#include <LiquidCrystal_I2C.h>
LiquidCrystal_I2C lcd(0x27, 16, 2);

#define SERIAL_RATE 115200
#define WWV_SIGNAL_PIN 14
#define PPS_OUTPUT_PIN 16
#define DEBUG1_OUTPUT_PIN 15

#define ONEBIT 1
#define ZEROBIT 2
#define MARKBIT 3

#define DEBUG false

// we sample once per ms:
#define NUM_SAMPLES_PER_FRAME 700

#define CLOCKS_PER_MS 10

char statusString[25]  = "LOS";

volatile unsigned int lowLatencyInState;
volatile unsigned int wwvbInState;
volatile unsigned int lastWWVBInState;

volatile unsigned int stateStableCounter = 0;
volatile unsigned int stateStableMillis = 0;
volatile unsigned int lastStateStableMillis = 0;

volatile unsigned int secondCounter = 0;
volatile unsigned int milliCounter = 0;
volatile unsigned int clockCounter = 0;

volatile unsigned int timeToTick = 0;
volatile unsigned int oldLastLowMillis = 0;
volatile unsigned int lastLowMillis = 0;
volatile unsigned int oldLastHighMillis = 0;
volatile unsigned int lastHighMillis = 0;
volatile unsigned int frameReadyToStart = 0;
volatile unsigned int beginFrameSearch = 0;
volatile unsigned int frameSamples = 0;
volatile unsigned int lossOfSignal = 1;
volatile unsigned int displayUpdateRequired = 1;
volatile unsigned int frameSearch = 0;
volatile unsigned int frameStart = 0;
volatile unsigned int frameStartTime = 0;
volatile unsigned int frameHigh = 0;
volatile unsigned int frameHighReadOut = 0;
volatile unsigned int frameLow = 0;
volatile unsigned int frameLowReadOut = 0;
volatile unsigned int frameCounter = 0;
volatile unsigned int frameReadyForRead = 0;
volatile unsigned int lastBitReceived = 0;
volatile unsigned int millisSinceBoot = 0;
volatile unsigned int ppsActivationTime;
volatile unsigned int millisSinceSignalStateChange = 0;
volatile unsigned int minuteSync = 0;

void ICACHE_RAM_ATTR WWVFallingEdge();
void ICACHE_RAM_ATTR OSCEdge();
void ICACHE_RAM_ATTR MilliEdge();
void ICACHE_RAM_ATTR SecondEdge();


#include "ESP8266TimerInterrupt.h"
ESP8266Timer ITimer;

void setup() {
    Serial.begin(SERIAL_RATE);
    while (!Serial);
    delay(200);
    Serial.print("\n\n\n");
    Serial.println("************************************************");
    Serial.println("************************************************");
    Serial.println("*** ESP8266 Ready.");
    Serial.println("************************************************");
    Serial.print(F("\nStarting WWVB on "));
    Serial.println(ARDUINO_BOARD);
    Serial.println(ESP8266_TIMER_INTERRUPT_VERSION);
    Serial.print(F("CPU Frequency = "));
    Serial.print(F_CPU / 1000000);
    Serial.println(F(" MHz"));

    pinMode(LED_BUILTIN, OUTPUT);
    pinMode(PPS_OUTPUT_PIN, OUTPUT);
    pinMode(DEBUG1_OUTPUT_PIN, OUTPUT);
    pinMode(WWV_SIGNAL_PIN, INPUT);

    // 100us timer:
    if (ITimer.attachInterruptInterval(100, TimerHandler)) {
        Serial.print(F("Starting ITimer OK, millis() = ")); Serial.println(millis());
    } else {
        Serial.println(F("Can't set ITimer. Select another freq. or timer"));
    }

    //attachInterrupt(digitalPinToInterrupt(LOSC_INPUT_PIN), OSCEdge, RISING);
    lcd.init();
    lcd.backlight();
    lcd.setCursor(0, 0);
    lcd.print("booting");

    ppsActivationTime = millis();
}

void TimerHandler() {
    //Serial.print(F("in timer OK, millis() = ")); Serial.println(millis());
    clockCounter++;
    if(clockCounter > CLOCKS_PER_MS) {
        clockCounter -= CLOCKS_PER_MS;

        // *****************************************************************************
        // LOW LATENCY HACK to respond in 100us to a falling
        // start-of-second edge
        // respond really fast to a falling edge if in the frameReadyToStart
        // state
        lowLatencyInState = digitalRead(WWV_SIGNAL_PIN);
        if(!lowLatencyInState && frameReadyToStart && !lossOfSignal && !frameStart) {
            // TICK!
            // falling edge, beginning of a new frame and second
            digitalWrite(PPS_OUTPUT_PIN, 1);
            timeToTick = 1;
            frameStart = 1;
            frameStartTime = millisSinceBoot;
            frameReadyToStart = 0;
            frameSearch = 0;
        }
        // *****************************************************************************
        MilliEdge();
    }
}

void SecondEdge() {
    secondCounter++;
    displayUpdateRequired = 1;
}

void MilliEdge() {
    digitalWrite(DEBUG1_OUTPUT_PIN, 1);
    wwvbInState = digitalRead(WWV_SIGNAL_PIN);

    milliCounter++;
    millisSinceBoot++;

    if(milliCounter > 1000) {
        milliCounter -= 1000;
        SecondEdge();
    }

    if(wwvbInState && (wwvbInState != lastWWVBInState)) {
        // we are on the rising edge, last low was 1ms ago
        oldLastLowMillis = lastLowMillis;
        lastLowMillis = millisSinceBoot - 1;
    }

    if(!wwvbInState && (wwvbInState != lastWWVBInState)) {
        // we are on the falling edge, last high was 1ms ago
        oldLastHighMillis = lastHighMillis;
        lastHighMillis = millisSinceBoot - 1;
    }


    if(wwvbInState != lastWWVBInState) {
        // we are on an edge
        stateStableMillis = 0;
    } else {
        // nothing happening
        stateStableMillis++;
    }

    if(wwvbInState && (stateStableMillis > 180) && (stateStableMillis < 2000)) {
        // if we are high but for less than 2s
        // main screen turn on
        lossOfSignal = 0;
        frameSearch = 1;
    }

    lastWWVBInState = wwvbInState;  // copy/save for next loop

    if((stateStableMillis > 2000) && !lossOfSignal) {
        // we have received nothing for 2 seconds, loss of signal:
        lossOfSignal = 1;
        frameStart = 0;
        frameCounter = 0;
        minuteSync = 0;
        digitalWrite(DEBUG1_OUTPUT_PIN, 0);
        return;
    }

    if(!frameStart && frameSearch && wwvbInState) {
        // if we have been high for 180ms (frameSearch) we are ready to start a new frame on the mark
        frameHigh = 0;
        frameLow = 0;
        frameReadyToStart = 1;
        digitalWrite(DEBUG1_OUTPUT_PIN, 0);
        return;
    }

    // frameReadyToStart -> frameStart (and PPS) happens in a 100us
    // ISR above.

    if (frameStart && (frameSamples < NUM_SAMPLES_PER_FRAME)) {
        frameSearch = 0;
        //begin sampling
        if (wwvbInState) {
            frameHigh++;
        } else {
            frameLow++;
        }
        frameSamples++;
        digitalWrite(DEBUG1_OUTPUT_PIN, 0);
        return;
    }

    if(frameStart && (frameSamples >= NUM_SAMPLES_PER_FRAME)) {
        frameReadyForRead = 1;
        frameHighReadOut = frameHigh;
        frameLowReadOut = frameLow;
        frameStart = 0;
        frameHigh = 0;
        frameLow = 0;
        frameSamples = 0;
    }
    digitalWrite(DEBUG1_OUTPUT_PIN, 0);
}

char pb[255];
void loop() {
    digitalWrite(LED_BUILTIN, !wwvbInState);

    if(timeToTick) {
        timeToTick = 0;
        TickSecond();
    }

    yield();

    if(frameReadyForRead) {
        frameReadyForRead = 0;
        processFrame();
    }

    yield();

    PPSLowIfRequired();

    yield();

    if (displayUpdateRequired) {
        updateDisplay();
        displayUpdateRequired = 0;
    }
}

void SetPPSHigh() {
    digitalWrite(PPS_OUTPUT_PIN, 1);
}

void SetPPSLow() {
    digitalWrite(PPS_OUTPUT_PIN, 0);
}

void SendPPS() {
    unsigned int tickInterval = millisSinceBoot - ppsActivationTime;
    ppsActivationTime = millisSinceBoot;
    SetPPSHigh();
}

void PPSLowIfRequired() {
    if ((millisSinceBoot - ppsActivationTime) > 500) {
        SetPPSLow();
    }
}

void TickSecond() {
    char buf[255];
    sprintf(buf, "*** TICK(%d): WWVB going low after %d ms high (EDGE)\n", frameCounter, millisSinceBoot - lastLowMillis);
    SendPPS();
    Serial.print(buf);
}

void processFrame() {
    char buf[255];
    sprintf(buf, "end of frame summary: frameHigh: %d, frameLow: %d\n", frameHighReadOut, frameLowReadOut);
    Serial.print(buf);
    float rawVal =
        (float)frameHighReadOut
        /
        ( (float)frameHighReadOut + (float)frameLowReadOut );

    rawVal *= 1000;
    unsigned int intRawVal = (int)rawVal;
    if (intRawVal > 100000) {
        intRawVal = 100000;
    }
    displayUpdateRequired++;
    registerBit(convertDutyCycleToBit(intRawVal));
}

int convertDutyCycleToBit(unsigned int rawVal) {
    char buf[255];
    /*

       20% - marker
       50% - one bit
       80% - zero bit
       our cutoff points will be 50% and 80%
     */
    char bitbuf[20];

    int output = 0;

    output = ZEROBIT;
    sprintf(bitbuf, "ZERO");

    if (rawVal < 800) {
        output = ONEBIT;
        sprintf(bitbuf, "ONE");
    }

    if (rawVal < 680) {
        output = MARKBIT;
        sprintf(bitbuf, "MARK");
    }

    sprintf(buf, "frame rawVal=%d, bit=%s\n", rawVal, bitbuf);
    Serial.print(buf);
    return output;
}

void registerBit(int doot) {
    if (minuteSync) {
        frameCounter++;
    }

    if (doot == MARKBIT) {
        if (lastBitReceived == MARKBIT) {
            // two mark bits in a row means we are in the first second of the minute
            frameCounter = 0;
            minuteSync = 1;
        }
    }

    if (!minuteSync) {
        frameCounter = 0;
    }

    sanityCheckFrame(doot);
    lastBitReceived = doot;
    logBit(doot);
}

void logBit(int doot) {

}

void lossOfSync(int errorFrame) {
    char buf[255];
    sprintf(buf, "ERROR: %d bit incorrect for framing, loss of sync!\n", errorFrame);
    Serial.print(buf);
    minuteSync = 0;
    displayUpdateRequired++;
}


void sanityCheckFrame(int doot) {
    if (
            (
             (frameCounter == 9)
             ||
             (frameCounter == 19)
             ||
             (frameCounter == 29)
             ||
             (frameCounter == 39)
             ||
             (frameCounter == 49)
            )
            && doot != MARKBIT) {
        lossOfSync(frameCounter);
    }

    if (
            (doot == MARKBIT)
            &&
            (
             (frameCounter != 0)
             &&
             (frameCounter != 9)
             &&
             (frameCounter != 19)
             &&
             (frameCounter != 29)
             &&
             (frameCounter != 39)
             &&
             (frameCounter != 49)
            )
       ) {
        lossOfSync(frameCounter);
    }
}

void updateDisplay() {
    //Serial.print("updateDisplay()\n");

    if (lossOfSignal) {
        sprintf(statusString, "LOS");
    }

    if (millisSinceBoot - frameStartTime < 10000) {
        sprintf(statusString, "RX(syncing)");
    }
    if (minuteSync) {
        sprintf(statusString, "RX(bit %d)", frameCounter);
    }

    char d[20];

    if (lastBitReceived == MARKBIT) {
        sprintf(d, "%d=MARK", frameCounter);
    }
    if (lastBitReceived == ONEBIT) {
        sprintf(d, "%d=ONE ", frameCounter);
    }
    if (lastBitReceived == ZEROBIT) {
        sprintf(d, "%d=ZERO", frameCounter);
    }

    lcd.clear();
    lcd.setCursor(0, 0);
    char msg[20];
    sprintf(msg, "up:%03d", secondCounter);
    lcd.print(msg);
    lcd.setCursor(0, 1);
    sprintf(msg, "s:%s", statusString);
    lcd.print(msg);

    if (minuteSync) {
        lcd.setCursor(10, 0);
        lcd.print(d);
    }

    if(DEBUG) {
        if(secondCounter % 10 == 0) {
            serialDebug();
        }
    }
}

void fastSerialDebug() {
    char buf[255];
    sprintf(buf,"stateStableMillis=%d\n",stateStableMillis);
    Serial.print(buf);
}

void serialDebug() {
    char buf[255];
    sprintf(buf,"lossOfSignal=%d\n",lossOfSignal);
    Serial.print(buf);
    sprintf(buf,"frameReadyToStart=%d\n",frameReadyToStart);
    Serial.print(buf);
    sprintf(buf,"beginFrameSearch=%d\n",beginFrameSearch);
    Serial.print(buf);
    sprintf(buf,"frameSearch=%d\n",frameSearch);
    Serial.print(buf);
    sprintf(buf,"frameStart=%d\n",frameStart);
    Serial.print(buf);
    sprintf(buf,"frameStartTime=%d\n",frameStartTime);
    Serial.print(buf);
    sprintf(buf,"millisSinceBoot=%d\n",millisSinceBoot);
    Serial.print(buf);
    sprintf(buf,"frameStartAge=%d\n",millisSinceBoot-frameStartTime);
    Serial.print(buf);
    sprintf(buf,"secondCounter=%d\n",secondCounter);
    Serial.print(buf);
    sprintf(buf,"timeToTick=%d\n",timeToTick);
    Serial.print(buf);
    sprintf(buf,"frameHigh=%d\n",frameHigh);
    Serial.print(buf);
    sprintf(buf,"frameLow=%d\n",frameLow);
    Serial.print(buf);
}