module Hanami
  module Model
    class Migrator
      # PostgreSQL adapter
      #
      # @since 0.4.0
      # @api private
      class PostgresAdapter < Adapter
        # @since 0.4.0
        # @api private
        HOST     = 'PGHOST'.freeze

        # @since 0.4.0
        # @api private
        PORT     = 'PGPORT'.freeze

        # @since 0.4.0
        # @api private
        USER     = 'PGUSER'.freeze

        # @since 0.4.0
        # @api private
        PASSWORD = 'PGPASSWORD'.freeze

        # @since 1.0.0
        # @api private
        DB_CREATION_ERROR = 'createdb: database creation failed. If the database exists, ' \
                            'then its console may be open. See this issue for more details: ' \
                            'https://github.com/hanami/model/issues/250'.freeze

        # @since 0.4.0
        # @api private
        def create
          set_environment_variables

          call_db_command('createdb') do |error_message|
            message = if error_message.match(/already exists/) # rubocop:disable Performance/RedundantMatch
                        DB_CREATION_ERROR
                      else
                        error_message
                      end

            raise MigrationError.new(message)
          end
        end

        # @since 0.4.0
        # @api private
        def drop
          set_environment_variables

          call_db_command('dropdb') do |error_message|
            message = if error_message.match(/does not exist/) # rubocop:disable Performance/RedundantMatch
                        "Cannot find database: #{database}"
                      else
                        error_message
                      end

            raise MigrationError.new(message)
          end
        end

        # @since 0.4.0
        # @api private
        def dump
          set_environment_variables
          dump_structure
          dump_migrations_data
        end

        # @since 0.4.0
        # @api private
        def load
          set_environment_variables
          load_structure
        end

        private

        # @since 0.4.0
        # @api private
        def set_environment_variables
          ENV[HOST]     = host      unless host.nil?
          ENV[PORT]     = port.to_s unless port.nil?
          ENV[PASSWORD] = password  unless password.nil?
          ENV[USER]     = username  unless username.nil?
        end

        # @since 0.4.0
        # @api private
        def dump_structure
          execute "pg_dump -s -x -O -T #{migrations_table} -f #{escape(schema)} #{database}"
        end

        # @since 0.4.0
        # @api private
        def load_structure
          execute "psql -X -q -f #{escape(schema)} #{database}" if schema.exist?
        end

        # @since 0.4.0
        # @api private
        def dump_migrations_data
          error = ->(err) { raise MigrationError.new(err) unless err =~ /no matching tables/i }
          execute "pg_dump -t #{migrations_table} #{database} >> #{escape(schema)}", error: error
        end

        # @since 0.5.1
        # @api private
        def call_db_command(command)
          require 'open3'

          begin
            Open3.popen3(command, database) do |_stdin, _stdout, stderr, wait_thr|
              yield stderr.read unless wait_thr.value.success? # wait_thr.value is the exit status
            end
          rescue SystemCallError => e
            yield e.message
          end
        end
      end
    end
  end
end