/***************************************************************************
 * A copy of the GNU GPL is appended to this file.                         *
 *                                                                         *
 * This licence is based on the nmap licence, and we express our gratitude *
 * for the work that went into producing it. There is no other connection  *
 * between RFIDler and nmap either expressed or implied.                   *
 *                                                                         *
 ********************** IMPORTANT RFIDler LICENSE TERMS ********************
 *                                                                         *
 *                                                                         *
 * All references to RFIDler herein imply all it's derivatives, namely:    *
 *                                                                         *
 * o RFIDler-LF Standard                                                   *
 * o RFIDler-LF Lite                                                       *
 * o RFIDler-LF Nekkid                                                     *
 *                                                                         *
 *                                                                         *
 * RFIDler is (C) 2013-2015 Aperture Labs Ltd.                             *
 *                                                                         *
 * This program is free software; you may redistribute and/or modify it    *
 * under the terms of the GNU General Public License as published by the   *
 * Free Software Foundation; Version 2 ("GPL"), BUT ONLY WITH ALL OF THE   *
 * CLARIFICATIONS AND EXCEPTIONS DESCRIBED HEREIN.  This guarantees your   *
 * right to use, modify, and redistribute this software under certain      *
 * conditions.  If you wish to embed RFIDler technology into proprietary   *
 * software or hardware, we sell alternative licenses                      *
 * (contact sales@aperturelabs.com).                                       *
 *                                                                         *
 * Note that the GPL places important restrictions on "derivative works",  *
 * yet it does not provide a detailed definition of that term.  To avoid   *
 * misunderstandings, we interpret that term as broadly as copyright law   *
 * allows.  For example, we consider an application to constitute a        *
 * derivative work for the purpose of this license if it does any of the   *
 * following with any software or content covered by this license          *
 * ("Covered Software"):                                                   *
 *                                                                         *
 * o Integrates source code from Covered Software.                         *
 *                                                                         *
 * o Is designed specifically to execute Covered Software and parse the    *
 * results (as opposed to typical shell or execution-menu apps, which will *
 * execute anything you tell them to).                                     *
 *                                                                         *
 * o Includes Covered Software in a proprietary executable installer.  The *
 * installers produced by InstallShield are an example of this.  Including *
 * RFIDler with other software in compressed or archival form does not     *
 * trigger this provision, provided appropriate open source decompression  *
 * or de-archiving software is widely available for no charge.  For the    *
 * purposes of this license, an installer is considered to include Covered *
 * Software even if it actually retrieves a copy of Covered Software from  *
 * another source during runtime (such as by downloading it from the       *
 * Internet).                                                              *
 *                                                                         *
 * o Links (statically or dynamically) to a library which does any of the  *
 * above.                                                                  *
 *                                                                         *
 * o Executes a helper program, module, or script to do any of the above.  *
 *                                                                         *
 * This list is not exclusive, but is meant to clarify our interpretation  *
 * of derived works with some common examples.  Other people may interpret *
 * the plain GPL differently, so we consider this a special exception to   *
 * the GPL that we apply to Covered Software.  Works which meet any of     *
 * these conditions must conform to all of the terms of this license,      *
 * particularly including the GPL Section 3 requirements of providing      *
 * source code and allowing free redistribution of the work as a whole.    *
 *                                                                         *
 * As another special exception to the GPL terms, Aperture Labs Ltd. grants*
 * permission to link the code of this program with any version of the     *
 * OpenSSL library which is distributed under a license identical to that  *
 * listed in the included docs/licenses/OpenSSL.txt file, and distribute   *
 * linked combinations including the two.                                  *
 *                                                                         *
 * Any redistribution of Covered Software, including any derived works,    *
 * must obey and carry forward all of the terms of this license, including *
 * obeying all GPL rules and restrictions.  For example, source code of    *
 * the whole work must be provided and free redistribution must be         *
 * allowed.  All GPL references to "this License", are to be treated as    *
 * including the terms and conditions of this license text as well.        *
 *                                                                         *
 * Because this license imposes special exceptions to the GPL, Covered     *
 * Work may not be combined (even as part of a larger work) with plain GPL *
 * software.  The terms, conditions, and exceptions of this license must   *
 * be included as well.  This license is incompatible with some other open *
 * source licenses as well.  In some cases we can relicense portions of    *
 * RFIDler or grant special permissions to use it in other open source     *
 * software.  Please contact sales@aperturelabs.com with any such requests.*
 * Similarly, we don't incorporate incompatible open source software into  *
 * Covered Software without special permission from the copyright holders. *
 *                                                                         *
 * If you have any questions about the licensing restrictions on using     *
 * RFIDler in other works, are happy to help.  As mentioned above, we also *
 * offer alternative license to integrate RFIDler into proprietary         *
 * applications and appliances.  These contracts have been sold to dozens  *
 * of software vendors, and generally include a perpetual license as well  *
 * as providing for priority support and updates.  They also fund the      *
 * continued development of RFIDler.  Please email sales@aperturelabs.com  *
 * for further information.                                                *
 * If you have received a written license agreement or contract for        *
 * Covered Software stating terms other than these, you may choose to use  *
 * and redistribute Covered Software under those terms instead of these.   *
 *                                                                         *
 * Source is provided to this software because we believe users have a     *
 * right to know exactly what a program is going to do before they run it. *
 * This also allows you to audit the software for security holes (none     *
 * have been found so far).                                                *
 *                                                                         *
 * Source code also allows you to port RFIDler to new platforms, fix bugs, *
 * and add new features.  You are highly encouraged to send your changes   *
 * to the RFIDler mailing list for possible incorporation into the         *
 * main distribution.  By sending these changes to Aperture Labs Ltd. or   *
 * one of the Aperture Labs Ltd. development mailing lists, or checking    *
 * them into the RFIDler source code repository, it is understood (unless  *
 * you specify otherwise) that you are offering the RFIDler Project        *
 * (Aperture Labs Ltd.) the unlimited, non-exclusive right to reuse,       *
 * modify, and relicense the code.  RFIDler will always be available Open  *
 * Source, but this is important because the inability to relicense code   *
 * has caused devastating problems for other Free Software projects (such  *
 * as KDE and NASM).  We also occasionally relicense the code to third     *
 * parties as discussed above. If you wish to specify special license      *
 * conditions of your contributions, just say so when you send them.       *
 *                                                                         *
 * This program 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 RFIDler   *
 * license file for more details (it's in a COPYING file included with     *
 * RFIDler, and also available from                                        *
 *   https://github.com/ApertureLabsLtd/RFIDler/COPYING                    *
 *                                                                         *
 ***************************************************************************/

// Author: Adam Laurie <adam@aperturelabs.com>
// Natalie Silvanovich
// Tony Naggs
//
// Credit also to Mr Blinky (Twitter @MstrBlinky) for publishing info on decoding Tamagotchi Friends NFC, eg http://mrblinky.net/tf/packet-sniffing.txt

#include "HardwareProfile.h"
#include "comms.h"
#include "rfidler.h"
#include "tamagotchi.h"
#include "util.h"

// temporary? Enable debug prints for bit level decode
#define VERBOSE_TAMA_LOGGING

// tunable constants for decode
const unsigned int KBitMinPulse = 15;           // nominal bit pulse: 100 uS
const unsigned int KBitMaxPulse = 130;
const unsigned int KOneMinGap = 550;            // nominal One Gap: 600 ~ 650 uS
const unsigned int KOneMaxGap = 750;
const unsigned int KZeroMinGap = 150;           // nominal Zero Gap: 250 uS
const unsigned int KZeroMaxGap = 400;
const unsigned int KBarrierMinPulse = 200;      // nominal Barrier: 200 uS gap, 500 uS clock burst
const unsigned int KBarrierMaxPulse = 600;

const unsigned KMaxTamaMessage = 32; // max known message len from tamagotchi (for email)

// decode externally sniffed PWM
BOOL tamagotchi_decode_pwm(unsigned int pulses[], unsigned int gaps[], unsigned int count)
{
    unsigned int    index, offset, outcount;
    BOOL            decoded= FALSE;
    BYTE            out[KMaxTamaMessage];

    // FIXME skip leading pulses of zero uS - can delete when sniff_pwm() no longer gives these to us
    offset= 0;
    while ((offset < count) && (pulses[offset] == 0))
    {
        offset++;
    }

#if defined(VERBOSE_TAMA_LOGGING)
	if (offset)
    	UserMessageNum("\r\noffset past zero pulses %d", offset);
#endif

    // decode
    for(index= 0, outcount= 0; ((index + offset) < count) && (outcount < (KMaxTamaMessage - 1));)
    {
        unsigned long temp = pulses[offset + index];

        // start of byte barrier?
        if ((temp >= KBarrierMinPulse) && (temp <= KBarrierMaxPulse) && ((index + offset) < (count - 7)))
        {
            unsigned int    bits = 0;
            BYTE b = 0;

#if defined(VERBOSE_TAMA_LOGGING)
            UserMessageNum("\r\nBarrier (%d) ", temp);
#endif
            // process the byte (note changes index)
            do {
                b <<= 1;
                // peek at the next pulse to make sure it is valid
                temp = pulses[offset + index + 1];

                // bit is invalid if next pulse is wrong size
                if ((temp < KBitMinPulse) || (temp > KBitMaxPulse))
                {
                    decoded = FALSE;
                    UserMessageNum("(bad pulse count %d) ", temp);
                    break; // bad pulse width
                }

                if (index == 0)
                    decoded = TRUE;

                // value of bit depends on gap size
                temp = gaps[offset + index];
                if ((temp >= KOneMinGap) && (temp <= KOneMaxGap))
                {
                    // 1
                    b += 1;
#if defined(VERBOSE_TAMA_LOGGING)
                   UserMessageNum("1 (gap %d) ", temp);
#endif
                }
                else if ((temp >= KZeroMinGap) && (temp <= KZeroMaxGap))
                {
                    // 0
#if defined(VERBOSE_TAMA_LOGGING)
                    UserMessageNum("0 (gap %d) ", temp);
#endif
                }
                else
                {
                    decoded = FALSE;
#if defined(VERBOSE_TAMA_LOGGING)
                    UserMessageNum("(bad gap %d) ", temp);
#endif
                    break; // bad gap
                }

                ++bits;
                ++index;
            }
            while (((offset + index) < count) && (bits < 8));

            if (bits == 8)
            {
                out[outcount++] = b;
#if defined(VERBOSE_TAMA_LOGGING)
                UserMessageNum(" 0x%02x", b);
#endif
            }
        }
        else
        {
#if defined(VERBOSE_TAMA_LOGGING)
            if (index > 0)
            {
                temp = gaps[offset + index - 1];
                if ((temp >= KOneMinGap) && (temp <= KOneMaxGap))
                    UserMessageNum("\r\n1 Gap: %d, ", temp);
                else if ((temp >= KZeroMinGap) && (temp <= KZeroMaxGap))
                    UserMessageNum("\r\n0 Gap: %d, ", temp);
                else
                    UserMessageNum("\r\n??? Gap: %d, ", temp);
            }

            temp = pulses[offset + index];
            if ((temp >= KBitMinPulse) && (temp <= KBitMaxPulse))
                UserMessageNum("Bit Pulse: %d", temp);
            else if ((temp >= KBarrierMinPulse) && (temp <= KBarrierMaxPulse))
                UserMessageNum("Barrier Pulse: %d", temp);
            else
                UserMessageNum("??? Pulse: %d", temp);
#endif
            decoded = FALSE;
        }
        ++index;
    }
    
    UserMessage("%s", "\r\n");

    if (decoded)
        decoded = VerifyTamaMessage(out, outcount);

    return decoded;
}


// sum bytes (except initial sync 0xf0 and received checksum)
// and if message seems valid display hex/text dump
BOOL VerifyTamaMessage(BYTE *out, unsigned int outcount)
{
    BOOL valid = FALSE;

    // check for sync & message length bytes
    if ((outcount > 5) && (out[0] == 0xf0) && (out[2] == outcount - 4))
    {
        BYTE checksum = ChecksumTamaMessage(out, outcount - 1);

        UserMessageNum("Message checking, calculated checksum: 0x%x\r\n", checksum);
        if (checksum == out[outcount-1])
        {
            valid = TRUE;
            DumpTamaMessage(out, outcount);
        }
    }

    return valid;
}


BYTE ChecksumTamaMessage(BYTE *out, unsigned int outcount)
{
    BYTE checksum = 0;
    unsigned int    index;

    // index starts at 1 to skip sync byte
    for (index= 1; index < outcount; index++ )
        checksum += out[index];

    return checksum;
}

void DumpTamaMessage(BYTE *out, unsigned int outcount)
{
    unsigned int index;
    char         text[KMaxTamaMessage + 1];

    // print message in hex
    for (index= 0; index < outcount; index++ )
    {
        BYTE b = out[index];

        UserMessageNum(" %02X", b);
        if ((index % 8) == 7)
            UserMessage(" ", NULL);

        // convert from Tamagotchi Alphabet (eg user assigned name, email)
        text[index] = TamaAlphabetConvert(b);
    }
    text[index] = 0;

    UserMessage("    %s\r\n", text);
}


char TamaAlphabetConvert(BYTE b)
{
    if (b < 26)
        return 'A' + b;
    else if (b >= 32 && b <= 41)
        return '0' + b - 32;
    else switch (b)
    {
        case 26: return ' ';
        case 27: return '.';
        case 28: return '\'';
        case 29: return '-';
        case 30: return '!';
        // unknown
        default: return '?';
    }
}