// Copyright (C) 2004-2021 Artifex Software, Inc.
//
// This file is part of MuPDF.
//
// MuPDF is free software: you can redistribute it and/or modify it under the
// terms of the GNU Affero General Public License as published by the Free
// Software Foundation, either version 3 of the License, or (at your option)
// any later version.
//
// MuPDF is distributed in the hope that it will be useful, but WITHOUT ANY
// WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
// FOR A PARTICULAR PURPOSE. See the GNU Affero General Public License for more
// details.
//
// You should have received a copy of the GNU Affero General Public License
// along with MuPDF. If not, see <https://www.gnu.org/licenses/agpl-3.0.en.html>
//
// Alternative licensing terms are available from the licensor.
// For commercial licensing, see <https://www.artifex.com/> or contact
// Artifex Software, Inc., 1305 Grant Avenue - Suite 200, Novato,
// CA 94945, U.S.A., +1(415)492-9861, for further information.

#include "mupdf/fitz.h"

#include "z-imp.h"

struct ahx
{
	fz_output *chain;
	int column;
};

static void ahx_write(fz_context *ctx, void *opaque, const void *data, size_t n)
{
	static const char tohex[16] = "0123456789ABCDEF";
	struct ahx *state = opaque;
	const unsigned char *p = data;
	while (n-- > 0)
	{
		int c = *p++;
		fz_write_byte(ctx, state->chain, tohex[(c>>4) & 15]);
		fz_write_byte(ctx, state->chain, tohex[(c) & 15]);
		state->column += 2;
		if (state->column == 64)
		{
			fz_write_byte(ctx, state->chain, '\n');
			state->column = 0;
		}
	}
}

static void ahx_close(fz_context *ctx, void *opaque)
{
	struct ahx *state = opaque;
	fz_write_byte(ctx, state->chain, '>');
}

static void ahx_drop(fz_context *ctx, void *opaque)
{
	struct ahx *state = opaque;
	fz_free(ctx, state);
}

fz_output *
fz_new_asciihex_output(fz_context *ctx, fz_output *chain)
{
	struct ahx *state = fz_malloc_struct(ctx, struct ahx);
	state->chain = chain;
	state->column = 0;
	return fz_new_output(ctx, 512, state, ahx_write, ahx_close, ahx_drop);
}

struct a85
{
	fz_output *chain;
	int column;
	unsigned int word, n;
};

static void a85_flush(fz_context *ctx, struct a85 *state)
{
	unsigned int v1, v2, v3, v4, v5;

	v5 = state->word;
	v4 = v5 / 85;
	v3 = v4 / 85;
	v2 = v3 / 85;
	v1 = v2 / 85;

	if (state->column >= 70)
	{
		fz_write_byte(ctx, state->chain, '\n');
		state->column = 0;
	}

	if (state->n == 4)
	{
		if (state->word == 0)
		{
			fz_write_byte(ctx, state->chain, 'z');
			state->column += 1;
		}
		else
		{
			fz_write_byte(ctx, state->chain, (v1 % 85) + '!');
			fz_write_byte(ctx, state->chain, (v2 % 85) + '!');
			fz_write_byte(ctx, state->chain, (v3 % 85) + '!');
			fz_write_byte(ctx, state->chain, (v4 % 85) + '!');
			fz_write_byte(ctx, state->chain, (v5 % 85) + '!');
			state->column += 5;
		}
	}
	else if (state->n == 3)
	{
		fz_write_byte(ctx, state->chain, (v2 % 85) + '!');
		fz_write_byte(ctx, state->chain, (v3 % 85) + '!');
		fz_write_byte(ctx, state->chain, (v4 % 85) + '!');
		fz_write_byte(ctx, state->chain, (v5 % 85) + '!');
		state->column += 4;
	}
	else if (state->n == 2)
	{
		fz_write_byte(ctx, state->chain, (v3 % 85) + '!');
		fz_write_byte(ctx, state->chain, (v4 % 85) + '!');
		fz_write_byte(ctx, state->chain, (v5 % 85) + '!');
		state->column += 3;
	}
	else if (state->n == 1)
	{
		fz_write_byte(ctx, state->chain, (v4 % 85) + '!');
		fz_write_byte(ctx, state->chain, (v5 % 85) + '!');
		state->column += 2;
	}

	state->word = 0;
	state->n = 0;
}

static void a85_write(fz_context *ctx, void *opaque, const void *data, size_t n)
{
	struct a85 *state = opaque;
	const unsigned char *p = data;
	while (n-- > 0)
	{
		unsigned int c = *p++;
		if (state->n == 4)
			a85_flush(ctx, state);
		state->word = (state->word << 8) | c;
		state->n++;
	}
}

static void a85_close(fz_context *ctx, void *opaque)
{
	struct a85 *state = opaque;
	a85_flush(ctx, state);
	fz_write_byte(ctx, state->chain, '~');
	fz_write_byte(ctx, state->chain, '>');
}

static void a85_drop(fz_context *ctx, void *opaque)
{
	struct a85 *state = opaque;
	fz_free(ctx, state);
}

fz_output *
fz_new_ascii85_output(fz_context *ctx, fz_output *chain)
{
	struct a85 *state = fz_malloc_struct(ctx, struct a85);
	state->chain = chain;
	state->column = 0;
	state->word = 0;
	state->n = 0;
	return fz_new_output(ctx, 512, state, a85_write, a85_close, a85_drop);
}

struct rle
{
	fz_output *chain;
	int state;
	int run;
	unsigned char buf[128];
};

enum { ZERO, ONE, DIFF, SAME };

static void rle_flush_same(fz_context *ctx, struct rle *enc)
{
	fz_write_byte(ctx, enc->chain, 257 - enc->run);
	fz_write_byte(ctx, enc->chain, enc->buf[0]);
}

static void rle_flush_diff(fz_context *ctx, struct rle *enc)
{
	fz_write_byte(ctx, enc->chain, enc->run - 1);
	fz_write_data(ctx, enc->chain, enc->buf, enc->run);
}

static void rle_write(fz_context *ctx, void *opaque, const void *data, size_t n)
{
	struct rle *enc = opaque;
	const unsigned char *p = data;
	while (n-- > 0)
	{
		int c = *p++;
		switch (enc->state)
		{
		case ZERO:
			enc->state = ONE;
			enc->run = 1;
			enc->buf[0] = c;
			break;

		case ONE:
			enc->state = DIFF;
			enc->run = 2;
			enc->buf[1] = c;
			break;

		case DIFF:
			/* Max run length */
			if (enc->run == 128)
			{
				rle_flush_diff(ctx, enc);
				enc->state = ONE;
				enc->run = 1;
				enc->buf[0] = c;
			}
			/* Run of three same */
			else if ((enc->run >= 2) && (c == enc->buf[enc->run-1]) && (c == enc->buf[enc->run-2]))
			{
				if (enc->run >= 3) {
					enc->run -= 2; /* skip last two in previous run */
					rle_flush_diff(ctx, enc);
				}
				enc->state = SAME;
				enc->run = 3;
				enc->buf[0] = c;
			}
			else
			{
				enc->buf[enc->run] = c;
				enc->run++;
			}
			break;

		case SAME:
			if ((enc->run == 128) || (c != enc->buf[0]))
			{
				rle_flush_same(ctx, enc);
				enc->state = ONE;
				enc->run = 1;
				enc->buf[0] = c;
			}
			else
			{
				enc->run++;
			}
		}
	}
}

static void rle_close(fz_context *ctx, void *opaque)
{
	struct rle *enc = opaque;
	switch (enc->state)
	{
		case ZERO: break;
		case ONE: rle_flush_diff(ctx, enc); break;
		case DIFF: rle_flush_diff(ctx, enc); break;
		case SAME: rle_flush_same(ctx, enc); break;
	}
	fz_write_byte(ctx, enc->chain, 128);
}

static void rle_drop(fz_context *ctx, void *opaque)
{
	struct rle *enc = opaque;
	fz_free(ctx, enc);
}

fz_output *
fz_new_rle_output(fz_context *ctx, fz_output *chain)
{
	struct rle *enc = fz_malloc_struct(ctx, struct rle);
	enc->chain = chain;
	enc->state = ZERO;
	enc->run = 0;
	return fz_new_output(ctx, 4096, enc, rle_write, rle_close, rle_drop);
}

struct arc4
{
	fz_output *chain;
	fz_arc4 arc4;
};

static void arc4_write(fz_context *ctx, void *opaque, const void *data, size_t n)
{
	struct arc4 *state = opaque;
	const unsigned char *p = data;
	unsigned char buffer[256];
	while (n > 0)
	{
		size_t x = (n > sizeof buffer) ? sizeof buffer : n;
		fz_arc4_encrypt(&state->arc4, buffer, p, x);
		fz_write_data(ctx, state->chain, buffer, x);
		p += x;
		n -= x;
	}
}

static void arc4_drop(fz_context *ctx, void *opaque)
{
	fz_free(ctx, opaque);
}

fz_output *
fz_new_arc4_output(fz_context *ctx, fz_output *chain, unsigned char *key, size_t keylen)
{
	struct arc4 *state = fz_malloc_struct(ctx, struct arc4);
	state->chain = chain;
	fz_arc4_init(&state->arc4, key, keylen);
	return fz_new_output(ctx, 256, state, arc4_write, NULL, arc4_drop);
}

struct deflate
{
	fz_output *chain;
	z_stream z;
};

static void deflate_write(fz_context *ctx, void *opaque, const void *data, size_t n)
{
	struct deflate *state = opaque;
	unsigned char buffer[32 << 10];
	int err;

	state->z.next_in = (Bytef*)data;
	state->z.avail_in = (uInt)n;
	do
	{
		state->z.next_out = buffer;
		state->z.avail_out = sizeof buffer;
		err = deflate(&state->z, Z_NO_FLUSH);
		if (err != Z_OK)
			fz_throw(ctx, FZ_ERROR_GENERIC, "zlib compression failed: %d", err);
		if (state->z.avail_out > 0)
			fz_write_data(ctx, state->chain, state->z.next_out, state->z.avail_out);
	} while (state->z.avail_out > 0);
}

static void deflate_close(fz_context *ctx, void *opaque)
{
	struct deflate *state = opaque;
	unsigned char buffer[32 << 10];
	int err;

	state->z.next_in = NULL;
	state->z.avail_in = 0;
	do
	{
		state->z.next_out = buffer;
		state->z.avail_out = sizeof buffer;
		err = deflate(&state->z, Z_FINISH);
		if (state->z.avail_out > 0)
			fz_write_data(ctx, state->chain, state->z.next_out, state->z.avail_out);
	} while (err == Z_OK);

	if (err != Z_STREAM_END)
		fz_throw(ctx, FZ_ERROR_GENERIC, "zlib compression failed: %d", err);
}

static void deflate_drop(fz_context *ctx, void *opaque)
{
	struct deflate *state = opaque;
	(void)deflateEnd(&state->z);
	fz_free(ctx, state);
}

fz_output *
fz_new_deflate_output(fz_context *ctx, fz_output *chain, int effort, int raw)
{
	int err;

	struct deflate *state = fz_malloc_struct(ctx, struct deflate);
	state->chain = chain;
	state->z.opaque = ctx;
	state->z.zalloc = fz_zlib_alloc;
	state->z.zfree = fz_zlib_free;
	err = deflateInit2(&state->z, effort, Z_DEFLATED, raw ? -15 : 15, 8, Z_DEFAULT_STRATEGY);
	if (err != Z_OK)
	{
		(void)deflateEnd(&state->z);
		fz_free(ctx, state);
		fz_throw(ctx, FZ_ERROR_GENERIC, "zlib deflateInit2 failed: %d", err);
	}
	return fz_new_output(ctx, 8192, state, deflate_write, deflate_close, deflate_drop);
}
