/* ScummVM - Graphic Adventure Engine
 *
 * ScummVM is the legal property of its developers, whose names
 * are too numerous to list here. Please refer to the COPYRIGHT
 * file distributed with this source distribution.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 *
 */

#include "glk/frotz/mem.h"
#include "glk/frotz/frotz.h"
#include "common/memstream.h"
#include "common/textconsole.h"

namespace Glk {
namespace Frotz {

Mem::Mem() : story_fp(nullptr), story_size(0), first_undo(nullptr), last_undo(nullptr),
		curr_undo(nullptr), undo_mem(nullptr), zmp(nullptr), prev_zmp(nullptr),
		undo_diff(nullptr), undo_count(0), reserve_mem(0) {
}

void Mem::initialize() {
	initializeStoryFile();
	loadGameHeader();
	initializeUndo();

	// Allocate memory for story data
	if ((zmp = (zbyte *)realloc(zmp, story_size)) == nullptr)
		error("Out of memory");

	// Load story file in chunks of 32KB
	uint n = 0x8000;
	for (uint size = 64; size < story_size; size += n) {
		if (story_size - size < 0x8000)
			n = story_size - size;

		if (story_fp->read(zmp + size, n) != n)
			error("Story file read error");
	}

	// Read header extension table
	hx_table_size = get_header_extension(HX_TABLE_SIZE);
	hx_unicode_table = get_header_extension(HX_UNICODE_TABLE);
	hx_flags = get_header_extension(HX_FLAGS);
}

void Mem::initializeStoryFile() {
	if (story_fp->size() < 64)
		error("This file is too small to be a Z-code file.");
}

void Mem::initializeUndo() {
	byte *reserved = nullptr;

	if (reserve_mem != 0) {
		if ((reserved = new byte[reserve_mem]) == nullptr)
			return;
	}

	// Allocate h_dynamic_size bytes for previous dynamic zmp state
	// + 1.5 h_dynamic_size for Quetzal diff + 2.
	undo_mem = new zbyte[(h_dynamic_size * 5) / 2 + 2];
	if (undo_mem != nullptr) {
		prev_zmp = undo_mem;
		undo_diff = undo_mem + h_dynamic_size;
		memcpy(prev_zmp, zmp, h_dynamic_size);
	} else {
		_undo_slots = 0;
	}

	if (reserve_mem != 0)
		delete reserved;
}

void Mem::loadGameHeader() {
	// Load header
	zmp = (byte *)malloc(64);
	story_fp->seek(0);
	story_fp->read(zmp, 64);

	Common::MemoryReadStream h(zmp, 64);
	loadHeader(h);

	// Calculate story file size in bytes
	if (h_file_size != 0) {
		story_size = (long)2 * h_file_size;

		if (h_version >= V4)
			story_size *= 2;
		if (h_version >= V6)
			story_size *= 2;
	} else {
		// Some old games lack the file size entry
		story_size = story_fp->size();
	}
}

zword Mem::get_header_extension(int entry) {
	zword addr;
	zword val;

	if (h_extension_table == 0 || entry > hx_table_size)
		return 0;

	addr = h_extension_table + 2 * entry;
	LOW_WORD(addr, val);

	return val;   
}

void Mem::set_header_extension(int entry, zword val) {
	zword addr;

	if (h_extension_table == 0 || entry > hx_table_size)
		return;

	addr = h_extension_table + 2 * entry;
	SET_WORD(addr, val);
}

void Mem::restart_header(void) {
	zword screen_x_size;
	zword screen_y_size;
	zbyte font_x_size;
	zbyte font_y_size;

	int i;

	SET_BYTE(H_CONFIG, h_config);
	SET_WORD(H_FLAGS, h_flags);

	if (h_version >= V4) {
		SET_BYTE(H_INTERPRETER_NUMBER, h_interpreter_number);
		SET_BYTE(H_INTERPRETER_VERSION, h_interpreter_version);
		SET_BYTE(H_SCREEN_ROWS, h_screen_rows);
		SET_BYTE(H_SCREEN_COLS, h_screen_cols);
	}

	// It's less trouble to use font size 1x1 for V5 games, especially because of
	// a bug in the unreleased German version of "Zork 1"

	if (h_version != V6) {
		screen_x_size = (zword)h_screen_cols;
		screen_y_size = (zword)h_screen_rows;
		font_x_size = 1;
		font_y_size = 1;
	} else {
		screen_x_size = h_screen_width;
		screen_y_size = h_screen_height;
		font_x_size = h_font_width;
		font_y_size = h_font_height;
	}

	if (h_version >= V5) {
		SET_WORD(H_SCREEN_WIDTH, screen_x_size);
		SET_WORD(H_SCREEN_HEIGHT, screen_y_size);
		SET_BYTE(H_FONT_HEIGHT, font_y_size);
		SET_BYTE(H_FONT_WIDTH, font_x_size);
		SET_BYTE(H_DEFAULT_BACKGROUND, h_default_background);
		SET_BYTE(H_DEFAULT_FOREGROUND, h_default_foreground);
	}

	if (h_version == V6)
		for (i = 0; i < 8; i++)
			storeb((zword)(H_USER_NAME + i), h_user_name[i]);

	SET_BYTE(H_STANDARD_HIGH, h_standard_high);
	SET_BYTE(H_STANDARD_LOW, h_standard_low);

	set_header_extension(HX_FLAGS, hx_flags);
	set_header_extension(HX_FORE_COLOUR, hx_fore_colour);
	set_header_extension(HX_BACK_COLOUR, hx_back_colour);
}

void Mem::storeb(zword addr, zbyte value) {
	if (addr >= h_dynamic_size)
		runtimeError(ERR_STORE_RANGE);

	if (addr == H_FLAGS + 1) {
		// flags register is modified

		h_flags &= ~(SCRIPTING_FLAG | FIXED_FONT_FLAG);
		h_flags |= value & (SCRIPTING_FLAG | FIXED_FONT_FLAG);

		flagsChanged(value);
	}

	SET_BYTE(addr, value);
}

void Mem::storew(zword addr, zword value) {
	storeb((zword)(addr + 0), hi(value));
	storeb((zword)(addr + 1), lo(value));
}

void Mem::free_undo(int count) {
	undo_t *p;

	if (count > undo_count)
		count = undo_count;
	while (count--) {
		p = first_undo;
		if (curr_undo == first_undo)
			curr_undo = curr_undo->next;
		first_undo = first_undo->next;
		free(p);
		undo_count--;
	}
	if (first_undo)
		first_undo->prev = NULL;
	else
		last_undo = NULL;
}

void Mem::reset_memory() {
	story_fp = nullptr;

	if (undo_mem) {
		free_undo(undo_count);
		delete[] undo_mem;
	}

	undo_mem = nullptr;
	undo_count = 0;
	free(zmp);
	zmp = nullptr;
}

long Mem::mem_diff(zbyte *a, zbyte *b, zword mem_size, zbyte *diff) {
	unsigned size = mem_size;
	zbyte *p = diff;
	unsigned j;
	zbyte c = 0;

	for (;;) {
		for (j = 0; size > 0 && (c = *a++ ^ *b++) == 0; j++)
			size--;
		if (size == 0) break;
		size--;
		if (j > 0x8000) {
			*p++ = 0;
			*p++ = 0xff;
			*p++ = 0xff;
			j -= 0x8000;
		}
		if (j > 0) {
			*p++ = 0;
			j--;
			if (j <= 0x7f) {
				*p++ = j;
			} else {
				*p++ = (j & 0x7f) | 0x80;
				*p++ = (j & 0x7f80) >> 7;
			}
		}

		*p++ = c;
		*(b - 1) ^= c;
	}

	return p - diff;
}

void Mem::mem_undiff(zbyte *diff, long diff_length, zbyte *dest) {
	zbyte c;

	while (diff_length) {
		c = *diff++;
		diff_length--;
		if (c == 0) {
			unsigned runlen;

			if (!diff_length)
				return;  // Incomplete run
			runlen = *diff++;
			diff_length--;
			if (runlen & 0x80) {
				if (!diff_length)
					return; // Incomplete extended run
				c = *diff++;
				diff_length--;
				runlen = (runlen & 0x7f) | (((unsigned)c) << 7);
			}

			dest += runlen + 1;
		} else {
			*dest++ ^= c;
		}
	}
}

} // End of namespace Scott
} // End of namespace Glk