/***************************************************************************
 Copyright (C) 2005 Christoph Reichenbach <reichenb@colorado.edu>

 This program is free software; you can redistribute it and/or
 modify it under the terms of the GNU General Public Licence as
 published by the Free Software Foundaton; either version 2 of the
 Licence, or (at your option) any later version.

 It is distributed in the hope that it will be useful, but
 WITHOUT ANY WARRANTY; without even the implied warranty of
 merchantibility or fitness for a particular purpose. See the
 GNU General Public Licence for more details.

 You should have received a copy of the GNU General Public Licence
 along with this program; see the file COPYING. If not, write to
 the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 Boston, MA 02111-1307, USA.

***************************************************************************/

#define NEED_SCI_VERSIONS
#include "sci/include/versions.h"
#include "sci/include/engine.h"
#include "sci/include/resource.h"
#include "sci/scicore/games.h"
#include "sci/scicore/exe.h"

/* Maxmimum number of bytes to hash from start of file */
#define VERSION_DETECT_HASH_SIZE 1000000

#define VERSION_DETECT_BUF_SIZE 4096

static int
scan_file(char *filename, sci_version_t *version) {
	char buf[VERSION_DETECT_BUF_SIZE];
	char result_string[10]; /* string-encoded result, copied from buf */
	int characters_left;
	int state = 0;
	/* 'state' encodes how far we have matched the version pattern
	**   "n.nnn.nnn"
	**
	**   n.nnn.nnn
	**  0123456789
	**
	** Since we cannot be certain that the pattern does not begin with an
	** alphanumeric character, some states are ambiguous.
	** The pattern is expected to be terminated with a non-alphanumeric
	** character.
	*/

	exe_file_t *f = exe_open(filename);

	if (!f)
		return 1;

	do {
		int i;
		int accept;

		characters_left = exe_read(f, buf, VERSION_DETECT_BUF_SIZE);

		for (i = 0; i < characters_left; i++) {
			const char ch = buf[i];
			accept = 0; /* By default, we don't like this character */

			if (isalnum((unsigned char) ch)) {
				accept = (state != 1
				          && state != 5
				          && state != 9);
			} else if (ch == '.') {
				accept = (state == 1
				          || state == 5);
			} else if (state == 9) {
				result_string[9] = 0; /* terminate string */

				if (!version_parse(result_string, version)) {
					exe_close(f);
					return 0; /* success! */
				}

				/* Continue searching. */
			}

			if (accept)
				result_string[state++] = ch;
			else
				state = 0;

		}

	} while (characters_left == VERSION_DETECT_BUF_SIZE);

	exe_close(f);
	return 1; /* failure */
}

static guint32
read_uint32(byte *data) {
	return (data[0] << 24) | (data[1] << 16) | (data[2] << 8) | data[3];
}

static guint16
read_uint16(byte *data) {
	return (data[0] << 8) | data[1];
}

static int
is_mac_exe(char *filename) {
	FILE *file;
	byte buf[4];
	guint32 val;
	unsigned int i;

	/* Mac executables have no extension */
	if (strchr(filename, '.'))
		return 0;

	file = fopen(filename, "rb");
	if (!file)
		return 0;

	if (fseek(file, 4, SEEK_SET) == -1) {
		fclose(file);
		return 0;
	}

	/* Read resource map offset */
	if (fread(buf, 1, 4, file) < 4) {
		fclose(file);
		return 0;
	}

	val = read_uint32(buf);

	if (fseek(file, val + 28, SEEK_SET) == -1) {
		fclose(file);
		return 0;
	}

	/* Read number of types in map */
	if (fread(buf, 1, 2, file) < 2) {
		fclose(file);
		return 0;
	}

	val = read_uint16(buf) + 1;

	for (i = 0; i < val; i++) {
		if (fread(buf, 1, 4, file) < 4) {
			fclose(file);
			return 0;
		}

		/* Look for executable code */
		if (!memcmp(buf, "CODE", 4)) {
			fclose(file);
			return 1;
		}

		/* Skip to next list entry */
		if (fseek(file, 4, SEEK_CUR) == -1) {
			fclose(file);
			return 0;
		}
	}

	fclose(file);
	return 0;
}

static int
is_exe(char *filename) {
	FILE *file;
	char buf[4];
	unsigned char header[] = {0x00, 0x00, 0x03, 0xf3};

	/* PC and Atari ST executable extensions */
	if (strstr(filename, ".exe") || strstr(filename, ".EXE")
	        || strstr(filename, ".prg") || strstr(filename, ".PRG"))
		return 1;

	/* Check for Amiga executable */
	if (strchr(filename, '.'))
		return 0;

	file = fopen(filename, "rb");
	if (!file)
		return 0;

	if (fread(buf, 1, 4, file) < 4) {
		fclose(file);
		return 0;
	}

	fclose(file);

	/* Check header bytes */
	return memcmp(buf, header, 4) == 0;
}

void
version_require_earlier_than(state_t *s, sci_version_t version) {
	if (s->version_lock_flag)
		return;

	if (version <= s->min_version) {
		sciprintf("Version autodetect conflict: Less than %d.%03d.%03d was requested, but "
		          "%d.%03d.%03d is the current minimum\n",
		          SCI_VERSION_MAJOR(version), SCI_VERSION_MINOR(version), SCI_VERSION_PATCHLEVEL(version),
		          SCI_VERSION_MAJOR(s->min_version), SCI_VERSION_MINOR(s->min_version),
		          SCI_VERSION_PATCHLEVEL(s->min_version));
		return;
	} else if (version < s->max_version) {
		s->max_version = version - 1;
		if (s->max_version < s->version)
			s->version = s->max_version;
	}
}

void
version_require_later_than(state_t *s, sci_version_t version) {
	if (s->version_lock_flag)
		return;

	if (version > s->max_version) {
		sciprintf("Version autodetect conflict: More than %d.%03d.%03d was requested, but less than"
		          "%d.%03d.%03d is required ATM\n",
		          SCI_VERSION_MAJOR(version), SCI_VERSION_MINOR(version), SCI_VERSION_PATCHLEVEL(version),
		          SCI_VERSION_MAJOR(s->max_version), SCI_VERSION_MINOR(s->max_version),
		          SCI_VERSION_PATCHLEVEL(s->max_version));
		return;
	} else if (version > s->min_version) {
		s->min_version = version;
		if (s->min_version > s->version)
			s->version = s->min_version;
	}
}

int
version_parse(const char *vn, sci_version_t *result) {
	char *endptr[3];
	int major = strtol(vn, &endptr[0], 10);
	int minor = strtol(vn + 2, &endptr[1], 10);
	int patchlevel = strtol(vn + 6, &endptr[2], 10);

	if (endptr[0] != vn + 1 || endptr[1] != vn + 5
	        || *endptr[2] != '\0') {
		sciprintf("Warning: Failed to parse version string '%s'\n", vn);
		return 1;
	}

	*result = SCI_VERSION(major, minor, patchlevel);
	return 0;
}

int
version_detect_from_executable(sci_version_t *result) {
	sci_dir_t dir;
	char *filename;
	int mac = 0;

	/* For Mac versions we need to search the resource fork */
	mac = !chdir(".rsrc");

	sci_init_dir(&dir);

	filename = sci_find_first(&dir, "*");

	while (filename) {
		if (mac ? is_mac_exe(filename) : is_exe(filename))
			if (!scan_file(filename, result)) {
				sci_finish_find(&dir);

				if (mac)
					chdir("..");

				return 0;
			}

		filename = sci_find_next(&dir);
	}

	if (mac)
		chdir("..");

	return 1;
}

#define HASHCODE_MAGIC_RESOURCE_000 0x55555555
#define HASHCODE_MAGIC_RESOURCE_001 0x00000001

const char *  /* Original version by Solomon Peachy */
version_guess_from_hashcode(sci_version_t *result, int *res_version, guint32 *code) {
	int i;
	int fd = -1;
	int left = VERSION_DETECT_HASH_SIZE;
	guint32 hash_code;
	guint8 buf[VERSION_DETECT_BUF_SIZE];

	if (IS_VALID_FD(fd = sci_open("resource.001", O_RDONLY | O_BINARY))) {
		hash_code = HASHCODE_MAGIC_RESOURCE_001;
	} else if (IS_VALID_FD(fd = sci_open("resource.000", O_RDONLY | O_BINARY))) {
		hash_code = HASHCODE_MAGIC_RESOURCE_000;
	} else {
		sciprintf("Warning: Could not find RESOURCE.000 or RESOURCE.001, cannot determine hash code\n");
		*code = 0;
		/* complete and utter failure */
		return NULL;
	}

	while (left > 0) {
		int len = read(fd, buf, left < VERSION_DETECT_BUF_SIZE ? left : VERSION_DETECT_BUF_SIZE);

		if (len == -1) {
			sciprintf("Warning: read error while computing hash code for resource file\n");
			*code = 0;
			return NULL;
		}

		if (len == 0)
			/* EOF */
			break;

		for (i = 0; i < len; i++)
			hash_code = (hash_code * 19) + *(buf + i);

		/* This is the string hashing algorithm used by Objective Caml 3.08; the general idea
		** of multiplying the previous hash code with a prime number between 5 and 23 appears
		** to be generally considered to be a "good" approach to exhausting the entire 32 bit
		** number space in a somewhat equal distribution. For large chunks of data, such as
		** SCI resource files, this should both perform well and yield a good distribution,
		** or at least that's what standard library designers have been assuming for quite a
		** while. */

		left -= len;
	}

	close(fd);

	*code = hash_code;

	for (i = 0 ; sci_games[i].name ; i++) {
		if ((unsigned int)sci_games[i].id == hash_code) {
			*result = sci_games[i].version;
			*res_version = sci_games[i].res_version;
			return sci_games[i].name;
		}
	}

	return NULL; /* Failed to find matching game */
}


#undef VERSION_DETECT_BUF_SIZE