package ssob

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

type Encoder struct {
	mutex sync.Mutex
	w     io.Writer
}

func NewEncoder(w io.Writer) *Encoder {
	enc := new(Encoder)
	enc.w = w
	return enc
}

func (enc *Encoder) Encode(e interface{}) (err error) {
	return enc.EncodeValue(reflect.ValueOf(e))
}

func (enc *Encoder) EncodeValue(value reflect.Value) (err error) {
	if value.Type() == reflect.TypeOf(errors.New("")) || value.Type() == reflect.TypeOf((*error)(nil)).Elem() {
		if value.IsNil() {
			return enc.Encode(string(""))
		} else {
			return enc.Encode(value.Interface().(error).Error())
		}
	}

	if value.Kind() == reflect.Invalid {
		return fmt.Errorf("ssob: Cannot encode nil: %w", ErrValueInvalid)
	}

	if value.Kind() == reflect.Ptr && value.IsNil() {
		return fmt.Errorf("ssob: Cannot encode nil of type %s: %w", value.Type().String(), ErrValueInvalid)
	}

	bb, err := marshal(value.Interface())
	if err != nil {
		return err
	}
	bl := MarshalInt32(int32(len(bb)))

	w := make([]byte, 4+len(bb))
	copy(w, bl)
	copy(w[4:], bb)

	enc.mutex.Lock()
	defer enc.mutex.Unlock()

	return binary.Write(enc.w, binary.BigEndian, w)
}