# frozen_string_literal: true

module Migrations::Importer
  class CopyStep < Step
    MappingType = ::Migrations::Importer::MappingType

    NOW = "NOW()"
    SYSTEM_USER_ID = Discourse::SYSTEM_USER_ID

    INSERT_MAPPED_IDS_SQL = <<~SQL
      INSERT INTO mapped.ids (original_id, type, discourse_id)
      VALUES (?, ?, ?)
    SQL

    class << self
      # stree-ignore
      def table_name(value = (getter = true; nil))
        return @table_name if getter
        @table_name = value
      end

      # stree-ignore
      def column_names(value = (getter = true; nil))
        return @column_names if getter
        @column_names = value
      end

      def timestamp_columns?
        @timestamp_columns ||=
          @column_names&.include?(:created_at) || @column_names&.include?(:updated_at)
      end

      def store_mapped_ids(value)
        @store_mapped_ids = value
      end

      def store_mapped_ids?
        !!@store_mapped_ids
      end

      # stree-ignore
      def total_rows_query(query = (getter = true; nil), *parameters)
        return [@total_rows_query, @total_rows_query_parameters] if getter

        @total_rows_query = query
        @total_rows_query_parameters = parameters
        nil
      end

      # stree-ignore
      def rows_query(query = (getter = true; nil), *parameters)
        return [@rows_query, @rows_query_parameters] if getter

        @rows_query = query
        @rows_query_parameters = parameters
        nil
      end
    end

    def initialize(intermediate_db, discourse_db, shared_data)
      super

      @last_id = 0
      @mapping_type = nil
    end

    def execute
      super
      with_progressbar(total_count) { copy_data }
      nil
    end

    private

    def copy_data
      table_name = self.class.table_name || self.class.name&.demodulize&.underscore
      column_names = self.class.column_names || @discourse_db.column_names(table_name)
      skipped_rows = []

      if self.class.store_mapped_ids?
        @last_id = @discourse_db.last_id_of(table_name)
        @mapping_type = find_mapping_type(table_name)
      end

      @discourse_db.copy_data(table_name, column_names, fetch_rows(skipped_rows)) do |inserted_rows|
        after_commit_of_inserted_rows(inserted_rows)

        if skipped_rows.any?
          after_commit_of_skipped_rows(skipped_rows)
          skipped_rows.clear
        end
      end

      @discourse_db.fix_last_id_of(table_name) if self.class.store_mapped_ids?
      @intermediate_db.commit_transaction
    end

    def fetch_rows(skipped_rows)
      Enumerator.new do |enumerator|
        query, parameters = self.class.rows_query
        @intermediate_db.query(query, *parameters) do |row|
          if (transformed_row = transform_row(row))
            enumerator << transformed_row
            @stats.reset
          else
            skipped_rows << row
            @stats.reset(skip_count: 1)
          end

          update_progressbar
        end
      end
    end

    def after_commit_of_inserted_rows(rows)
      return unless self.class.store_mapped_ids?

      rows.each do |row|
        @intermediate_db.insert(INSERT_MAPPED_IDS_SQL, [row[:original_id], @mapping_type, row[:id]])
      end

      nil
    end

    def after_commit_of_skipped_rows(rows)
      return unless self.class.store_mapped_ids?

      rows.each do |row|
        if row[:id] && row[:original_id]
          @intermediate_db.insert(
            INSERT_MAPPED_IDS_SQL,
            [row[:original_id], @mapping_type, row[:id]],
          )
        end
      end

      nil
    end

    def transform_row(row)
      row[:id] = (@last_id += 1) if self.class.store_mapped_ids? && row[:id].nil?

      if self.class.timestamp_columns?
        row[:created_at] ||= NOW
        row[:updated_at] = row[:created_at]
      end

      row
    end

    def find_mapping_type(table_name)
      constant_name = table_name.to_s.upcase

      if MappingType.const_defined?(constant_name)
        MappingType.const_get(constant_name)
      else
        raise "MappingType::#{constant_name} is not defined"
      end
    end

    def total_count
      query, parameters = self.class.total_rows_query
      @intermediate_db.count(query, *parameters)
    end
  end
end