Initial release of Discourse

lib/export/json_encoder.rb

@@ -0,0 +1,75 @@
+module Export
+
+  class SchemaArgumentsError < RuntimeError; end
+
+  # TODO: Use yajl-ruby for performance.
+  #       https://github.com/brianmario/yajl-ruby
+
+  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? and 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 and 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( @schema_data.merge(@table_data).to_json )
+      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