package commands

import (
	"crypto/cipher"
	"crypto/des"
	"io"
	"os"
)

type DecryptDESCommand struct {
	SourceFileName string `long:"src" alias:"i" required:"true" description:"input-filename"`
	DestFileName   string `long:"dest" alias:"o" required:"true" description:"output-filename"`
}

func (command *DecryptDESCommand) Execute(args []string) error {
	inputFile, err := os.Open(command.SourceFileName)
	if err != nil {
		return err
	}
	defer inputFile.Close()
	outputFile, err := os.Create(command.DestFileName)
	if err != nil {
		return err
	}
	defer outputFile.Close()

	inputFileStat, err := inputFile.Stat()
	if err != nil {
		return err
	}

	pdata := make([]byte, inputFileStat.Size())
	_, err = io.ReadFull(inputFile, pdata)
	if err != nil {
		return err
	}

	block, err := des.NewTripleDESCipher([]byte("HAVNCPSCMTTUNERAIRTRACER"))
	if err != nil {
		return err
	}
	iv := []byte("VEDKDJSP")

	decrypter := cipher.NewCBCDecrypter(block, iv)
	decrypted := make([]byte, len(pdata))
	decrypter.CryptBlocks(decrypted, pdata)

	_, err = outputFile.Write(decrypted)
	if err != nil {
		return err
	}

	return nil
}