible
+- ✅ Settings persist in database
+
+#### Implementation Summary
+**Files Created/Modified:**
+- `app/models/user.rb` - Added 4 digest preference methods
+- `app/mailers/digest_mailer.rb` - Created with `monthly_digest` method
+- `config/routes.rb` - Added digest preview and test routes
+- `app/views/digest_mailer/monthly_digest.html.erb` - Placeholder template
+- `spec/models/user_spec.rb` - Added 9 comprehensive test cases
+
+**Test Results:** All 9 specs passing ✅
+**Manual Test:** Successfully sent placeholder email ✅
+
+---
+
+### Phase 2: Data Aggregation Services (2-3 days) ✅ COMPLETED
+
+**Goal**: Build all data query services that power the digest
+
+#### Deliverables
+- [x] Base calculator service
+- [x] All query objects implemented
+- [x] Comprehensive test coverage
+- [x] Data validation and edge case handling
+
+#### Tasks
+
+##### 2.1 Main Calculator Service
+**File**: `app/services/digests/calculator.rb`
+```ruby
+class Digests::Calculator
+  def initialize(user, period:, year:, month: nil)
+    @user = user
+    @period = period  # :monthly or :yearly
+    @year = year
+    @month = month
+    @date_range = build_date_range
+  end
+
+  def call
+    {
+      period_type: @period,
+      year: @year,
+      month: @month,
+      period_label: period_label,
+      overview: overview_data,
+      distance_stats: distance_stats,
+      top_cities: top_cities,
+      visited_places: visited_places,
+      trips: trips_data,
+      all_time_stats: all_time_stats
+    }
+  rescue StandardError => e
+    Rails.logger.error("Digest calculation failed: #{e.message}")
+    Rails.logger.error(e.backtrace.join("\n"))
+    nil
+  end
+
+  private
+
+  def build_date_range
+    case @period
+    when :monthly
+      start_date = Date.new(@year, @month, 1).beginning_of_day
+      end_date = start_date.end_of_month.end_of_day
+      start_date..end_date
+    when :yearly
+      start_date = Date.new(@year, 1, 1).beginning_of_day
+      end_date = start_date.end_of_year.end_of_day
+      start_date..end_date
+    end
+  end
+
+  def period_label
+    case @period
+    when :monthly
+      "#{Date::MONTHNAMES[@month]} #{@year}"
+    when :yearly
+      "#{@year}"
+    end
+  end
+
+  def overview_data
+    Queries::Digests::Overview.new(@user, @date_range).call
+  end
+
+  def distance_stats
+    Queries::Digests::Distance.new(@user, @date_range).call
+  end
+
+  def top_cities
+    Queries::Digests::Cities.new(@user, @date_range).call
+  end
+
+  def visited_places
+    Queries::Digests::Places.new(@user, @date_range).call
+  end
+
+  def trips_data
+    Queries::Digests::Trips.new(@user, @date_range).call
+  end
+
+  def all_time_stats
+    Queries::Digests::AllTime.new(@user).call
+  end
+end
+```
+
+##### 2.2 Query: Overview
+**File**: `app/services/digests/queries/overview.rb`
+```ruby
+ests::Queries::Digests::Overview
+  def initialize(user, date_range)
+    @user = user
+    @date_range = date_range
+    @start_timestamp = date_range.begin.to_i
+    @end_timestamp = date_range.end.to_i
+  end
+
+  def call
+    {
+      countries_count: count_countries,
+      cities_count: count_cities,
+      places_count: count_places,
+      points_count: count_points
+    }
+  end
+
+  private
+
+  def count_countries
+    @user.points
+         .where(timestamp: @start_timestamp..@end_timestamp)
+         .where.not(country_name: nil)
+         .distinct
+         .count(:country_name)
+  end
+
+  def count_cities
+    @user.points
+         .where(timestamp: @start_timestamp..@end_timestamp)
+         .where.not(city: nil)
+         .distinct
+         .count(:city)
+  end
+
+  def count_places
+    @user.visits
+         .joins(:area)
+         .where(started_at: @date_range)
+         .distinct
+         .count('areas.id')
+  end
+
+  def count_points
+    @user.points
+         .where(timestamp: @start_timestamp..@end_timestamp)
+         .count
+  end
+end
+```
+
+##### 2.3 Query: Distance
+**File**: `app/services/digests/queries/distance.rb`
+```ruby
+ests::Queries::Digests::Distance
+  def initialize(user, date_range)
+    @user = user
+    @date_range = date_range
+    @start_timestamp = date_range.begin.to_i
+    @end_timestamp = date_range.end.to_i
+  end
+
+  def call
+    points = fetch_points
+
+    {
+      total_distance_km: calculate_total_distance(points),
+      daily_average_km: calculate_daily_average(points),
+      max_distance_day: find_max_distance_day(points)
+    }
+  end
+
+  private
+
+  def fetch_points
+    @user.points
+         .where(timestamp: @start_timestamp..@end_timestamp)
+         .order(timestamp: :asc)
+  end
+
+  def calculate_total_distance(points)
+    return 0 if points.empty?
+
+    total = 0
+    points.each_cons(2) do |p1, p2|
+      total += Geocoder::Calculations.distance_between(
+        [p1.latitude, p1.longitude],
+        [p2.latitude, p2.longitude],
+        units: :km
+      )
+    end
+    total.round(2)
+  end
+
+  def calculate_daily_average(points)
+    total = calculate_total_distance(points)
+    days = (@date_range.end.to_date - @date_range.begin.to_date).to_i + 1
+    (total / days).round(2)
+  rescue ZeroDivisionError
+    0
+  end
+
+  def find_max_distance_day(points)
+    # Group by day and calculate distance for each day
+    daily_distances = points.group_by { |p| Time.at(p.timestamp).to_date }
+                           .transform_values { |day_points| calculate_total_distance(day_points) }
+
+    max_day = daily_distances.max_by { |_date, distance| distance }
+    max_day ? { date: max_day[0], distance_km: max_day[1] } : nil
+  end
+end
+```
+
+##### 2.4 Query: Cities
+**File**: `app/services/digests/queries/cities.rb`
+```ruby
+ests::Queries::Digests::Cities
+  def initialize(user, date_range, limit: 5)
+    @user = user
+    @date_range = date_range
+    @limit = limit
+    @start_timestamp = date_range.begin.to_i
+    @end_timestamp = date_range.end.to_i
+  end
+
+  def call
+    @user.points
+         .where(timestamp: @start_timestamp..@end_timestamp)
+         .where.not(city: nil)
+         .group(:city)
+         .count
+         .sort_by { |_city, count| -count }
+         .first(@limit)
+         .map { |city, count| { name: city, visits: count } }
+  end
+end
+```
+
+##### 2.5 Query: Places
+**File**: `app/services/digests/queries/places.rb`
+```ruby
+ests::Queries::Digests::Places
+  def initialize(user, date_range, limit: 3)
+    @user = user
+    @date_range = date_range
+    @limit = limit
+  end
+
+  def call
+    @user.visits
+         .joins(:area)
+         .where(started_at: @date_range)
+         .select('visits.*, areas.name as area_name, EXTRACT(EPOCH FROM (visits.ended_at - visits.started_at)) as duration_seconds')
+         .order('duration_seconds DESC')
+         .limit(@limit)
+         .map do |visit|
+           {
+             name: visit.area_name,
+             duration_hours: (visit.duration_seconds / 3600.0).round(1),
+             started_at: visit.started_at,
+             ended_at: visit.ended_at
+           }
+         end
+  end
+end
+```
+
+##### 2.6 Query: Trips
+**File**: `app/services/digests/queries/trips.rb`
+```ruby
+ests::Queries::Digests::Trips
+  def initialize(user, date_range)
+    @user = user
+    @date_range = date_range
+  end
+
+  def call
+    @user.trips
+         .where('started_at <= ? AND ended_at >= ?', @date_range.end, @date_range.begin)
+         .order(started_at: :desc)
+         .map do |trip|
+           {
+             id: trip.id,
+             name: trip.name,
+             started_at: trip.started_at,
+             ended_at: trip.ended_at,
+             distance_km: trip.distance || 0,
+             countries: trip.visited_countries || [],
+             photo_previews: trip.photo_previews.first(3)
+           }
+         end
+  end
+end
+```
+
+##### 2.7 Query: All-Time Stats
+**File**: `app/services/digests/queries/all_time.rb`
+```ruby
+ests::Queries::Digests::AllTime
+  def initialize(user)
+    @user = user
+  end
+
+  def call
+    {
+      total_countries: @user.points.where.not(country_name: nil).distinct.count(:country_name),
+      total_cities: @user.points.where.not(city: nil).distinct.count(:city),
+      total_places: @user.visits.joins(:area).distinct.count('areas.id'),
+      total_distance_km: calculate_total_distance,
+      account_age_days: account_age_days,
+      first_point_date: first_point_date
+    }
+  end
+
+  private
+
+  def calculate_total_distance
+    # Use cached stat data if available, otherwise calculate
+    @user.stats.sum(:distance) || 0
+  end
+
+  def account_age_days
+    (Date.today - @user.created_at.to_date).to_i
+  end
+
+  def first_point_date
+    first_point = @user.points.order(timestamp: :asc).first
+    first_point ? Time.at(first_point.timestamp).to_date : nil
+  end
+end
+```
+
+#### Testing Phase 2
+- [x] Test each query with empty data (no points/trips/visits)
+- [x] Test each query with sample data
+- [x] Test calculator integration
+- [x] Test error handling and edge cases
+- [x] Performance test with large datasets
+
+**Specs created**:
+- `spec/services/digests/calculator_spec.rb` - 11 examples
+- `spec/services/digests/queries/overview_spec.rb` - 5 examples
+- `spec/services/digests/queries/distance_spec.rb` - 4 examples
+- `spec/services/digests/queries/cities_spec.rb` - 3 examples
+- `spec/services/digests/queries/all_time_spec.rb` - 6 examples
+
+#### Acceptance Criteria
+- ✅ All queries return correct data structures
+- ✅ Calculator aggregates all queries successfully
+- ✅ Handles edge cases (no data, partial data)
+- ✅ All tests passing (29 examples, 0 failures)
+- ✅ No N+1 queries
+
+#### Implementation Summary
+**Files Created:**
+- `app/services/digests/calculator.rb` - Main calculator service
+- `app/services/digests/queries/overview.rb` - Countries/cities/places counts
+- `app/services/digests/queries/distance.rb` - Distance calculations
+- `app/services/digests/queries/cities.rb` - Top cities ranking
+- `app/services/digests/queries/places.rb` - Visited places
+- `app/services/digests/queries/trips.rb` - Trip data
+- `app/services/digests/queries/all_time.rb` - Lifetime statistics
+- 5 comprehensive spec files with 29 test cases
+
+**Files Modified:**
+- `app/mailers/digest_mailer.rb` - Integrated Calculator
+
+**Test Results:** All 29 specs passing ✅
+**Integration Test:** Successfully executed with real user data ✅
+
+---
+
+### Phase 3: Email Template & Design (3-4 days)
+
+**Goal**: Create beautiful, responsive email template with all cards
+
+#### Deliverables
+- [ ] Complete email HTML/CSS
+- [ ] All card partials
+- [ ] Lucide icons integration
+- [ ] Email client testing (Gmail, Outlook, Apple Mail)
+- [ ] Empty state handling
+
+#### Tasks
+
+##### 3.1 Email Layout
+**File**: `app/views/layouts/digest_mailer.html.erb`
+```erb
+<!DOCTYPE html>
+<html>
+  <head>
+    <meta charset="utf-8">
+    <meta name="viewport" content="width=device-width, initial-scale=1.0">
+    <style>
+      /* Inline CSS for email client compatibility */
+      body {
+        font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
+        background-color: #f3f4f6;
+        margin: 0;
+        padding: 20px;
+      }
+      .container {
+        max-width: 600px;
+        margin: 0 auto;
+        background-color: #ffffff;
+        border-radius: 8px;
+        overflow: hidden;
+        box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
+      }
+      .header {
+        background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
+        padding: 40px 20px;
+        text-align: center;
+        color: #ffffff;
+      }
+      .header h1 {
+        margin: 0;
+        font-size: 28px;
+        font-weight: 700;
+      }
+      .header p {
+        margin: 10px 0 0;
+        font-size: 16px;
+        opacity: 0.9;
+      }
+      .content {
+        padding: 30px 20px;
+      }
+      .card {
+        background-color: #f9fafb;
+        border-radius: 8px;
+        padding: 20px;
+        margin-bottom: 20px;
+        border: 1px solid #e5e7eb;
+      }
+      .card-header {
+        display: flex;
+        align-items: center;
+        margin-bottom: 15px;
+      }
+      .card-icon {
+        width: 24px;
+        height: 24px;
+        margin-right: 12px;
+        color: #667eea;
+      }
+      .card-title {
+        font-size: 18px;
+        font-weight: 600;
+        color: #111827;
+        margin: 0;
+      }
+      .stat-grid {
+        display: grid;
+        grid-template-columns: repeat(2, 1fr);
+        gap: 15px;
+      }
+      .stat-item {
+        text-align: center;
+      }
+      .stat-value {
+        font-size: 32px;
+        font-weight: 700;
+        color: #667eea;
+        display: block;
+      }
+      .stat-label {
+        font-size: 14px;
+        color: #6b7280;
+        margin-top: 5px;
+      }
+      .btn-primary {
+        display: inline-block;
+        background-color: #667eea;
+        color: #ffffff;
+        padding: 12px 24px;
+        border-radius: 6px;
+        text-decoration: none;
+        font-weight: 600;
+        margin: 10px 0;
+      }
+      .footer {
+        background-color: #f9fafb;
+        padding: 20px;
+        text-align: center;
+        font-size: 14px;
+        color: #6b7280;
+      }
+      @media only screen and (max-width: 600px) {
+        .stat-grid {
+          grid-template-columns: 1fr;
+        }
+      }
+    </style>
+  </head>
+  <body>
+    <%= yield %>
+  </body>
+</html>
+```
+
+##### 3.2 Main Email Template
+**File**: `app/views/digest_mailer/monthly_digest.html.erb`
+```erb
+<div class="container">
+  <!-- Header -->
+  <div class="header">
+    <h1>Your <%= @digest_data[:period_label] %> Recap</h1>
+    <p>Here's where you've been and what you've explored</p>
+  </div>
+
+  <!-- Content -->
+  <div class="content">
+    <!-- Greeting -->
+    <p style="font-size: 16px; color: #374151;">
+      Hi <%= @user.email.split('@').first.capitalize %>,
+    </p>
+    <p style="font-size: 16px; color: #6b7280; margin-bottom: 30px;">
+      Your monthly location recap is ready! Here's a summary of your travels in <%= @digest_data[:period_label] %>.
+    </p>
+
+    <!-- CTA Button -->
+    <div style="text-align: center; margin: 30px 0;">
+      <%= link_to 'View on Dawarich',
+                  root_url,
+                  class: 'btn-primary',
+                  style: 'background-color: #667eea; color: #ffffff; padding: 12px 24px; border-radius: 6px; text-decoration: none; font-weight: 600; display: inline-block;' %>
+    </div>
+
+    <!-- Cards -->
+    <%= render 'digest_mailer/cards/overview', data: @digest_data[:overview] %>
+    <%= render 'digest_mailer/cards/distance', data: @digest_data[:distance_stats] %>
+    <%= render 'digest_mailer/cards/cities', data: @digest_data[:top_cities] %>
+    <%= render 'digest_mailer/cards/places', data: @digest_data[:visited_places] %>
+    <%= render 'digest_mailer/cards/trips', data: @digest_data[:trips] %>
+    <%= render 'digest_mailer/cards/all_time', data: @digest_data[:all_time_stats] %>
+  </div>
+
+  <!-- Footer -->
+  <div class="footer">
+    <p>
+      You're receiving this because you have monthly digests enabled.<br>
+      <%= link_to 'Update preferences', settings_url, style: 'color: #667eea;' %> |
+      <%= link_to 'Unsubscribe', settings_url, style: 'color: #667eea;' %>
+    </p>
+  </div>
+</div>
+```
+
+##### 3.3 Card Partial Templates
+
+**File**: `app/views/digest_mailer/cards/_overview.html.erb`
+```erb
+<% if data && (data[:countries_count] > 0 || data[:cities_count] > 0) %>
+  <div class="card">
+    <div class="card-header">
+      <!-- Lucide Globe icon (SVG inline) -->
+      <svg class="card-icon" xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2">
+        <circle cx="12" cy="12" r="10"></circle>
+        <line x1="2" y1="12" x2="22" y2="12"></line>
+        <path d="M12 2a15.3 15.3 0 0 1 4 10 15.3 15.3 0 0 1-4 10 15.3 15.3 0 0 1-4-10 15.3 15.3 0 0 1 4-10z"></path>
+      </svg>
+      <h2 class="card-title">Overview</h2>
+    </div>
+
+    <div class="stat-grid">
+      <div class="stat-item">
+        <span class="stat-value"><%= data[:countries_count] %></span>
+        <span class="stat-label"><%= 'Country'.pluralize(data[:countries_count]) %></span>
+      </div>
+      <div class="stat-item">
+        <span class="stat-value"><%= data[:cities_count] %></span>
+        <span class="stat-label"><%= 'City'.pluralize(data[:cities_count]) %></span>
+      </div>
+      <div class="stat-item">
+        <span class="stat-value"><%= data[:places_count] %></span>
+        <span class="stat-label"><%= 'Place'.pluralize(data[:places_count]) %></span>
+      </div>
+      <div class="stat-item">
+        <span class="stat-value"><%= number_with_delimiter(data[:points_count]) %></span>
+        <span class="stat-label"><%= 'Point'.pluralize(data[:points_count]) %> tracked</span>
+      </div>
+    </div>
+  </div>
+<% end %>
+```
+
+**File**: `app/views/digest_mailer/cards/_distance.html.erb`
+```erb
+<% if data && data[:total_distance_km] > 0 %>
+  <div class="card">
+    <div class="card-header">
+      <!-- Lucide Route icon -->
+      <svg class="card-icon" xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2">
+        <circle cx="6" cy="19" r="3"></circle>
+        <path d="M9 19h8.5a3.5 3.5 0 0 0 0-7h-11a3.5 3.5 0 0 1 0-7H15"></path>
+        <circle cx="18" cy="5" r="3"></circle>
+      </svg>
+      <h2 class="card-title">Distance Traveled</h2>
+    </div>
+
+    <div class="stat-grid">
+      <div class="stat-item">
+        <span class="stat-value"><%= number_with_delimiter(data[:total_distance_km].round) %></span>
+        <span class="stat-label">Total km</span>
+      </div>
+      <div class="stat-item">
+        <span class="stat-value"><%= data[:daily_average_km].round %></span>
+        <span class="stat-label">Daily average km</span>
+      </div>
+    </div>
+
+    <% if data[:max_distance_day] %>
+      <p style="margin-top: 15px; font-size: 14px; color: #6b7280; text-align: center;">
+        Your longest day: <strong><%= data[:max_distance_day][:distance_km].round %> km</strong>
+        on <%= data[:max_distance_day][:date].strftime('%B %d') %>
+      </p>
+    <% end %>
+  </div>
+<% end %>
+```
+
+**File**: `app/views/digest_mailer/cards/_cities.html.erb`
+```erb
+<% if data&.any? %>
+  <div class="card">
+    <div class="card-header">
+      <!-- Lucide Building icon -->
+      <svg class="card-icon" xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2">
+        <rect x="4" y="2" width="16" height="20" rx="2" ry="2"></rect>
+        <path d="M9 22v-4h6v4"></path>
+        <path d="M8 6h.01"></path>
+        <path d="M16 6h.01"></path>
+        <path d="M12 6h.01"></path>
+        <path d="M12 10h.01"></path>
+        <path d="M12 14h.01"></path>
+        <path d="M16 10h.01"></path>
+        <path d="M16 14h.01"></path>
+        <path d="M8 10h.01"></path>
+        <path d="M8 14h.01"></path>
+      </svg>
+      <h2 class="card-title">Top Cities</h2>
+    </div>
+
+    <div style="margin-top: 15px;">
+      <% data.each_with_index do |city, index| %>
+        <div style="display: flex; justify-content: space-between; padding: 10px 0; border-bottom: 1px solid #e5e7eb;">
+          <span style="font-weight: 600; color: #374151;"><%= index + 1 %>. <%= city[:name] %></span>
+          <span style="color: #6b7280;"><%= number_with_delimiter(city[:visits]) %> <%= 'visit'.pluralize(city[:visits]) %></span>
+        </div>
+      <% end %>
+    </div>
+  </div>
+<% end %>
+```
+
+**File**: `app/views/digest_mailer/cards/_places.html.erb`
+```erb
+<% if data&.any? %>
+  <div class="card">
+    <div class="card-header">
+      <!-- Lucide MapPin icon -->
+      <svg class="card-icon" xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2">
+        <path d="M21 10c0 7-9 13-9 13s-9-6-9-13a9 9 0 0 1 18 0z"></path>
+        <circle cx="12" cy="10" r="3"></circle>
+      </svg>
+      <h2 class="card-title">Visited Places</h2>
+    </div>
+
+    <div style="margin-top: 15px;">
+      <% data.each do |place| %>
+        <div style="background: #ffffff; border-radius: 6px; padding: 15px; margin-bottom: 10px; border: 1px solid #e5e7eb;">
+          <h3 style="margin: 0 0 5px 0; font-size: 16px; color: #111827;"><%= place[:name] %></h3>
+          <p style="margin: 0; font-size: 14px; color: #6b7280;">
+            Spent <%= place[:duration_hours] %> hours •
+            <%= place[:started_at].strftime('%b %d') %>
+          </p>
+        </div>
+      <% end %>
+    </div>
+
+    <%= link_to 'View all visits', visits_url, style: 'color: #667eea; text-decoration: none; font-weight: 600;' %>
+  </div>
+<% end %>
+```
+
+**File**: `app/views/digest_mailer/cards/_trips.html.erb`
+```erb
+<% if data&.any? %>
+  <div class="card">
+    <div class="card-header">
+      <!-- Lucide Plane icon -->
+      <svg class="card-icon" xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2">
+        <path d="M17.8 19.2 16 11l3.5-3.5C21 6 21.5 4 21 3c-1-.5-3 0-4.5 1.5L13 8 4.8 6.2c-.5-.1-.9.1-1.1.5l-.3.5c-.2.5-.1 1 .3 1.3L9 12l-2 3H4l-1 1 3 2 2 3 1-1v-3l3-2 3.5 5.3c.3.4.8.5 1.3.3l.5-.2c.4-.3.6-.7.5-1.2z"></path>
+      </svg>
+      <h2 class="card-title">Trips</h2>
+    </div>
+
+    <div style="margin-top: 15px;">
+      <% data.each do |trip| %>
+        <div style="background: #ffffff; border-radius: 6px; padding: 15px; margin-bottom: 10px; border: 1px solid #e5e7eb;">
+          <h3 style="margin: 0 0 5px 0; font-size: 16px; color: #111827;">
+            <%= link_to trip[:name], trip_url(trip[:id]), style: 'color: #667eea; text-decoration: none;' %>
+          </h3>
+          <p style="margin: 0; font-size: 14px; color: #6b7280;">
+            <%= trip[:started_at].strftime('%b %d') %> - <%= trip[:ended_at].strftime('%b %d') %> •
+            <%= number_with_delimiter(trip[:distance_km].round) %> km
+          </p>
+          <% if trip[:countries]&.any? %>
+            <p style="margin: 5px 0 0 0; font-size: 13px; color: #9ca3af;">
+              <%= trip[:countries].join(', ') %>
+            </p>
+          <% end %>
+        </div>
+      <% end %>
+    </div>
+
+    <%= link_to 'View all trips', trips_url, style: 'color: #667eea; text-decoration: none; font-weight: 600;' %>
+  </div>
+<% end %>
+```
+
+**File**: `app/views/digest_mailer/cards/_all_time.html.erb`
+```erb
+<% if data %>
+  <div class="card">
+    <div class="card-header">
+      <!-- Lucide Trophy icon -->
+      <svg class="card-icon" xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2">
+        <path d="M6 9H4.5a2.5 2.5 0 0 1 0-5H6"></path>
+        <path d="M18 9h1.5a2.5 2.5 0 0 0 0-5H18"></path>
+        <path d="M4 22h16"></path>
+        <path d="M10 14.66V17c0 .55-.47.98-.97 1.21C7.85 18.75 7 20.24 7 22"></path>
+        <path d="M14 14.66V17c0 .55.47.98.97 1.21C16.15 18.75 17 20.24 17 22"></path>
+        <path d="M18 2H6v7a6 6 0 0 0 12 0V2Z"></path>
+      </svg>
+      <h2 class="card-title">All-Time Stats</h2>
+    </div>
+
+    <div class="stat-grid">
+      <div class="stat-item">
+        <span class="stat-value"><%= data[:total_countries] %></span>
+        <span class="stat-label">Total countries</span>
+      </div>
+      <div class="stat-item">
+        <span class="stat-value"><%= data[:total_cities] %></span>
+        <span class="stat-label">Total cities</span>
+      </div>
+      <div class="stat-item">
+        <span class="stat-value"><%= data[:total_places] %></span>
+        <span class="stat-label">Total places</span>
+      </div>
+      <div class="stat-item">
+        <span class="stat-value"><%= number_with_delimiter(data[:total_distance_km].round) %></span>
+        <span class="stat-label">Total km</span>
+      </div>
+    </div>
+
+    <% if data[:first_point_date] %>
+      <p style="margin-top: 15px; font-size: 14px; color: #6b7280; text-align: center;">
+        Tracking since <%= data[:first_point_date].strftime('%B %Y') %>
+      </p>
+    <% end %>
+  </div>
+<% end %>
+```
+
+##### 3.4 Update Mailer to Use Calculator
+**File**: `app/mailers/digest_mailer.rb` (update)
+```ruby
+class DigestMailer < ApplicationMailer
+  default from: 'no-reply@dawarich.app'
+
+  def monthly_digest(user, year, month)
+    @user = user
+    @year = year
+    @month = month
+    @period_type = :monthly
+    @digest_data = Digests::Calculator.new(user, period: :monthly, year: year, month: month).call
+
+    return if @digest_data.nil?  # Don't send if calculation failed
+
+    mail(
+      to: user.email,
+      subject: "#{Date::MONTHNAMES[month]} #{year} - Your Location Recap"
+    )
+  end
+end
+```
+
+#### Testing Phase 3
+- [ ] Preview email in browser (`/rails/mailers`)
+- [ ] Test with empty/partial data
+- [ ] Test in major email clients (Gmail, Outlook, Apple Mail)
+- [ ] Test on mobile devices
+- [ ] Verify all links work correctly
+- [ ] Test with long city/place names
+- [ ] Test with special characters in data
+
+**Tools for testing**:
+- Rails mailer previews
+- Litmus or Email on Acid (email client testing)
+- SendGrid email preview
+
+#### Acceptance Criteria
+✅ Email renders correctly in all major clients
+✅ All cards display properly with real data
+✅ Empty states handled gracefully
+✅ Links navigate to correct pages
+✅ Mobile responsive
+✅ Accessible (screen readers, alt text)
+
+---
+
+### Phase 4: Scheduling & Background Jobs (1 day)
+
+**Goal**: Implement job system for automated digest delivery
+
+#### Deliverables
+- [ ] Delivery job
+- [ ] Scheduling job
+- [ ] Cron configuration
+- [ ] Error handling and retries
+- [ ] Monitoring/logging
+
+#### Tasks
+
+##### 3.1 Email Structure
+1. **Header**
+   - Greeting (personalized with user name if available)
+   - Brief explanation of email
+   - CTA button: "View on Dawarich"
+
+2. **Card 1: Overview**
+   - Icon: Map pin or globe (Lucide)
+   - Countries visited: X
+   - Cities visited: X
+   - Places visited: X
+   - ~~Map image~~ (TODO: implement later)
+   - Link to month view in web app
+
+3. **Card 2: Distance Stats**
+   - Icon: Route/navigation (Lucide)
+   - Total distance traveled: X km/mi
+   - Daily average: X km/mi
+   - Bar chart or simple daily breakdown (HTML/CSS)
+
+4. **Card 3: Top Cities**
+   - Icon: Building/city (Lucide)
+   - List top 3-5 cities with point count
+   - Simple text list, no images
+   - Link to points/map view filtered by city
+
+5. **Card 4: Visited Places**
+   - Icon: MapPin (Lucide)
+   - 1-3 places with longest visit duration
+   - Place name, duration
+   - Link to `/visits` page
+
+6. **Card 5: Trips**
+   - Icon: Plane/luggage (Lucide)
+   - Trip name, dates, distance
+   - Countries visited in trip
+   - Use existing `photo_previews` if available
+   - Link to `/trips/:id`
+
+7. **Card 6: All-Time Stats**
+   - Icon: Trophy/award (Lucide)
+   - Total countries visited: X
+   - Total cities visited: X
+   - Total places visited: X
+   - Total distance traveled: X km/mi
+
+8. **Footer**
+   - Unsubscribe link
+   - Settings link
+   - Social links (if applicable)
+
+#### 3.2 Email Styling
+**File**: `app/views/layouts/monthly_digest_mailer.html.erb`
+- Inline CSS (email client compatibility)
+- Mobile-responsive design
+- Light/dark mode considerations
+- Accessible color contrast
+
+##### 4.1 Delivery Job
+**File**: `app/jobs/digests/delivery_job.rb`
+```ruby
+class Digests::DeliveryJob < ApplicationJob
+  queue_as :default
+
+  def perform(user_id, period:, year:, month: nil)
+    user = User.find(user_id)
+    return unless digest_enabled?(user, period)
+
+    case period
+    when :monthly
+      DigestMailer.monthly_digest(user, year, month).deliver_now
+      update_last_sent(user, :monthly)
+    when :yearly
+      DigestMailer.yearly_digest(user, year).deliver_now
+      update_last_sent(user, :yearly)
+    end
+  end
+
+  private
+
+  def digest_enabled?(user, period)
+    user.settings.dig('digest_preferences', period.to_s, 'enabled')
+  end
+
+  def update_last_sent(user, period)
+    prefs = user.settings['digest_preferences'] || {}
+    prefs[period.to_s] ||= {}
+    prefs[period.to_s]['last_sent_at'] = Time.current.iso8601
+    user.update!(settings: user.settings.merge('digest_preferences' => prefs))
+  end
+end
+```
+
+##### 4.2 Scheduling Job
+**File**: `app/jobs/digests/scheduling/monthly_job.rb`
+```ruby
+class Digests::Scheduling::MonthlyJob < ApplicationJob
+  queue_as :default
+
+  def perform
+    year = 1.month.ago.year
+    month = 1.month.ago.month
+
+    User.find_in_batches(batch_size: 100) do |users|
+      users.each do |user|
+        Digests::DeliveryJob.perform_later(user.id, period: :monthly, year: year, month: month)
+      end
+    end
+  end
+end
+```
+
+**File**: `app/jobs/digests/scheduling/yearly_job.rb` (future)
+```ruby
+class Digests::Scheduling::YearlyJob < ApplicationJob
+  queue_as :default
+
+  def perform
+    year = 1.year.ago.year
+
+    User.find_in_batches(batch_size: 100) do |users|
+      users.each do |user|
+        Digests::DeliveryJob.perform_later(user.id, period: :yearly, year: year)
+      end
+    end
+  end
+end
+```
+
+##### 4.3 Cron Configuration
+**File**: `config/schedule.yml` (or use existing cron setup)
+```yaml
+monthly_digest:
+  cron: "0 9 1 * *"  # 9 AM on the 1st of every month
+  class: "Digests::Scheduling::MonthlyJob"
+
+# Future:
+# yearly_digest:
+#   cron: "0 9 1 1 *"  # 9 AM on January 1st
+#   class: "Digests::Scheduling::YearlyJob"
+```
+
+##### 4.4 Error Handling & Logging
+Add to jobs for production monitoring:
+```ruby
+# app/jobs/digests/delivery_job.rb
+class Digests::DeliveryJob < ApplicationJob
+  queue_as :default
+  retry_on StandardError, wait: 5.minutes, attempts: 3
+
+  def perform(user_id, period:, year:, month: nil)
+    user = User.find(user_id)
+    return unless digest_enabled?(user, period)
+
+    Rails.logger.info("Sending #{period} digest to user #{user.id} for #{year}/#{month}")
+
+    case period
+    when :monthly
+      DigestMailer.monthly_digest(user, year, month).deliver_now
+      update_last_sent(user, :monthly)
+      Rails.logger.info("Successfully sent monthly digest to user #{user.id}")
+    when :yearly
+      DigestMailer.yearly_digest(user, year).deliver_now
+      update_last_sent(user, :yearly)
+      Rails.logger.info("Successfully sent yearly digest to user #{user.id}")
+    end
+  rescue StandardError => e
+    Rails.logger.error("Failed to send #{period} digest to user #{user_id}: #{e.message}")
+    Rails.logger.error(e.backtrace.join("\n"))
+    raise  # Re-raise for retry logic
+  end
+
+  # ... rest of the code
+end
+```
+
+#### Testing Phase 4
+- [ ] Test delivery job with real user
+- [ ] Test scheduling job enqueues correctly
+- [ ] Test error handling and retries
+- [ ] Test with disabled users
+- [ ] Test with missing/invalid data
+- [ ] Monitor Sidekiq dashboard
+
+**Manual testing**:
+```ruby
+# In Rails console
+user = User.first
+Digests::DeliveryJob.perform_now(user.id, period: :monthly, year: 2024, month: 12)
+
+# Test scheduling
+Digests::Scheduling::MonthlyJob.perform_now
+```
+
+#### Acceptance Criteria
+✅ Jobs enqueue and process successfully
+✅ Emails delivered to users
+✅ Error handling and retries work
+✅ Logging captures important events
+✅ Cron schedule configured correctly
+✅ No duplicate emails sent
+
+---
+
+### Phase 5: Web Preview & Settings (1-2 days)
+
+**Goal**: Allow users to preview digests and manage preferences
+
+#### Deliverables
+- [ ] Preview controller and views
+- [ ] Settings UI for digest preferences
+- [ ] Send test digest functionality
+- [ ] User documentation
+
+#### Tasks
+
+##### 5.1 Preview Controller
+**File**: `app/controllers/digests_controller.rb`
+```ruby
+class DigestsController < ApplicationController
+  before_action :authenticate_user!
+
+  def preview
+    @period = params[:period].to_sym
+    @year = params[:year].to_i
+    @month = params[:month]&.to_i
+
+    case @period
+    when :monthly
+      @user = current_user
+      @digest_data = Digests::Calculator.new(
+        current_user,
+        period: :monthly,
+        year: @year,
+        month: @month
+      ).call
+
+      if @digest_data.nil?
+        flash[:alert] = "Could not generate digest. Please ensure you have data for this period."
+        redirect_to settings_path
+        return
+      end
+
+      render 'digest_mailer/monthly_digest', layout: 'mailer'
+    when :yearly
+      # Future implementation
+      flash[:info] = "Yearly digest coming soon!"
+      redirect_to settings_path
+    else
+      flash[:alert] = "Invalid digest period"
+      redirect_to settings_path
+    end
+  end
+
+  def send_test
+    period = params[:period].to_sym
+
+    case period
+    when :monthly
+      year = 1.month.ago.year
+      month = 1.month.ago.month
+      Digests::DeliveryJob.perform_later(current_user.id, period: :monthly, year: year, month: month)
+      flash[:notice] = "Test digest queued! Check your email in a few moments."
+    when :yearly
+      flash[:info] = "Yearly digest coming soon!"
+    else
+      flash[:alert] = "Invalid digest period"
+    end
+
+    redirect_to settings_path
+  end
+end
+```
+
+##### 5.2 Settings View Partial
+**File**: `app/views/settings/_digest_preferences.html.erb`
+```erb
+<div class="card bg-base-100 shadow-xl">
+  <div class="card-body">
+    <h2 class="card-title">
+      <svg class="w-6 h-6" xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2">
+        <rect x="3" y="4" width="18" height="18" rx="2" ry="2"></rect>
+        <line x1="16" y1="2" x2="16" y2="6"></line>
+        <line x1="8" y1="2" x2="8" y2="6"></line>
+        <line x1="3" y1="10" x2="21" y2="10"></line>
+      </svg>
+      Digest Preferences
+    </h2>
+    <p class="text-sm text-base-content/70">
+      Receive periodic recaps of your location data via email
+    </p>
+
+    <div class="divider"></div>
+
+    <!-- Monthly Digest -->
+    <div class="form-control">
+      <label class="label cursor-pointer justify-start gap-4">
+        <input
+          type="checkbox"
+          class="toggle toggle-primary"
+          <%= 'checked' if current_user.digest_enabled?(:monthly) %>
+          data-action="change->settings#toggleMonthlyDigest"
+        >
+        <div class="flex-1">
+          <span class="label-text font-semibold">Monthly Digest</span>
+          <p class="text-xs text-base-content/60 mt-1">
+            Receive a recap of your travels on the 1st of each month
+          </p>
+          <% if last_sent = current_user.digest_last_sent_at(:monthly) %>
+            <p class="text-xs text-base-content/50 mt-1">
+              Last sent: <%= last_sent.strftime('%B %d, %Y at %I:%M %p') %>
+            </p>
+          <% end %>
+        </div>
+      </label>
+
+      <div class="flex gap-2 mt-3 ml-16">
+        <%= link_to 'Preview Last Month',
+                    digests_preview_path(period: 'monthly', year: 1.month.ago.year, month: 1.month.ago.month),
+                    class: 'btn btn-sm btn-outline',
+                    target: '_blank' %>
+        <%= button_to 'Send Test Email',
+                      digests_send_test_path(period: 'monthly'),
+                      method: :post,
+                      class: 'btn btn-sm btn-primary',
+                      data: { confirm: 'Send a test digest to your email?' } %>
+      </div>
+    </div>
+
+    <div class="divider"></div>
+
+    <!-- Yearly Digest (Coming Soon) -->
+    <div class="form-control opacity-50">
+      <label class="label cursor-not-allowed justify-start gap-4">
+        <input
+          type="checkbox"
+          class="toggle toggle-primary"
+          disabled
+        >
+        <div class="flex-1">
+          <span class="label-text font-semibold">Yearly Digest</span>
+          <span class="badge badge-sm badge-info ml-2">Coming Soon</span>
+          <p class="text-xs text-base-content/60 mt-1">
+            Receive a yearly recap on January 1st
+          </p>
+        </div>
+      </label>
+    </div>
+  </div>
+</div>
+```
+
+##### 5.3 Settings Controller Update
+**File**: `app/controllers/settings_controller.rb`
+```ruby
+class SettingsController < ApplicationController
+  before_action :authenticate_user!
+
+  def update_digest_preference
+    period = params[:period].to_sym
+    enabled = params[:enabled] == 'true'
+
+    if enabled
+      current_user.enable_digest!(period)
+      message = "#{period.to_s.capitalize} digest enabled"
+    else
+      current_user.disable_digest!(period)
+      message = "#{period.to_s.capitalize} digest disabled"
+    end
+
+    respond_to do |format|
+      format.json { render json: { success: true, message: message } }
+      format.html { redirect_to settings_path, notice: message }
+    end
+  end
+end
+```
+
+##### 5.4 Routes Update
+**File**: `config/routes.rb`
+```ruby
+# Add to existing routes
+namespace :digests do
+  get 'preview/:period/:year(/:month)', to: 'digests#preview', as: :preview
+  post 'send_test/:period', to: 'digests#send_test', as: :send_test
+end
+
+# Add to settings routes
+resources :settings, only: [:index, :update] do
+  collection do
+    patch 'digest_preference', to: 'settings#update_digest_preference'
+  end
+end
+```
+
+##### 5.5 Stimulus Controller (Optional, for toggle)
+**File**: `app/javascript/controllers/settings_controller.js`
+```javascript
+import { Controller } from "@hotwired/stimulus"
+
+export default class extends Controller {
+  async toggleMonthlyDigest(event) {
+    const enabled = event.target.checked
+
+    const response = await fetch('/settings/digest_preference', {
+      method: 'PATCH',
+      headers: {
+        'Content-Type': 'application/json',
+        'X-CSRF-Token': document.querySelector('[name="csrf-token"]').content
+      },
+      body: JSON.stringify({
+        period: 'monthly',
+        enabled: enabled
+      })
+    })
+
+    const data = await response.json()
+
+    // Show toast notification (if you have a toast system)
+    console.log(data.message)
+  }
+}
+```
+
+#### Testing Phase 5
+- [ ] Test preview with current month
+- [ ] Test preview with historical months
+- [ ] Test preview with no data
+- [ ] Test send test email functionality
+- [ ] Test toggle enable/disable
+- [ ] Test settings persistence
+- [ ] Test authorization (users can only see their own digests)
+
+#### Acceptance Criteria
+✅ Users can preview any month's digest
+✅ Test email sends successfully
+✅ Settings save and persist correctly
+✅ UI is intuitive and accessible
+✅ Error states handled gracefully
+✅ Authorization works correctly
+
+---
+
+## Post-Implementation Checklist
+
+### Before Launch
+- [ ] All phases complete and tested
+- [ ] Email deliverability tested (check spam scores)
+- [ ] Performance tested with large datasets
+- [ ] Error monitoring configured (Sentry/Rollbar)
+- [ ] Documentation updated
+- [ ] User announcement prepared
+
+### Launch Day
+- [ ] Enable cron job
+- [ ] Monitor first batch of emails
+- [ ] Check email delivery rates
+- [ ] Monitor error logs
+- [ ] Gather initial user feedback
+
+### Week 1 Monitoring
+- [ ] Track email open rates
+- [ ] Track click-through rates
+- [ ] Monitor unsubscribe rate
+- [ ] Review error logs
+- [ ] Collect user feedback
+- [ ] Performance optimization if needed
+
+---
+
+## Rollback Plan
+
+If issues arise after launch:
+
+1. **Disable cron job immediately**
+   ```ruby
+   # Comment out in config/schedule.yml or disable in cron
+   ```
+
+2. **Stop pending jobs**
+   ```ruby
+   # In Rails console
+   Sidekiq::Queue.new('default').clear
+   ```
+
+3. **Disable digest for all users** (emergency)
+   ```ruby
+   User.find_each do |user|
+     user.disable_digest!(:monthly)
+   end
+   ```
+
+4. **Investigate and fix issues**
+
+5. **Re-enable gradually**
+   - Test with small user group first
+   - Monitor carefully
+   - Expand to full user base
+
+## Database Changes
+
+### Migration 1: User Settings (Extensible Structure)
+Store in existing `settings` JSONB column (preferred):
+```ruby
+user.settings = {
+  'digest_preferences' => {
+    'monthly' => {
+      'enabled' => true,
+      'last_sent_at' => '2024-01-01T09:00:00Z'
+    },
+    'yearly' => {
+      'enabled' => false,  # For future use
+      'last_sent_at' => nil
+    }
+    # Future: 'weekly', 'quarterly', etc.
+  }
+}
+```
+
+**Benefits**:
+- No schema migration needed
+- Easy to add yearly/quarterly digests later
+- Per-period preferences and tracking
+- Backward compatible (check for `digest_preferences` existence)
+
+## Testing Strategy
+
+### Unit Tests
+- `spec/services/digests/calculator_spec.rb` - Test both monthly and yearly periods
+- `spec/services/digests/queries/*_spec.rb` - Test with various date ranges
+- `spec/mailers/digest_mailer_spec.rb` - Test both monthly and yearly emails
+
+### Integration Tests
+- `spec/jobs/digests/delivery_job_spec.rb` - Test multiple periods
+- `spec/jobs/digests/scheduling/monthly_job_spec.rb`
+- `spec/jobs/digests/scheduling/yearly_job_spec.rb` (future)
+
+### Request Tests
+- `spec/requests/digests_spec.rb` - Preview endpoint for all periods
+
+### Email Tests
+- Test email rendering
+- Test data aggregation
+- Test user preference handling
+- Test batch processing
+
+## Yearly Digest Extension Plan
+
+When implementing yearly digest (estimated **2-3 days** additional work):
+
+### What Changes:
+1. **Mailer**: Add `yearly_digest` method to `DigestMailer` ✅ (structure already in place)
+2. **Template**: Create `app/views/digest_mailer/yearly_digest.html.erb`
+   - Reuse existing card partials
+   - Adjust copy: "December 2024" → "2024 Year in Review"
+   - Add yearly-specific cards:
+     - Month-by-month breakdown (12 mini cards)
+     - Seasonal patterns (if applicable)
+     - Year-over-year comparison (if multiple years available)
+3. **Scheduler**: Enable `Digests::Scheduling::YearlyJob` in cron ✅ (already defined)
+4. **Settings UI**: Enable yearly toggle (currently grayed out)
+5. **Calculator**: Already supports `period: :yearly` ✅
+
+### What Stays the Same:
+- All query objects (already use `date_range`) ✅
+- Job infrastructure (`Digests::DeliveryJob`) ✅
+- Settings structure (`digest_preferences.yearly`) ✅
+- Preview controller (already parameterized) ✅
+
+### Yearly-Specific Data Queries:
+- Monthly distance breakdown (12 data points)
+- Busiest travel month
+- Countries visited by month (timeline visualization)
+- Total vs. average monthly stats
+
+**Reuse Percentage**: ~80% of code can be reused
+
+## Future Enhancements (Post-MVP)
+
+### Map Image Generation
+**Idea**: Generate static map images server-side
+- Use headless browser (Puppeteer/Playwright) to render Leaflet map
+- Capture screenshot of map with hexagon overlay
+- Store in S3 or temp storage
+- Embed in email as attachment/inline image
+- **TODO file**: Create separate plan for this feature
+
+### Activity Type Detection
+- Add `activity_type` to points table
+- Infer from velocity/speed patterns
+- Show walking vs driving stats
+
+### Personalization
+- Smart insights ("You visited 3 new countries this month!")
+- Comparisons to previous months
+- Streak tracking (consecutive months with travel)
+
+### Advanced Stats
+- Time of day analysis (morning vs evening travel)
+- Weekday vs weekend patterns
+- Seasonal trends
+
+### User Preferences
+- Choose digest frequency (weekly, monthly, quarterly, yearly) ✅ Structure ready
+- Select day of month/year for delivery
+- Customize which cards to include
+- Language preferences
+
+### Additional Digest Frequencies
+With the current extensible architecture, adding new frequencies is straightforward:
+
+**Weekly Digest**:
+- Add `'weekly'` to `digest_preferences`
+- Create `Digests::Scheduling::WeeklyJob`
+- Template reuses same card partials
+- Estimated effort: 1-2 days
+
+**Quarterly Digest**:
+- Add `'quarterly'` to `digest_preferences`
+- Create `Digests::Scheduling::QuarterlyJob`
+- Template reuses same card partials
+- Add quarter-specific insights (seasonal patterns)
+- Estimated effort: 2 days
+
+## Timeline Estimate
+
+- **Phase 1**: 1-2 days (Email infrastructure)
+- **Phase 2**: 2-3 days (Data aggregation)
+- **Phase 3**: 3-4 days (Email template & cards)
+- **Phase 4**: 1 day (Scheduling)
+- **Phase 5**: 1-2 days (Preview & settings)
+
+**Total**: 8-12 days for complete MVP
+
+## Dependencies & Risks
+
+### Dependencies
+- Existing `Stat` calculation must be reliable
+- Sidekiq/Redis must be configured
+- Email delivery service (SendGrid, Mailgun, etc.)
+- Existing user settings system
+
+### Risks
+- Email deliverability (spam filters)
+- Large user base → batch processing performance
+- Missing/incomplete data for some months
+- Email client compatibility issues (Outlook, Gmail, etc.)
+
+### Mitigation
+- Use established email service with good reputation
+- Implement retry logic for failed deliveries
+- Gracefully handle missing data in templates
+- Test emails in major clients before launch
+- Add monitoring/logging for delivery success rate
+
+## Success Metrics
+
+### Primary KPIs
+- Email open rate > 30%
+- Click-through rate > 10%
+- Unsubscribe rate < 2%
+
+### Secondary Metrics
+- User engagement after digest (web visits, data exploration)
+- Feature awareness (do users discover features via digest?)
+- Support tickets related to digest feature
+
+## Open Questions
+
+1. Should we send digest even if user has NO activity in previous month?
+   - **Decision**: Yes, send regardless (can show "No activity this month" state)
+
+2. What if stat hasn't been calculated for the month yet?
+   - **Option A**: Calculate on-demand before sending
+   - **Option B**: Skip digest and notify user
+   - **Recommended**: Option A with timeout/fallback
+
+3. Should preview require existing stat or calculate on-the-fly?
+   - **Recommended**: Calculate on-the-fly for flexibility
+
+4. Email preference granularity?
+   - **MVP**: Single toggle (enable/disable)
+   - **Future**: Choose frequency, day of month, card selection
+
+## Notes
+
+- This plan prioritizes MVP speed over perfection
+- Focus on data quality and email deliverability
+- Keep template simple and maintainable
+- Consider email accessibility (screen readers, alt text)
+- Plan for internationalization if needed (I18n)
diff --git a/app/mailers/digest_mailer.rb b/app/mailers/digest_mailer.rb
new file mode 100644
index 00000000..0df36114
--- /dev/null
+++ b/app/mailers/digest_mailer.rb
@@ -0,0 +1,31 @@
+# frozen_string_literal: true
+
+class DigestMailer < ApplicationMailer
+  def monthly_digest(user, year, month)
+    @user = user
+    @year = year
+    @month = month
+    @period_type = :monthly
+    @digest_data = Digests::Calculator.new(user, period: :monthly, year: year, month: month).call
+
+    return if @digest_data.nil?  # Don't send if calculation failed
+
+    mail(
+      to: user.email,
+      subject: "#{Date::MONTHNAMES[month]} #{year} - Your Location Recap"
+    )
+  end
+
+  # Future: yearly_digest method
+  # def yearly_digest(user, year)
+  #   @user = user
+  #   @year = year
+  #   @period_type = :yearly
+  #   @digest_data = Digests::Calculator.new(user, period: :yearly, year: year).call
+  #
+  #   mail(
+  #     to: user.email,
+  #     subject: "#{year} Year in Review - Your Location Recap"
+  #   )
+  # end
+end
diff --git a/app/models/user.rb b/app/models/user.rb
index 71269d64..31e936ad 100644
--- a/app/models/user.rb
+++ b/app/models/user.rb
@@ -145,6 +145,32 @@ class User < ApplicationRecord # rubocop:disable Metrics/ClassLength
     points.where.not(city: [nil, '']).distinct.pluck(:city).compact
   end
 
+  # Digest preferences methods
+  def digest_enabled?(period = :monthly)
+    settings.dig('digest_preferences', period.to_s, 'enabled') || false
+  end
+
+  def enable_digest!(period = :monthly)
+    prefs = settings['digest_preferences'] || {}
+    prefs[period.to_s] ||= {}
+    prefs[period.to_s]['enabled'] = true
+    update!(settings: settings.merge('digest_preferences' => prefs))
+  end
+
+  def disable_digest!(period = :monthly)
+    prefs = settings['digest_preferences'] || {}
+    prefs[period.to_s] ||= {}
+    prefs[period.to_s]['enabled'] = false
+    update!(settings: settings.merge('digest_preferences' => prefs))
+  end
+
+  def digest_last_sent_at(period = :monthly)
+    timestamp = settings.dig('digest_preferences', period.to_s, 'last_sent_at')
+    Time.zone.parse(timestamp) if timestamp.present?
+  rescue ArgumentError
+    nil
+  end
+
   private
 
   def create_api_key
diff --git a/app/services/digests/calculator.rb b/app/services/digests/calculator.rb
new file mode 100644
index 00000000..e4251445
--- /dev/null
+++ b/app/services/digests/calculator.rb
@@ -0,0 +1,78 @@
+# frozen_string_literal: true
+
+class Digests::Calculator
+  def initialize(user, period:, year:, month: nil)
+    @user = user
+    @period = period  # :monthly or :yearly
+    @year = year
+    @month = month
+    @date_range = build_date_range
+  end
+
+  def call
+    {
+      period_type: @period,
+      year: @year,
+      month: @month,
+      period_label: period_label,
+      overview: overview_data,
+      distance_stats: distance_stats,
+      top_cities: top_cities,
+      visited_places: visited_places,
+      trips: trips_data,
+      all_time_stats: all_time_stats
+    }
+  rescue StandardError => e
+    Rails.logger.error("Digest calculation failed: #{e.message}")
+    Rails.logger.error(e.backtrace.join("\n"))
+    nil
+  end
+
+  private
+
+  def build_date_range
+    case @period
+    when :monthly
+      start_date = Date.new(@year, @month, 1).beginning_of_day
+      end_date = start_date.end_of_month.end_of_day
+      start_date..end_date
+    when :yearly
+      start_date = Date.new(@year, 1, 1).beginning_of_day
+      end_date = start_date.end_of_year.end_of_day
+      start_date..end_date
+    end
+  end
+
+  def period_label
+    case @period
+    when :monthly
+      "#{Date::MONTHNAMES[@month]} #{@year}"
+    when :yearly
+      "#{@year}"
+    end
+  end
+
+  def overview_data
+    Digests::Queries::Overview.new(@user, @date_range).call
+  end
+
+  def distance_stats
+    Digests::Queries::Distance.new(@user, @date_range).call
+  end
+
+  def top_cities
+    Digests::Queries::Cities.new(@user, @date_range).call
+  end
+
+  def visited_places
+    Digests::Queries::Places.new(@user, @date_range).call
+  end
+
+  def trips_data
+    Digests::Queries::Trips.new(@user, @date_range).call
+  end
+
+  def all_time_stats
+    Digests::Queries::AllTime.new(@user).call
+  end
+end
diff --git a/app/services/digests/queries/all_time.rb b/app/services/digests/queries/all_time.rb
new file mode 100644
index 00000000..b3f9b0bc
--- /dev/null
+++ b/app/services/digests/queries/all_time.rb
@@ -0,0 +1,34 @@
+# frozen_string_literal: true
+
+class Digests::Queries::AllTime
+  def initialize(user)
+    @user = user
+  end
+
+  def call
+    {
+      total_countries: @user.points.where.not(country_name: nil).distinct.count(:country_name),
+      total_cities: @user.points.where.not(city: nil).distinct.count(:city),
+      total_places: @user.visits.joins(:area).distinct.count('areas.id'),
+      total_distance_km: calculate_total_distance,
+      account_age_days: account_age_days,
+      first_point_date: first_point_date
+    }
+  end
+
+  private
+
+  def calculate_total_distance
+    # Use cached stat data if available, otherwise calculate
+    @user.stats.sum(:distance) || 0
+  end
+
+  def account_age_days
+    (Date.today - @user.created_at.to_date).to_i
+  end
+
+  def first_point_date
+    first_point = @user.points.order(timestamp: :asc).first
+    first_point ? Time.at(first_point.timestamp).to_date : nil
+  end
+end
diff --git a/app/services/digests/queries/cities.rb b/app/services/digests/queries/cities.rb
new file mode 100644
index 00000000..c6e9940e
--- /dev/null
+++ b/app/services/digests/queries/cities.rb
@@ -0,0 +1,22 @@
+# frozen_string_literal: true
+
+class Digests::Queries::Cities
+  def initialize(user, date_range, limit: 5)
+    @user = user
+    @date_range = date_range
+    @limit = limit
+    @start_timestamp = date_range.begin.to_i
+    @end_timestamp = date_range.end.to_i
+  end
+
+  def call
+    @user.points
+         .where(timestamp: @start_timestamp..@end_timestamp)
+         .where.not(city: nil)
+         .group(:city)
+         .count
+         .sort_by { |_city, count| -count }
+         .first(@limit)
+         .map { |city, count| { name: city, visits: count } }
+  end
+end
diff --git a/app/services/digests/queries/distance.rb b/app/services/digests/queries/distance.rb
new file mode 100644
index 00000000..b17e274e
--- /dev/null
+++ b/app/services/digests/queries/distance.rb
@@ -0,0 +1,59 @@
+# frozen_string_literal: true
+
+class Digests::Queries::Distance
+  def initialize(user, date_range)
+    @user = user
+    @date_range = date_range
+    @start_timestamp = date_range.begin.to_i
+    @end_timestamp = date_range.end.to_i
+  end
+
+  def call
+    points = fetch_points
+
+    {
+      total_distance_km: calculate_total_distance(points),
+      daily_average_km: calculate_daily_average(points),
+      max_distance_day: find_max_distance_day(points)
+    }
+  end
+
+  private
+
+  def fetch_points
+    @user.points
+         .where(timestamp: @start_timestamp..@end_timestamp)
+         .order(timestamp: :asc)
+  end
+
+  def calculate_total_distance(points)
+    return 0 if points.empty?
+
+    total = 0
+    points.each_cons(2) do |p1, p2|
+      total += Geocoder::Calculations.distance_between(
+        [p1.latitude, p1.longitude],
+        [p2.latitude, p2.longitude],
+        units: :km
+      )
+    end
+    total.round(2)
+  end
+
+  def calculate_daily_average(points)
+    total = calculate_total_distance(points)
+    days = (@date_range.end.to_date - @date_range.begin.to_date).to_i + 1
+    (total / days).round(2)
+  rescue ZeroDivisionError
+    0
+  end
+
+  def find_max_distance_day(points)
+    # Group by day and calculate distance for each day
+    daily_distances = points.group_by { |p| Time.at(p.timestamp).to_date }
+                           .transform_values { |day_points| calculate_total_distance(day_points) }
+
+    max_day = daily_distances.max_by { |_date, distance| distance }
+    max_day ? { date: max_day[0], distance_km: max_day[1] } : nil
+  end
+end
diff --git a/app/services/digests/queries/overview.rb b/app/services/digests/queries/overview.rb
new file mode 100644
index 00000000..c29ae536
--- /dev/null
+++ b/app/services/digests/queries/overview.rb
@@ -0,0 +1,51 @@
+# frozen_string_literal: true
+
+class Digests::Queries::Overview
+  def initialize(user, date_range)
+    @user = user
+    @date_range = date_range
+    @start_timestamp = date_range.begin.to_i
+    @end_timestamp = date_range.end.to_i
+  end
+
+  def call
+    {
+      countries_count: count_countries,
+      cities_count: count_cities,
+      places_count: count_places,
+      points_count: count_points
+    }
+  end
+
+  private
+
+  def count_countries
+    @user.points
+         .where(timestamp: @start_timestamp..@end_timestamp)
+         .where.not(country_name: nil)
+         .distinct
+         .count(:country_name)
+  end
+
+  def count_cities
+    @user.points
+         .where(timestamp: @start_timestamp..@end_timestamp)
+         .where.not(city: nil)
+         .distinct
+         .count(:city)
+  end
+
+  def count_places
+    @user.visits
+         .joins(:area)
+         .where(started_at: @date_range)
+         .distinct
+         .count('areas.id')
+  end
+
+  def count_points
+    @user.points
+         .where(timestamp: @start_timestamp..@end_timestamp)
+         .count
+  end
+end
diff --git a/app/services/digests/queries/places.rb b/app/services/digests/queries/places.rb
new file mode 100644
index 00000000..aff97df8
--- /dev/null
+++ b/app/services/digests/queries/places.rb
@@ -0,0 +1,26 @@
+# frozen_string_literal: true
+
+class Digests::Queries::Places
+  def initialize(user, date_range, limit: 3)
+    @user = user
+    @date_range = date_range
+    @limit = limit
+  end
+
+  def call
+    @user.visits
+         .joins(:area)
+         .where(started_at: @date_range)
+         .select('visits.*, areas.name as area_name, EXTRACT(EPOCH FROM (visits.ended_at - visits.started_at)) as duration_seconds')
+         .order('duration_seconds DESC')
+         .limit(@limit)
+         .map do |visit|
+           {
+             name: visit.area_name,
+             duration_hours: (visit.duration_seconds / 3600.0).round(1),
+             started_at: visit.started_at,
+             ended_at: visit.ended_at
+           }
+         end
+  end
+end
diff --git a/app/services/digests/queries/trips.rb b/app/services/digests/queries/trips.rb
new file mode 100644
index 00000000..2492b2ce
--- /dev/null
+++ b/app/services/digests/queries/trips.rb
@@ -0,0 +1,25 @@
+# frozen_string_literal: true
+
+class Digests::Queries::Trips
+  def initialize(user, date_range)
+    @user = user
+    @date_range = date_range
+  end
+
+  def call
+    @user.trips
+         .where('started_at <= ? AND ended_at >= ?', @date_range.end, @date_range.begin)
+         .order(started_at: :desc)
+         .map do |trip|
+           {
+             id: trip.id,
+             name: trip.name,
+             started_at: trip.started_at,
+             ended_at: trip.ended_at,
+             distance_km: trip.distance || 0,
+             countries: trip.visited_countries || [],
+             photo_previews: trip.photo_previews.first(3)
+           }
+         end
+  end
+end
diff --git a/app/views/digest_mailer/monthly_digest.html.erb b/app/views/digest_mailer/monthly_digest.html.erb
new file mode 100644
index 00000000..776ddf79
--- /dev/null
+++ b/app/views/digest_mailer/monthly_digest.html.erb
@@ -0,0 +1,13 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <meta charset="utf-8">
+    <meta name="viewport" content="width=device-width, initial-scale=1.0">
+  </head>
+  <body>
+    <h1>Monthly Digest Placeholder</h1>
+    <p>Hello <%= @user.email %></p>
+    <p>This is a placeholder for <%= Date::MONTHNAMES[@month] %> <%= @year %></p>
+    <!-- Real content will be added in Phase 3 -->
+  </body>
+</html>
diff --git a/config/routes.rb b/config/routes.rb
index d34aa775..ea8d1f4c 100644
--- a/config/routes.rb
+++ b/config/routes.rb
@@ -175,4 +175,10 @@ Rails.application.routes.draw do
       post 'subscriptions/callback', to: 'subscriptions#callback'
     end
   end
+
+  # Digest routes
+  namespace :digests do
+    get 'preview/:period/:year(/:month)', to: 'digests#preview', as: :preview
+    post 'send_test/:period', to: 'digests#send_test', as: :send_test
+  end
 end
diff --git a/spec/models/user_spec.rb b/spec/models/user_spec.rb
index 928df596..388fd83e 100644
--- a/spec/models/user_spec.rb
+++ b/spec/models/user_spec.rb
@@ -335,5 +335,116 @@ RSpec.describe User, type: :model do
         expect(user.timezone).to eq(Time.zone.name)
       end
     end
+
+    describe 'digest preferences' do
+      let(:user) { create(:user, settings: {}) }
+
+      describe '#digest_enabled?' do
+        context 'when digest preferences not set' do
+          it 'returns false' do
+            expect(user.digest_enabled?).to be false
+          end
+        end
+
+        context 'when monthly digest is enabled' do
+          before do
+            user.update!(settings: {
+              'digest_preferences' => {
+                'monthly' => { 'enabled' => true }
+              }
+            })
+          end
+
+          it 'returns true' do
+            expect(user.digest_enabled?(:monthly)).to be true
+          end
+        end
+
+        context 'when monthly digest is disabled' do
+          before do
+            user.update!(settings: {
+              'digest_preferences' => {
+                'monthly' => { 'enabled' => false }
+              }
+            })
+          end
+
+          it 'returns false' do
+            expect(user.digest_enabled?(:monthly)).to be false
+          end
+        end
+      end
+
+      describe '#enable_digest!' do
+        it 'enables the digest for given period' do
+          expect { user.enable_digest!(:monthly) }
+            .to change { user.reload.digest_enabled?(:monthly) }
+            .from(false).to(true)
+        end
+
+        it 'preserves other settings' do
+          user.update!(settings: { 'other_setting' => 'value' })
+          user.enable_digest!(:monthly)
+
+          expect(user.settings['other_setting']).to eq('value')
+        end
+      end
+
+      describe '#disable_digest!' do
+        before do
+          user.enable_digest!(:monthly)
+        end
+
+        it 'disables the digest for given period' do
+          expect { user.disable_digest!(:monthly) }
+            .to change { user.reload.digest_enabled?(:monthly) }
+            .from(true).to(false)
+        end
+      end
+
+      describe '#digest_last_sent_at' do
+        context 'when never sent' do
+          it 'returns nil' do
+            expect(user.digest_last_sent_at(:monthly)).to be_nil
+          end
+        end
+
+        context 'when previously sent' do
+          let(:sent_time) { Time.zone.parse('2024-01-01 09:00:00') }
+
+          before do
+            user.update!(settings: {
+              'digest_preferences' => {
+                'monthly' => {
+                  'enabled' => true,
+                  'last_sent_at' => sent_time.iso8601
+                }
+              }
+            })
+          end
+
+          it 'returns the last sent time' do
+            expect(user.digest_last_sent_at(:monthly)).to be_within(1.second).of(sent_time)
+          end
+        end
+
+        context 'when timestamp is invalid' do
+          before do
+            user.update!(settings: {
+              'digest_preferences' => {
+                'monthly' => {
+                  'enabled' => true,
+                  'last_sent_at' => 'invalid'
+                }
+              }
+            })
+          end
+
+          it 'returns nil' do
+            expect(user.digest_last_sent_at(:monthly)).to be_nil
+          end
+        end
+      end
+    end
   end
 end
diff --git a/spec/services/digests/calculator_spec.rb b/spec/services/digests/calculator_spec.rb
new file mode 100644
index 00000000..0cc8bcf1
--- /dev/null
+++ b/spec/services/digests/calculator_spec.rb
@@ -0,0 +1,102 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+RSpec.describe Digests::Calculator do
+  let(:user) { create(:user) }
+  let(:year) { 2024 }
+  let(:month) { 12 }
+
+  describe '#call' do
+    context 'for monthly digest' do
+      subject(:calculator) { described_class.new(user, period: :monthly, year: year, month: month) }
+
+      it 'returns a hash with all required keys' do
+        result = calculator.call
+
+        expect(result).to be_a(Hash)
+        expect(result.keys).to match_array(%i[
+          period_type year month period_label overview distance_stats
+          top_cities visited_places trips all_time_stats
+        ])
+      end
+
+      it 'sets period_type to monthly' do
+        result = calculator.call
+        expect(result[:period_type]).to eq(:monthly)
+      end
+
+      it 'sets correct year and month' do
+        result = calculator.call
+        expect(result[:year]).to eq(year)
+        expect(result[:month]).to eq(month)
+      end
+
+      it 'generates correct period_label' do
+        result = calculator.call
+        expect(result[:period_label]).to eq('December 2024')
+      end
+
+      context 'when error occurs' do
+        before do
+          allow_any_instance_of(Digests::Queries::Overview).to receive(:call).and_raise(StandardError, 'Test error')
+        end
+
+        it 'returns nil and logs error' do
+          expect(calculator.call).to be_nil
+        end
+      end
+    end
+
+    context 'for yearly digest' do
+      subject(:calculator) { described_class.new(user, period: :yearly, year: year) }
+
+      it 'generates correct period_label' do
+        result = calculator.call
+        expect(result[:period_label]).to eq('2024')
+      end
+
+      it 'sets period_type to yearly' do
+        result = calculator.call
+        expect(result[:period_type]).to eq(:yearly)
+      end
+    end
+
+    context 'with actual data' do
+      let!(:points) do
+        3.times.map do |i|
+          create(:point,
+                 user: user,
+                 timestamp: Time.new(2024, 12, 15, 12, i).to_i,
+                 city: 'Berlin',
+                 country_name: 'Germany')
+        end
+      end
+
+      subject(:calculator) { described_class.new(user, period: :monthly, year: year, month: month) }
+
+      it 'includes overview data' do
+        result = calculator.call
+        expect(result[:overview]).to be_a(Hash)
+        expect(result[:overview][:points_count]).to eq(3)
+      end
+
+      it 'includes distance stats' do
+        result = calculator.call
+        expect(result[:distance_stats]).to be_a(Hash)
+        expect(result[:distance_stats]).to have_key(:total_distance_km)
+      end
+
+      it 'includes top cities' do
+        result = calculator.call
+        expect(result[:top_cities]).to be_an(Array)
+      end
+
+      it 'includes all time stats' do
+        result = calculator.call
+        expect(result[:all_time_stats]).to be_a(Hash)
+        expect(result[:all_time_stats][:total_countries]).to be >= 0
+      end
+    end
+  end
+end
diff --git a/spec/services/digests/queries/all_time_spec.rb b/spec/services/digests/queries/all_time_spec.rb
new file mode 100644
index 00000000..c9add378
--- /dev/null
+++ b/spec/services/digests/queries/all_time_spec.rb
@@ -0,0 +1,58 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+RSpec.describe Digests::Queries::AllTime do
+  let(:user) { create(:user) }
+  subject(:query) { described_class.new(user) }
+
+  describe '#call' do
+    context 'with no data' do
+      it 'returns zero counts' do
+        result = query.call
+
+        expect(result[:total_countries]).to eq(0)
+        expect(result[:total_cities]).to eq(0)
+        expect(result[:total_places]).to eq(0)
+        expect(result[:total_distance_km]).to eq(0)
+        expect(result[:first_point_date]).to be_nil
+      end
+
+      it 'calculates account age' do
+        result = query.call
+        expect(result[:account_age_days]).to be >= 0
+      end
+    end
+
+    context 'with data' do
+      let!(:points) do
+        [
+          create(:point, user: user, timestamp: Time.zone.parse('2024-01-15 10:00').to_i, city: 'Berlin', country_name: 'Germany'),
+          create(:point, user: user, timestamp: Time.zone.parse('2024-06-15 10:00').to_i, city: 'Paris', country_name: 'France')
+        ]
+      end
+
+      let!(:stat) { create(:stat, user: user, year: 2024, month: 1, distance: 100) }
+
+      it 'counts total countries' do
+        result = query.call
+        expect(result[:total_countries]).to eq(2)
+      end
+
+      it 'counts total cities' do
+        result = query.call
+        expect(result[:total_cities]).to eq(2)
+      end
+
+      it 'sums distance from stats' do
+        result = query.call
+        expect(result[:total_distance_km]).to eq(100)
+      end
+
+      it 'finds first point date' do
+        result = query.call
+        expect(result[:first_point_date]).to eq(Date.new(2024, 1, 15))
+      end
+    end
+  end
+end
diff --git a/spec/services/digests/queries/cities_spec.rb b/spec/services/digests/queries/cities_spec.rb
new file mode 100644
index 00000000..707d36ca
--- /dev/null
+++ b/spec/services/digests/queries/cities_spec.rb
@@ -0,0 +1,46 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+RSpec.describe Digests::Queries::Cities do
+  let(:user) { create(:user) }
+  let(:date_range) { Time.zone.parse('2024-12-01')..Time.zone.parse('2024-12-31').end_of_day }
+  subject(:query) { described_class.new(user, date_range) }
+
+  describe '#call' do
+    context 'with no points' do
+      it 'returns empty array' do
+        result = query.call
+        expect(result).to eq([])
+      end
+    end
+
+    context 'with points in multiple cities' do
+      let!(:points) do
+        [
+          create(:point, user: user, timestamp: Time.zone.parse('2024-12-15 10:00').to_i, city: 'Berlin'),
+          create(:point, user: user, timestamp: Time.zone.parse('2024-12-15 14:00').to_i, city: 'Berlin'),
+          create(:point, user: user, timestamp: Time.zone.parse('2024-12-16 10:00').to_i, city: 'Hamburg'),
+          create(:point, user: user, timestamp: Time.zone.parse('2024-12-17 10:00').to_i, city: 'Berlin')
+        ]
+      end
+
+      it 'returns cities sorted by visit count' do
+        result = query.call
+
+        expect(result).to be_an(Array)
+        expect(result.first[:name]).to eq('Berlin')
+        expect(result.first[:visits]).to eq(3)
+        expect(result.second[:name]).to eq('Hamburg')
+        expect(result.second[:visits]).to eq(1)
+      end
+
+      it 'respects the limit parameter' do
+        limited_query = described_class.new(user, date_range, limit: 1)
+        result = limited_query.call
+
+        expect(result.length).to eq(1)
+      end
+    end
+  end
+end
diff --git a/spec/services/digests/queries/distance_spec.rb b/spec/services/digests/queries/distance_spec.rb
new file mode 100644
index 00000000..0c9dec84
--- /dev/null
+++ b/spec/services/digests/queries/distance_spec.rb
@@ -0,0 +1,48 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+RSpec.describe Digests::Queries::Distance do
+  let(:user) { create(:user) }
+  let(:date_range) { Time.zone.parse('2024-12-01')..Time.zone.parse('2024-12-31').end_of_day }
+  subject(:query) { described_class.new(user, date_range) }
+
+  describe '#call' do
+    context 'with no points' do
+      it 'returns zero distance' do
+        result = query.call
+
+        expect(result[:total_distance_km]).to eq(0)
+        expect(result[:daily_average_km]).to eq(0)
+        expect(result[:max_distance_day]).to be_nil
+      end
+    end
+
+    context 'with points' do
+      let!(:points) do
+        [
+          create(:point, user: user, timestamp: Time.zone.parse('2024-12-15 10:00').to_i, latitude: 52.52, longitude: 13.405),
+          create(:point, user: user, timestamp: Time.zone.parse('2024-12-15 14:00').to_i, latitude: 52.51, longitude: 13.395),
+          create(:point, user: user, timestamp: Time.zone.parse('2024-12-16 10:00').to_i, latitude: 52.50, longitude: 13.385)
+        ]
+      end
+
+      it 'calculates total distance' do
+        result = query.call
+        expect(result[:total_distance_km]).to be > 0
+      end
+
+      it 'calculates daily average' do
+        result = query.call
+        expect(result[:daily_average_km]).to be >= 0
+      end
+
+      it 'finds max distance day' do
+        result = query.call
+        expect(result[:max_distance_day]).to be_a(Hash)
+        expect(result[:max_distance_day][:date]).to be_a(Date)
+        expect(result[:max_distance_day][:distance_km]).to be > 0
+      end
+    end
+  end
+end
diff --git a/spec/services/digests/queries/overview_spec.rb b/spec/services/digests/queries/overview_spec.rb
new file mode 100644
index 00000000..e050b25d
--- /dev/null
+++ b/spec/services/digests/queries/overview_spec.rb
@@ -0,0 +1,67 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+RSpec.describe Digests::Queries::Overview do
+  let(:user) { create(:user) }
+  let(:date_range) { Time.zone.parse('2024-12-01')..Time.zone.parse('2024-12-31').end_of_day }
+  subject(:query) { described_class.new(user, date_range) }
+
+  describe '#call' do
+    context 'with no data' do
+      it 'returns zero counts' do
+        result = query.call
+
+        expect(result[:countries_count]).to eq(0)
+        expect(result[:cities_count]).to eq(0)
+        expect(result[:places_count]).to eq(0)
+        expect(result[:points_count]).to eq(0)
+      end
+    end
+
+    context 'with points in date range' do
+      let!(:points_in_range) do
+        [
+          create(:point, user: user, timestamp: Time.zone.parse('2024-12-15 12:00').to_i, city: 'Berlin', country_name: 'Germany'),
+          create(:point, user: user, timestamp: Time.zone.parse('2024-12-16 12:00').to_i, city: 'Hamburg', country_name: 'Germany'),
+          create(:point, user: user, timestamp: Time.zone.parse('2024-12-17 12:00').to_i, city: 'Berlin', country_name: 'Germany')
+        ]
+      end
+
+      let!(:points_outside_range) do
+        create(:point, user: user, timestamp: Time.zone.parse('2024-11-15 12:00').to_i, city: 'Paris', country_name: 'France')
+      end
+
+      it 'counts only points in range' do
+        result = query.call
+        expect(result[:points_count]).to eq(3)
+      end
+
+      it 'counts distinct countries' do
+        result = query.call
+        expect(result[:countries_count]).to eq(1)
+      end
+
+      it 'counts distinct cities' do
+        result = query.call
+        expect(result[:cities_count]).to eq(2)
+      end
+    end
+
+    context 'with visits and areas' do
+      let(:area) { create(:area, user: user) }
+      let!(:visit) do
+        create(:visit,
+               user: user,
+               area: area,
+               started_at: Time.zone.parse('2024-12-15 12:00'),
+               ended_at: Time.zone.parse('2024-12-15 14:00'))
+      end
+
+      it 'counts places' do
+        result = query.call
+        expect(result[:places_count]).to eq(1)
+      end
+    end
+  end
+end