package meta

import (
	"bytes"
	"io"

	"github.com/pkg/errors"
	"github.com/vmihailenco/msgpack/v5"
	"github.com/vmihailenco/msgpack/v5/msgpcode"
)

var FieldNotFound = errors.New("field not found")

var NoOpenContainer = errors.New("there is no open container")

type msgpackReader struct {
	dec   *msgpack.Decoder
	stack []readContainer
	curr  readContainer
}

type readContainer struct {
	started bool
	length  int
	assoc   bool
	values  map[string]msgpack.RawMessage
	reader  io.Reader
	readCnt int
}

func NewMsgpackReader(r io.Reader) Reader {
	return &msgpackReader{
		dec:   msgpack.NewDecoder(r),
		stack: make([]readContainer, 0, 2),
		curr: readContainer{
			reader: r,
		},
	}
}

func (rd *msgpackReader) readField() (string, error) {
	field, err := rd.dec.DecodeString()
	if err != nil {
		return "", errors.WithStack(err)
	}
	return field, nil
}

func (rd *msgpackReader) ReadInt8(v *int8, targetField string) error {
	if !rd.curr.started || !rd.curr.assoc {
		return decodeInt8(rd.dec, v)
	}

	if b, ok := rd.curr.values[targetField]; ok {
		dec := msgpack.NewDecoder(bytes.NewReader(b))
		return decodeInt8(dec, v)
	}

	for i := rd.curr.readCnt; i < rd.curr.length; i++ {
		field, err := rd.readField()
		if err != nil {
			return err
		}
		if field == targetField {
			rd.curr.readCnt = i + 1
			return decodeInt8(rd.dec, v)
		}

		raw, err := rd.dec.DecodeRaw()
		if err != nil {
			return errors.WithStack(err)
		}
		rd.curr.values[field] = raw
	}

	return FieldNotFound
}

func (rd *msgpackReader) ReadInt16(v *int16, targetField string) error {
	if !rd.curr.started || !rd.curr.assoc {
		return decodeInt16(rd.dec, v)
	}

	if b, ok := rd.curr.values[targetField]; ok {
		dec := msgpack.NewDecoder(bytes.NewReader(b))
		return decodeInt16(dec, v)
	}

	for i := rd.curr.readCnt; i < rd.curr.length; i++ {
		field, err := rd.readField()
		if err != nil {
			return err
		}
		if field == targetField {
			rd.curr.readCnt = i + 1
			return decodeInt16(rd.dec, v)
		}

		raw, err := rd.dec.DecodeRaw()
		if err != nil {
			return errors.WithStack(err)
		}
		rd.curr.values[field] = raw
	}

	return FieldNotFound
}

func (rd *msgpackReader) ReadInt32(v *int32, targetField string) error {
	if !rd.curr.started || !rd.curr.assoc {
		return decodeInt32(rd.dec, v)
	}

	if b, ok := rd.curr.values[targetField]; ok {
		dec := msgpack.NewDecoder(bytes.NewReader(b))
		return decodeInt32(dec, v)
	}

	for i := rd.curr.readCnt; i < rd.curr.length; i++ {
		field, err := rd.readField()
		if err != nil {
			return err
		}
		if field == targetField {
			rd.curr.readCnt = i + 1
			return decodeInt32(rd.dec, v)
		}

		raw, err := rd.dec.DecodeRaw()
		if err != nil {
			return errors.WithStack(err)
		}
		rd.curr.values[field] = raw
	}

	return FieldNotFound
}

func (rd *msgpackReader) ReadInt64(v *int64, targetField string) error {
	if !rd.curr.started || !rd.curr.assoc {
		return decodeInt64(rd.dec, v)
	}

	if b, ok := rd.curr.values[targetField]; ok {
		dec := msgpack.NewDecoder(bytes.NewReader(b))
		return decodeInt64(dec, v)
	}

	for i := rd.curr.readCnt; i < rd.curr.length; i++ {
		field, err := rd.readField()
		if err != nil {
			return err
		}
		if field == targetField {
			rd.curr.readCnt = i + 1
			return decodeInt64(rd.dec, v)
		}

		raw, err := rd.dec.DecodeRaw()
		if err != nil {
			return errors.WithStack(err)
		}
		rd.curr.values[field] = raw
	}

	return FieldNotFound
}

func (rd *msgpackReader) ReadUint8(v *uint8, targetField string) error {
	if !rd.curr.started || !rd.curr.assoc {
		return decodeUint8(rd.dec, v)
	}

	if b, ok := rd.curr.values[targetField]; ok {
		dec := msgpack.NewDecoder(bytes.NewReader(b))
		return decodeUint8(dec, v)
	}

	for i := rd.curr.readCnt; i < rd.curr.length; i++ {
		field, err := rd.readField()
		if err != nil {
			return err
		}
		if field == targetField {
			rd.curr.readCnt = i + 1
			return decodeUint8(rd.dec, v)
		}

		raw, err := rd.dec.DecodeRaw()
		if err != nil {
			return errors.WithStack(err)
		}
		rd.curr.values[field] = raw
	}

	return FieldNotFound
}

func (rd *msgpackReader) ReadUint16(v *uint16, targetField string) error {
	if !rd.curr.started || !rd.curr.assoc {
		return decodeUint16(rd.dec, v)
	}

	if b, ok := rd.curr.values[targetField]; ok {
		dec := msgpack.NewDecoder(bytes.NewReader(b))
		return decodeUint16(dec, v)
	}

	for i := rd.curr.readCnt; i < rd.curr.length; i++ {
		field, err := rd.readField()
		if err != nil {
			return err
		}
		if field == targetField {
			rd.curr.readCnt = i + 1
			return decodeUint16(rd.dec, v)
		}

		raw, err := rd.dec.DecodeRaw()
		if err != nil {
			return errors.WithStack(err)
		}
		rd.curr.values[field] = raw
	}

	return FieldNotFound
}

func (rd *msgpackReader) ReadUint32(v *uint32, targetField string) error {
	if !rd.curr.started || !rd.curr.assoc {
		return decodeUint32(rd.dec, v)
	}

	if b, ok := rd.curr.values[targetField]; ok {
		dec := msgpack.NewDecoder(bytes.NewReader(b))
		return decodeUint32(dec, v)
	}

	for i := rd.curr.readCnt; i < rd.curr.length; i++ {
		field, err := rd.readField()
		if err != nil {
			return err
		}
		if field == targetField {
			rd.curr.readCnt = i + 1
			return decodeUint32(rd.dec, v)
		}

		raw, err := rd.dec.DecodeRaw()
		if err != nil {
			return errors.WithStack(err)
		}
		rd.curr.values[field] = raw
	}

	return FieldNotFound
}

func (rd *msgpackReader) ReadUint64(v *uint64, targetField string) error {
	if !rd.curr.started || !rd.curr.assoc {
		return decodeUint64(rd.dec, v)
	}

	if b, ok := rd.curr.values[targetField]; ok {
		dec := msgpack.NewDecoder(bytes.NewReader(b))
		return decodeUint64(dec, v)
	}

	for i := rd.curr.readCnt; i < rd.curr.length; i++ {
		field, err := rd.readField()
		if err != nil {
			return err
		}
		if field == targetField {
			rd.curr.readCnt = i + 1
			return decodeUint64(rd.dec, v)
		}

		raw, err := rd.dec.DecodeRaw()
		if err != nil {
			return errors.WithStack(err)
		}
		rd.curr.values[field] = raw
	}

	return FieldNotFound
}

func (rd *msgpackReader) ReadBool(v *bool, targetField string) error {
	if !rd.curr.started || !rd.curr.assoc {
		return decodeBool(rd.dec, v)
	}

	if b, ok := rd.curr.values[targetField]; ok {
		dec := msgpack.NewDecoder(bytes.NewReader(b))
		return decodeBool(dec, v)
	}

	for i := rd.curr.readCnt; i < rd.curr.length; i++ {
		field, err := rd.readField()
		if err != nil {
			return err
		}
		if field == targetField {
			rd.curr.readCnt = i + 1
			return decodeBool(rd.dec, v)
		}

		raw, err := rd.dec.DecodeRaw()
		if err != nil {
			return errors.WithStack(err)
		}
		rd.curr.values[field] = raw
	}

	return FieldNotFound
}

func (rd *msgpackReader) ReadFloat32(v *float32, targetField string) error {
	if !rd.curr.started || !rd.curr.assoc {
		return decodeFloat32(rd.dec, v)
	}

	if b, ok := rd.curr.values[targetField]; ok {
		dec := msgpack.NewDecoder(bytes.NewReader(b))
		return decodeFloat32(dec, v)
	}

	for i := rd.curr.readCnt; i < rd.curr.length; i++ {
		field, err := rd.readField()
		if err != nil {
			return err
		}
		if field == targetField {
			rd.curr.readCnt = i + 1
			return decodeFloat32(rd.dec, v)
		}

		raw, err := rd.dec.DecodeRaw()
		if err != nil {
			return errors.WithStack(err)
		}
		rd.curr.values[field] = raw
	}

	return FieldNotFound
}

func (rd *msgpackReader) ReadFloat64(v *float64, targetField string) error {
	if !rd.curr.started || !rd.curr.assoc {
		return decodeFloat64(rd.dec, v)
	}

	if b, ok := rd.curr.values[targetField]; ok {
		dec := msgpack.NewDecoder(bytes.NewReader(b))
		return decodeFloat64(dec, v)
	}

	for i := rd.curr.readCnt; i < rd.curr.length; i++ {
		field, err := rd.readField()
		if err != nil {
			return err
		}
		if field == targetField {
			rd.curr.readCnt = i + 1
			return decodeFloat64(rd.dec, v)
		}

		raw, err := rd.dec.DecodeRaw()
		if err != nil {
			return errors.WithStack(err)
		}
		rd.curr.values[field] = raw
	}

	return FieldNotFound
}

func (rd *msgpackReader) ReadString(v *string, targetField string) error {
	if !rd.curr.started || !rd.curr.assoc {
		return decodeString(rd.dec, v)
	}

	if b, ok := rd.curr.values[targetField]; ok {
		dec := msgpack.NewDecoder(bytes.NewReader(b))
		return decodeString(dec, v)
	}

	for i := rd.curr.readCnt; i < rd.curr.length; i++ {
		field, err := rd.readField()
		if err != nil {
			return err
		}
		if field == targetField {
			rd.curr.readCnt = i + 1
			return decodeString(rd.dec, v)
		}

		raw, err := rd.dec.DecodeRaw()
		if err != nil {
			return errors.WithStack(err)
		}
		rd.curr.values[field] = raw
	}

	return FieldNotFound
}

func (rd *msgpackReader) ReadBytes(v *[]byte, targetField string) error {
	if !rd.curr.started || !rd.curr.assoc {
		return decodeBytes(rd.dec, v)
	}

	if b, ok := rd.curr.values[targetField]; ok {
		dec := msgpack.NewDecoder(bytes.NewReader(b))
		return decodeBytes(dec, v)
	}

	for i := rd.curr.readCnt; i < rd.curr.length; i++ {
		field, err := rd.readField()
		if err != nil {
			return err
		}
		if field == targetField {
			rd.curr.readCnt = i + 1
			return decodeBytes(rd.dec, v)
		}

		raw, err := rd.dec.DecodeRaw()
		if err != nil {
			return errors.WithStack(err)
		}
		rd.curr.values[field] = raw
	}

	return FieldNotFound
}

func (rd *msgpackReader) BeginContainer(targetField string) error {
	if !rd.curr.started || !rd.curr.assoc {
		return rd.beginContainer(targetField)
	}

	if b, ok := rd.curr.values[targetField]; ok {
		rd.dec.Reset(bytes.NewReader(b))
		return rd.beginContainer(targetField)
	}

	for i := rd.curr.readCnt; i < rd.curr.length; i++ {
		field, err := rd.readField()
		if err != nil {
			return err
		}
		if field == targetField {
			rd.curr.readCnt = i + 1
			return rd.beginContainer(targetField)
		}

		raw, err := rd.dec.DecodeRaw()
		if err != nil {
			return errors.WithStack(err)
		}
		rd.curr.values[field] = raw
		rd.curr.readCnt = i + 1
	}

	return FieldNotFound
}

func (rd *msgpackReader) beginContainer(field string) error {
	code, err := rd.dec.PeekCode()
	if err != nil {
		return errors.WithStack(err)
	}

	switch {
	case msgpcode.IsFixedMap(code), code == msgpcode.Map16, code == msgpcode.Map32:
		l, err := rd.dec.DecodeMapLen()
		if err != nil {
			return errors.WithStack(err)
		}
		rd.stack = append(rd.stack, rd.curr)
		rd.curr = readContainer{
			started: true,
			length:  l,
			assoc:   true,
			values:  make(map[string]msgpack.RawMessage, l),
			reader:  rd.dec.Buffered(),
		}

	case msgpcode.IsFixedArray(code), code == msgpcode.Array16, code == msgpcode.Array32:
		l, err := rd.dec.DecodeArrayLen()
		if err != nil {
			return errors.WithStack(err)
		}
		rd.stack = append(rd.stack, rd.curr)
		rd.curr = readContainer{
			started: true,
			length:  l,
			assoc:   false,
			reader:  rd.dec.Buffered(),
		}

	default:
		return errors.Errorf("there is no container for field `%s`", field)
	}
	return nil
}

func (rd *msgpackReader) EndContainer() error {
	if len(rd.stack) == 0 {
		return NoOpenContainer
	}
	rd.curr = rd.stack[len(rd.stack)-1]
	rd.stack = rd.stack[:len(rd.stack)-1]
	rd.dec.Reset(rd.curr.reader)
	return nil
}

func (rd *msgpackReader) ContainerSize() (int, error) {
	return rd.curr.length, nil
}

func (rd *msgpackReader) IsContainerAssoc() (bool, error) {
	return rd.curr.assoc, nil
}

func (rd *msgpackReader) Skip() error {
	return errors.WithStack(rd.dec.Skip())
}

func (rd *msgpackReader) TryReadMask() (bool, FieldsMask, error) {
	maskLen, err := rd.dec.DecodeArrayLen()
	if err != nil {
		if err == io.EOF {
			return false, FieldsMask{}, nil
		}
		return false, FieldsMask{}, errors.WithStack(err)
	}

	var mask FieldsMask
	for i := 0; i < maskLen; i++ {
		maskPart, err := rd.dec.DecodeUint64()
		if err != nil {
			return false, FieldsMask{}, errors.WithStack(err)
		}
		mask.SetPartFromUint64(i, maskPart)
	}

	return true, mask, nil
}

func decodeUint8(dec *msgpack.Decoder, v *uint8) error {
	tmp, err := dec.DecodeUint8()
	if err != nil {
		return errors.WithStack(err)
	}
	*v = tmp
	return nil
}

func decodeUint16(dec *msgpack.Decoder, v *uint16) error {
	tmp, err := dec.DecodeUint16()
	if err != nil {
		return errors.WithStack(err)
	}
	*v = tmp
	return nil
}

func decodeUint32(dec *msgpack.Decoder, v *uint32) error {
	tmp, err := dec.DecodeUint32()
	if err != nil {
		return errors.WithStack(err)
	}
	*v = tmp
	return nil
}

func decodeUint64(dec *msgpack.Decoder, v *uint64) error {
	tmp, err := dec.DecodeUint64()
	if err != nil {
		return errors.WithStack(err)
	}
	*v = tmp
	return nil
}

func decodeInt8(dec *msgpack.Decoder, v *int8) error {
	tmp, err := dec.DecodeInt8()
	if err != nil {
		return errors.WithStack(err)
	}
	*v = tmp
	return nil
}

func decodeInt16(dec *msgpack.Decoder, v *int16) error {
	tmp, err := dec.DecodeInt16()
	if err != nil {
		return errors.WithStack(err)
	}
	*v = tmp
	return nil
}

func decodeInt32(dec *msgpack.Decoder, v *int32) error {
	tmp, err := dec.DecodeInt32()
	if err != nil {
		return errors.WithStack(err)
	}
	*v = tmp
	return nil
}

func decodeInt64(dec *msgpack.Decoder, v *int64) error {
	tmp, err := dec.DecodeInt64()
	if err != nil {
		return errors.WithStack(err)
	}
	*v = tmp
	return nil
}

func decodeBool(dec *msgpack.Decoder, v *bool) error {
	tmp, err := dec.DecodeBool()
	if err != nil {
		return errors.WithStack(err)
	}
	*v = tmp
	return nil
}

func decodeFloat32(dec *msgpack.Decoder, v *float32) error {
	tmp, err := dec.DecodeFloat32()
	if err != nil {
		return errors.WithStack(err)
	}
	*v = tmp
	return nil
}

func decodeFloat64(dec *msgpack.Decoder, v *float64) error {
	tmp, err := dec.DecodeFloat64()
	if err != nil {
		return errors.WithStack(err)
	}
	*v = tmp
	return nil
}

func decodeString(dec *msgpack.Decoder, v *string) error {
	tmp, err := dec.DecodeString()
	if err != nil {
		return errors.WithStack(err)
	}
	*v = tmp
	return nil
}

func decodeBytes(dec *msgpack.Decoder, v *[]byte) error {
	tmp, err := dec.DecodeBytes()
	if err != nil {
		return errors.WithStack(err)
	}
	*v = tmp
	return nil
}