package pgx

import (
	"encoding/binary"
)

const (
	protocolVersionNumber = 196608 // 3.0
)

const (
	backendKeyData       = 'K'
	authenticationX      = 'R'
	readyForQuery        = 'Z'
	rowDescription       = 'T'
	dataRow              = 'D'
	commandComplete      = 'C'
	errorResponse        = 'E'
	noticeResponse       = 'N'
	parseComplete        = '1'
	parameterDescription = 't'
	bindComplete         = '2'
	notificationResponse = 'A'
	emptyQueryResponse   = 'I'
	noData               = 'n'
	closeComplete        = '3'
	flush                = 'H'
	copyInResponse       = 'G'
	copyData             = 'd'
	copyFail             = 'f'
	copyDone             = 'c'
)

type startupMessage struct {
	options map[string]string
}

func newStartupMessage() *startupMessage {
	return &startupMessage{map[string]string{}}
}

func (s *startupMessage) Bytes() (buf []byte) {
	buf = make([]byte, 8, 128)
	binary.BigEndian.PutUint32(buf[4:8], uint32(protocolVersionNumber))
	for key, value := range s.options {
		buf = append(buf, key...)
		buf = append(buf, 0)
		buf = append(buf, value...)
		buf = append(buf, 0)
	}
	buf = append(buf, ("\000")...)
	binary.BigEndian.PutUint32(buf[0:4], uint32(len(buf)))
	return buf
}

// Oid (Object Identifier Type) is, according to https://www.postgresql.org/docs/current/static/datatype-oid.html,
// used internally by PostgreSQL as a primary key for various system tables. It is currently implemented
// as an unsigned four-byte integer. Its definition can be found in src/include/postgres_ext.h
// in the PostgreSQL sources.
type Oid uint32

type FieldDescription struct {
	Name            string
	Table           Oid
	AttributeNumber int16
	DataType        Oid
	DataTypeSize    int16
	DataTypeName    string
	Modifier        int32
	FormatCode      int16
}

// PgError represents an error reported by the PostgreSQL server. See
// http://www.postgresql.org/docs/9.3/static/protocol-error-fields.html for
// detailed field description.
type PgError struct {
	Severity         string
	Code             string
	Message          string
	Detail           string
	Hint             string
	Position         int32
	InternalPosition int32
	InternalQuery    string
	Where            string
	SchemaName       string
	TableName        string
	ColumnName       string
	DataTypeName     string
	ConstraintName   string
	File             string
	Line             int32
	Routine          string
}

func (pe PgError) Error() string {
	return pe.Severity + ": " + pe.Message + " (SQLSTATE " + pe.Code + ")"
}

func newWriteBuf(c *Conn, t byte) *WriteBuf {
	buf := append(c.wbuf[0:0], t, 0, 0, 0, 0)
	c.writeBuf = WriteBuf{buf: buf, sizeIdx: 1, conn: c}
	return &c.writeBuf
}

// WriteBuf is used build messages to send to the PostgreSQL server. It is used
// by the Encoder interface when implementing custom encoders.
type WriteBuf struct {
	buf     []byte
	sizeIdx int
	conn    *Conn
}

func (wb *WriteBuf) startMsg(t byte) {
	wb.closeMsg()
	wb.buf = append(wb.buf, t, 0, 0, 0, 0)
	wb.sizeIdx = len(wb.buf) - 4
}

func (wb *WriteBuf) closeMsg() {
	binary.BigEndian.PutUint32(wb.buf[wb.sizeIdx:wb.sizeIdx+4], uint32(len(wb.buf)-wb.sizeIdx))
}

func (wb *WriteBuf) WriteByte(b byte) {
	wb.buf = append(wb.buf, b)
}

func (wb *WriteBuf) WriteCString(s string) {
	wb.buf = append(wb.buf, []byte(s)...)
	wb.buf = append(wb.buf, 0)
}

func (wb *WriteBuf) WriteInt16(n int16) {
	b := make([]byte, 2)
	binary.BigEndian.PutUint16(b, uint16(n))
	wb.buf = append(wb.buf, b...)
}

func (wb *WriteBuf) WriteInt32(n int32) {
	b := make([]byte, 4)
	binary.BigEndian.PutUint32(b, uint32(n))
	wb.buf = append(wb.buf, b...)
}

func (wb *WriteBuf) WriteUint32(n uint32) {
	b := make([]byte, 4)
	binary.BigEndian.PutUint32(b, n)
	wb.buf = append(wb.buf, b...)
}

func (wb *WriteBuf) WriteInt64(n int64) {
	b := make([]byte, 8)
	binary.BigEndian.PutUint64(b, uint64(n))
	wb.buf = append(wb.buf, b...)
}

func (wb *WriteBuf) WriteBytes(b []byte) {
	wb.buf = append(wb.buf, b...)
}