dawarich/app/models/concerns/distanceable.rb

# frozen_string_literal: true

module Distanceable
  extend ActiveSupport::Concern

  DISTANCE_UNITS = {
    km: 1000, # to meters
    mi: 1609.34, # to meters
    m: 1, # already in meters
    ft: 0.3048, # to meters
    yd: 0.9144 # to meters
  }.freeze

  module ClassMethods
    def total_distance(points = nil, unit = :km)
      # Handle method being called directly on relation vs with array
      if points.nil?
        calculate_distance_for_relation(unit)
      else
        calculate_distance_for_array(points, unit)
      end
    end

    private

    def calculate_distance_for_relation(unit)
      unless DISTANCE_UNITS.key?(unit.to_sym)
        raise ArgumentError, "Invalid unit. Supported units are: #{DISTANCE_UNITS.keys.join(', ')}"
      end

      distance_in_meters = connection.select_value(<<-SQL.squish)
        WITH points_with_previous AS (
          SELECT
            lonlat,
            LAG(lonlat) OVER (ORDER BY timestamp) as prev_lonlat
          FROM (#{to_sql}) AS points
        )
        SELECT COALESCE(
          SUM(
            ST_Distance(
              lonlat::geography,
              prev_lonlat::geography
            )
          ),
          0
        )
        FROM points_with_previous
        WHERE prev_lonlat IS NOT NULL
      SQL

      distance_in_meters.to_f / DISTANCE_UNITS[unit.to_sym]
    end

    def calculate_distance_for_array(points, unit = :km)
      unless DISTANCE_UNITS.key?(unit.to_sym)
        raise ArgumentError, "Invalid unit. Supported units are: #{DISTANCE_UNITS.keys.join(', ')}"
      end

      return 0 if points.length < 2

      total_meters = points.each_cons(2).sum do |point1, point2|
        connection.select_value(
          'SELECT ST_Distance(ST_GeomFromEWKT($1)::geography, ST_GeomFromEWKT($2)::geography)',
          nil,
          [point1.lonlat, point2.lonlat]
        )
      end

      total_meters.to_f / DISTANCE_UNITS[unit.to_sym]
    end
  end

  def distance_to(other_point, unit = :km)
    unless DISTANCE_UNITS.key?(unit.to_sym)
      raise ArgumentError, "Invalid unit. Supported units are: #{DISTANCE_UNITS.keys.join(', ')}"
    end

    # Extract coordinates based on what type other_point is
    other_lonlat = extract_point(other_point)
    return nil if other_lonlat.nil?

    # Calculate distance in meters using PostGIS
    distance_in_meters = self.class.connection.select_value(<<-SQL.squish)
      SELECT ST_Distance(
        ST_GeomFromEWKT('#{lonlat}')::geography,
        ST_GeomFromEWKT('#{other_lonlat}')::geography
      )
    SQL

    # Convert to requested unit
    distance_in_meters.to_f / DISTANCE_UNITS[unit.to_sym]
  end

  private

  def extract_point(point)
    case point
    when Array
      unless point.length == 2
        raise ArgumentError,
              'Coordinates array must contain exactly 2 elements [latitude, longitude]'
      end

      RGeo::Geographic.spherical_factory(srid: 4326).point(point[1], point[0])
    when self.class
      point.lonlat
    end
  end
end