// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package block

import (
	"bytes";
	"fmt";
	"io";
	"testing";
	"testing/iotest";
)

// Simple Cipher for testing: adds an incrementing amount
// to each byte in each
type IncCipher struct {
	blockSize int;
	delta byte;
	encrypting bool;
}

func (c *IncCipher) BlockSize() int {
	return c.blockSize;
}

func (c *IncCipher) Encrypt(src, dst []byte) {
	if !c.encrypting {
		panicln("encrypt: not encrypting");
	}
	if len(src) != c.blockSize || len(dst) != c.blockSize {
		panicln("encrypt: wrong block size", c.blockSize, len(src), len(dst));
	}
	c.delta++;
	for i, b := range src {
		dst[i] = b + c.delta;
	}
}

func (c *IncCipher) Decrypt(src, dst []byte) {
	if c.encrypting {
		panicln("decrypt: not decrypting");
	}
	if len(src) != c.blockSize || len(dst) != c.blockSize {
		panicln("decrypt: wrong block size", c.blockSize, len(src), len(dst));
	}
	c.delta--;
	for i, b := range src {
		dst[i] = b + c.delta;
	}
}

func TestECBEncrypter(t *testing.T) {
	var plain, crypt [256]byte;
	for i := 0; i < len(plain); i++ {
		plain[i] = byte(i);
	}
	b := new(bytes.Buffer);
	for block := 1; block <= 64; block *= 2 {
		// compute encrypted version
		delta := byte(0);
		for i := 0; i < len(crypt); i++ {
			if i % block == 0 {
				delta++;
			}
			crypt[i] = plain[i] + delta;
		}

		for frag := 0; frag < 2; frag++ {
			c := &IncCipher{block, 0, true};
			b.Reset();
			r := bytes.NewBuffer(&plain);
			w := NewECBEncrypter(c, b);

			// copy plain into w in increasingly large chunks: 1, 1, 2, 4, 8, ...
			// if frag != 0, move the 1 to the end to cause fragmentation.
			if frag == 0 {
				_, err := io.Copyn(r, w, 1);
				if err != nil {
					t.Errorf("block=%d frag=0: first Copyn: %s", block, err);
					continue;
				}
			}
			for n := 1; n <= len(plain)/2; n *= 2 {
				_, err := io.Copyn(r, w, int64(n));
				if err != nil {
					t.Errorf("block=%d frag=%d: Copyn %d: %s", block, frag, n, err);
				}
			}
			if frag != 0 {
				_, err := io.Copyn(r, w, 1);
				if err != nil {
					t.Errorf("block=%d frag=1: last Copyn: %s", block, err);
					continue;
				}
			}

			// check output
			data := b.Bytes();
			if len(data) != len(crypt) {
				t.Errorf("block=%d frag=%d: want %d bytes, got %d", block, frag, len(crypt), len(data));
				continue;
			}

			if string(data) != string(&crypt) {
				t.Errorf("block=%d frag=%d: want %x got %x", block, frag, data, crypt);
			}
		}
	}
}

func testECBDecrypter(t *testing.T, maxio int) {
	var readers = []func(io.Reader) io.Reader {
		func (r io.Reader) io.Reader { return r },
		iotest.OneByteReader,
		iotest.HalfReader,
	};
	var plain, crypt [256]byte;
	for i := 0; i < len(plain); i++ {
		plain[i] = byte(255 - i);
	}
	b := new(bytes.Buffer);
	for block := 1; block <= 64 && block <= maxio; block *= 2 {
		// compute encrypted version
		delta := byte(0);
		for i := 0; i < len(crypt); i++ {
			if i % block == 0 {
				delta++;
			}
			crypt[i] = plain[i] + delta;
		}

		for mode := 0; mode < len(readers); mode++ {
			for frag := 0; frag < 2; frag++ {
				test := fmt.Sprintf("block=%d mode=%d frag=%d maxio=%d", block, mode, frag, maxio);
				c := &IncCipher{block, 0, false};
				b.Reset();
				r := NewECBDecrypter(c, readers[mode](bytes.NewBuffer(crypt[0:maxio])));

				// read from crypt in increasingly large chunks: 1, 1, 2, 4, 8, ...
				// if frag == 1, move the 1 to the end to cause fragmentation.
				if frag == 0 {
					_, err := io.Copyn(r, b, 1);
					if err != nil {
						t.Errorf("%s: first Copyn: %s", test, err);
						continue;
					}
				}
				for n := 1; n <= maxio/2; n *= 2 {
					_, err := io.Copyn(r, b, int64(n));
					if err != nil {
						t.Errorf("%s: Copyn %d: %s", test, n, err);
					}
				}
				if frag != 0 {
					_, err := io.Copyn(r, b, 1);
					if err != nil {
						t.Errorf("%s: last Copyn: %s", test, err);
						continue;
					}
				}

				// check output
				data := b.Bytes();
				if len(data) != maxio {
					t.Errorf("%s: want %d bytes, got %d", test, maxio, len(data));
					continue;
				}

				if string(data) != string(plain[0:maxio]) {
					t.Errorf("%s: input=%x want %x got %x", test, crypt[0:maxio], plain[0:maxio], data);
				}
			}
		}
	}
}

func TestECBDecrypter(t *testing.T) {
	// Do shorter I/O sizes first; they're easier to debug.
	for n := 1; n <= 256 && !t.Failed(); n *= 2 {
		testECBDecrypter(t, n);
	}
}