/*

TTN module
Wrapper to use TTN with the LMIC library

Copyright (C) 2018 by Xose Pérez <xose dot perez at gmail dot com>

This code requires the MCCI LoRaWAN LMIC library
by IBM, Matthis Kooijman, Terry Moore, ChaeHee Won, Frank Rose
https://github.com/mcci-catena/arduino-lmic

This program 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.

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
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>.

*/

#include <hal/hal.h>
#include <SPI.h>
#include <vector>
#include <Preferences.h>
#include "configuration.h"
#include "credentials.h"

// -----------------------------------------------------------------------------
// Globals
// -----------------------------------------------------------------------------

// LMIC GPIO configuration
const lmic_pinmap lmic_pins = {
    .nss = NSS_GPIO,
    .rxtx = LMIC_UNUSED_PIN,
    .rst = RESET_GPIO,
    .dio = {DIO0_GPIO, DIO1_GPIO, DIO2_GPIO},
};


// Message counter, stored in RTC memory, survives deep sleep.
static RTC_DATA_ATTR uint32_t count = 0;

#ifdef USE_ABP
// These callbacks are only used in over-the-air activation, so they are
// left empty here (we cannot leave them out completely unless
// DISABLE_JOIN is set in config.h, otherwise the linker will complain).
void os_getArtEui (u1_t* buf) { }
void os_getDevEui (u1_t* buf) { }
void os_getDevKey (u1_t* buf) { }
#endif

#ifdef USE_OTAA
void os_getArtEui (u1_t* buf) { memcpy_P(buf, APPEUI, 8); }
void os_getDevEui (u1_t* buf) { memcpy_P(buf, DEVEUI, 8); }
void os_getDevKey (u1_t* buf) { memcpy_P(buf, APPKEY, 16); }
#endif

std::vector<void(*)(uint8_t message)> _lmic_callbacks;

// -----------------------------------------------------------------------------
// Private methods
// -----------------------------------------------------------------------------

void _ttn_callback(uint8_t message) {
    for (uint8_t i=0; i<_lmic_callbacks.size(); i++) {
        (_lmic_callbacks[i])(message);
    }
}

void forceTxSingleChannelDr() {
    // Disables all channels, except for the one defined by SINGLE_CHANNEL_GATEWAY
    // This only affects uplinks; for downlinks the default
    // channels or the configuration from the OTAA Join Accept are used.
    #ifdef SINGLE_CHANNEL_GATEWAY
    for(int i=0; i<9; i++) { // For EU; for US use i<71
        if(i != SINGLE_CHANNEL_GATEWAY) {
            LMIC_disableChannel(i);
        }
    }
    #endif

    // Set data rate (SF) and transmit power for uplink
    ttn_sf(LORAWAN_SF);
}

// LMIC library will call this method when an event is fired
void onEvent(ev_t event) {
    switch(event) {
    case EV_JOINED:
        #ifdef SINGLE_CHANNEL_GATEWAY
        forceTxSingleChannelDr();
        #endif

        // Disable link check validation (automatically enabled
        // during join, but because slow data rates change max TX
        // size, we don't use it in this example.
        if(!LORAWAN_ADR){
            LMIC_setLinkCheckMode(0); // Link check problematic if not using ADR. Must be set after join
        }
        break;
    case EV_TXCOMPLETE:
        Serial.println(F("EV_TXCOMPLETE (inc. RX win. wait)"));
        if (LMIC.txrxFlags & TXRX_ACK) {
            Serial.println(F("Received ack"));
            _ttn_callback(EV_ACK);
        }
        if (LMIC.dataLen) {
            Serial.print(F("Data Received: "));
            Serial.write(LMIC.frame+LMIC.dataBeg, LMIC.dataLen);
            Serial.println();
            _ttn_callback(EV_RESPONSE);
        }
        break;
    default:
        break;
    }

    // Send message callbacks
    _ttn_callback(event);
}

// -----------------------------------------------------------------------------
// Public methods
// -----------------------------------------------------------------------------

void ttn_register(void (*callback)(uint8_t message)) {
    _lmic_callbacks.push_back(callback);
}

size_t ttn_response_len() {
    return LMIC.dataLen;
}

void ttn_response(uint8_t * buffer, size_t len) {
    for (uint8_t i = 0; i < LMIC.dataLen; i++) {
        buffer[i] = LMIC.frame[LMIC.dataBeg + i];
    }
}

// If the value for LORA packet counts is unknown, restore from flash
static void initCount() {
  if(count == 0) {
    Preferences p;
    p.begin("lora", true);
    count = p.getUInt("count", 0);
    p.end();
  }
}


bool ttn_setup() {
    initCount();

    // SPI interface
    SPI.begin(SCK_GPIO, MISO_GPIO, MOSI_GPIO, NSS_GPIO);

    // LMIC init
    return ( 1 == os_init_ex( (const void *) &lmic_pins ) );
}

void ttn_join() {
    // Reset the MAC state. Session and pending data transfers will be discarded.
    LMIC_reset();

    #ifdef CLOCK_ERROR
    LMIC_setClockError(MAX_CLOCK_ERROR * CLOCK_ERROR / 100);
    #endif

        #if defined(CFG_eu868)

            // Set up the channels used by the Things Network, which corresponds
            // to the defaults of most gateways. Without this, only three base
            // channels from the LoRaWAN specification are used, which certainly
            // works, so it is good for debugging, but can overload those
            // frequencies, so be sure to configure the full frequency range of
            // your network here (unless your network autoconfigures them).
            // Setting up channels should happen after LMIC_setSession, as that
            // configures the minimal channel set.
            LMIC_setupChannel(0, 868100000, DR_RANGE_MAP(DR_SF12, DR_SF7),  BAND_CENTI);      // g-band
            LMIC_setupChannel(1, 868300000, DR_RANGE_MAP(DR_SF12, DR_SF7B), BAND_CENTI);      // g-band
            LMIC_setupChannel(2, 868500000, DR_RANGE_MAP(DR_SF12, DR_SF7),  BAND_CENTI);      // g-band
            LMIC_setupChannel(3, 867100000, DR_RANGE_MAP(DR_SF12, DR_SF7),  BAND_CENTI);      // g-band
            LMIC_setupChannel(4, 867300000, DR_RANGE_MAP(DR_SF12, DR_SF7),  BAND_CENTI);      // g-band
            LMIC_setupChannel(5, 867500000, DR_RANGE_MAP(DR_SF12, DR_SF7),  BAND_CENTI);      // g-band
            LMIC_setupChannel(6, 867700000, DR_RANGE_MAP(DR_SF12, DR_SF7),  BAND_CENTI);      // g-band
            LMIC_setupChannel(7, 867900000, DR_RANGE_MAP(DR_SF12, DR_SF7),  BAND_CENTI);      // g-band
            LMIC_setupChannel(8, 868800000, DR_RANGE_MAP(DR_FSK,  DR_FSK),  BAND_MILLI);      // g2-band

        #elif defined(CFG_us915)

            // NA-US channels 0-71 are configured automatically
            // but only one group of 8 should (a subband) should be active
            // TTN recommends the second sub band, 1 in a zero based count.
            // https://github.com/TheThingsNetwork/gateway-conf/blob/master/US-global_conf.json
            LMIC_selectSubBand(1);

        #endif

        // TTN defines an additional channel at 869.525Mhz using SF9 for class B
        // devices' ping slots. LMIC does not have an easy way to define set this
        // frequency and support for class B is spotty and untested, so this
        // frequency is not configured here.

        // Disable link check validation
        LMIC_setLinkCheckMode(0);

        #ifdef SINGLE_CHANNEL_GATEWAY
        forceTxSingleChannelDr();
        #else
        // Set default rate and transmit power for uplink (note: txpow seems to be ignored by the library)
        ttn_sf(LORAWAN_SF);
        #endif

    #if defined(USE_ABP)

        // Set static session parameters. Instead of dynamically establishing a session
        // by joining the network, precomputed session parameters are be provided.
        uint8_t appskey[sizeof(APPSKEY)];
        uint8_t nwkskey[sizeof(NWKSKEY)];
        memcpy_P(appskey, APPSKEY, sizeof(APPSKEY));
        memcpy_P(nwkskey, NWKSKEY, sizeof(NWKSKEY));
        LMIC_setSession(0x1, DEVADDR, nwkskey, appskey);

        // TTN uses SF9 for its RX2 window.
        LMIC.dn2Dr = DR_SF9;

        // Trigger a false joined
        _ttn_callback(EV_JOINED);

    #elif defined(USE_OTAA)

      #ifdef SINGLE_CHANNEL_GATEWAY
      // LMiC will already have decided to send on one of the 3 default
      // channels; ensure it uses the one we want
      LMIC.txChnl = SINGLE_CHANNEL_GATEWAY;
      #endif

      // Make LMiC initialize the default channels, choose a channel, and
      // schedule the OTAA join
      LMIC_startJoining();

    #endif
}

void ttn_sf(unsigned char sf) {
    LMIC_setDrTxpow(sf, 14);
}

void ttn_adr(bool enabled) {
    LMIC_setAdrMode(enabled);
    LMIC_setLinkCheckMode(!enabled);
}

uint32_t ttn_get_count() {
  return count;
}

static void ttn_set_cnt() {
    LMIC_setSeqnoUp(count);

    // We occasionally mirror our count to flash, to ensure that if we lose power we will at least start with a count that is almost correct 
    // (otherwise the TNN network will discard packets until count once again reaches the value they've seen).  We limit these writes to a max rate
    // of one write every 5 minutes.  Which should let the FLASH last for 300 years (given the ESP32 NVS algoritm)
    static uint32_t lastWriteMsec = UINT32_MAX; // Ensure we write at least once
    uint32_t now = millis();
    if(now < lastWriteMsec || (now - lastWriteMsec) > 5 * 60 * 1000L) { // write if we roll over (50 days) or 5 mins
        lastWriteMsec = now;

        Preferences p;
        p.begin("lora", false);
        p.putUInt("count", count);
        p.end();
    }
}

void ttn_send(uint8_t * data, uint8_t data_size, uint8_t port, bool confirmed){
    ttn_set_cnt(); // we are about to send using the current packet count

    // Check if there is not a current TX/RX job running
    if (LMIC.opmode & OP_TXRXPEND) {
        _ttn_callback(EV_PENDING);
        return;
    }

    // Prepare upstream data transmission at the next possible time.
    // Parameters are port, data, length, confirmed
    LMIC_setTxData2(port, data, data_size, confirmed ? 1 : 0);

    _ttn_callback(EV_QUEUED);
    count++;
}

void ttn_loop() {
    os_runloop_once();
}