package pgx

import (
	"database/sql/driver"
	"math"
	"reflect"
	"time"

	"github.com/jackc/pgx/pgconn"
	"github.com/jackc/pgx/pgio"
	"github.com/jackc/pgx/pgtype"
)

const (
	copyData      = 'd'
	copyFail      = 'f'
	copyDone      = 'c'
	varHeaderSize = 4
)

type FieldDescription struct {
	Name            string
	Table           pgtype.OID
	AttributeNumber uint16
	DataType        pgtype.OID
	DataTypeSize    int16
	DataTypeName    string
	Modifier        int32
	FormatCode      int16
}

func (fd FieldDescription) Length() (int64, bool) {
	switch fd.DataType {
	case pgtype.TextOID, pgtype.ByteaOID:
		return math.MaxInt64, true
	case pgtype.VarcharOID, pgtype.BPCharArrayOID:
		return int64(fd.Modifier - varHeaderSize), true
	default:
		return 0, false
	}
}

func (fd FieldDescription) PrecisionScale() (precision, scale int64, ok bool) {
	switch fd.DataType {
	case pgtype.NumericOID:
		mod := fd.Modifier - varHeaderSize
		precision = int64((mod >> 16) & 0xffff)
		scale = int64(mod & 0xffff)
		return precision, scale, true
	default:
		return 0, 0, false
	}
}

func (fd FieldDescription) Type() reflect.Type {
	switch fd.DataType {
	case pgtype.Float8OID:
		return reflect.TypeOf(float64(0))
	case pgtype.Float4OID:
		return reflect.TypeOf(float32(0))
	case pgtype.Int8OID:
		return reflect.TypeOf(int64(0))
	case pgtype.Int4OID:
		return reflect.TypeOf(int32(0))
	case pgtype.Int2OID:
		return reflect.TypeOf(int16(0))
	case pgtype.VarcharOID, pgtype.BPCharArrayOID, pgtype.TextOID:
		return reflect.TypeOf("")
	case pgtype.BoolOID:
		return reflect.TypeOf(false)
	case pgtype.NumericOID:
		return reflect.TypeOf(float64(0))
	case pgtype.DateOID, pgtype.TimestampOID, pgtype.TimestamptzOID:
		return reflect.TypeOf(time.Time{})
	case pgtype.ByteaOID:
		return reflect.TypeOf([]byte(nil))
	default:
		return reflect.TypeOf(new(interface{})).Elem()
	}
}

// Notice represents a notice response message reported by the PostgreSQL
// server. Be aware that this is distinct from LISTEN/NOTIFY notification.
type Notice pgconn.PgError

// appendParse appends a PostgreSQL wire protocol parse message to buf and returns it.
func appendParse(buf []byte, name string, query string, parameterOIDs []pgtype.OID) []byte {
	buf = append(buf, 'P')
	sp := len(buf)
	buf = pgio.AppendInt32(buf, -1)
	buf = append(buf, name...)
	buf = append(buf, 0)
	buf = append(buf, query...)
	buf = append(buf, 0)

	buf = pgio.AppendInt16(buf, int16(len(parameterOIDs)))
	for _, oid := range parameterOIDs {
		buf = pgio.AppendUint32(buf, uint32(oid))
	}
	pgio.SetInt32(buf[sp:], int32(len(buf[sp:])))

	return buf
}

// appendDescribe appends a PostgreSQL wire protocol describe message to buf and returns it.
func appendDescribe(buf []byte, objectType byte, name string) []byte {
	buf = append(buf, 'D')
	sp := len(buf)
	buf = pgio.AppendInt32(buf, -1)
	buf = append(buf, objectType)
	buf = append(buf, name...)
	buf = append(buf, 0)
	pgio.SetInt32(buf[sp:], int32(len(buf[sp:])))

	return buf
}

// appendSync appends a PostgreSQL wire protocol sync message to buf and returns it.
func appendSync(buf []byte) []byte {
	buf = append(buf, 'S')
	buf = pgio.AppendInt32(buf, 4)

	return buf
}

// appendBind appends a PostgreSQL wire protocol bind message to buf and returns it.
func appendBind(
	buf []byte,
	destinationPortal,
	preparedStatement string,
	connInfo *pgtype.ConnInfo,
	parameterOIDs []pgtype.OID,
	arguments []interface{},
	resultFormatCodes []int16,
) ([]byte, error) {
	buf = append(buf, 'B')
	sp := len(buf)
	buf = pgio.AppendInt32(buf, -1)
	buf = append(buf, destinationPortal...)
	buf = append(buf, 0)
	buf = append(buf, preparedStatement...)
	buf = append(buf, 0)

	var err error
	arguments, err = convertDriverValuers(arguments)
	if err != nil {
		return nil, err
	}

	buf = pgio.AppendInt16(buf, int16(len(parameterOIDs)))
	for i, oid := range parameterOIDs {
		buf = pgio.AppendInt16(buf, chooseParameterFormatCode(connInfo, oid, arguments[i]))
	}

	buf = pgio.AppendInt16(buf, int16(len(arguments)))
	for i, oid := range parameterOIDs {
		var err error
		buf, err = encodePreparedStatementArgument(connInfo, buf, oid, arguments[i])
		if err != nil {
			return nil, err
		}
	}

	buf = pgio.AppendInt16(buf, int16(len(resultFormatCodes)))
	for _, fc := range resultFormatCodes {
		buf = pgio.AppendInt16(buf, fc)
	}
	pgio.SetInt32(buf[sp:], int32(len(buf[sp:])))

	return buf, nil
}

func convertDriverValuers(args []interface{}) ([]interface{}, error) {
	for i, arg := range args {
		switch arg := arg.(type) {
		case pgtype.BinaryEncoder:
		case pgtype.TextEncoder:
		case driver.Valuer:
			v, err := callValuerValue(arg)
			if err != nil {
				return nil, err
			}
			args[i] = v
		}
	}
	return args, nil
}

// appendExecute appends a PostgreSQL wire protocol execute message to buf and returns it.
func appendExecute(buf []byte, portal string, maxRows uint32) []byte {
	buf = append(buf, 'E')
	sp := len(buf)
	buf = pgio.AppendInt32(buf, -1)

	buf = append(buf, portal...)
	buf = append(buf, 0)
	buf = pgio.AppendUint32(buf, maxRows)

	pgio.SetInt32(buf[sp:], int32(len(buf[sp:])))

	return buf
}

// appendQuery appends a PostgreSQL wire protocol query message to buf and returns it.
func appendQuery(buf []byte, query string) []byte {
	buf = append(buf, 'Q')
	sp := len(buf)
	buf = pgio.AppendInt32(buf, -1)
	buf = append(buf, query...)
	buf = append(buf, 0)
	pgio.SetInt32(buf[sp:], int32(len(buf[sp:])))

	return buf
}