#include "3dstypes.h"
#include "3ds.h"
#include "draw.h"
#include "libc.h"
#include "crypto.h"
#include "FS.h"

extern void *start_addr;
extern void *end_addr;

/*
4 bytes number of entries
entry:
    16 bytes CTR
    16 bytes keyY
    4 bytes length in megabytes(round up)
    64 bytes output filename in utf16(could use something like "/ncchcode1.romfs.xorpad")

#define entry_ctr 0+4 //+4 because first int in the array is not an entry
#define entry_keyY 16+4
#define entry_megabytes 32+4
#define entry_filename 36+4
*/

struct ncch_info_entry {
    uint8_t  CTR[16];
    uint8_t  keyY[16];
    uint32_t size_mb;
    wchar_t  filename[32];
};

struct ncch_info {
    uint32_t n_entries;
    struct ncch_info_entry entries[20];
};

void ncch_info_createpad(struct ncch_info_entry *info)
{
    #define BUFFER_ADDR ((volatile uint8_t*)0x20000000)
    #define BLOCK_SIZE  (0x10000)

    uint32_t handle = FileOpen(info->filename);
    setup_aeskey(0x2C, AES_BIG_INPUT|AES_NORMAL_INPUT, info->keyY);
    use_aeskey(0x2C);

    uint8_t ctr[16];
    memcpy(ctr, info->CTR, 16);

    uint8_t zero_buf[16];
    uint32_t size_bytes = info->size_mb*1024*1024;
    uint32_t i, j;
    for (i = 0; i < size_bytes; i += BLOCK_SIZE) {
        for (j = 0; (j < BLOCK_SIZE) && (i+j < size_bytes); j+= 16) {
            memset(zero_buf, 0, 16);
            set_ctr(AES_BIG_INPUT|AES_NORMAL_INPUT, ctr);
            aes_decrypt(zero_buf, (void*)BUFFER_ADDR+j, ctr, 1);
            add_ctr(ctr, 1);
        }
        FlushProcessDataCache(0xFFFF8001, (void*)BUFFER_ADDR, BLOCK_SIZE);
        FileWriteOffset(handle, (void*)BUFFER_ADDR, BLOCK_SIZE, i);
    }
}

static volatile u32 runOnce = 1;
int main()
{
    while(!runOnce) {};
    runOnce = 0;
    FlushProcessDataCache(0xFFFF8001, (void*)start_addr, start_addr-end_addr);
    ClearScreen(0x0);
    DEBUG("3DS CTR DECRYPTOR by VOiD, refactored by xerpi");

    struct ncch_info info;

    DEBUG("Opening /ncchinfo.bin ...");
    u32 handle = FileOpen(L"/ncchinfo.bin");
    FileRead(handle, &info, 4); //Read number of entries
    DEBUG("\tDone!");

    if (!info.n_entries || info.n_entries > 20) {
        ERROR("Nothing to do.(%i) :/", info.n_entries);
        return 0;
    }
    FileRead(handle, &info, sizeof(struct ncch_info));
    DEBUG("Found %i entries", info.n_entries);

    int i;
    for(i = 0; i < info.n_entries; i++) {
        /*createpad(info.entries[i].CTR,
                  info.entries[i].keyY,
                  info.entries[i].filename,
                  info.entries[i].size_mb,
                  i+1);*/
        DEBUG("Creating pad %i, size: %iMB ...", i+1, info.entries[i].filename);
        ncch_info_createpad(&info.entries[i]);
        DEBUG("\tDone!");
    }

    DEBUG("Finished!");
    return 0;
}