package rest

import (
	"io"

	"git.ali33.ru/fcg-xvii/go-tools/json"
)

// конверторы

// Int64ToBytes упаковывает int64 в срез байтов заданной длины
func Int64ToBytes(num int64, byteCount int) []byte {
	bytes := make([]byte, byteCount)
	for i := 0; i < byteCount; i++ {
		shift := uint((byteCount - 1 - i) * 8)
		bytes[i] = byte(num >> shift)
	}
	return bytes
}

// BytesToInt64 конвертирует срез байтов в int64
func BytesToInt64(bytes []byte) int64 {
	var num int64
	for _, b := range bytes {
		num = (num << 8) | int64(b)
	}
	return num
}

func ioError(field string, err error) IErrorArgs {
	return NewError(
		"ErrIO",
		json.Map{
			"field": field,
			"error": err.Error(),
		},
	)
}

// чтение

func ReadBuf(r io.Reader, size int, field string) ([]byte, IErrorArgs) {
	buf := make([]byte, size)
	if _, err := r.Read(buf); err != nil {
		return nil, ioError(field, err)
	}
	return buf, nil
}

func ReadBufSize(r io.Reader, lenSize int, field string) ([]byte, IErrorArgs) {
	var size int64
	if err := ReadInt64(r, lenSize, field+"_size", &size); err != nil {
		return nil, err
	}
	buf, err := ReadBuf(r, int(size), field)
	return buf, err
}

func ReadInt64(r io.Reader, size int, field string, result *int64) IErrorArgs {
	buf := make([]byte, size)
	if _, err := r.Read(buf); err != nil {
		return ioError(field, err)
	}
	*result = BytesToInt64(buf)
	return nil
}

func ReadString(r io.Reader, lenSize int, field string, result *string) IErrorArgs {
	strBuf, err := ReadBufSize(r, lenSize, field)
	if err != nil {
		return err
	}
	*result = string(strBuf)
	return nil
}

func ReadByte(r io.Reader, field string, result *byte) IErrorArgs {
	buf, err := ReadBuf(r, 1, field)
	if err != nil {
		return err
	}
	*result = buf[0]
	return nil
}

// запись

func WriteBuf(w io.Writer, buf []byte, field string) IErrorArgs {
	if _, err := w.Write(buf); err != nil {
		return ioError(field, err)
	}
	return nil
}

func WriteInt64(w io.Writer, val int64, size int, field string) IErrorArgs {
	buf := Int64ToBytes(val, size)
	return WriteBuf(w, buf, field)
}

func WriteString(w io.Writer, val, field string, lenSize int) IErrorArgs {
	// длина
	if err := WriteInt64(w, int64(len(val)), lenSize, field+"_size"); err != nil {
		return err
	}
	// строка
	if len(val) == 0 {
		return nil
	}
	return WriteBuf(w, []byte(val), field)
}

func WriteByte(w io.Writer, val byte, field string) IErrorArgs {
	return WriteBuf(w, []byte{val}, field)
}

func WriteBufSize(w io.Writer, val []byte, lenSize int, field string) IErrorArgs {
	// длина
	if err := WriteInt64(w, int64(len(val)), lenSize, field+"_size"); err != nil {
		return err
	}
	// буфер
	return WriteBuf(w, val, field)
}