#include "parallel.h"

#include <stdint.h>

#include "Arduino.h"

namespace {

constexpr int kParallelDataPins[] = {
        D9, D8, D7, D6, D5, D4, D3, D2,
};

constexpr int kParallelBusyPin = D14;
constexpr int kParallelAckPin = D15;
constexpr int kParallelPaperoutPin = D12;
constexpr int kParallelSelectPin = D11;

constexpr int kParallelNibblePins[] = {
        kParallelSelectPin,
        kParallelPaperoutPin,
        kParallelAckPin,
        kParallelBusyPin,
};

constexpr bool kParallelNibbleInverted[] = {
        false,
        false,
        false,
        true,
};

constexpr int kParallelStrobePin = D10;

volatile bool strobe_pending = false;
volatile uint8_t strobe_byte = 0;

void strobeIsr() {
    strobe_pending = true;
    strobe_byte = readParallel();
}

} // namespace

uint8_t readParallel() {
    uint8_t out = 0;
    for (int i = 0; i < 8; i++) {
        if (digitalReadFast(digitalPinToPinName(kParallelDataPins[i])) ==
            HIGH) {
            out |= (1 << i);
        }
    }
    if (digitalReadFast(digitalPinToPinName(kParallelStrobePin)) == HIGH) {
        out |= (1 << 8);
    }
    return out;
}

#define BIT(x, n) ((x & (1 << n)) ? HIGH : LOW)

void writeParallel(uint8_t nibble) {
    for (int i = 0; i < 4; i++) {
        int lvl = BIT(nibble, i);
        if (kParallelNibbleInverted[i]) {
            lvl = lvl == HIGH ? LOW : HIGH;
        }
        digitalWriteFast(digitalPinToPinName(kParallelNibblePins[i]), lvl);
    }
}

bool strobeOccurred(uint8_t &byte) {
    bool pending;
    {
        noInterrupts();
        pending = strobe_pending;
        byte = strobe_byte;
        strobe_pending = false;
        interrupts();
    }

    return pending;
}

void setupParallel() {
    for (int i = 0; i < sizeof(kParallelDataPins) / sizeof(int); i++) {
        pinMode(kParallelDataPins[i], INPUT);
    }
    for (int i = 0; i < sizeof(kParallelNibblePins) / sizeof(int); i++) {
        pinMode(kParallelNibblePins[i], OUTPUT);
        digitalWrite(kParallelNibblePins[i], HIGH);
    }
    pinMode(kParallelStrobePin, INPUT);

    attachInterrupt(digitalPinToInterrupt(kParallelStrobePin), strobeIsr,
                    FALLING);
}