'use strict';

const { settings } = require('./settings');
const { compareEvents } = require('./events');

const EPG_HORIZON_MS = 14 * 24 * 60 * 60 * 1000;
const EPG_PAST_MS = 6 * 60 * 60 * 1000;

function xmlEscape(value) {
  return String(value == null ? '' : value)
    .replace(/&/g, '&')
    .replace(/</g, '&lt;')
    .replace(/>/g, '&gt;')
    .replace(/"/g, '&quot;')
    .replace(/'/g, '&apos;');
}

function xmltvDate(date) {
  return `${date.toISOString().slice(0, 19).replace(/[-:T]/g, '')} +0000`;
}

function buildXmltv(scheduler, now = Date.now()) {
  const state = scheduler.state;
  const count = state.slots.length;
  const programmes = [];
  const slotEnds = new Array(count).fill(now);
  const assignedKeys = new Set();

  for (let index = 0; index < count; index += 1) {
    const slot = state.slots[index];
    const event = slot && slot.eventKey ? state.events.get(slot.eventKey) : null;
    if (!event) continue;
    assignedKeys.add(event.key);
    programmes.push({ slot: index, event, startAt: event.startAt, endAt: event.endAt });
    slotEnds[index] = Math.max(slotEnds[index], event.endAt.getTime());
  }

  const future = (state.upcoming || [])
    .filter((event) => !assignedKeys.has(event.key))
    .filter((event) => event.endAt.getTime() > now)
    .filter((event) => event.startAt.getTime() <= now + EPG_HORIZON_MS)
    .slice()
    .sort(compareEvents);

  for (const event of future) {
    const duration = event.endAt.getTime() - event.startAt.getTime();
    let bestSlot = -1;
    let bestEnd = Infinity;
    for (let index = 0; index < count; index += 1) {
      if (slotEnds[index] <= event.startAt.getTime()) {
        if (slotEnds[index] < bestEnd) {
          bestEnd = slotEnds[index];
          bestSlot = index;
        }
      }
    }
    if (bestSlot === -1) {
      for (let index = 0; index < count; index += 1) {
        if (slotEnds[index] < bestEnd) {
          bestEnd = slotEnds[index];
          bestSlot = index;
        }
      }
    }
    if (bestSlot === -1) continue;
    const startAt = Math.max(event.startAt.getTime(), bestEnd);
    const endAt = startAt + duration;
    if (event.endAt.getTime() <= bestEnd) continue;
    programmes.push({
      slot: bestSlot,
      event,
      startAt: new Date(startAt),
      endAt: new Date(endAt),
    });
    slotEnds[bestSlot] = endAt;
  }

  const bySlot = Array.from({ length: count }, () => []);
  for (const programme of programmes) {
    if (programme.endAt.getTime() < now - EPG_PAST_MS) continue;
    bySlot[programme.slot].push(programme);
  }
  for (const list of bySlot) {
    list.sort((a, b) => a.startAt.getTime() - b.startAt.getTime());
  }

  const lines = ['<?xml version="1.0" encoding="UTF-8"?>'];
  lines.push('<!DOCTYPE tv SYSTEM "xmltv.dtd">');
  lines.push('<tv generator-info-name="xtream-ppv-bundler">');
  for (let index = 0; index < count; index += 1) {
    lines.push(`  <channel id="jupiler-${index + 1}">`);
    lines.push(`    <display-name>Jupiler ${index + 1}</display-name>`);
    lines.push('  </channel>');
  }
  for (let index = 0; index < count; index += 1) {
    for (const programme of bySlot[index]) {
      const event = programme.event;
      lines.push(
        `  <programme start="${xmltvDate(programme.startAt)}" stop="${xmltvDate(programme.endAt)}" channel="jupiler-${index + 1}">`
      );
      lines.push(`    <title lang="nl">${xmlEscape(event.title)}</title>`);
      if (event.league) {
        lines.push(`    <sub-title lang="nl">${xmlEscape(event.league)}</sub-title>`);
      }
      lines.push(
        `    <desc lang="nl">${xmlEscape(`[${event.league || settings.searchTerm}] ${event.title}`)}</desc>`
      );
      lines.push(`    <category lang="nl">Sport</category>`);
      lines.push('  </programme>');
    }
  }
  lines.push('</tv>');
  return `${lines.join('\n')}\n`;
}

module.exports = { buildXmltv, xmlEscape, xmltvDate };