#include <iostream>
#include <fstream>
#include <cstring>

struct Patch
{
    char *orig;
    char *patch;
    int size;
};

char * memmem(char *src, int src_size, char *pattern, int pattern_size);

int main(int argc, char **argv)
{
    const static Patch PATCHES[] = {
                                     //Patches for map tooltip

                                     //Is unplayable religion
                                     {
                                       {
                                         "\x80\x78\x71\x00" //CMP [EAX+71], 0
                                         "\x0F\x85\xD7\x00\x00\x00" //JNE +0xD7
                                       },
                                       {
                                         "\x80\x78\x71\x00" //CMP [EAX+71], 0
                                         "\xE9\xD8\x00\x00\x00" //JMP +0xD8
                                         "\x90" //NOP
                                       },
                                       10
                                     },
                                     //Is a republic
                                     {
                                       {
                                         "\x83\xFE\x01" //CMP ESI, 1
                                         "\x0F\x85\x36\x01\x00\x00" //JNE +0x136
                                       },
                                       {
                                         "\x83\xFE\x01" //CMP ESI, 1
                                         "\xE9\x37\x01\x00\x00" //JMP +0x137
                                         "\x90" //NOP
                                       },
                                       9
                                     },
                                     //Is a theocracy
                                     {
                                       {
                                         "\x83\xFE\x02" //CMP ESI, 2
                                         "\x74\x33" //JE +0x33
                                       },
                                       {
                                         "\x83\xFE\x02" //CMP ESI, 2
                                         "\x90" //NOP
                                         "\x90" //NOP
                                       },
                                       5
                                     },
                                     //Playable test? - jumps to RETN
                                     {
                                       {
                                         "\x80\xB8\xF8\x02\x00\x00\x00" //CMP [EAX+2F8], 0
                                         "\x0F\x84\x23\xFD\xFF\xFF" //JE -0x2DD
                                       },
                                       {
                                         "\x80\xB8\xF8\x02\x00\x00\x00" //CMP [EAX+2F8], 0
                                         "\xE9\x24\xFD\xFF\xFF" //JMP -0x2DC
                                         "\x90" //NOP
                                       },
                                       13
                                     },

                                     //Patches for "Play" button

                                     //Is a theocracy
                                     {
                                       {
                                         "\x38\x98\xF8\x02\x00\x00" //CMP [EAX+2F8], BL
                                         "\x0F\x85\x15\x01\x00\x00" //JNE +0x115
                                       },
                                       {
                                         "\x38\x98\xF8\x02\x00\x00" //CMP [EAX+2F8], BL
                                         "\x90" //NOP
                                         "\x90" //NOP
                                         "\x90" //NOP
                                         "\x90" //NOP
                                         "\x90" //NOP
                                         "\x90" //NOP
                                       },
                                       12
                                     },
                                     //Is unplayable religion
                                     //Is a republic
                                     {
                                       {
                                         "\x0F\x84\xAD\x00\x00\x00" //JE +0xAD
                                         "\x39\x5D\xE8" //CMP [EBP-18], BL
                                         "\x0F\x85\xA4\x00\x00\x00" //JNE +0xA4
                                       },
                                       {
                                         "\x90" //NOP
                                         "\x90" //NOP
                                         "\x90" //NOP
                                         "\x90" //NOP
                                         "\x90" //NOP
                                         "\x90" //NOP
                                         "\x39\x5D\xE8" //CMP [EBP-18], BL
                                         "\x90" //NOP
                                         "\x90" //NOP
                                         "\x90" //NOP
                                         "\x90" //NOP
                                         "\x90" //NOP
                                         "\x90" //NOP
                                       },
                                       15
                                     },
                                     //Unplayable tooltip on button hover
                                     {
                                       {                                           
                                         "\x3B\xF3" //CMP ESI, EBX
                                         "\x0F\x84\x87\x07\x00\x00" //JE +0x787
                                       },
                                       {
                                         "\x3B\xF3"  //CMP ESI, EBX
                                         "\xE9\x88\x07\x00\x00"  //JMP +0x788
                                         "\x90" //NOP
                                       },
                                       8
                                     },
                                   };

    const static int NUM_PATCHES = 7;

    if (argc != 3)
    {
        std::cerr << "Invalid arguments" << std::endl;
        std::cerr << "Usage: " << argv[0] << " " << "<input file> <output file>" << std::endl;
        return 1;
    }

    std::fstream in_file;

    in_file.open(argv[1], std::ios::in | std::ios::binary | std::ios::ate);

    if (!in_file.is_open())
    {
        std::cerr << "Unable to open " << argv[1] << " for reading" << std::endl;
        return 1;
    }

    int file_size = in_file.tellg();
    char *buf = new char[file_size];

    in_file.seekg(0, std::ios::beg);
    in_file.read(buf, file_size);

    in_file.close();

    char *patch_point;

    for (int i = 0; i < NUM_PATCHES; i++)
    {
        const Patch *p = &PATCHES[i];
        patch_point = memmem(buf, file_size, p->orig, p->size);
        if (patch_point != NULL)
        {
            std::cout << "Patching " << p->size << " bytes at offset " << (int) patch_point - (int) buf << std::endl;
            std::memcpy(patch_point, p->patch, p->size);
        }
        else 
        {
            std::cerr << "Failed to find patch location " << i << ", dying" << std::endl;
            return 1;
        }
    }

    std::fstream out_file;

    out_file.open(argv[2], std::ios::out | std::ios::binary | std::ios::trunc);

    if (!out_file.is_open())
    {
        std::cerr << "Unable to open " << argv[2] << " for writing" << std::endl;
        return 1;
    }

    out_file.write(buf, file_size);

    out_file.close();

    delete[] buf;

	return 0;
}

char * memmem(char *src, int src_size, char *pattern, int pattern_size) 
{
    char *pos = src;

    do 
    {

        pos = (char *) std::memchr(pos, pattern[0], src + src_size - pos);
        if (pos != NULL)
        {
            if (pos + pattern_size < src + src_size)
            {
                if (std::memcmp(pos, pattern, pattern_size) == 0)
                {
                    break;
                } else
                {
                    pos++;
                }
            }
            else
            {
                pos = NULL;
            }
        }
    } while (pos != NULL);

    return pos;
}