# frozen_string_literal: true

require 'georuby'
require 'sequel'
require 'sequel-postgis-georuby'
require 'singleton'

module TacScribe
  # Acts as the interface to the back-end datastore and hides all datastore
  # implementation details from callers. Note that ruby does not support
  # exception chaining we are not wrapping exceptions yet. This will happen
  # when  https://bugs.ruby-lang.org/issues/8257 is fixed.
  class Datastore
    include Singleton
    include GeoRuby::SimpleFeatures

    attr_accessor :db, :written, :deleted

    @configuration = nil
    @db = nil

    def configuration
      @configuration ||= Configuration.new
    end

    def configure
      configuration
      yield(@configuration) if block_given?
    end

    # Contains all the connection configuration required for connectin
    # to a postgresql database. Defaults to localhost with ubuntu presets
    class Configuration
      attr_accessor :host, :port, :database, :username, :password

      def initialize
        @host = 'localhost'
        @port = '5432'
        @database = 'tac_scribe'
        @username = 'tac_scribe'
        @password = 'tac_scribe'
      end
    end

    def connect
      configure
      @db = Sequel.connect(connection_string, max_connections: 49)
      @db.extension :postgis_georuby
    end

    def truncate_table
      @db[:units].truncate
    end

    def write_objects(objects)
      @db[:units].insert_conflict(
        constraint: :units_pkey,
        update: { position: Sequel[:excluded][:position],
                  altitude: Sequel[:excluded][:altitude],
                  heading: Sequel[:excluded][:heading],
                  updated_at: Sequel[:excluded][:updated_at],
                  deleted: Sequel[:excluded][:deleted] }
      )
                 .multi_insert(objects)
      deleted_ids = @db[:units].where(deleted: true).select_map(:id)
      @db[:units].where(deleted: true).delete
      self.written = objects.size
      self.deleted = deleted_ids.size

      deleted_ids
    end

    private

    def connection_string
      if RUBY_PLATFORM == 'java'
        "jdbc:postgresql://#{@configuration.host}:#{@configuration.port}/" \
        "#{@configuration.database}?user=#{@configuration.username}&" \
        "password=#{configuration.password}"
      else
        "postgres://#{@configuration.username}:#{@configuration.password}@" \
        "#{@configuration.host}:#{@configuration.port}" \
        "/#{@configuration.database}"
      end
    end
  end
end