"use strict";

const fs = require('mz/fs'),
  exec = require('mz/child_process').exec,
  EventEmitter = require('events'),
  Epoll = require('epoll').Epoll,
  _ = require('uci-utils')

const pWaitFor = require('p-wait-for')
const pathExists = require('path-exists');
const debounce = require('debounce');

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 // default 'both'
    this.delay = opts.delay // default = 50
    this.pull = opts.pull // default = pu
    this.puller = opts.puller ? opts.puller : (num, state) => { return `raspi-gpio set ${num} ${state}` } // default rpi using raspi-gpio
      // this.puller = (num, state) => { return `raspi-gpio set ${num} ${state}` }
    this.dbt = opts.debounce ? opts.debounce : 200
    this.poller = new Epoll(
      debounce((err, fd, events) => {
        if (err) { this.emit('error', err) } else {
          // this.clear().then(this.emit('fired', this.hook))
          this.emit('fired', this.hook)
        }
      }, this.dbt, true) // true = leading
    )
  }

  init() {

    process.on('SIGINT', () => {
      this.exit().then((resp) => console.log("\n", resp)) // unexport on cntrl-c
        .catch(err => console.log("error:", err))
    })

    return _.pSeries([
      this.exit(),
      this._pull(this.num, this.pull),
      this._export(this.num),
      this._direction('in', this.delay),
      () => this._edge(this.edge), // TODO determine why these need additional function
      () => this._fd()
    ])

  }

  // manual firing for testing
  fire(name = 'fired') {
    this.emit(name, this.hook)
  }

  clear() {
    let buffer = Buffer.from([0x00])
    return fs.read(this.valuefd, buffer, 0, 1, 0).then(() => { return Promise.resolve('interrupt cleared') })
  }

  exit() {
    return new Promise((resolve, reject) => {
      pathExists(this.path)
        .then((exists) => {
          if (exists) {
            fs.writeFile(GPIO_ROOT_PATH + 'unexport', this.num)
              .then(() => {
                if (this.valuefd) {
                  this.stop()
                  fs.close(this.valuefd)
                }
                this._pull(this.num, 'pn')
              })
              .then(resolve('unexported and exited'))
          } else {
            resolve('already unexported')
          }
        })
        .catch(err => resolve(err))
    })
  }

  start() {
    // this.inter(port).on('fired', () => {
    //   console.log(`interrupt port ${port}  hook me \n ${relays}`)
    //     // hook.bind(this)(port)
    //
    // })
    return this.clear().then(() => this.poller.add(this.valuefd, Epoll.EPOLLPRI | Epoll.EPOLLONESHOT));
  }

  reset() {
    return this.clear().then(() => this.poller.modify(this.valuefd, Epoll.EPOLLPRI | Epoll.EPOLLONESHOT));
  }

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

  /*******private methods*********/

  _pull(num, state = 'pu') {
    if (this.puller === 'external') { return Promise.resolve('pull must be set externally') } else {
      return exec(this.puller(num, state))
        .then(() => { return Promise.resolve(`pull set ${state}`) })
    }
  }

  _fd() {
    return fs.open(this.path + 'value', 'r+')
      .then(fd => {
        this.valuefd = fd
        return Promise.resolve(`value fd set ${fd}`)
      })
  }

  _export(num) {
    return new Promise(function (resolve, reject) {
      fs.writeFile(GPIO_ROOT_PATH + 'export', num)
        .then(() => { return resolve('exported') })
        .catch((err) => { return reject(err) })
    })
  }

  _direction(dir = 'in', delay = 50) {
    return pWaitFor(() => pathExists(this.path + 'direction'))
      .then(_.pDelay(delay))
      .then(() => {
        return fs.writeFile(dir + 'direction', dir)
          .then(() => {
            return Promise.resolve(`direction set ${dir}`)
          })
      })
  }

  _edge(edge = 'both') {
    return fs.writeFile(this.path + 'edge', edge)
      .then(() => {
        return Promise.resolve(`edge set ${edge}`)
      })
  }

}

module.exports = {
  Interrupt
}