/*
 *  spreadspace avr utils
 *
 *
 *  Copyright (C) 2013 Christian Pointner <equinox@spreadspace.org>
 *                     Othmar Gsenger <otti@wirdorange.org>
 *
 *  This file is part of spreadspace avr utils.
 *
 *  spreadspace avr utils 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
 *  any later version.
 *
 *  spreadspace avr utils 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 spreadspace avr utils. If not, see <http://www.gnu.org/licenses/>.
 */

#include <avr/io.h>
#include <avr/wdt.h>
#include <avr/interrupt.h>
#include <avr/power.h>

#include <stdio.h>
#include <string.h>

#include "util.h"
#include "led.h"

#include "LUFA/Drivers/Peripheral/TWI.h"
#include "LUFA/Drivers/Peripheral/Serial.h"
#include "LUFA/Drivers/Misc/RingBuffer.h"

#include <avr/eeprom.h>
#define EEPROM_SIZE 1024

typedef uint8_t keyslot_t[8];
keyslot_t EEMEM keyslots[EEPROM_SIZE/sizeof(keyslot_t)];

#define TAG_STA_PIN PINB
#define TAG_STA_BIT 7
#define CARD_PRESENT (!((TAG_STA_PIN >> TAG_STA_BIT) & 1))

const uint8_t SL018_ADDR = 0xa0;
const uint8_t SL018_WRITE = 0;
const uint8_t SL018_READ  = 1;
#define SL018_RESET 0xFF

const char* SL018_cmd_tostring(const uint8_t status) 
{
  switch(status) {
  case 0x01: return "Select Mifare card";
  case 0x02: return "Login to a sector";
  case 0x03: return "Read a data block";
  case 0x04: return "Write a data block";
  case 0x05: return "Read a value block";
  case 0x06: return "Initialize a value block";
  case 0x07: return "Write master key";
  case 0x08: return "Increment value";
  case 0x09: return "Decrement value";
  case 0x0A: return "Copy value";
  case 0x10: return "Read a data page";
  case 0x11: return "Write a data page";
  case 0x40: return "Control the red led";
  case 0xF0: return "Get firmware version";
  case SL018_RESET: return "Reset";
  default: return "unknown status";
  }
}

const char* SL018_status_tostring(const uint8_t status) 
{
  switch(status) {
  case 0x0: return "Operation succeed";
  case 0x1: return "No tag";
  case 0x2: return "Login succeed";
  case 0x3: return "Login fail";
  case 0x4: return "Read fail";
  case 0x5: return "Write fail";
  case 0x6: return "Unable to read after write";
  case 0xA: return "Collision occur";
  case 0xC: return "Load key fail";
  case 0xD: return "Not authenticate";
  case 0xE: return "Not a value block";
  default: return "unknown status";
  }
}

const uint8_t SL018CMD_ComSelectCard[]          ={1,0x01};
const uint8_t SL018CMD_ComRedLedOn[]            ={2,0x40,1};
const uint8_t SL018CMD_ComRedLedOff[]           ={2,0x40,0};
const uint8_t SL018CMD_ComGetFirmwareVersion[]  ={1,0xF0};
const uint8_t SL018CMD_ComReset[]               ={1,SL018_RESET};

uint8_t recv_twi_buf[256];
typedef struct __attribute__((__packed__))
{
  uint8_t len;
  uint8_t command;
  uint8_t status;
  uint8_t data[sizeof(recv_twi_buf)-3];
} sl018_message_t;

sl018_message_t* recv_twi_msg = (sl018_message_t *)&recv_twi_buf;
uint8_t card_status =0;

FILE usb_stream;
FILE serial_stream;
FILE * stdio = &serial_stream;

/*
             LUFA Library
     Copyright (C) Dean Camera, 2012.

  dean [at] fourwalledcubicle [dot] com
           www.lufa-lib.org
*/


#include <LUFA/Drivers/USB/USB.h>
#include "lufa-descriptor-usbserial.h"

USB_ClassInfo_CDC_Device_t VirtualSerial_CDC_Interface =
  {
    .Config =
      {
        .ControlInterfaceNumber         = 0,

        .DataINEndpointNumber           = CDC_TX_EPNUM,
        .DataINEndpointSize             = CDC_TXRX_EPSIZE,
        .DataINEndpointDoubleBank       = false,

        .DataOUTEndpointNumber          = CDC_RX_EPNUM,
        .DataOUTEndpointSize            = CDC_TXRX_EPSIZE,
        .DataOUTEndpointDoubleBank      = false,

        .NotificationEndpointNumber     = CDC_NOTIFICATION_EPNUM,
        .NotificationEndpointSize       = CDC_NOTIFICATION_EPSIZE,
        .NotificationEndpointDoubleBank = false,
      },
  };

void EVENT_USB_Device_ConfigurationChanged(void)
{
  CDC_Device_ConfigureEndpoints(&VirtualSerial_CDC_Interface);
  CDC_Device_CreateStream(&VirtualSerial_CDC_Interface,&usb_stream);
  stdio = &usb_stream;
}

void EVENT_USB_Device_ControlRequest(void)
{
  CDC_Device_ProcessControlRequest(&VirtualSerial_CDC_Interface);
}

void EVENT_USB_Device_Disconnect(void)
{
  stdio = &serial_stream;
}
/* end LUFA CDC-ACM specific definitions*/



int16_t stdio_bytes_received(void)
{
  if(stdio == &usb_stream)
    return CDC_Device_BytesReceived(&VirtualSerial_CDC_Interface);
  else
    return (int16_t)Serial_IsCharReceived();
}

bool sl018_cmd_raw(const uint8_t* send_twi_buf, bool wait_for_answer)
{
  uint8_t pos = 0;
      //uint8_t ret;
  if (TWI_StartTransmission(SL018_ADDR | SL018_WRITE,10) == TWI_ERROR_NoError) {
    for(pos=0; pos<=send_twi_buf[0]; pos++)
      if( ! TWI_SendByte(send_twi_buf[pos])) {
        TWI_StopTransmission();
        return 1;
      }
        // Must stop transmission afterwards to release the bus
    TWI_StopTransmission();
  } else 
    return 1;

  if(!wait_for_answer) return 0;

  _delay_ms(50);

  if (TWI_StartTransmission(SL018_ADDR | SL018_READ,10) == TWI_ERROR_NoError) {
    TWI_ReceiveByte(recv_twi_buf, 0);
    for(pos=1; pos<=recv_twi_buf[0]; pos++)
      if (! TWI_ReceiveByte(&recv_twi_buf[pos], (pos == recv_twi_buf[0]) ? 1:0 ) ) {
        TWI_StopTransmission();
        return 1;
      }
        // Must stop transmission afterwards to release the bus
    TWI_StopTransmission();
  } else
    return 1;

  return 0;
}

bool sl018_reset()
{
  if(sl018_cmd_raw(SL018CMD_ComReset, 0)) {
    fprintf(stdio, "I2C error\n\r");
    return 0;
  }
  return 1;
}

bool sl018_cmd(const uint8_t* send_twi_buf)
{
  if(sl018_cmd_raw(send_twi_buf, 1)) {
    fprintf(stdio, "I2C error\n\r");
    return 0;
  } else {
    if(recv_twi_msg->len < 2) {
      fprintf(stdio,"SL018 Cmd,Error: short Message received\n\r");
      return 0;
    }
    if(recv_twi_msg->status) {
      fprintf(stdio,"SL018 Cmd,Error: '%s','%s'\n\r",SL018_cmd_tostring(recv_twi_msg->command),SL018_status_tostring(recv_twi_msg->status));
      return 0;
    }
    sl018_message_t * send_twi_msg = (sl018_message_t *)send_twi_buf;
    if(send_twi_msg->command != recv_twi_msg->command) {
      fprintf(stdio,"SL018 Cmd,Error: mismatch: send, rcv: %02X,%02X\n\r",send_twi_msg->command,recv_twi_msg->command);
    }
  }
  return 1;
}



void flash_eeprom_from_stdio(void)
{
  keyslot_t keyslot;
  uint8_t keyslot_pos=0;
  uint8_t byte_pos=0;
  fprintf(stdio,"Flashing keys:\n\r");
  fflush(stdio);
  for(keyslot_pos=0;keyslot_pos<EEPROM_SIZE/sizeof(keyslot);) {
    CDC_Device_USBTask(&VirtualSerial_CDC_Interface);
    USB_USBTask();

    int16_t bytes_received = stdio_bytes_received();
    while(bytes_received >0) {
      keyslot[byte_pos++]=fgetc(stdio);
      bytes_received--;
      if (byte_pos == sizeof(keyslot)) {
        byte_pos=0;
        eeprom_update_block(&keyslot,&keyslots[keyslot_pos],sizeof(keyslot));
        keyslot_pos++;
        fprintf(stdio,".");
        fflush(stdio);
        led_toggle();
      }
    }
  }
  fprintf(stdio,"\n");
  led_off();
}

void dump_eeprom_to_stdio(void)
{
  keyslot_t keyslot;
  uint8_t keyslot_pos=0;

  for(keyslot_pos=0;keyslot_pos<EEPROM_SIZE/sizeof(keyslot);keyslot_pos++) {
    eeprom_read_block(&keyslot,&keyslots[keyslot_pos],sizeof(keyslot));
    for (uint8_t i=0; i< sizeof(keyslot); i++)
      fprintf(stdio,"%02X",keyslot[i]);
    fprintf(stdio,"\n\r");
  }
}

void handle_stdio(uint8_t cmd)
{  
  switch(cmd) {
    case 'r': 
             reset2bootloader(); 
             break;
    case '0': 
             if(sl018_reset())
               fprintf(stdio, "ok\n\r");
             break;

    case 'f': //get cardreader firmware version
             if(sl018_cmd(SL018CMD_ComGetFirmwareVersion))
               fprintf(stdio, "%s\n\r",recv_twi_msg->data);
             break;
    case '4': //turn cardreader led off
             if(sl018_cmd(SL018CMD_ComRedLedOff))
               fprintf(stdio, "ok\n\r");
             break;
    case '5': //turn cardreader led on
             if(sl018_cmd(SL018CMD_ComRedLedOn))
               fprintf(stdio, "ok\n\r");
             break;
    case 'e': //flash eeprom
             flash_eeprom_from_stdio();
             break;
    case 'd': //dump eeprom - this breaks security!
             dump_eeprom_to_stdio();
             break;
    case 's': //get eeprom size
             fprintf(stdio,"%d\n\r",EEPROM_SIZE);
             break;
    default: fprintf(stdio, "error, unknown command %02X '%c'\n\r",cmd, cmd); return;
  }
}



/* this generates a Fletcher8 checksum  */
/* code from: http://stackoverflow.com/questions/13491700/8-bit-fletcher-checksum-of-16-byte-data */
uint8_t generate_csum(uint8_t* data)
{
  uint16_t sum1 = 0xf, sum2 = 0xf, len = sizeof(keyslot_t) - 1;
  do { sum2 += ( sum1 += *data++ ); } while (--len);
  return sum2<<4 | sum1;
}

uint8_t compare_keyslots(const keyslot_t a, const keyslot_t b)
{
  uint8_t tmp=0, i;
      // constant time compare
  for(i=0; i<sizeof(keyslot_t); ++i)
    tmp |= a[i] ^ b[i];
  return tmp;
}

bool check_card(const uint8_t * uid, uint8_t uid_len)
{
  keyslot_t card;
  keyslot_t eeprom_ks;
  memset(card, 0, sizeof(card));
  uid_len = uid_len > sizeof(keyslot_t) ? sizeof(keyslot_t) : uid_len;
  for (uint8_t pos=0; pos<uid_len; pos++)
    card[pos]=uid[uid_len-pos-1];
  card[sizeof(keyslot_t) - 1]=generate_csum(card);
  keyslot_t * ks=keyslots;
  bool valid=0;
  for(uint8_t ks_num=0;ks_num<(EEPROM_SIZE/sizeof(card));ks_num++) {
    eeprom_read_block(&eeprom_ks,&ks[ks_num],sizeof(eeprom_ks));
    if(!compare_keyslots(card, eeprom_ks)) {
      valid=1;
      // break;  // this would break security (not const time)
    }
  }
  if(valid)
    return 1;
  return 0;
}

void handle_card(void)
{
  uint8_t pos;
  fprintf(stdio, "CARD IN: ");
  if(sl018_cmd(SL018CMD_ComSelectCard))
  {
    uint8_t uid_len = recv_twi_msg->len - sizeof(recv_twi_msg->command) - sizeof(recv_twi_msg->status) - 1;
    for (pos=uid_len-1; pos< 255; pos--)
      fprintf(stdio,"%02X",recv_twi_msg->data[pos]);

    fprintf(stdio, "\n\r");
    uint8_t type = recv_twi_msg->data[uid_len];
    if (0<type && type < 7) {
      if(check_card(recv_twi_msg->data,uid_len)) {
        sl018_cmd(SL018CMD_ComRedLedOn);
        fprintf(stdio,"Card allowed - opening/closing door\n\r"); // TODO: open/close door!
        _delay_ms(255);
        sl018_cmd(SL018CMD_ComRedLedOff);
      } else {
        fprintf(stdio,"Card not found in Database\n\r");
      }
    } else {
      fprintf(stdio,"Unknown Card Type %02x\n\r",type);
    }
  }  
}



int main(void)
{
  MCUSR &= ~(1 << WDRF);
  wdt_disable();

  cpu_init();
  led_init();
  USB_Init();
  TWI_Init(TWI_BIT_PRESCALE_1, TWI_BITLENGTH_FROM_FREQ(1, 200000));
  sei();
  Serial_Init(115200,false);
  Serial_CreateStream(&serial_stream);
  
  sl018_reset();
  for(;;) {
    CDC_Device_USBTask(&VirtualSerial_CDC_Interface);
    USB_USBTask();

    int16_t bytes_received = stdio_bytes_received();
    if(bytes_received > 0)
      handle_stdio(fgetc(stdio));

    if(CARD_PRESENT != card_status) {
      card_status = CARD_PRESENT;
      if(card_status)
        handle_card();
    }
  }
}