module Export class SchemaArgumentsError < RuntimeError; end class JsonEncoder def initialize @table_data = {} end def tmp_directory @tmp_directory ||= begin f = File.join( Rails.root, 'tmp', Time.now.strftime('export%Y%m%d%H%M%S') ) Dir.mkdir(f) unless Dir[f].present? f end end def json_output_stream @json_output_stream ||= File.new( File.join( tmp_directory, 'tables.json' ), 'w+b' ) end def write_schema_info(args) raise SchemaArgumentsError unless args[:source].present? && args[:version].present? @schema_data = { schema: { source: args[:source], version: args[:version] } } end def write_table(table_name, columns) @table_data[table_name] ||= {} @table_data[table_name][:fields] = columns.map(&:name) @table_data[table_name][:rows] ||= [] row_count = 0 begin rows = yield(row_count) if rows row_count += rows.size @table_data[table_name][:rows] << rows end # TODO: write to multiple files as needed. # one file per table? multiple files per table? end while rows && rows.size > 0 @table_data[table_name][:rows].flatten!(1) @table_data[table_name][:row_count] = @table_data[table_name][:rows].size end def finish @schema_data[:schema][:table_count] = @table_data.keys.count json_output_stream.write( Oj.dump(@schema_data.merge(@table_data), :mode => :compat) ) json_output_stream.close @filenames = [File.join( tmp_directory, 'tables.json' )] end def filenames @filenames ||= [] end def cleanup_temp FileUtils.rm_rf(tmp_directory) if Dir[tmp_directory].present? end end end