"use strict";

const fs = require('fs'),
  EventEmitter = require('events'),
  Epoll = require('epoll').Epoll

const GPIO_ROOT_PATH = '/sys/class/gpio/'

class Interrupt extends EventEmitter {
  // bus is i2c-bus bus object
  constructor(pin_number, opts = {}) {
    super()
    this.num = pin_number;
    this.hook = opts.hook // will be passed back with the emit
    this.path = GPIO_ROOT_PATH + 'gpio' + this.num + '/'
    this.edge = opts.edge ? opts.edge : 'falling'
    this.debounce = opts.debounce ? opts.debounce : 200
    this.poller = new Epoll(function (err, fd, events) {
      if (err) { this.emit('error', err) }
      this.clear()
      this.emit('fired', this.hook)
    }.bind(this))
  }

  init() {

    try {
      if (fs.existsSync(this.path)) { this.exit() }

      fs.writeFileSync(GPIO_ROOT_PATH + 'export', this.gpio);
      fs.writeFileSync(this.path + 'direction', 'in');
      fs.writeFileSync(this.path + 'edge', this.edge);
      this.valueFd = fs.openSync(this.path + 'value', 'r+'); // Cache fd for performance.

      this.clear();
      this.start()

      process.on('SIGINT', function () {
        console.log('\ncleaning up interrupt before exiting')
        this.exit();
      })
    } catch (err) { return Promise.reject(err) }

    return Promise.resolve('interrupt ready')

  }

  fire(name = 'fired') {
    this.emit(name, this.hook)
  }

  clear() {
    fs.readSync(this.valuefd, null, 0, 1, 0);
  }

  exit() {
    if (this.valuefd) {
      this.stop()
      fs.closeSync(this.valueFd)
    }
    try {
      fs.writeFileSync(GPIO_ROOT_PATH + 'unexport', this.gpio);
    } catch (ignore) {}

  }

  start() {
    this.poller.add(this.valuefd, Epoll.EPOLLPRI);
  }

  stop() {
    this.poller.remove(this.valuefd).close();
  }

}

module.exports = {
  Interrupt
}