/*
 * ttm_unpack: An unpacker for the game "To the Moon"'s datafiles.
 *
 * Copyright (c) 2012, 2021 David Gow <david@ingeniumdigital.com>
 *
 * Permission to use, copy, modify, and/or distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR
 * IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

/*
 * To compile: 	cc -o ttm_unpack ttm_unpack.c
 *
 * To run:	cd <path to To the Moon>
 * 		ttm_unpack [optional packname]
 * 		mv To\ the\ Moon.rgssad To\ the\ Moon.rgssad.old
 */

#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <string.h>
#include <sys/stat.h>

uint32_t decryptState = 0xdeadcafe;

void advanceDecryptor()
{
	decryptState = decryptState * 7 + 3;
}

void extractAll(FILE *packfile)
{
	uint32_t sig;
	fread(&sig,sizeof(sig),1,packfile);
	/* 'RGSS' */
	if (sig != 0x53534752)
	{
		printf("Error: not a valid 'To the Moon' datafile.\n");
		exit(-1);
	}
	fread(&sig,sizeof(sig),1,packfile);
	/* 'AD\0\1' */
	if (sig != 0x01004441)
	{
		printf("Error: not a valid 'To the Moon' datafile.\n");
		exit(-1);
	}

	int numFiles = 0;

	// For each file...
	while (!feof(packfile))
	{
		// Get the length of the filename
		uint32_t fileNameLen;
		fread(&fileNameLen,sizeof(fileNameLen),1,packfile);
		fileNameLen ^= decryptState;
		advanceDecryptor();

		// feof(), of course, won't trigger unless we've tried to read _after_ the
		// end of the file, so re-check here.
		if (feof(packfile)) break;

		// Read and decrypt the filename
		char *fileName = calloc(fileNameLen+1, 1);
		fread(fileName,sizeof(char),fileNameLen,packfile);

		// Better make this compile as c89
		int i;
		for (i = 0; i < fileNameLen; ++i)
		{
			fileName[i] ^= (decryptState & 0xFF);
			advanceDecryptor();

			// A nice hack to mkdir everything.
			if (fileName[i] == '\\')
			{
				fileName[i] = '\0';
#ifdef WIN32
				mkdir(fileName);
#else
				mkdir(fileName, S_IRWXU);
#endif
				fileName[i] = '/';
			}
		}

		printf("Extracting: \"%s\"...\n",fileName);

		// Get the file size
		uint32_t fileSize;
		fread(&fileSize, sizeof(fileSize),1,packfile);
		fileSize ^= decryptState;
		advanceDecryptor();

		// Save off the decryptor state, we need to restore it later
		uint32_t oldDecryptState = decryptState;

		// Open an output file
		FILE *outFile = fopen(fileName,"wb");

		if (!outFile)
		{
			printf("Error: could not create \"%s\".\n",fileName);
			printf("Check that you have write permissions to the current directory.\n");
			printf("Extraction will now halt.\n");
			fclose(packfile);
			exit(-1);
		}

		// Read and decrypt the file
		long idx;
		for (idx = 0; idx < fileSize; ++idx)
		{
			char c = fgetc(packfile);
			char xorValue = ((char*)(&decryptState))[(idx&3)];
			c ^= xorValue;
			fputc(c, outFile);
			if ((idx&3) == 3) advanceDecryptor();
		}
		
		// Close
		fclose(outFile);

		// And finally, restore the decryptor state.
		// This is a bit weird, but seems to have been done
		// to make sure the game has fast random-access to packed
		// files.
		decryptState = oldDecryptState;
		numFiles++;
	}
	printf("Extracted %d files!\n", numFiles);
}

int main(int argc, char **argv)
{
	char *filename = "To the Moon.rgssad";
	if (argc > 1)
	{
		filename = argv[1];
	}
	FILE *packfile = fopen(filename, "rb");
	if (!packfile)
	{
		printf("Error: could not open pack file \"%s\".\n", filename);
		printf("Make sure you're in the game directory.\n");
		return -1;
	}
	extractAll(packfile);
	fclose(packfile);
	return 0;
}