import {
  Plugin,
  Configurable,
  EventListener,
  DependencyLoad
} from '@squeebot/core/lib/plugin';

import { async as ical } from 'node-ical';

import { logger } from '@squeebot/core/lib/core';
import { Formatter, IMessage, MessageResolver } from '@squeebot/core/lib/types';
import { fullIDMatcher, readableTime } from '@squeebot/core/lib/common';

interface CalendarConfiguration {
  name: string;
  url: string;
  timeFrame: number;
  overrideDescription?: string;
  rooms: string[];
}

interface Event {
  id: string;
  name: string;
  start: number;
  end: number;
  description: string;
  from: CalendarConfiguration;
}

const loaded: CalendarConfiguration[] = [];
let memcache: Event[] = [];

function nts(): number {
  return Math.floor(Date.now() / 1000);
}

function utcNoHours(start: number): Date {
  const fts = new Date(start);
  return new Date(Date.UTC(fts.getFullYear(), fts.getMonth(), fts.getDate()));
}

function eventsFor(msg: IMessage): Event[] {
  return memcache.filter((ev: Event) => {
    if (!msg.fullRoomID) {
      return false;
    }

    if (!ev.from.rooms.length) {
      return true;
    }

    let matchesOne = false;
    for (const room of ev.from.rooms) {
      if (fullIDMatcher(msg.fullRoomID, room)) {
        matchesOne = true;
      }
    }

    return matchesOne;
  });
}

function sortStartTime(a: Event, b: Event): number {
  return a.start - b.end;
}

function colorize(events: Event[], format: Formatter): string[] {
  const colorized: string[] = [];

  for (const event of events) {
    let color = 'gold';

    if (event.start <= nts() && event.end > nts()) {
      color = 'green';
    } else if (event.end < nts()) {
      color = 'red';
    }

    colorized.push(format.color(color, event.name));
  }

  return colorized;
}

function tellEvent(eventData: Event, msg: IMessage, countdown = true): void {
  if (!eventData) {
    return;
  }

  const keys = [];
  let startColor = 'gold';
  let tstamp = '';

  if (eventData.start > nts()) {
    const timeLeftStamp = countdown ? 'in ' +
      readableTime(eventData.start - nts()) : new Date(eventData.start * 1000);
    tstamp = 'starts ' + timeLeftStamp + '.';
  } else if (eventData.start <= nts() && eventData.end > nts()) {
    const timeLeftStamp = countdown ? 'in ' +
      readableTime(eventData.end - nts()) : new Date(eventData.end * 1000);
    startColor = 'green';
    tstamp = 'ends ' + timeLeftStamp + '.';
  } else {
    startColor = 'red';
    tstamp = 'is over :(';
  }

  let name = eventData.name;
  if (name.length > 64) {
    name = name.substr(0, 64) + '...';
  }

  let description = eventData.description;
  if (description.length > 120) {
    description = description.substr(0, 120) + '...';
  }

  keys.push(['field', 'Event', { type: 'title', color: 'green' }]);
  keys.push(['field', name, { color: startColor }]);
  keys.push(['bold', tstamp]);
  keys.push(['field', description || '', { type: 'content' }]);

  msg.resolve(keys);
}

async function fetchCalendars(): Promise<void> {
  memcache = [];
  for (const cfg of loaded) {
    let result;
    let events = 0;
    try {
      result = await ical.fromURL(cfg.url);
    } catch (e: any) {
      logger.error('Calendar %s fetch failed:', cfg.name, e.stack);
    }

    for (const key in result) {
      const data = result[key];
      if (!data.type || data.type !== 'VEVENT') {
        continue;
      }

      const start = Math.floor(new Date(data.start).getTime() / 1000);
      const end = Math.floor(new Date(data.end).getTime() / 1000);

      // Recurring events handling
      if ('rrule' in data) {
        const rrule = (data as any).rrule as any;
        const recurring = rrule.between(utcNoHours(Date.now()),
          utcNoHours(Date.now() + cfg.timeFrame * 1000), true);
        const originalDuration = end - start;
        for (const date of recurring) {
          const newStart = Math.floor(new Date(date).getTime() / 1000);
          const newEnd = newStart + originalDuration;
          if (newStart > nts() + cfg.timeFrame || newEnd < nts()) {
            continue;
          }

          memcache.push({
            id: key,
            name: (data as any).summary,
            start: newStart,
            end: newEnd,
            from: cfg,
            description: (data as any).description || '',
          });

          events++;
        }
        continue;
      }

      // Skip events that are over and start beyond the time frame
      if (start > nts() + cfg.timeFrame || end < nts()) {
        continue;
      }

      memcache.push({
        id: key,
        name: data.summary,
        start,
        end,
        from: cfg,
        description: data.description || '',
      });

      events++;
    }

    logger.log('[calendar] Fetched %d events from %s.', events, cfg.name);
  }
}

@Configurable({
  calendars: [],
  updateInterval: '30 * * * *',
})
class CalendarPlugin extends Plugin {
  @EventListener('pluginUnload')
  public unloadEventHandler(plugin: string | Plugin): void {
    if (plugin === this.name || plugin === this) {
      this.emit('pluginUnloaded', this);
    }
  }

  @DependencyLoad('simplecommands')
  addCalendarCommands(cmd: any): void {
    const cmds = [
      {
        name: 'events',
        plugin: this.name,
        execute: async (msg: IMessage, msr: MessageResolver, spec: any, prefix: string, ...simplified: any[]): Promise<boolean> => {
          if (simplified[0] && simplified[0] === 'refresh') {
            await fetchCalendars();
          }

          let events = eventsFor(msg);
          if (!events.length) {
            msg.resolve('Events in %s: None currently scheduled.', msg.target?.name);
            return true;
          }

          events = events.filter((ev: Event) =>
            ev.start < nts() + ev.from.timeFrame && ev.end > nts())
            .slice(0, 8);

          if (!events.length) {
            msg.resolve('Events in %s: None currently scheduled.', msg.target?.name);
            return true;
          }

          events = events.sort(sortStartTime);

          msg.resolve('Events in %s:', msg.target?.name,
            colorize(events, msg.source.format).join(', '));
          return true;
        },
        description: 'Show a list of upcoming and ongoing events in the current room',
      },
      {
        name: 'event',
        plugin: this.name,
        execute: async (msg: IMessage, msr: MessageResolver, spec: any, prefix: string, ...simplified: any[]): Promise<boolean> => {
          let evt = simplified[0];
          let countdown = true;
          let slice = 0;
          if (evt && evt === '-d' || evt === 'get-date' || evt === 'get-time') {
            countdown = false;
            evt = simplified[1];
            slice = 1;
          }

          if (!evt) {
            msg.resolve('Please specify an event!');
            return true;
          }

          const query = simplified.slice(slice).join(' ');
          let events = eventsFor(msg);
          if (!events.length) {
            msg.resolve('There are no events in %s.', msg.target?.name);
            return true;
          }

          events = events.filter((ev: Event) => {
            if (ev.start > nts() + ev.from.timeFrame || ev.end < nts()) {
              return false;
            }

            return ev.name.toLowerCase().match(query.toLowerCase()) != null;
          }).slice(0, 8);

          if (!events.length) {
            msg.resolve('No events match "%s".', query);
            return true;
          } else if (events.length > 1) {
            msg.resolve('Multiple events match "%s"! Here\'s the first one:', query);
            events = events.sort(sortStartTime);
          }

          tellEvent(events[0], msg, countdown);
          return true;
        },
        usage: '<event>',
        description: 'Show details of an event',
      }
    ];
    cmd.registerCommand(cmds);
  }

  loadConfig(): void {
    for (const cfg of this.config.get('calendars', [])) {
      if (!cfg.name || !cfg.url) {
        logger.error('[%s] Invalid calendar configuration.', this.name);
        continue;
      }
      loaded.push(cfg);
    }
  }

  @DependencyLoad('cron')
  public initializeCron(cronPlugin: any): void {
    const expression = this.config.get('updateInterval', '30 * * * *');
    cronPlugin.registerTimer(
      this,
      expression,
      () => fetchCalendars().catch(
        (error) => logger.error('[calendar] fetch error:', error.stack),
      )
    );
  }

  initialize(): void {
    this.loadConfig();
    fetchCalendars().catch(
      (e) => logger.error('[%s] fetch error:', this.name, e.stack));
  }
}

module.exports = CalendarPlugin;