/*
    Copyright 2016-2021 Arisotura

    This file is part of melonDS.

    melonDS 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 3 of the License, or (at your option)
    any later version.

    melonDS 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 melonDS. If not, see http://www.gnu.org/licenses/.
*/

#include <stdio.h>

#include "DSi.h"
#include "DSi_AES.h"
#include "DSi_NAND.h"

#include "sha1/sha1.hpp"
#include "tiny-AES-c/aes.hpp"

#include "fatfs/ff.h"


namespace DSi_NAND
{

u8 FATIV[16];
u8 FATKey[16];

u8 ESKey[16];


void Init()
{
    // init NAND crypto

    SHA1_CTX sha;
    u8 tmp[20];
    u8 keyX[16], keyY[16];

    SHA1Init(&sha);
    SHA1Update(&sha, DSi::eMMC_CID, 16);
    SHA1Final(tmp, &sha);

    DSi_AES::Swap16(FATIV, tmp);

    *(u32*)&keyX[0] = (u32)DSi::ConsoleID;
    *(u32*)&keyX[4] = (u32)DSi::ConsoleID ^ 0x24EE6906;
    *(u32*)&keyX[8] = (u32)(DSi::ConsoleID >> 32) ^ 0xE65B601D;
    *(u32*)&keyX[12] = (u32)(DSi::ConsoleID >> 32);

    *(u32*)&keyY[0] = 0x0AB9DC76;
    *(u32*)&keyY[4] = 0xBD4DC4D3;
    *(u32*)&keyY[8] = 0x202DDD1D;
    *(u32*)&keyY[12] = 0xE1A00005;

    DSi_AES::DeriveNormalKey(keyX, keyY, tmp);
    DSi_AES::Swap16(FATKey, tmp);


    *(u32*)&keyX[0] = 0x4E00004A;
    *(u32*)&keyX[4] = 0x4A00004E;
    *(u32*)&keyX[8] = (u32)(DSi::ConsoleID >> 32) ^ 0xC80C4B72;
    *(u32*)&keyX[12] = (u32)DSi::ConsoleID;

    memcpy(keyY, &DSi::ARM7iBIOS[0x8308], 16);

    DSi_AES::DeriveNormalKey(keyX, keyY, tmp);
    DSi_AES::Swap16(ESKey, tmp);
}


void SetupFATCrypto(AES_ctx* ctx, u32 ctr)
{
    u8 iv[16];
    memcpy(iv, FATIV, 16);

    u32 res;
    res = iv[15] + (ctr & 0xFF);
    iv[15] = (res & 0xFF);
    res = iv[14] + ((ctr >> 8) & 0xFF) + (res >> 8);
    iv[14] = (res & 0xFF);
    res = iv[13] + ((ctr >> 16) & 0xFF) + (res >> 8);
    iv[13] = (res & 0xFF);
    res = iv[12] + (ctr >> 24) + (res >> 8);
    iv[12] = (res & 0xFF);
    iv[11] += (res >> 8);
    for (int i = 10; i >= 0; i--)
    {
        if (iv[i+1] == 0) iv[i]++;
        else break;
    }

    AES_init_ctx_iv(ctx, FATKey, iv);
}

u32 ReadFATBlock(u64 addr, u32 len, u8* buf)
{
    u32 ctr = (u32)(addr >> 4);

    AES_ctx ctx;
    SetupFATCrypto(&ctx, ctr);

    fseek(DSi::SDMMCFile, addr, SEEK_SET);
    u32 res = fread(buf, len, 1, DSi::SDMMCFile);
    if (!res) return 0;

    for (u32 i = 0; i < len; i += 16)
    {
        u8 tmp[16];
        DSi_AES::Swap16(tmp, &buf[i]);
        AES_CTR_xcrypt_buffer(&ctx, tmp, 16);
        DSi_AES::Swap16(&buf[i], tmp);
    }

    return len;
}

u32 WriteFATBlock(u64 addr, u32 len, u8* buf)
{
    u32 ctr = (u32)(addr >> 4);

    AES_ctx ctx;
    SetupFATCrypto(&ctx, ctr);

    fseek(DSi::SDMMCFile, addr, SEEK_SET);

    for (u32 s = 0; s < len; s += 0x200)
    {
        u8 tempbuf[0x200];

        for (u32 i = 0; i < 0x200; i += 16)
        {
            u8 tmp[16];
            DSi_AES::Swap16(tmp, &buf[s+i]);
            AES_CTR_xcrypt_buffer(&ctx, tmp, 16);
            DSi_AES::Swap16(&tempbuf[i], tmp);
        }

        u32 res = fwrite(tempbuf, len, 1, DSi::SDMMCFile);
        if (!res) return 0;
    }

    return len;
}


UINT FF_ReadNAND(BYTE* buf, LBA_t sector, UINT num)
{
    // TODO: allow selecting other partitions?
    u64 baseaddr = 0x10EE00;

    u64 blockaddr = baseaddr + (sector * 0x200ULL);

    u32 res = ReadFATBlock(blockaddr, num*0x200, buf);
    return res >> 9;
}

UINT FF_WriteNAND(BYTE* buf, LBA_t sector, UINT num)
{
    // TODO: allow selecting other partitions?
    u64 baseaddr = 0x10EE00;

    u64 blockaddr = baseaddr + (sector * 0x200ULL);

    u32 res = WriteFATBlock(blockaddr, num*0x200, buf);
    return res >> 9;
}


bool ESDecrypt(u8* data, u32 len)
{
    AES_ctx ctx;
    u8 iv[16];
    u8 mac[16];

    iv[0] = 0x02;
    for (int i = 0; i < 12; i++) iv[1+i] = data[len+0x1C-i];
    iv[13] = 0x00;
    iv[14] = 0x00;
    iv[15] = 0x01;

    AES_init_ctx_iv(&ctx, ESKey, iv);

    u32 blklen = (len + 0xF) & ~0xF; printf("blk=%x\n", blklen);
    mac[0] = 0x3A;
    for (int i = 1; i < 13; i++) mac[i] = iv[i];
    mac[13] = (blklen >> 16) & 0xFF;
    mac[14] = (blklen >> 8) & 0xFF;
    mac[15] = blklen & 0xFF;

    AES_ECB_encrypt(&ctx, mac);

    u32 coarselen = len & ~0xF;
    for (u32 i = 0; i < coarselen; i += 16)
    {
        u8 tmp[16];

        DSi_AES::Swap16(tmp, &data[i]);

        AES_CTR_xcrypt_buffer(&ctx, tmp, 16);
        for (int i = 0; i < 16; i++) mac[i] ^= tmp[i];
        AES_ECB_encrypt(&ctx, mac);

        DSi_AES::Swap16(&data[i], tmp);
    }

    u32 remlen = len - coarselen;
    if (remlen)
    {
        u8 rem[16];

        u32 ivnum = (coarselen >> 4) + 1;
        iv[13] = (ivnum >> 16) & 0xFF;
        iv[14] = (ivnum >> 8) & 0xFF;
        iv[15] = ivnum & 0xFF;

        memset(rem, 0, 16);
        AES_ctx_set_iv(&ctx, iv);
        AES_CTR_xcrypt_buffer(&ctx, rem, 16);

        for (int i = 0; i < remlen; i++)
            rem[15-i] = data[coarselen+i];

        AES_ctx_set_iv(&ctx, iv);
        AES_CTR_xcrypt_buffer(&ctx, rem, 16);
        for (int i = 0; i < 16; i++) mac[i] ^= rem[i];
        AES_ECB_encrypt(&ctx, mac);

        for (int i = 0; i < remlen; i++)
            data[coarselen+i] = rem[15-i];
    }

    ctx.Iv[13] = 0x00;
    ctx.Iv[14] = 0x00;
    ctx.Iv[15] = 0x00;
    AES_CTR_xcrypt_buffer(&ctx, mac, 16);

    u8 footer[16];

    iv[0] = 0x00;
    iv[1] = 0x00;
    iv[2] = 0x00;
    for (int i = 0; i < 12; i++) iv[3+i] = data[len+0x1C-i];
    iv[15] = 0x00;

    for (int i = 0; i < 16; i++)
        footer[15-i] = data[len+0x10+i];

    AES_ctx_set_iv(&ctx, iv);
    AES_CTR_xcrypt_buffer(&ctx, footer, 16);

    data[len+0x10] = footer[15];
    data[len+0x1D] = footer[2];
    data[len+0x1E] = footer[1];
    data[len+0x1F] = footer[0];

    u32 footerlen = footer[0] | (footer[1] << 8) | (footer[2] << 16);
    if (footerlen != len)
    {
        printf("ESDecrypt: bad length %d (expected %d)\n", len, footerlen);
        return false;
    }

    for (int i = 0; i < 16; i++)
    {
        if (data[len+i] != mac[15-i])
        {
            printf("ESDecrypt: bad MAC\n");
            return false;
        }
    }

    return true;
}


void PatchTSC()
{
    ff_disk_open(FF_ReadNAND, FF_WriteNAND);

    FRESULT res;
    FATFS fs;
    res = f_mount(&fs, "0:", 0);
    if (res != FR_OK)
    {
        printf("NAND mounting failed: %d\n", res);
        goto mount_fail;
    }

    for (int i = 0; i < 2; i++)
    {
        char filename[64];
        sprintf(filename, "0:/shared1/TWLCFG%d.dat", i);

        FIL file;
        res = f_open(&file, filename, FA_OPEN_EXISTING | FA_READ | FA_WRITE);
        if (res != FR_OK)
        {
            printf("NAND: editing file %s failed: %d\n", filename, res);
            continue;
        }

        u8 contents[0x1B0];
        u32 nres;
        f_lseek(&file, 0);
        f_read(&file, contents, 0x1B0, &nres);

        // fix touchscreen coords
        *(u16*)&contents[0xB8] = 0;
        *(u16*)&contents[0xBA] = 0;
        contents[0xBC] = 0;
        contents[0xBD] = 0;
        *(u16*)&contents[0xBE] = 255<<4;
        *(u16*)&contents[0xC0] = 191<<4;
        contents[0xC2] = 255;
        contents[0xC3] = 191;

        SHA1_CTX sha;
        SHA1Init(&sha);
        SHA1Update(&sha, &contents[0x88], 0x128);
        SHA1Final(&contents[0], &sha);

        f_lseek(&file, 0);
        f_write(&file, contents, 0x1B0, &nres);

        f_close(&file);
    }

mount_fail:
    f_unmount("0:");
    ff_disk_close();
}


void ImportTest()
{
    char* tmdfile = "cavestory.tmd";
    char* appfile = "cavestory.nds";

    ff_disk_open(FF_ReadNAND, FF_WriteNAND);

    FRESULT res;
    FATFS fs;
    res = f_mount(&fs, "0:", 0);
    if (res != FR_OK)
    {
        printf("NAND mounting failed: %d\n", res);
        f_unmount("0:");
        ff_disk_close();
        return;
    }

    u8 tmd[0x208];
    {
        FILE* f = fopen(tmdfile, "rb");
        fread(tmd, 0x208, 1, f);
        fclose(f);
    }

    u8 version = tmd[0x1E7];
    printf(".app version: %08x\n", version);

    {
        DIR ticketdir;
        FILINFO info;
        FRESULT res;

        res = f_opendir(&ticketdir, "0:/ticket/00030004");
        printf("dir res: %d\n", res);

        res = f_readdir(&ticketdir, &info);
        if (res)
        {
            printf("bad read res: %d\n", res);
        }

        if (!info.fname[0])
        {
            printf("VERY BAD!! DIR IS EMPTY\n");
            // TODO ERROR MANAGEMENT!!
        }

        printf("- %s\n", info.fname);
        char ticketfname[128];
        sprintf(ticketfname, "0:/ticket/00030004/%s", info.fname);

        f_closedir(&ticketdir);

        FIL ticketfile;
        res = f_open(&ticketfile, ticketfname, FA_OPEN_EXISTING | FA_READ);
        //

        u8 ticket[708];
        u32 nread;
        f_read(&ticketfile, ticket, 708, &nread);
        //

        f_close(&ticketfile);

        // DECRYPT!!
        /*{
            u8 iv[16];

            iv[0] = 0x02;
            for (int i = 0; i < 12; i++) iv[1+i] = ticket[0x2A4 + 0x1C - i];
            iv[13] = 0x00;
            iv[14] = 0x00;
            iv[15] = 0x01;

            AES_ctx aes;
            AES_init_ctx_iv(&aes, ESKey, iv);

            for (u32 i = 0; i < 0x290; i += 16)
            {
                u8 tmp[16];

                DSi_AES::Swap16(tmp, &ticket[i]);
                AES_CTR_xcrypt_buffer(&aes, tmp, 16);
                DSi_AES::Swap16(&ticket[i], tmp);
            }
        }*/
        ESDecrypt(ticket, 0x2A4);

        FILE* dorp = fopen("assticket.bin", "wb");
        fwrite(ticket, 708, 1, dorp);
        fclose(dorp);
    }

    f_unmount("0:");
    ff_disk_close();
}

}