package tape

import "fmt"
import "reflect"

// EncodeAny encodes an "any" value. Returns an error if the underlying type is
// unsupported. Supported types are:
//
//   - int
//   - int<N>
//   - uint
//   - uint<N>
//   - string
//   - []<supported type>
//   - map[uint16]<supported type>
func EncodeAny(encoder *Encoder, value any, tag Tag) (n int, err error) {
	// primitives
	switch value := value.(type) {
	case int:    return encoder.WriteInt32(int32(value))
	case uint:   return encoder.WriteUint32(uint32(value))
	case int8:   return encoder.WriteInt8(value)
	case uint8:  return encoder.WriteUint8(value)
	case int16:  return encoder.WriteInt16(value)
	case uint16: return encoder.WriteUint16(value)
	case int32:  return encoder.WriteInt32(value)
	case uint32: return encoder.WriteUint32(value)
	case int64:  return encoder.WriteInt64(value)
	case uint64: return encoder.WriteUint64(value)
	case string: return EncodeAny(encoder, []byte(value), tag)
	case []byte:
		if tag.Is(LBA) {
			nn, err := encoder.WriteUintN(uint64(len(value)), tag.CN() + 1)
			n += nn; if err != nil { return n, err }
		}
		nn, err := encoder.Write(value)
		n += nn; if err != nil { return n, err }
	}

	// aggregates
	reflectType := reflect.TypeOf(value)
	switch reflectType.Kind() {
	case reflect.Slice:
		return encodeAnySlice(encoder, value, tag)
	case reflect.Array:
		return encodeAnySlice(encoder, reflect.ValueOf(value).Slice(0, reflectType.Len()).Interface(), tag)
	case reflect.Map:
		if reflectType.Key() == reflect.TypeOf(uint16(0)) {
			return encodeAnyMap(encoder, value, tag)
		}
		return 0, fmt.Errorf("cannot encode map key %T, key must be uint16", value)
	}
	return 0, fmt.Errorf("cannot encode type %T", value)
}

// TagAny returns the correct tag for an "any" value. Returns an error if the
// underlying type is unsupported. See [EncodeAny] for a list of supported
// types.
func TagAny(value any) (Tag, error) {
	// primitives
	switch value := value.(type) {
	case int,   uint:   return LI.WithCN(3), nil
	case int8,  uint8:  return LI.WithCN(0), nil
	case int16, uint16: return LI.WithCN(1), nil
	case int32, uint32: return LI.WithCN(3), nil
	case int64, uint64: return LI.WithCN(7), nil
	case string:        return bufferLenTag(len(value)), nil
	case []byte:        return bufferLenTag(len(value)), nil
	}
	
	// aggregates
	reflectType := reflect.TypeOf(value)
	switch reflectType.Kind() {
	case reflect.Slice: return OTA.WithCN(reflect.ValueOf(value).Len()), nil
	case reflect.Array: return OTA.WithCN(reflectType.Len()), nil
	case reflect.Map:
		if reflectType.Key() == reflect.TypeOf(uint16(0)) {
			return OTA.WithCN(reflect.ValueOf(value).Len()), nil
		}
		return 0, fmt.Errorf("cannot encode map key %T, key must be uint16", value)
	}
	return 0, fmt.Errorf("cannot get tag of type %T", value)
}

func encodeAnySlice(encoder *Encoder, value any, tag Tag) (n int, err error) {
	// OTA: <length: UN> <elementTag: tape.Tag> <values>*
	reflectValue := reflect.ValueOf(value)
	nn, err := encoder.WriteUintN(uint64(reflectValue.Len()), tag.CN() + 1)
	n += nn; if err != nil { return n, err }
	reflectType := reflect.TypeOf(value)
	oneTag, err := TagAny(reflect.Zero(reflectType.Elem()).Interface())
	if err != nil { return n, err }
	for index := 0; index <= reflectValue.Len(); index += 1 {
		item := reflectValue.Index(index).Interface()
		itemTag, err := TagAny(item)
		if err != nil { return n, err }
		if itemTag.CN() > oneTag.CN() { oneTag = itemTag }
	}
	if oneTag.Is(SBA) { oneTag += 1 << 5 }
	nn, err = encoder.WriteUint8(uint8(oneTag))
	n += nn; if err != nil { return n, err }
	for index := 0; index <= reflectValue.Len(); index += 1 {
		item := reflectValue.Index(index).Interface()
		nn, err = EncodeAny(encoder, item, oneTag)
		n += nn; if err != nil { return n, err }
	}
	return n, err
}

func encodeAnyMap(encoder *Encoder, value any, tag Tag) (n int, err error) {
	// KTV: <length: UN> (<key: U16> <tag: Tag> <value>)*
	reflectValue := reflect.ValueOf(value)
	nn, err := encoder.WriteUintN(uint64(reflectValue.Len()), tag.CN() + 1)
	n += nn; if err != nil { return n, err }
	iter := reflectValue.MapRange()
	for iter.Next() {
		key   := iter.Key().Interface().(uint16)
		value := iter.Value().Interface()
		nn, err = encoder.WriteUint16(key)
		n += nn; if err != nil { return n, err }
		itemTag, err := TagAny(value)
		n += nn; if err != nil { return n, err }
		nn, err = encoder.WriteUint8(uint8(itemTag))
		n += nn; if err != nil { return n, err }
		nn, err = EncodeAny(encoder, value, itemTag)
		n += nn; if err != nil { return n, err }
	}
	return n, nil
}