package pgx

import (
	"bytes"
	"database/sql/driver"
	"encoding/json"
	"fmt"
	"reflect"

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

// PostgreSQL oids for common types
const (
	BoolOid             = 16
	ByteaOid            = 17
	CharOid             = 18
	NameOid             = 19
	Int8Oid             = 20
	Int2Oid             = 21
	Int4Oid             = 23
	TextOid             = 25
	OidOid              = 26
	TidOid              = 27
	XidOid              = 28
	CidOid              = 29
	JsonOid             = 114
	CidrOid             = 650
	CidrArrayOid        = 651
	Float4Oid           = 700
	Float8Oid           = 701
	UnknownOid          = 705
	InetOid             = 869
	BoolArrayOid        = 1000
	Int2ArrayOid        = 1005
	Int4ArrayOid        = 1007
	TextArrayOid        = 1009
	ByteaArrayOid       = 1001
	VarcharArrayOid     = 1015
	Int8ArrayOid        = 1016
	Float4ArrayOid      = 1021
	Float8ArrayOid      = 1022
	AclitemOid          = 1033
	AclitemArrayOid     = 1034
	InetArrayOid        = 1041
	VarcharOid          = 1043
	DateOid             = 1082
	TimestampOid        = 1114
	TimestampArrayOid   = 1115
	DateArrayOid        = 1182
	TimestampTzOid      = 1184
	TimestampTzArrayOid = 1185
	RecordOid           = 2249
	UuidOid             = 2950
	JsonbOid            = 3802
)

// PostgreSQL format codes
const (
	TextFormatCode   = 0
	BinaryFormatCode = 1
)

const maxUint = ^uint(0)
const maxInt = int(maxUint >> 1)
const minInt = -maxInt - 1

// DefaultTypeFormats maps type names to their default requested format (text
// or binary). In theory the Scanner interface should be the one to determine
// the format of the returned values. However, the query has already been
// executed by the time Scan is called so it has no chance to set the format.
// So for types that should always be returned in binary the format should be
// set here.
var DefaultTypeFormats map[string]int16

// internalNativeGoTypeFormats lists the encoding type for native Go types (not handled with Encoder interface)
var internalNativeGoTypeFormats map[pgtype.Oid]int16

func init() {
	DefaultTypeFormats = map[string]int16{
		"_aclitem":     TextFormatCode, // Pg's src/backend/utils/adt/acl.c has only in/out (text) not send/recv (bin)
		"_bool":        BinaryFormatCode,
		"_bytea":       BinaryFormatCode,
		"_cidr":        BinaryFormatCode,
		"_float4":      BinaryFormatCode,
		"_float8":      BinaryFormatCode,
		"_inet":        BinaryFormatCode,
		"_int2":        BinaryFormatCode,
		"_int4":        BinaryFormatCode,
		"_int8":        BinaryFormatCode,
		"_text":        BinaryFormatCode,
		"_timestamp":   BinaryFormatCode,
		"_timestamptz": BinaryFormatCode,
		"_varchar":     BinaryFormatCode,
		"aclitem":      TextFormatCode, // Pg's src/backend/utils/adt/acl.c has only in/out (text) not send/recv (bin)
		"bool":         BinaryFormatCode,
		"bytea":        BinaryFormatCode,
		"char":         BinaryFormatCode,
		"cid":          BinaryFormatCode,
		"cidr":         BinaryFormatCode,
		"date":         BinaryFormatCode,
		"float4":       BinaryFormatCode,
		"float8":       BinaryFormatCode,
		"inet":         BinaryFormatCode,
		"int2":         BinaryFormatCode,
		"int4":         BinaryFormatCode,
		"int8":         BinaryFormatCode,
		"oid":          BinaryFormatCode,
		"record":       BinaryFormatCode,
		"tid":          BinaryFormatCode,
		"timestamp":    BinaryFormatCode,
		"timestamptz":  BinaryFormatCode,
		"xid":          BinaryFormatCode,
	}

	internalNativeGoTypeFormats = map[pgtype.Oid]int16{
		BoolArrayOid:        BinaryFormatCode,
		BoolOid:             BinaryFormatCode,
		ByteaArrayOid:       BinaryFormatCode,
		ByteaOid:            BinaryFormatCode,
		CidrArrayOid:        BinaryFormatCode,
		CidrOid:             BinaryFormatCode,
		DateOid:             BinaryFormatCode,
		Float4ArrayOid:      BinaryFormatCode,
		Float4Oid:           BinaryFormatCode,
		Float8ArrayOid:      BinaryFormatCode,
		Float8Oid:           BinaryFormatCode,
		InetArrayOid:        BinaryFormatCode,
		InetOid:             BinaryFormatCode,
		Int2ArrayOid:        BinaryFormatCode,
		Int2Oid:             BinaryFormatCode,
		Int4ArrayOid:        BinaryFormatCode,
		Int4Oid:             BinaryFormatCode,
		Int8ArrayOid:        BinaryFormatCode,
		Int8Oid:             BinaryFormatCode,
		JsonbOid:            BinaryFormatCode,
		JsonOid:             BinaryFormatCode,
		OidOid:              BinaryFormatCode,
		RecordOid:           BinaryFormatCode,
		TextArrayOid:        BinaryFormatCode,
		TimestampArrayOid:   BinaryFormatCode,
		TimestampOid:        BinaryFormatCode,
		TimestampTzArrayOid: BinaryFormatCode,
		TimestampTzOid:      BinaryFormatCode,
		VarcharArrayOid:     BinaryFormatCode,
	}
}

// SerializationError occurs on failure to encode or decode a value
type SerializationError string

func (e SerializationError) Error() string {
	return string(e)
}

// Encode encodes arg into wbuf as the type oid. This allows implementations
// of the Encoder interface to delegate the actual work of encoding to the
// built-in functionality.
func Encode(wbuf *WriteBuf, oid pgtype.Oid, arg interface{}) error {
	if arg == nil {
		wbuf.WriteInt32(-1)
		return nil
	}

	switch arg := arg.(type) {
	case pgtype.BinaryEncoder:
		buf := &bytes.Buffer{}
		null, err := arg.EncodeBinary(wbuf.conn.ConnInfo, buf)
		if err != nil {
			return err
		}
		if null {
			wbuf.WriteInt32(-1)
		} else {
			wbuf.WriteInt32(int32(buf.Len()))
			wbuf.WriteBytes(buf.Bytes())
		}
		return nil
	case pgtype.TextEncoder:
		buf := &bytes.Buffer{}
		null, err := arg.EncodeText(wbuf.conn.ConnInfo, buf)
		if err != nil {
			return err
		}
		if null {
			wbuf.WriteInt32(-1)
		} else {
			wbuf.WriteInt32(int32(buf.Len()))
			wbuf.WriteBytes(buf.Bytes())
		}
		return nil
	case driver.Valuer:
		v, err := arg.Value()
		if err != nil {
			return err
		}
		return Encode(wbuf, oid, v)
	case string:
		return encodeString(wbuf, oid, arg)
	case []byte:
		return encodeByteSlice(wbuf, oid, arg)
	}

	refVal := reflect.ValueOf(arg)

	if refVal.Kind() == reflect.Ptr {
		if refVal.IsNil() {
			wbuf.WriteInt32(-1)
			return nil
		}
		arg = refVal.Elem().Interface()
		return Encode(wbuf, oid, arg)
	}

	if dt, ok := wbuf.conn.ConnInfo.DataTypeForOid(oid); ok {
		value := dt.Value
		err := value.Set(arg)
		if err != nil {
			return err
		}

		buf := &bytes.Buffer{}
		null, err := value.(pgtype.BinaryEncoder).EncodeBinary(wbuf.conn.ConnInfo, buf)
		if err != nil {
			return err
		}
		if null {
			wbuf.WriteInt32(-1)
		} else {
			wbuf.WriteInt32(int32(buf.Len()))
			wbuf.WriteBytes(buf.Bytes())
		}
		return nil
	}

	if strippedArg, ok := stripNamedType(&refVal); ok {
		return Encode(wbuf, oid, strippedArg)
	}
	return SerializationError(fmt.Sprintf("Cannot encode %T into oid %v - %T must implement Encoder or be converted to a string", arg, oid, arg))
}

func stripNamedType(val *reflect.Value) (interface{}, bool) {
	switch val.Kind() {
	case reflect.Int:
		convVal := int(val.Int())
		return convVal, reflect.TypeOf(convVal) != val.Type()
	case reflect.Int8:
		convVal := int8(val.Int())
		return convVal, reflect.TypeOf(convVal) != val.Type()
	case reflect.Int16:
		convVal := int16(val.Int())
		return convVal, reflect.TypeOf(convVal) != val.Type()
	case reflect.Int32:
		convVal := int32(val.Int())
		return convVal, reflect.TypeOf(convVal) != val.Type()
	case reflect.Int64:
		convVal := int64(val.Int())
		return convVal, reflect.TypeOf(convVal) != val.Type()
	case reflect.Uint:
		convVal := uint(val.Uint())
		return convVal, reflect.TypeOf(convVal) != val.Type()
	case reflect.Uint8:
		convVal := uint8(val.Uint())
		return convVal, reflect.TypeOf(convVal) != val.Type()
	case reflect.Uint16:
		convVal := uint16(val.Uint())
		return convVal, reflect.TypeOf(convVal) != val.Type()
	case reflect.Uint32:
		convVal := uint32(val.Uint())
		return convVal, reflect.TypeOf(convVal) != val.Type()
	case reflect.Uint64:
		convVal := uint64(val.Uint())
		return convVal, reflect.TypeOf(convVal) != val.Type()
	case reflect.String:
		convVal := val.String()
		return convVal, reflect.TypeOf(convVal) != val.Type()
	}

	return nil, false
}

// Decode decodes from vr into d. d must be a pointer. This allows
// implementations of the Decoder interface to delegate the actual work of
// decoding to the built-in functionality.
func Decode(vr *ValueReader, d interface{}) error {
	switch v := d.(type) {
	case *string:
		*v = decodeText(vr)
	default:
		if v := reflect.ValueOf(d); v.Kind() == reflect.Ptr {
			el := v.Elem()
			switch el.Kind() {
			// if d is a pointer to pointer, strip the pointer and try again
			case reflect.Ptr:
				// -1 is a null value
				if vr.Len() == -1 {
					if !el.IsNil() {
						// if the destination pointer is not nil, nil it out
						el.Set(reflect.Zero(el.Type()))
					}
					return nil
				}
				if el.IsNil() {
					// allocate destination
					el.Set(reflect.New(el.Type().Elem()))
				}
				d = el.Interface()
				return Decode(vr, d)
			case reflect.String:
				el.SetString(decodeText(vr))
				return nil
			}
		}
		return fmt.Errorf("Scan cannot decode into %T", d)
	}

	return nil
}

func decodeText(vr *ValueReader) string {
	if vr.Len() == -1 {
		vr.Fatal(ProtocolError("Cannot decode null into string"))
		return ""
	}

	if vr.Type().FormatCode == BinaryFormatCode {
		vr.Fatal(ProtocolError("cannot decode binary value into string"))
		return ""
	}

	return vr.ReadString(vr.Len())
}

func decodeTextAllowBinary(vr *ValueReader) string {
	if vr.Len() == -1 {
		vr.Fatal(ProtocolError("Cannot decode null into string"))
		return ""
	}

	return vr.ReadString(vr.Len())
}

func encodeString(w *WriteBuf, oid pgtype.Oid, value string) error {
	w.WriteInt32(int32(len(value)))
	w.WriteBytes([]byte(value))
	return nil
}

func decodeBytea(vr *ValueReader) []byte {
	if vr.Len() == -1 {
		return nil
	}

	if vr.Type().DataType != ByteaOid {
		vr.Fatal(ProtocolError(fmt.Sprintf("Cannot decode oid %v into []byte", vr.Type().DataType)))
		return nil
	}

	if vr.Type().FormatCode != BinaryFormatCode {
		vr.Fatal(ProtocolError(fmt.Sprintf("Unknown field description format code: %v", vr.Type().FormatCode)))
		return nil
	}

	return vr.ReadBytes(vr.Len())
}

func encodeByteSlice(w *WriteBuf, oid pgtype.Oid, value []byte) error {
	w.WriteInt32(int32(len(value)))
	w.WriteBytes(value)

	return nil
}

func decodeJSON(vr *ValueReader, d interface{}) error {
	if vr.Len() == -1 {
		return nil
	}

	if vr.Type().DataType != JsonOid {
		vr.Fatal(ProtocolError(fmt.Sprintf("Cannot decode oid %v into json", vr.Type().DataType)))
	}

	bytes := vr.ReadBytes(vr.Len())
	err := json.Unmarshal(bytes, d)
	if err != nil {
		vr.Fatal(err)
	}
	return err
}

func encodeJSON(w *WriteBuf, oid pgtype.Oid, value interface{}) error {
	if oid != JsonOid {
		return fmt.Errorf("cannot encode JSON into oid %v", oid)
	}

	s, err := json.Marshal(value)
	if err != nil {
		return fmt.Errorf("Failed to encode json from type: %T", value)
	}

	w.WriteInt32(int32(len(s)))
	w.WriteBytes(s)

	return nil
}

func decodeJSONB(vr *ValueReader, d interface{}) error {
	if vr.Len() == -1 {
		return nil
	}

	if vr.Type().DataType != JsonbOid {
		err := ProtocolError(fmt.Sprintf("Cannot decode oid %v into jsonb", vr.Type().DataType))
		vr.Fatal(err)
		return err
	}

	bytes := vr.ReadBytes(vr.Len())
	if vr.Type().FormatCode == BinaryFormatCode {
		if bytes[0] != 1 {
			err := ProtocolError(fmt.Sprintf("Unknown jsonb format byte: %x", bytes[0]))
			vr.Fatal(err)
			return err
		}
		bytes = bytes[1:]
	}

	err := json.Unmarshal(bytes, d)
	if err != nil {
		vr.Fatal(err)
	}
	return err
}

func encodeJSONB(w *WriteBuf, oid pgtype.Oid, value interface{}) error {
	if oid != JsonbOid {
		return fmt.Errorf("cannot encode JSON into oid %v", oid)
	}

	s, err := json.Marshal(value)
	if err != nil {
		return fmt.Errorf("Failed to encode json from type: %T", value)
	}

	w.WriteInt32(int32(len(s) + 1))
	w.WriteByte(1) // JSONB format header
	w.WriteBytes(s)

	return nil
}