import ICAL from "ical.js";
import shows from "./shows";

function max(a, b) {
  if (a < b) return b;
  return a;
}

/**
 * Represent a schedule (ie: a .ics file)
 */
class RadioSchedule {
  constructor(calendar, radio) {
    this.calendar = calendar; // ICAL.Calendar
    this.radio = radio; // radiomanifest.Radio
  }

  /**
   * Get a list of all known {@link vEvent}s
   *
   * @returns {Array<external:ICAL~Component>}
   * */
  getEvents() {
    return this.calendar.getAllSubcomponents("vevent");
  }

  /**
   * @returns {RadioShow} tries to get a matching show, or create a new one
   */
  getShowByEvent(ev) {
    if (ev === null) return null;
    if (this.radio !== undefined) {
      const showid = RadioSchedule.veventGetShowID(ev);
      var show = this.radio.getShowByName(showid);
      if (show === null || show === undefined) {
        return new shows.RadioShow(RadioSchedule.veventGetSummary(ev));
      }
      return show;
    }
    return new shows.RadioShow(RadioSchedule.veventGetSummary(ev));
  }

  /**
   * @returns {external:ICAL~Component} if nothing is going on right now, `null` is returned
   */
  getNowEvent(now) {
    var ev_now = this.getEvents().filter(function (vevent) {
      const ev = new ICAL.Event(vevent);
      return isNow(ev, now);
    });
    ev_now.sort((e1, e2) => {
      return this.veventGetPriority(e1) - this.veventGetPriority(e2);
    });
    if (ev_now.length === 0) return null;
    return ev_now[0];
  }

  /**
   * @returns {RadioShow} if nothing is going on right now, `null` is returned
   */
  getNowShow(now) {
    const ev = this.getNowEvent(now);
    return this.getShowByEvent(ev);
  }

  /**
   * @returns {NextEvent} if there is none, `null` is returned
   */
  getNextEvent(now) {
    var nowEvent = this.getNowEvent(now);
    let future_events = this.getEvents()
      .filter((e) => {
        return e != nowEvent;
      })
      .map((e) => {
        const vEvent = new ICAL.Event(e);
        return { event: e, time: getNext(vEvent, now) };
      })
      .filter((x) => {
        return x.time !== null && x.time !== undefined;
      });
    // since ".sort()" is guaranteed to be stable, we can sort by priority, then by date, so that two events
    // starting at the same time will be sorted observing priority
    future_events.sort(
      (x1, x2) =>
        this.veventGetPriority(x1.event) - this.veventGetPriority(x2.event),
    );
    future_events.sort((x, y) => x.time.toUnixTime() - y.time.toUnixTime());

    if (future_events.length === 0) {
      return null;
    }
    return future_events[0];
  }

  /**
   * @returns {NextShow} if there is no next show, null will be returned
   */
  getNextShow(now) {
    const next = this.getNextEvent(now);
    if (next === null) return null;
    const ev = next.event;
    const show = this.getShowByEvent(ev);
    return { show: show, time: next.time };
  }
  static veventGetSummary(vevent) {
    return vevent.getFirstProperty("summary").getFirstValue();
  }
  static veventGetShowID(vevent) {
    return RadioSchedule.veventGetSummary(vevent); // XXX: X-Show-ID
  }

  /**
   * @return {integer} a normalized version of priority, easier to compare
   */
  veventGetPriority(ev) {
    const prop = ev.getFirstProperty("priority");
    let prio;
    if (prop === null) {
      prio = null;
    } else {
      prio = prop.getFirstValue();
    }
    if (prio === null || prio === 0) {
      prio = 100;
    }
    return prio;
  }
}

function isNow(vEvent, now) {
  if (now === undefined) {
    now = ICAL.Time.now();
  }
  if (vEvent.isRecurring()) {
    return isNowRecurring(vEvent, now);
  }
  return now < vEvent.endDate && now > vEvent.startDate;
}

function isNowRecurring(vEvent, now) {
  var expand = vEvent.iterator(vEvent.startDate);
  var next, next_end;

  while ((next = expand.next())) {
    next_end = next.clone();
    next_end.addDuration(vEvent.duration);

    if (next_end > now) {
      break;
    }
  }
  return now < next_end && now > next;
}

/*
 * @private
 * @param {external:ICAL~Component} vEvent a _recurring_ vEvent
 * @param {external:ICAL~Time} [now]
 * @return {external:ICAL~Time} first future occurrence of this event
 */
function getNext(vEvent, now) {
  if (now === undefined) {
    now = ICAL.Time.now();
  }
  if (vEvent.isRecurring()) {
    return getNextRecurring(vEvent, now);
  }
  if (vEvent.endDate > now) {
    const val = max(now, vEvent.startDate);
    return val;
  }
  return null;
}

/*
 * @private
 * @param {external:ICAL~Component} vEvent a _recurring_ vEvent
 * @param {external:ICAL~Time} now
 * @return {external:ICAL~Time} first future occurrence of this event
 */
function getNextRecurring(vEvent, now) {
  var expand = vEvent.iterator(vEvent.startDate);
  var next, next_end;

  while ((next = expand.next())) {
    const start = next.clone();
    next_end = start.clone();
    next_end.addDuration(vEvent.duration);
    if (next_end <= now) {
      continue;
    }
    return max(start, now);
  }
  return null;
}

async function get(manifest) {
  if (manifest.scheduleURL) {
    let resp = null;
    try {
      resp = await fetch(manifest.scheduleURL);
    } catch (e) {
      true;
    }
    if (resp !== null) {
      try {
        const text = await resp.text();
        return parse(text);
      } catch (e) {
        console.error("Error while parsing schedule", e);
        throw e;
      }
    }
  }
}

/**
 * Parse ICAL and get a RadioSchedule
 *
 * @param {string} text The text, in ICS format
 * @returns {RadioSchedule}
 */
function parse(text) {
  var jcalData = ICAL.parse(text);
  var vcalendar = new ICAL.Component(jcalData);

  return new RadioSchedule(vcalendar);
}

export default {
  get: get,
  parse: parse,
  RadioSchedule: RadioSchedule,
};

/**
 * @typedef {Object} NextShow
 * @property {RadioShow} show The next show scheduled
 * @property {external:ICAL~Time} time When it will start
 */

/**
 * @typedef {Object} NextEvent
 * @property {RadioShow} event The next show scheduled
 * @property {external:ICAL~Time} time When it will start
 */

/**
 * @external ICAL
 * @see https://mozilla-comm.github.io/ical.js/api/index.html
 */

/**
 * @class Component
 * @memberof external:ICAL
 * @inner
 * @see https://mozilla-comm.github.io/ical.js/api/ICAL.Component.html
 */

/**
 * @class Time
 * @memberof external:ICAL
 * @inner
 * @see https://mozilla-comm.github.io/ical.js/api/ICAL.Time.html
 */