package pgproto3

import (
	"encoding/binary"
	"errors"
	"fmt"
	"io"

	"github.com/jackc/pgx/chunkreader"
)

type Frontend struct {
	cr *chunkreader.ChunkReader
	w  io.Writer

	// Backend message flyweights
	authentication       Authentication
	backendKeyData       BackendKeyData
	bindComplete         BindComplete
	closeComplete        CloseComplete
	commandComplete      CommandComplete
	copyBothResponse     CopyBothResponse
	copyData             CopyData
	copyInResponse       CopyInResponse
	copyOutResponse      CopyOutResponse
	dataRow              DataRow
	emptyQueryResponse   EmptyQueryResponse
	errorResponse        ErrorResponse
	functionCallResponse FunctionCallResponse
	noData               NoData
	noticeResponse       NoticeResponse
	notificationResponse NotificationResponse
	parameterDescription ParameterDescription
	parameterStatus      ParameterStatus
	parseComplete        ParseComplete
	readyForQuery        ReadyForQuery
	rowDescription       RowDescription
}

func NewFrontend(r io.Reader, w io.Writer) (*Frontend, error) {
	cr := chunkreader.NewChunkReader(r)
	return &Frontend{cr: cr, w: w}, nil
}

func (b *Frontend) Send(msg FrontendMessage) error {
	return errors.New("not implemented")
}

func (b *Frontend) Receive() (BackendMessage, error) {
	header, err := b.cr.Next(5)
	if err != nil {
		return nil, err
	}

	msgType := header[0]
	bodyLen := int(binary.BigEndian.Uint32(header[1:])) - 4

	var msg BackendMessage
	switch msgType {
	case '1':
		msg = &b.parseComplete
	case '2':
		msg = &b.bindComplete
	case '3':
		msg = &b.closeComplete
	case 'A':
		msg = &b.notificationResponse
	case 'C':
		msg = &b.commandComplete
	case 'd':
		msg = &b.copyData
	case 'D':
		msg = &b.dataRow
	case 'E':
		msg = &b.errorResponse
	case 'G':
		msg = &b.copyInResponse
	case 'H':
		msg = &b.copyOutResponse
	case 'I':
		msg = &b.emptyQueryResponse
	case 'K':
		msg = &b.backendKeyData
	case 'n':
		msg = &b.noData
	case 'N':
		msg = &b.noticeResponse
	case 'R':
		msg = &b.authentication
	case 'S':
		msg = &b.parameterStatus
	case 't':
		msg = &b.parameterDescription
	case 'T':
		msg = &b.rowDescription
	case 'V':
		msg = &b.functionCallResponse
	case 'W':
		msg = &b.copyBothResponse
	case 'Z':
		msg = &b.readyForQuery
	default:
		return nil, fmt.Errorf("unknown message type: %c", msgType)
	}

	msgBody, err := b.cr.Next(bodyLen)
	if err != nil {
		return nil, err
	}

	err = msg.Decode(msgBody)
	return msg, err
}