package pgtype

import (
	"encoding/binary"

	"github.com/jackc/pgio"
	errors "golang.org/x/xerrors"
)

type Composite struct {
	fields []Value
	Status Status
}

// NewComposite creates a Composite object, which acts as a "schema" for
// SQL composite values.
// To pass Composite as SQL parameter first set it's fields, either by
// passing initialized Value{} instances to NewComposite or by calling
// SetFields method
// To read composite fields back pass result of Scan() method
// to query Scan function.
func NewComposite(fields ...Value) *Composite {
	return &Composite{fields, Present}
}

func (src Composite) Get() interface{} {
	switch src.Status {
	case Present:
		return src
	case Null:
		return nil
	default:
		return src.Status
	}
}

// Set is called internally when passing query arguments.
func (dst *Composite) Set(src interface{}) error {
	if src == nil {
		*dst = Composite{Status: Null}
		return nil
	}

	switch value := src.(type) {
	case []Value:
		if len(value) != len(dst.fields) {
			return errors.Errorf("Number of fields don't match. Composite has %d fields", len(dst.fields))
		}
		for i, v := range value {
			if err := dst.fields[i].Set(v); err != nil {
				return err
			}
		}
		dst.Status = Present
	default:
		return errors.Errorf("Can not convert %v to Composite", src)
	}

	return nil
}

// AssignTo should never be called on composite value directly
func (src Composite) AssignTo(dst interface{}) error {
	return errors.New("Pass Composite.Scan() to deconstruct composite")
}

func (src Composite) EncodeBinary(ci *ConnInfo, buf []byte) (newBuf []byte, err error) {
	switch src.Status {
	case Null:
		return nil, nil
	case Undefined:
		return nil, errUndefined
	}
	return EncodeRow(ci, buf, src.fields...)
}

// DecodeBinary implements BinaryDecoder interface.
// Opposite to Record, fields in a composite act as a "schema"
// and decoding fails if SQL value can't be assigned due to
// type mismatch
func (dst *Composite) DecodeBinary(ci *ConnInfo, buf []byte) (err error) {
	if buf == nil {
		dst.Status = Null
		return nil
	}

	scanner, err := NewCompositeBinaryScanner(buf)
	if err != nil {
		return err
	}
	if len(dst.fields) != scanner.FieldCount() {
		return errors.Errorf("SQL composite can't be read, field count mismatch. expected %d , found %d", len(dst.fields), scanner.FieldCount())
	}

	for i := 0; scanner.Scan(); i++ {
		binaryDecoder, ok := dst.fields[i].(BinaryDecoder)
		if !ok {
			return errors.New("Composite field doesn't support binary protocol")
		}

		if err = binaryDecoder.DecodeBinary(ci, scanner.Bytes()); err != nil {
			return err
		}
	}

	if scanner.Err() != nil {
		return scanner.Err()
	}

	dst.Status = Present

	return nil
}

// Scan is a helper function to perform "nested" scan of
// a composite value when scanning a query result row.
// isNull is set if scanned value is NULL
// Rest of arguments are set in the order of fields in the composite
//
// Use of Scan method doesn't modify original composite
func (src Composite) Scan(isNull *bool, dst ...interface{}) BinaryDecoderFunc {
	return func(ci *ConnInfo, buf []byte) error {
		if err := src.DecodeBinary(ci, buf); err != nil {
			return err
		}

		if src.Status == Null {
			*isNull = true
			return nil
		}

		for i, f := range src.fields {
			if err := f.AssignTo(dst[i]); err != nil {
				return err
			}
		}
		return nil
	}
}

// SetFields sets Composite's fields to corresponding values
func (dst *Composite) SetFields(values ...interface{}) error {
	if len(values) != len(dst.fields) {
		return errors.Errorf("Number of fields don't match. Composite has %d fields", len(dst.fields))
	}
	for i, v := range values {
		if err := dst.fields[i].Set(v); err != nil {
			return err
		}
	}
	dst.Status = Present
	return nil
}

type CompositeBinaryScanner struct {
	rp  int
	src []byte

	fieldCount int32
	fieldBytes []byte
	fieldOID   uint32
	err        error
}

// NewCompositeBinaryScanner a scanner over a binary encoded composite balue.
func NewCompositeBinaryScanner(src []byte) (CompositeBinaryScanner, error) {
	rp := 0
	if len(src[rp:]) < 4 {
		return CompositeBinaryScanner{}, errors.Errorf("Record incomplete %v", src)
	}

	fieldCount := int32(binary.BigEndian.Uint32(src[rp:]))
	rp += 4

	return CompositeBinaryScanner{
		rp:         rp,
		src:        src,
		fieldCount: fieldCount,
	}, nil
}

// Scan advances the scanner to the next field. It returns false after the last field is read or an error occurs. After
// Scan returns false, the Err method can be called to check if any errors occurred.
func (cfs *CompositeBinaryScanner) Scan() bool {
	if cfs.err != nil {
		return false
	}

	if cfs.rp == len(cfs.src) {
		return false
	}

	if len(cfs.src[cfs.rp:]) < 8 {
		cfs.err = errors.Errorf("Record incomplete %v", cfs.src)
		return false
	}
	cfs.fieldOID = binary.BigEndian.Uint32(cfs.src[cfs.rp:])
	cfs.rp += 4

	fieldLen := int(int32(binary.BigEndian.Uint32(cfs.src[cfs.rp:])))
	cfs.rp += 4

	if fieldLen >= 0 {
		if len(cfs.src[cfs.rp:]) < fieldLen {
			cfs.err = errors.Errorf("Record incomplete rp=%d src=%v", cfs.rp, cfs.src)
			return false
		}
		cfs.fieldBytes = cfs.src[cfs.rp : cfs.rp+fieldLen]
		cfs.rp += fieldLen
	} else {
		cfs.fieldBytes = nil
	}

	return true
}

func (cfs *CompositeBinaryScanner) FieldCount() int {
	return int(cfs.fieldCount)
}

// Bytes returns the bytes of the field most recently read by Scan().
func (cfs *CompositeBinaryScanner) Bytes() []byte {
	return cfs.fieldBytes
}

// OID returns the OID of the field most recently read by Scan().
func (cfs *CompositeBinaryScanner) OID() uint32 {
	return cfs.fieldOID
}

// Err returns any error encountered by the scanner.
func (cfs *CompositeBinaryScanner) Err() error {
	return cfs.err
}

type CompositeTextScanner struct {
	rp  int
	src []byte

	fieldBytes []byte
	err        error
}

// NewCompositeTextScanner a scanner over a text encoded composite balue.
func NewCompositeTextScanner(src []byte) (CompositeTextScanner, error) {
	if len(src) < 2 {
		return CompositeTextScanner{}, errors.Errorf("Record incomplete %v", src)
	}

	if src[0] != '(' {
		return CompositeTextScanner{}, errors.Errorf("composite text format must start with '('")
	}

	if src[len(src)-1] != ')' {
		return CompositeTextScanner{}, errors.Errorf("composite text format must end with ')'")
	}

	return CompositeTextScanner{
		rp:  1,
		src: src,
	}, nil
}

// Scan advances the scanner to the next field. It returns false after the last field is read or an error occurs. After
// Scan returns false, the Err method can be called to check if any errors occurred.
func (cfs *CompositeTextScanner) Scan() bool {
	if cfs.err != nil {
		return false
	}

	if cfs.rp == len(cfs.src) {
		return false
	}

	switch cfs.src[cfs.rp] {
	case ',', ')': // null
		cfs.rp++
		cfs.fieldBytes = nil
		return true
	case '"': // quoted value
		cfs.rp++
		cfs.fieldBytes = make([]byte, 0, 16)
		for {
			ch := cfs.src[cfs.rp]

			if ch == '"' {
				cfs.rp++
				if cfs.src[cfs.rp] == '"' {
					cfs.fieldBytes = append(cfs.fieldBytes, '"')
					cfs.rp++
				} else {
					break
				}
			} else {
				cfs.fieldBytes = append(cfs.fieldBytes, ch)
				cfs.rp++
			}
		}
		cfs.rp++
		return true
	default: // unquoted value
		start := cfs.rp
		for {
			ch := cfs.src[cfs.rp]
			if ch == ',' || ch == ')' {
				break
			}
			cfs.rp++
		}
		cfs.fieldBytes = cfs.src[start:cfs.rp]
		cfs.rp++
		return true
	}
}

// Bytes returns the bytes of the field most recently read by Scan().
func (cfs *CompositeTextScanner) Bytes() []byte {
	return cfs.fieldBytes
}

// Err returns any error encountered by the scanner.
func (cfs *CompositeTextScanner) Err() error {
	return cfs.err
}

// RecordStart adds record header to the buf
func RecordStart(buf []byte, fieldCount int) []byte {
	return pgio.AppendUint32(buf, uint32(fieldCount))
}

// RecordAdd adds record field to the buf
func RecordAdd(buf []byte, oid uint32, fieldBytes []byte) []byte {
	buf = pgio.AppendUint32(buf, oid)
	buf = pgio.AppendUint32(buf, uint32(len(fieldBytes)))
	buf = append(buf, fieldBytes...)
	return buf
}

// RecordAddNull adds null value as a field to the buf
func RecordAddNull(buf []byte, oid uint32) []byte {
	return pgio.AppendInt32(buf, int32(-1))
}