package ssob

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

func MarshalString(in string) (ret []byte) {
	l := int32(len(in))
	b := MarshalInt32(l)
	ret = make([]byte, int(l)+len(b))
	copy(ret, b)
	copy(ret[4:], []byte(in))
	return ret
}

func MarshalInt8(in int8) (ret []byte) {
	return []byte{byte(in)}
}

func MarshalUint8(in uint8) (ret []byte) {
	return []byte{byte(in)}
}

func MarshalInt16(in int16) (ret []byte) {
	out := make([]byte, 2)

	binary.BigEndian.PutUint16(out, uint16(in))
	return out
}

func MarshalUint16(in uint16) (ret []byte) {
	out := make([]byte, 2)

	binary.BigEndian.PutUint16(out, in)
	return out
}

func MarshalInt32(in int32) (ret []byte) {
	out := make([]byte, 4)

	binary.BigEndian.PutUint32(out, uint32(in))
	return out
}

func MarshalUint32(in uint32) (ret []byte) {
	out := make([]byte, 4)

	binary.BigEndian.PutUint32(out, in)
	return out
}

func MarshalFloat32(in float32) (ret []byte) {
	out := make([]byte, 4)

	binary.BigEndian.PutUint32(out, uint32(in))
	return out
}

func MarshalInt64(in int64) (ret []byte) {
	out := make([]byte, 8)

	binary.BigEndian.PutUint64(out, uint64(in))
	return out
}

func MarshalUint64(in uint64) (ret []byte) {
	out := make([]byte, 8)

	binary.BigEndian.PutUint64(out, in)
	return out
}

func MarshalFloat64(in float64) (ret []byte) {
	out := make([]byte, 8)

	binary.BigEndian.PutUint64(out, uint64(in))
	return out
}

type MarshalFunc func(e interface{}) (ret []byte, err error)

var encoderCache map[string]MarshalFunc

func init() {
	encoderCache = make(map[string]MarshalFunc)
	RegisterEncoder("int8", func(e interface{}) (ret []byte, err error) {
		if i, ok := e.(int8); ok {
			return MarshalInt8(i), nil
		}
		return nil, errors.New("ssob: Incompatible type - expected int8")
	})
	RegisterEncoder("uint8", func(e interface{}) (ret []byte, err error) {
		if i, ok := e.(uint8); ok {
			return MarshalUint8(i), nil
		}
		return nil, errors.New("ssob: Incompatible type - expected uint8")
	})
	RegisterEncoder("int16", func(e interface{}) (ret []byte, err error) {
		if i, ok := e.(int16); ok {
			return MarshalInt16(i), nil
		}
		return nil, errors.New("ssob: Incompatible type - expected int16")
	})
	RegisterEncoder("uint16", func(e interface{}) (ret []byte, err error) {
		if i, ok := e.(uint16); ok {
			return MarshalUint16(i), nil
		}
		return nil, errors.New("ssob: Incompatible type - expected uint16")
	})
	RegisterEncoder("int32", func(e interface{}) (ret []byte, err error) {
		if i, ok := e.(int32); ok {
			return MarshalInt32(i), nil
		}
		return nil, errors.New("ssob: Incompatible type - expected int32")
	})
	RegisterEncoder("uint32", func(e interface{}) (ret []byte, err error) {
		if i, ok := e.(uint32); ok {
			return MarshalUint32(i), nil
		}
		return nil, errors.New("ssob: Incompatible type - expected uint32")
	})
	RegisterEncoder("float32", func(e interface{}) (ret []byte, err error) {
		if i, ok := e.(float32); ok {
			return MarshalFloat32(i), nil
		}
		return nil, errors.New("ssob: Incompatible type - expected float32")
	})
	RegisterEncoder("int64", func(e interface{}) (ret []byte, err error) {
		if i, ok := e.(int64); ok {
			return MarshalInt64(i), nil
		}
		return nil, errors.New("ssob: Incompatible type - expected int64")
	})
	RegisterEncoder("uint64", func(e interface{}) (ret []byte, err error) {
		if i, ok := e.(uint64); ok {
			return MarshalUint64(i), nil
		}
		return nil, errors.New("ssob: Incompatible type - expected uint64")
	})
	RegisterEncoder("float64", func(e interface{}) (ret []byte, err error) {
		if i, ok := e.(float64); ok {
			return MarshalFloat64(i), nil
		}
		return nil, errors.New("ssob: Incompatible type - expected float64")
	})
	RegisterEncoder("string", func(e interface{}) (ret []byte, err error) {
		if i, ok := e.(string); ok {
			return MarshalString(i), nil
		}
		return nil, errors.New("ssob: Incompatible type - expected string")
	})
}

func encRegister(e interface{}) (err error) {
	v := reflect.ValueOf(e)
	t := reflect.TypeOf(e)
	switch t.Kind() {
	case reflect.Invalid:
		return errors.New("ssob: Invalid type")
	case reflect.Slice:
		f := func(e interface{}) (ret []byte, err error) {
			v := reflect.ValueOf(e)
			l := v.Len()
			slen := MarshalInt32(int32(l))
			blen := 4
			bs := make([][]byte, l)
			for i := 0; i < l; i++ {
				bs[i], err = marshal(v.Index(i).Interface())
				if err != nil {
					return nil, err
				}
				blen += len(bs[i])
			}

			ret = make([]byte, blen)
			i := copy(ret, slen)
			for c := 0; c < l; c++ {
				i += copy(ret[i:], bs[c])
			}

			return ret, nil
		}
		encoderCache[string(t.Kind())] = f
	case reflect.Map:
		f := func(e interface{}) (ret []byte, err error) {
			v := reflect.ValueOf(e)
			l := v.Len()
			ret = MarshalInt32(int32(l))
			for _, ek := range v.MapKeys() {
				ee := v.MapIndex(ek)
				b, err := marshal(ek.Interface())
				if err != nil {
					return nil, err
				}
				ret = append(ret, b...)

				b, err = marshal(ee.Interface())
				if err != nil {
					return nil, err
				}
				ret = append(ret, b...)
			}
			return ret, nil
		}
		encoderCache[string(t.Kind())] = f
	case reflect.Struct:
		f := func(e interface{}) (ret []byte, err error) {
			n := v.NumField()
			bs := make([][]byte, n)
			blen := 0
			for i := 0; i < n; i++ {
				bs[i], err = marshal(v.Field(i).Interface())
				if err != nil {
					return nil, err
				}
				blen += len(bs[i])
			}
			ret = make([]byte, blen)
			i := 0
			for c := 0; c < n; c++ {
				i += copy(ret[i:], bs[c])
			}
			return ret, nil
		}
		encoderCache[t.Name()] = f
	default:
		return errors.New("ssob: Unknown type " + string(v.Kind()))
	}

	return nil
}

func marshalBaseType(e interface{}) (ret []byte, err error) {
	switch t := e.(type) {
	case int8:
		return encoderCache["int8"](t)
	case uint8:
		return encoderCache["uint8"](t)
	case int16:
		return encoderCache["int16"](t)
	case uint16:
		return encoderCache["uint16"](t)
	case int32:
		return encoderCache["int32"](t)
	case uint32:
		return encoderCache["uint32"](t)
	case int64:
		return encoderCache["int64"](t)
	case uint64:
		return encoderCache["uint64"](t)
	case float32:
		return encoderCache["float32"](t)
	case float64:
		return encoderCache["float64"](t)
	case string:
		return encoderCache["string"](t)
	default:
		return nil, errors.New("ssob: No base type")
	}
}

func marshal(e interface{}) (ret []byte, err error) {
	ret, err = marshalBaseType(e)
	if err == nil {
		return ret, err
	}

	var key string
	t := reflect.TypeOf(e)
	v := reflect.ValueOf(e)
	if t.Kind() == reflect.Ptr {
		if v.IsNil() {
			return nil, errors.New("ssob: Cannot marshal nil pointer")
		}
		p := reflect.Indirect(v)
		return marshal(p.Interface())
	}
	if t.Kind() == reflect.Struct {
		key = reflect.TypeOf(e).Name()
	} else {
		key = string(t.Kind())
	}

	if f, ok := encoderCache[key]; ok {
		return f(e)
	} else {
		err = encRegister(e)
		if err != nil {
			return nil, err
		}
	}

	return marshal(e)
}

func RegisterEncoder(name string, f MarshalFunc) {
	encoderCache[name] = f
}