/*
 * Copyright (C) 2017 hatkirby
 * Copyright (C) 2017 slipstream/RoL
 * Copyright (C) 2016 FIX94
 *
 * This software may be modified and distributed under the terms
 * of the MIT license.  See the LICENSE file for details.
 */
#include <gccore.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <malloc.h>
#include "link.h"
#include "encoding.h"

//from my tests 50us seems to be the lowest
//safe si transfer delay in between calls
#define SI_TRANS_DELAY 50

extern u8 gba_mb_gba[];
extern u32 gba_mb_gba_size;

void printmain()
{
  printf("\x1b[2J");
  printf("\x1b[37m");
  printf("Pokemon Gen III Data Extractor by hatkirby\n");
  printf("Based on gba-gen3multiboot by slipstream/RoL\n");
  printf("Based on GBA Link Cable Dumper v1.6 by FIX94\n");
}

u8 *resbuf,*cmdbuf;

volatile u32 transval = 0;
void transcb(s32 chan, u32 ret)
{
  transval = 1;
}

volatile u32 resval = 0;
void acb(s32 res, u32 val)
{
  resval = val;
}

unsigned int docrc(u32 crc,u32 val)
{
  u32 result;

  result = val ^ crc;
  for (int i = 0; i < 0x20; i++)
  {
    if (result & 1)
    {
      result >>= 1;
      result ^= 0xA1C1;
    } else {
      result >>= 1;
    }
  }

  return result;
}

void doreset()
{
  cmdbuf[0] = 0xFF; //reset
  transval = 0;
  SI_Transfer(1, cmdbuf, 1, resbuf, 3, transcb, SI_TRANS_DELAY);

  while (transval == 0);
}

void getstatus()
{
  cmdbuf[0] = 0; //status
  transval = 0;
  SI_Transfer(1, cmdbuf, 1, resbuf, 3, transcb, SI_TRANS_DELAY);

  while (transval == 0);
}

void endproc()
{
  doreset();
  printf("Start pressed, exit\n");
  VIDEO_WaitVSync();
  VIDEO_WaitVSync();
  exit(0);
}

u32 recv()
{
  memset(resbuf,0,32);
  cmdbuf[0]=0x14; //read
  transval = 0;
  SI_Transfer(1, cmdbuf, 1, resbuf, 5, transcb, SI_TRANS_DELAY);

  while (transval == 0);
  printf("%08lx\n", *(vu32*)resbuf);
  return *(vu32*)resbuf;
}

void send(u32 msg)
{
  cmdbuf[0] = 0x15;
  cmdbuf[1] = (msg >> 0) & 0xFF;
  cmdbuf[2] = (msg >> 8) & 0xFF;
  cmdbuf[3] = (msg >> 16) & 0xFF;
  cmdbuf[4] = (msg >> 24) & 0xFF;

  transval = 0;
  resbuf[0] = 0;
  SI_Transfer(1, cmdbuf, 5, resbuf, 1, transcb, SI_TRANS_DELAY);

  while (transval == 0);
}

void warnError(char *msg)
{
  puts(msg);
  VIDEO_WaitVSync();
  VIDEO_WaitVSync();
  sleep(2);
}

void fatalError(char *msg)
{
  puts(msg);
  VIDEO_WaitVSync();
  VIDEO_WaitVSync();
  sleep(5);
  exit(0);
}

u32 genKeyA()
{
  u32 retries = 0;

  for (;;)
  {
    u32 key = 0;

    if (retries > 32)
    {
      key = 0xDD654321;
    } else {
      key = (rand() & 0x00ffffff) | 0xDD000000;
    }

    u32 unk = (key % 2 != 0);
    u32 v12 = key;
    for (u32 v13 = 1; v13 < 32; v13++)
    {
      v12 >>= 1;
      unk += (v12 % 2 != 0);
    }

    if ((unk >= 10 && unk <= 24))
    {
      if (retries > 4)
      {
        printf("KeyA retries = %ld", retries);
      }

      printf("KeyA = 0x%08lx\n", key);

      return key;
    }

    retries++;
  }
}

u32 checkKeyB(u32 KeyBRaw)
{
  if ((KeyBRaw & 0xFF) != 0xEE)
  {
    printf("Invalid KeyB - lowest 8 bits should be 0xEE, actually 0x%02x\n",
        ((u8)(KeyBRaw)));

    return 0;
  }

  u32 KeyB = KeyBRaw & 0xffffff00;
  u32 val = KeyB;
  u32 unk = (val < 0);
  for (u32 i = 1; i < 24; i++)
  {
    val <<= 1;
    unk += (val < 0);
  }

  if (unk > 14)
  {
    printf("Invalid KeyB - high 24 bits bad: 0x%08lx\n", KeyB);

    return 0;
  }

  printf("Valid KeyB: 0x%08lx\n", KeyB);

  return KeyB;
}

u32 deriveKeyC(u32 keyCderive, u32 kcrc)
{
  u32 keyc = 0;
  u32 keyCi = 0;

  do
  {
    u32 v5 = 0x1000000 * keyCi - 1;
    u32 keyCattempt = docrc(kcrc,v5);

    if (keyCderive == keyCattempt)
    {
      keyc = v5;

      printf("Found keyC: %08lx\n",keyc);

      return keyc;
    }

    keyCi++;
  } while (keyCi < 256);

  return keyc;
}

u32 getMsg()
{
  u32 val = 0;
  while (val == 0)
  {
    val = __builtin_bswap32(recv());
    sleep(1);
  }

  send(0);
  while (recv()!=0) {sleep(1);};
  send(0);

  return val;
}

int main(int argc, char *argv[])
{
  void *xfb = NULL;
  GXRModeObj *rmode = NULL;
  VIDEO_Init();
  rmode = VIDEO_GetPreferredMode(NULL);
  xfb = MEM_K0_TO_K1(SYS_AllocateFramebuffer(rmode));
  VIDEO_Configure(rmode);
  VIDEO_SetNextFramebuffer(xfb);
  VIDEO_SetBlack(FALSE);
  VIDEO_Flush();
  VIDEO_WaitVSync();
  if(rmode->viTVMode&VI_NON_INTERLACE) VIDEO_WaitVSync();
  int x = 24, y = 32, w, h;
  w = rmode->fbWidth - (32);
  h = rmode->xfbHeight - (48);
  CON_InitEx(rmode, x, y, w, h);
  VIDEO_ClearFrameBuffer(rmode, xfb, COLOR_BLACK);
  PAD_Init();
  cmdbuf = memalign(32,32);
  resbuf = memalign(32,32);

  for (;;)
  {
    printmain();

    printf("Press A to begin, press Start to quit.\n");
    if (waitForButtons(PAD_BUTTON_A | PAD_BUTTON_START) & PAD_BUTTON_START)
    {
      endproc();
    }

    printf("Waiting for a GBA in port 2...\n");
    resval = 0;

    SI_GetTypeAsync(1,acb);
    while(1)
    {
      if (resval)
      {
        if (resval == 0x80 || resval & 8)
        {
          resval = 0;
          SI_GetTypeAsync(1,acb);
        } else if (resval)
        {
          break;
        }
      }

      PAD_ScanPads();
      VIDEO_WaitVSync();
      if (PAD_ButtonsHeld(0) & PAD_BUTTON_START)
      {
        getstatus();
        endproc();
      }
    }

    if (resval & SI_GBA)
    {
      printf("GBA Found! Waiting on BIOS\n");

      resbuf[2]=0;

      // wait for the BIOS to hand over to the game
      do
      {
        doreset();
      } while (!(resbuf[1] > 4));

      printf("BIOS handed over to game, waiting on game\n");

      do
      {
        doreset();
      } while ((resbuf[0] != 0) || !(resbuf[2] & 0x10));

      // receive the game-code from GBA side.
      u32 gamecode = recv();

      printf("Ready, sending multiboot ROM\n");

      unsigned int sendsize = ((gba_mb_gba_size+7)&~7);

      // generate KeyA
      unsigned int ourkey = genKeyA();

      //printf("Our Key: %08x\n", ourkey);
      printf("Sending game code that we got: 0x%08lx\n",
          __builtin_bswap32(gamecode));

      // send the game code back, then KeyA.
      send(__builtin_bswap32(gamecode));
      send(ourkey);

      // get KeyB from GBA, check it to make sure its valid, then xor with KeyA
      // to derive the initial CRC value and the sessionkey.
      u32 sessionkeyraw = 0;
      do
      {
        sessionkeyraw = recv();
      } while (sessionkeyraw == gamecode);

      sessionkeyraw = checkKeyB(__builtin_bswap32(sessionkeyraw));
      if (sessionkeyraw == 0)
      {
        warnError("Cannot continue.\n");

        continue;
      }

      u32 sessionkey = sessionkeyraw ^ ourkey;
      u32 kcrc = sessionkey;
      printf("start kCRC=%08lx\n",kcrc);

      sessionkey = (sessionkey*0x6177614b)+1;

      // send hacked up send-size in uint32s
      u32 hackedupsize = (sendsize >> 3) - 1;

      printf("Sending hacked up size 0x%08lx\n",hackedupsize);
      send(hackedupsize);

      //unsigned int fcrc = 0x00bb;
      // send over multiboot binary header, in the clear until the end of the
      // nintendo logo. GBA checks this, if nintendo logo does not match the
      // one in currently inserted cart's ROM, it will not accept any more data.
      for (int i = 0; i < 0xA0; i+=4)
      {
        vu32 rom_dword = *(vu32*)(gba_mb_gba+i);
        send(__builtin_bswap32(rom_dword));
      }

      printf("\n");
      printf("Header done! Sending ROM...\n");

      // Add each uint32 of the multiboot image to the checksum, encrypt the
      // uint32 with the session key, increment the session key, send the
      // encrypted uint32.
      for (int i = 0xA0; i < sendsize; i+=4)
      {
        u32 dec = (
            (((gba_mb_gba[i+3]) << 24) & 0xff000000) |
            (((gba_mb_gba[i+2]) << 16) & 0x00ff0000) |
            (((gba_mb_gba[i+1]) << 8)  & 0x0000ff00) |
            (((gba_mb_gba[i])   << 0)  & 0x000000ff)
            );

        u32 enc = (dec - kcrc) ^ sessionkey;
        kcrc = docrc(kcrc,dec);
        sessionkey = (sessionkey * 0x6177614B) + 1;
        //enc^=((~(i+(0x20<<20)))+1);
        //enc^=0x6f646573;//0x20796220;

        send(enc);
      }

      //fcrc |= (sendsize<<16);
      printf("ROM done! CRC: %08lx\n", kcrc);
      //get crc back (unused)

      // Get KeyC derivation material from GBA (eventually)
      u32 keyCderive = 0;
      do
      {
        keyCderive = recv();
      } while (keyCderive <= 0xfeffffff);

      keyCderive = __builtin_bswap32(keyCderive);
      keyCderive >>= 8;

      printf("KeyC derivation material: %08lx\n",keyCderive);

      // (try to) find the KeyC, using the checksum of the multiboot image, and
      // the derivation material that GBA sent to us
      u32 keyc = deriveKeyC(keyCderive,kcrc);
      if (keyc == 0)
      {
        printf("Could not find keyC - kcrc=0x%08lx\n",kcrc);
        warnError("Cannot continue.\n");

        continue;
      }

      // derive the boot key from the found KeyC, and send to GBA. if this is
      // not correct, GBA will not jump to the multiboot image it was sent.
      u32 bootkey = docrc(0xBB,keyc) | 0xbb000000;
      printf("BootKey = 0x%08lx\n",bootkey);

      send(bootkey);
      sleep(2);

      printf("Waiting for GBA...\n");
      while (recv() != 0) {sleep(1);};
      send(0);

      VIDEO_WaitVSync();

      // Get game
      // -1 - unsupported game
      //  1 - Ruby
      //  2 - Sapphire
      //  3 - FireRed
      //  4 - LeafGreen
      //  5 - Emerald
      u32 gameId = getMsg();
      if (gameId == -1)
      {
        warnError("ERROR: Unsupported GBA game inserted!\n");

        continue;
      }

      printf("\nPokemon ");
      switch (gameId)
      {
        case 1: printf("Ruby"); break;
        case 2: printf("Sapphire"); break;
        case 3: printf("FireRed"); break;
        case 4: printf("LeafGreen"); break;
        case 5: printf("Emerald"); break;
      }

      printf("\n");
      VIDEO_WaitVSync();

      u32 isValid = getMsg();
      if (isValid == -1)
      {
        warnError("ERROR: Unsupported game version inserted!\n");

        continue;
      }

      // Get trainer name
      u8 trainerName[8];

      u32 tnd = getMsg();
      trainerName[0] = (tnd & 0xFF000000) >> 24;
      trainerName[1] = (tnd & 0x00FF0000) >> 16;
      trainerName[2] = (tnd & 0x0000FF00) >> 8;
      trainerName[3] = (tnd & 0x000000FF);

      tnd = getMsg();
      trainerName[4] = (tnd & 0xFF000000) >> 24;
      trainerName[5] = (tnd & 0x00FF0000) >> 16;
      trainerName[6] = (tnd & 0x0000FF00) >> 8;
      trainerName[7] = (tnd & 0x000000FF);

      // Get trainer ID
      u32 trainerId = getMsg();

      printf("Trainer: ");

      for (int i = 0; i < 8; i++)
      {
        if (trainerName[i] == 0xFF)
        {
          break;
        } else {
          printf("%c", debugGen3Decode(trainerName[i]));
        }
      }

      printf(" (%ld)\n", trainerId);

      // Wait for confirmation.
      printf("Press A to import the data from this game.\n");
      printf("Press B to cancel.\n");
      VIDEO_WaitVSync();

      if (waitForButtons(PAD_BUTTON_A | PAD_BUTTON_B) & PAD_BUTTON_B)
      {
        continue;
      }
    }
  }

  return 0;
}