// On-call: who is on duty now, the week around it, and your own next shifts.
// Read-only for now; the TUI edits the schedule.

import * as api from './api.js';
import { h, clear, icon, spinner } from './ui.js';
import { isoDate, mondayOf, addDays, isoWeek, initial } from './format.js';
import { myID } from './state.js';

const view = () => document.getElementById('view-oncall');

let weekStart = mondayOf(new Date());
let data = null;
let error = null;

const dayName = new Intl.DateTimeFormat(undefined, { weekday: 'short' });
const dayDate = new Intl.DateTimeFormat(undefined, { day: 'numeric', month: 'short' });

export function show() {
  if (!data) clear(view(), spinner());
  refresh();
}

export async function refresh() {
  const start = weekStart;
  const today = new Date();
  try {
    const [now, week, upcoming] = await Promise.all([
      api.onCallNow(),
      api.schedule(isoDate(start), isoDate(addDays(start, 6))),
      api.schedule(isoDate(today), isoDate(addDays(today, 60))),
    ]);
    if (start !== weekStart) return;
    data = { now, week, upcoming };
    error = null;
  } catch (err) {
    error = err.message;
  }
  render();
}

function shiftWeek(n) {
  weekStart = addDays(weekStart, 7 * n);
  refresh();
}

function render() {
  if (!data) {
    clear(view(), error ? h('div', { class: 'load-error', text: error }) : spinner());
    return;
  }
  clear(view(),
    error && h('div', { class: 'load-error', text: `Showing older data: ${error}` }),
    nowCard(),
    weekCard(),
    myShifts(),
  );
}

function you(userID) {
  return userID === myID() ? h('span', { class: 'you', text: 'you' }) : null;
}

function nowCard() {
  const n = data.now;
  return h('div', { class: 'card now-card' },
    h('div', { class: `avatar ${n ? '' : 'none'}`, text: n ? initial(n.username) : '–' }),
    h('div', {},
      h('div', { class: 'now-label', text: 'On call now' }),
      h('div', { class: 'now-name' }, n ? n.username : 'Nobody', n && you(n.user_id)),
    ),
  );
}

function weekCard() {
  const byDate = new Map(data.week.map((e) => [e.date, e]));
  const today = isoDate(new Date());
  const days = [];
  for (let i = 0; i < 7; i++) {
    const d = addDays(weekStart, i);
    const key = isoDate(d);
    const e = byDate.get(key);
    days.push(h('li', { class: `day ${key === today ? 'today' : ''} ${key < today ? 'past' : ''}` },
      h('span', { class: 'day-name', text: dayName.format(d) }),
      h('span', { class: 'day-date', text: dayDate.format(d) }),
      h('span', { class: `day-who ${e ? '' : 'nobody'}` }, e ? e.username : 'nobody', e && you(e.user_id)),
    ));
  }
  const thisWeek = isoDate(weekStart) === isoDate(mondayOf(new Date()));
  return [
    h('div', { class: 'page-head' },
      h('h2', { text: thisWeek ? 'This week' : 'Week' }),
      h('div', { class: 'week-nav' },
        h('button', { class: 'btn btn-ghost btn-icon', type: 'button', 'aria-label': 'Previous week', onclick: () => shiftWeek(-1) },
          icon('chevronLeft')),
        h('button', {
          class: 'btn btn-ghost label',
          type: 'button',
          title: 'Back to this week',
          onclick: () => { weekStart = mondayOf(new Date()); refresh(); },
          text: `Week ${isoWeek(weekStart)}`,
        }),
        h('button', { class: 'btn btn-ghost btn-icon', type: 'button', 'aria-label': 'Next week', onclick: () => shiftWeek(1) },
          icon('chevronRight')),
      ),
    ),
    h('ul', { class: 'card days' }, days),
  ];
}

// myShifts groups your upcoming dates into runs of consecutive days.
function myShifts() {
  const mine = data.upcoming.filter((e) => e.user_id === myID()).map((e) => e.date).sort();
  const runs = [];
  for (const date of mine) {
    const last = runs[runs.length - 1];
    if (last && isoDate(addDays(parse(last.to), 1)) === date) last.to = date;
    else runs.push({ from: date, to: date });
  }
  const fmt = (s) => `${dayName.format(parse(s))} ${dayDate.format(parse(s))}`;
  return [
    h('div', { class: 'page-head' }, h('h2', { text: 'Your next shifts' })),
    h('div', { class: 'card' },
      runs.length
        ? h('ul', { class: 'shift-list' }, runs.slice(0, 8).map((r) =>
          h('li', {},
            h('span', { text: r.from === r.to ? fmt(r.from) : `${fmt(r.from)} – ${fmt(r.to)}` }),
            h('span', { class: 'muted', text: days(r) })),
        ))
        : h('div', { class: 'empty', text: 'Nothing scheduled in the next 60 days.' })),
  ];
}

function parse(s) {
  const [y, m, d] = s.split('-').map(Number);
  return new Date(y, m - 1, d);
}

function days(r) {
  const n = Math.round((parse(r.to) - parse(r.from)) / 86400000) + 1;
  return n === 1 ? '1 day' : `${n} days`;
}