Pg: module { # pg.b

	bytes_to_int : fn(b : array of byte) : (int, int);
	bytes_to_big : fn(b : array of byte) : (int, big);
	int_to_bytes : fn(i, length : int) : array of byte;
	big_to_bytes : fn(i : big, length : int) : array of byte;

	Recordset : adt {
		fields : array of ref Field;
		rows : array of array of array of byte;
		to_string : fn(r: self ref Recordset) : string;
	};

	Data : adt {
		bytes : array of byte;
		ptr : int;
		extend_bytes: fn(data : self ref Data, n : int) : int;
		append: fn(data : self ref Data, bytes : array of byte) : int;
		write: fn (data : self ref Data, txt : string) : int;
		md5: fn(data : self ref Data) : string;
		puts: fn (data : self ref Data, txt : string) : int;
		put_notnil_s: fn (data : self ref Data, key, value : string) : int;
		send : fn(data : self ref Data, io : ref Iobuf, tag : int) : int;
		to_string : fn(data : self ref Data) : string;
	};

	Field : adt {
		name : string;
		table_oid : int; # int32  - zero if not known
		column_attribute_number : int; # int16
		data_type_oid : int; # int32 
		data_type_size : int; # int16 -ive means variable width
		type_modifier : int; # int32 type specific
		format_code : int; # 0 for text 1 for binary
		read: fn(f: self ref Field, io : ref Iobuf);
		to_string : fn(data : self ref Field) : string;
	};

	Response : adt {
		code : int;
		data : string;
		read : fn (r : self ref Response, io : ref Iobuf) : int;
		to_string : fn (r : self ref Response) : string;
	};

	Parameter : adt {
		key : string;
		value : string;
		read : fn (r : self ref Parameter, io : ref Iobuf) : int;
		to_string : fn (p : self ref Parameter) : string;
	};

	Frontend_Message : adt {
		tag : int;
		pick {
			StartupMessage => # nil
				protocol_version : int; # 196608
				user : string;
				database : string;
				options : string;
				parameters : string;
			PasswordMessage => # p
				password : string;
			Query => # Q
				sql : string;
			CopyData => # d
				data : array of byte;
			CopyFail => # f
				err : string;
			CopyDone => # c
			Parse => #P
				name : string;
				query : string;
				data_type_oids : array of int;
			Bind => # B
				portal : string;
				name : string;
				parameter_format_codes : array of int;
				parameters : array of array of byte;
				result_format_codes : array of int;
			Execute => # E
				portal : string;
				rows_to_return : int;
			Sync => # S
			Describe => # D
				item_type : byte; # 'S' or 'P'
				name : string;
			Close => # C
				item_type: byte; # 'S' or 'P'
				name : string;
			Flush => # H
			Terminate => # X
		}
	};

	Backend_Message :adt {
		tag : int;
		to_string : fn(b_msg : self ref Backend_Message) : string;
		pick {
			Error => # E
				responses : list of ref Response;
			NoticeResponse => # N
				responses : list of ref Response;
			Authentication => # R
				auth_type : int;
					# 0 AuthenticationOK, 
					# 2 Kerberos V5
					# 3 Clear Text
					# 4 Crypt (with 2 byte salt)
					# 5 MD5 (with 4 byte salt)
					# 6 SCM Credential
				salt : array of byte;
			ReadyForQuery => # Z
				status : int;
			RowDescription => # T
				fields : array of ref Field;
			DataRow => # D
				columns : array of array of byte;
			CopyData => # d
				data : array of byte;
			CopyDone => # c
			CopyInResponse => # G
				copy_format : byte; # 0 or 1
				format_codes : array of int;
			CopyOutResponse => # H
				copy_format : byte; # 0 or 1
				format_codes : array of int;
			CommandComplete => # C
				cmd : string;
				oid : int;
				rows : int;
			ParseComplete => # 1
			BindComplete => # 2
			CloseComplete => # 3
			PortalSuspended => # s
			EmptyQueryResponse => # I
			NoData => # n
			ParameterDescription => # t
				oids : array of int;
			Unknown =>
				data : array of byte;
		}
	};

	not_implemented : adt {
		id : int;
		pick {
			V => # FunctionCallResponse
				length : int; # -1 for NULL
				data : array of byte;
			A => # NotificationResponse
				process_id : int;
				condition : string;
				info : string; # expected to be always empty atm.
		}
	};

	Connection: adt {
		debug : int;
		user, database, password : string;
		fd : ref Sys->FD;
		notices : chan of ref Backend_Message;
		rx : chan of ref Backend_Message;
		tx : chan of ref Frontend_Message;
		status : int;
		process_id : int;
		key : int;
		parameters : list of ref Parameter;
		connect : fn(connection: self ref Connection, ip, port, options, parameters : string) : int;
		set_parameter : fn(c : self ref Connection, p : ref Parameter);
		query : fn(c: self ref Connection, sql : string) : ref Recordset;
		parse : fn(c: self ref Connection, name: string, sql : string, data_type_oids : array of int) : int;
		describe : fn(c: self ref Connection, item_type : byte, name : string);
		execute : fn(c: self ref Connection, portal, name : string, parameter_format_codes : array of int, parameters : array of array of byte, result_format_codes : array of int, rows_to_return : int) : ref Recordset;
		disconnect : fn(c: self ref Connection);
	};
};