package ssob

import (
	"encoding/binary"
	"errors"
	"fmt"
	"reflect"
)

func UnmarshalString(in []byte) (ret string, n int, err error) {
	if len(in) < 8 {
		return "", 0, errors.New("ssob: Invalid input to decode string")
	}
	l := int64(binary.BigEndian.Uint64(in))

	if len(in[8:]) < int(l) {
		return "", 0, errors.New("ssob: Invalid length of string")
	}
	return string(in[8 : l+8]), int(l) + 8, nil
}

func UnmarshalInt8(in []byte) (ret int8, n int, err error) {
	if len(in) < 1 {
		return 0, 0, errors.New("ssob: Invalid input to decode int8")
	}

	return int8(in[0]), 1, nil
}

func UnmarshalUint8(in []byte) (ret uint8, n int, err error) {
	if len(in) < 1 {
		return 0, 0, errors.New("ssob: Invalid input to decode uint8")
	}

	return uint8(in[0]), 1, nil
}

func UnmarshalInt16(in []byte) (ret int16, n int, err error) {
	if len(in) < 2 {
		return 0, 0, errors.New("ssob: Invalid input to decode int16")
	}

	return int16(binary.BigEndian.Uint16(in[0:2])), 2, nil
}

func UnmarshalUint16(in []byte) (ret uint16, n int, err error) {
	if len(in) < 2 {
		return 0, 0, errors.New("ssob: Invalid input to decode uint16")
	}

	return binary.BigEndian.Uint16(in[0:1]), 2, nil
}

func UnmarshalInt32(in []byte) (ret int32, n int, err error) {
	if len(in) < 4 {
		return 0, 0, errors.New("ssob: Invalid input to decode int32")
	}

	return int32(binary.BigEndian.Uint32(in[0:4])), 4, nil
}

func UnmarshalUint32(in []byte) (ret uint32, n int, err error) {
	if len(in) < 4 {
		return 0, 0, errors.New("ssob: Invalid input to decode uint32")
	}

	return binary.BigEndian.Uint32(in[0:4]), 4, nil
}

func UnmarshalFloat32(in []byte) (ret float32, n int, err error) {
	if len(in) < 4 {
		return 0, 0, errors.New("ssob: Invalid input to decode float32")
	}

	return float32(binary.BigEndian.Uint64(in[0:4])), 4, nil
}

func UnmarshalInt64(in []byte) (ret int64, n int, err error) {
	if len(in) < 8 {
		return 0, 0, errors.New("ssob: Invalid input to decode int64")
	}

	return int64(binary.BigEndian.Uint64(in[0:8])), 8, nil
}

func UnmarshalUint64(in []byte) (ret uint64, n int, err error) {
	if len(in) < 8 {
		return 0, 0, errors.New("ssob: Invalid input to decode uint64")
	}

	return binary.BigEndian.Uint64(in[0:8]), 8, nil
}

func UnmarshalFloat64(in []byte) (ret float64, n int, err error) {
	if len(in) < 8 {
		return 0, 0, errors.New("ssob: Invalid input to decode float64")
	}

	return float64(binary.BigEndian.Uint64(in[0:8])), 8, nil
}

type unmarshalFunc func(e interface{}, in []byte) (n int, err error)

var decoderCache map[string]unmarshalFunc

func init() {
	decoderCache = make(map[string]unmarshalFunc)
	decRegister(int8(0))
	decRegister(uint8(0))
	decRegister(int16(0))
	decRegister(uint16(0))
	decRegister(int32(0))
	decRegister(uint32(0))
	decRegister(float32(0))
	decRegister(int64(0))
	decRegister(uint64(0))
	decRegister(float64(0))
	decRegister(string(""))
}

func decRegister(e interface{}) (err error) {
	t := reflect.TypeOf(e)
	v := reflect.ValueOf(e)
	switch t.Kind() {
	case reflect.Invalid:
		return errors.New("ssob: Invalid type")
	case reflect.Slice:
		return errors.New("ssob: Unsupported type")
	case reflect.Struct:
		f := func(e interface{}, in []byte) (n int, err error) {
			t := reflect.TypeOf(e)
			v := reflect.ValueOf(e)
			pos := 0

			if t.Kind() != reflect.Ptr || v.IsNil() {
				return 0, errors.New("ssob: Cannot unmarshal to nil pointer")
			}

			vi := reflect.Indirect(v)
			l := vi.NumField()
			for i := 0; i < l; i++ {
				ni, err := unmarshal(vi.Field(i).Addr().Interface(), in[pos:])
				pos += ni
				if err != nil {
					return pos, err
				}
			}

			return pos, nil
		}
		decoderCache[t.Name()] = f
	case reflect.Int8:
		f := func(e interface{}, in []byte) (n int, err error) {
			if i, ok := e.(*int8); ok {
				if i == nil {
					return 0, errors.New("ssob: Cannot unmarshal to nil pointer")
				}
				*i, n, err = UnmarshalInt8(in)
				if err != nil {
					return 0, err
				}
				return n, err
			}
			return 0, errors.New("ssob: Incompatible type " + string(v.Kind()) + " - expected *int8")
		}
		decoderCache[string(v.Kind())] = f
	case reflect.Uint8:
		f := func(e interface{}, in []byte) (n int, err error) {
			if i, ok := e.(*uint8); ok {
				if i == nil {
					return 0, errors.New("ssob: Cannot unmarshal to nil pointer")
				}
				*i, n, err = UnmarshalUint8(in)
				if err != nil {
					return 0, err
				}
				return n, err
			}
			return 0, errors.New("ssob: Incompatible type " + string(v.Kind()) + " - expected *uint8")
		}
		decoderCache[string(v.Kind())] = f
	case reflect.Int16:
		f := func(e interface{}, in []byte) (n int, err error) {
			if i, ok := e.(*int16); ok {
				if i == nil {
					return 0, errors.New("ssob: Cannot unmarshal to nil pointer")
				}
				*i, n, err = UnmarshalInt16(in)
				if err != nil {
					return 0, err
				}
				return n, err
			}
			return 0, errors.New("ssob: Incompatible type " + string(v.Kind()) + " - expected *int16")
		}
		decoderCache[string(v.Kind())] = f
	case reflect.Uint16:
		f := func(e interface{}, in []byte) (n int, err error) {
			if i, ok := e.(*uint16); ok {
				if i == nil {
					return 0, errors.New("ssob: Cannot unmarshal to nil pointer")
				}
				*i, n, err = UnmarshalUint16(in)
				if err != nil {
					return 0, err
				}
				return n, err
			}
			return 0, errors.New("ssob: Incompatible type " + string(v.Kind()) + " - expected *uint16")
		}
		decoderCache[string(v.Kind())] = f
	case reflect.Int32:
		f := func(e interface{}, in []byte) (n int, err error) {
			if i, ok := e.(*int32); ok {
				if i == nil {
					return 0, errors.New("ssob: Cannot unmarshal to nil pointer")
				}
				*i, n, err = UnmarshalInt32(in)
				if err != nil {
					return 0, err
				}
				return n, err
			}
			return 0, errors.New("ssob: Incompatible type " + string(v.Kind()) + " - expected *int32")
		}
		decoderCache[string(v.Kind())] = f
	case reflect.Uint32:
		f := func(e interface{}, in []byte) (n int, err error) {
			if i, ok := e.(*uint32); ok {
				if i == nil {
					return 0, errors.New("ssob: Cannot unmarshal to nil pointer")
				}
				*i, n, err = UnmarshalUint32(in)
				if err != nil {
					return 0, err
				}
				return n, err
			}
			return 0, errors.New("ssob: Incompatible type " + string(v.Kind()) + " - expected *uint32")
		}
		decoderCache[string(v.Kind())] = f
	case reflect.Float32:
		f := func(e interface{}, in []byte) (n int, err error) {
			if i, ok := e.(*float32); ok {
				if i == nil {
					return 0, errors.New("ssob: Cannot unmarshal to nil pointer")
				}
				*i, n, err = UnmarshalFloat32(in)
				if err != nil {
					return 0, err
				}
				return n, err
			}
			return 0, errors.New("ssob: Incompatible type " + string(v.Kind()) + " - expected *float32")
		}
		decoderCache[string(v.Kind())] = f
	case reflect.Int64:
		f := func(e interface{}, in []byte) (n int, err error) {
			if i, ok := e.(*int64); ok {
				if i == nil {
					return 0, errors.New("ssob: Cannot unmarshal to nil pointer")
				}
				*i, n, err = UnmarshalInt64(in)
				if err != nil {
					return 0, err
				}
				return n, err
			}
			return 0, errors.New("ssob: Incompatible type " + string(v.Kind()) + " - expected *int64")
		}
		decoderCache[string(v.Kind())] = f
	case reflect.Uint64:
		f := func(e interface{}, in []byte) (n int, err error) {
			if i, ok := e.(*uint64); ok {
				if i == nil {
					return 0, errors.New("ssob: Cannot unmarshal to nil pointer")
				}
				*i, n, err = UnmarshalUint64(in)
				if err != nil {
					return 0, err
				}
				return n, err
			}
			return 0, errors.New("ssob: Incompatible type " + string(v.Kind()) + " - expected *uint64")
		}
		decoderCache[string(v.Kind())] = f
	case reflect.Float64:
		f := func(e interface{}, in []byte) (n int, err error) {
			if i, ok := e.(*float64); ok {
				if i == nil {
					return 0, errors.New("ssob: Cannot unmarshal to nil pointer")
				}
				*i, n, err = UnmarshalFloat64(in)
				if err != nil {
					return 0, err
				}
				return n, err
			}
			return 0, errors.New("ssob: Incompatible type " + string(v.Kind()) + " - expected *float64")
		}
		decoderCache[string(v.Kind())] = f
	case reflect.String:
		f := func(e interface{}, in []byte) (n int, err error) {
			if i, ok := e.(*string); ok {
				if i == nil {
					return 0, errors.New("ssob: Cannot unmarshal to nil pointer")
				}
				*i, n, err = UnmarshalString(in)
				if err != nil {
					return 0, err
				}
				return n, err
			}
			return 0, errors.New("ssob: Incompatible type " + string(v.Kind()) + " - expected *string")
		}
		decoderCache[string(v.Kind())] = f
	default:
		return errors.New("ssob: Unknown type " + string(v.Kind()))
	}

	return nil
}

func unmarshal(e interface{}, in []byte) (n int, err error) {
	var key string
	t := reflect.TypeOf(e)
	v := reflect.ValueOf(e)
	if t.Kind() != reflect.Ptr || v.IsNil() {
		return 0, errors.New("ssob: Need a pointer that is fully allocated for unmarshalling")
	}

	p := reflect.Indirect(v)
	if p.Kind() != reflect.Ptr {
		if p.Kind() == reflect.Struct {
			key = reflect.TypeOf(p.Interface()).Name()
		} else {
			key = string(p.Kind())
		}

		if f, ok := decoderCache[key]; ok {
			return f(v.Interface(), in)
		} else {
			fmt.Println("Not found")
			err = decRegister(p.Interface())
			if err != nil {
				return 0, err
			}
		}
	}

	return unmarshal(e, in)
}

func RegisterDecoder(name string, f func(e interface{}, in []byte) (n int, err error)) {
	decoderCache[name] = f
}