/*
 * Rollcage Stage II Bump Map Fix - by InDigo176
 * 2009-12-29
 *
 * This patch basically just adds
 *  if (esi == 9) {
 *      esi--;
 *  }
 * to be run before every call to SetTextureStageState(ecx, edx, esi);
 *
 * The problem is that the game is using D3DTOP_ADDSIGNED2X (9) instead of
 * just D3DTOP_ADDSIGNED (8).
 *
 */

#include <stdio.h>
#include <malloc.h>
#include <tchar.h>
#define WIN32_LEAN_AND_MEAN /* skip rarely used stuff */
#include <windows.h>

#define TITLE "Rollcage Stage II Bump Map Fix - by InDigo176"

char *get_path(size_t *maxlen);
void show_error(const char *msg);

int APIENTRY _tWinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
        LPTSTR lpCmdLine, int nCmdShow)
{
    size_t maxlen = 32768; /* max path length */
    char *path = NULL;
    FILE *fd = NULL;

    /* this is the jump to the payload we're going to add
     * JMP 004B3C2E */
    const unsigned char jump_to_hack[5] = {0xE9, 0xBB, 0x8C, 0x02, 0x00}; 

    /* this is the payload placed below the original code
     * it also contains operations that got overwritten by the jump */
    const unsigned char hack[16] = {0x83, 0xFE, 0x09, /* CMP ESI,9 */
                                    0x75, 0x01,       /* JNZ SHORT +01 */
                                    0x4E,             /* DEC ESI */

                                    /* these below got overwritten by the
                                     * jump and need to be placed back */
                                    0x56,             /* PUSH ESI */
                                    0x52,             /* PUSH EDX */
                                    0x51,             /* PUSH ECX */
                                    0x8B, 0x18,       /* MOV EBX,[EAX] */

                                    /* JMP 0048AF73 (jump back) */
                                    0xE9, 0x35, 0x73, 0xFD, 0xFF};

    path = get_path(&maxlen);
    if (!path) {
        show_error("Cannot locate Rollcage Stage II!\n"
            "Please make sure it is installed.");
        return FALSE;
    }

    strcpy(path+maxlen-1, "\\BIN\\Rollcage D3D.exe");

    fd = fopen(path, "r+b");
    if (!fd) {
        show_error("Cannot open file!\nTry running this patch as "
            "Administrator and make sure Rollcage Stage "
            "II is installed correctly.");
        return FALSE;
    }
    free(path);

    /* add the jump */
    if (fseek(fd, 0x0008AF6EL, SEEK_SET) != 0) {
        show_error("Unexpected read error.");
        return FALSE;
    }
    switch (fgetc(fd)) { 
        case 0x56: /* PUSH ESI */
            break;
        case 0xE9: /* JMP */
            MessageBoxA(NULL, "Patch already applied.", TITLE,
                MB_ICONINFORMATION|MB_OK);
            return FALSE;
        default:
            show_error("Wrong version of Rollcage Stage II installed.\n"
                "Please install v1.0c patch first!");
            return FALSE;
    }
    if (fseek(fd, -1L, SEEK_CUR) != 0) {
        show_error("Unexpected read error.");
        return FALSE;
    }
    if (fwrite(jump_to_hack, 1, 5, fd) != 5 || fflush(fd) != 0) {
        show_error("Unexpected write error.");
        return FALSE;
    }
    
    /* add the payload */
    if (fseek(fd, 0x000B3C2EL, SEEK_SET) != 0) {
        show_error("Unexpected read error.");
        return FALSE;
    }
    if (fgetc(fd) != 0x00) { /* just an extra check */
        show_error("Wrong version of Rollcage Stage II installed.\n"
            "Please install v1.0c patch first!");
        return FALSE;
    }
    if (fseek(fd, -1L, SEEK_CUR) != 0) {
        show_error("Unexpected read error.");
        return FALSE;
    }
    if (fwrite(hack, 1, 16, fd) != 16 || fflush(fd) != 0) {
        show_error("Unexpected write error.");
        return FALSE;
    }

    if (fclose(fd) != 0) {
        MessageBoxA(NULL, "Something went wrong!\n"
            "The patch maybe didn't get applied.", TITLE, MB_ICONWARNING|MB_OK);
        return FALSE;
    }
    
    MessageBoxA(NULL, "Patch applied successfully!", TITLE,
        MB_ICONINFORMATION|MB_OK);

    return FALSE;
}

char *get_path(size_t *maxlen) {
    HKEY hkey;
    char *path;

    if (RegOpenKeyExA(HKEY_LOCAL_MACHINE,
        "Software\\Psygnosis\\Rollcage Stage II\\Installer", 0,
        KEY_READ, &hkey) != ERROR_SUCCESS) {
            return NULL;
    }
    
    path = malloc(*maxlen);
    if (!path) {
        return NULL;
    }

    *maxlen -= 21; /* ensure there's space for "\BIN\Rollcage D3D.exe" */

    if (RegQueryValueExA(hkey, "Destination", NULL, NULL,
        (LPBYTE)path, (LPDWORD)maxlen) != ERROR_SUCCESS) {
            free(path);
            path = NULL;
    }
    RegCloseKey(hkey);

    return path;
}

void show_error(const char *msg) {
    MessageBoxA(NULL, msg, TITLE, MB_ICONERROR|MB_OK);
}