// WANDERER - a crypto doodle that appears to give adequate
// protection to data in a stream cipher context (?)
//
// Properties visualized using https://github.com/circulosmeos/circle
//
// test command-line 'main' program
package main

// TODOs:
// -use a crypto rand (eg mtwist64) instead of go pkg rand?
// -define s-box rotation/shuffle schema
// -devise p-box schema
// ...

import (
	"flag"
	"io"
	"log"
	"os"

	"blitter.com/go/cryptmt"
)

const (
	invalidKey = "FATAL_UNSPECIFIED_KEY"
	minKeyLen  = 8
)

var (
	k string
)

/* Wrap the cipher in a type which implements the
 * Reader and Writer interfaces to enable its use via
 * io.Copy(). As evident below, DO NOT rely on
 * Write() by itself to do anything other than output
 * what should have been encrypted or decrypted by
 * Read()!
 *
 * (That is, calling Write() directly, as should be
 *  obvious below,does nothing to do with crypto.)
 *
 * To use the cipher outside of io.Copy(), use
 * the crypto/cipher.StreamReader/StreamWriter interfaces
 * which will make use of the cipher's XORKeyStream method.
 */
type Encoder struct {
	r io.Reader
	w io.Writer
	c *cryptmt.Cipher
}

func (c *Encoder) Read(p []byte) (n int, err error) {
	n, err = c.r.Read(p)
	if err == nil {
		for idx := 0; idx < n; idx++ {
			p[idx] = c.c.Yield(p[idx])
		}
	}
	return n, err
}

func (c *Encoder) Write(p []byte) (n int, err error) {
	n, err = c.w.Write(p)
	return n, err
}

func main() {
	flag.StringVar(&k, "k", "WARNING_DEFAULT_KEY", "Key (NOTE insecure specified on command line)")
	flag.Parse()

	if k == invalidKey {
		log.Fatal("no key specified")
	}
	if len(k) < minKeyLen {
		log.Fatal("key is too small")
	}

	c := &Encoder{}
	c.r = os.Stdin
	c.w = os.Stdout
	c.c = cryptmt.New([]byte(k))
	_, _ = io.Copy(c, c)
}