// Statistics: how many incidents, how fast they are answered, and when and
// what the alerts are. The same figures the TUI's Stats tab shows, over a
// range picked with the chips. The server scopes them to the caller's teams.

import * as api from './api.js';
import { h, clear, emptyState, spinner } from './ui.js';
import { duration } from './format.js';

const DAY_MS = 24 * 60 * 60 * 1000;

// `days` counts back from today, inclusive; the server reads from/to as UTC
// dates, so these are too.
const RANGES = [
  { id: 'today', label: 'Today', days: 1 },
  { id: '7d', label: '7d', days: 7 },
  { id: '30d', label: '30d', days: 30 },
  { id: '90d', label: '90d', days: 90 },
  { id: 'all', label: 'All', days: null },
];

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

let range = '30d';
let data = null;
let error = null;

const utcDate = (ms) => new Date(ms).toISOString().slice(0, 10);

function query(r) {
  if (!r.days) return {};
  const now = Date.now();
  return { from: utcDate(now - (r.days - 1) * DAY_MS), to: utcDate(now) };
}

export function show() {
  render();
  refresh();
}

export async function refresh() {
  const requested = range;
  const q = query(RANGES.find((x) => x.id === range));
  try {
    const [incidents, top, byHour, byDay] = await Promise.all([
      api.statsIncidents(q),
      api.statsTop({ ...q, limit: 10 }),
      api.statsByHour(q),
      api.statsByDay(q),
    ]);
    if (requested !== range) return;
    data = { incidents, top, byHour, byDay };
    error = null;
  } catch (err) {
    if (requested !== range) return;
    error = err.message;
  }
  render();
}

function setRange(id) {
  if (id === range) return;
  range = id;
  data = null;
  render();
  refresh();
}

function render() {
  const chips = h('div', { class: 'chips', role: 'tablist', 'aria-label': 'Time range' },
    RANGES.map((r) => h('button', {
      class: 'chip',
      type: 'button',
      role: 'tab',
      'aria-selected': String(r.id === range),
      onclick: () => setRange(r.id),
      text: r.label,
    })));

  let body;
  if (error && !data) body = h('div', { class: 'load-error', text: error });
  else if (!data) body = spinner();
  else if (!data.incidents.total && !data.byHour.some((x) => x.count)) {
    body = emptyState('No data in this range', '', 'chart');
  } else {
    body = h('div', { class: 'stats' },
      error && h('div', { class: 'load-error', text: `Showing older data: ${error}` }),
      tiles(data.incidents),
      data.top.length > 0 && card('Top alerts', topAlerts(data.top)),
      card('Alerts by hour (UTC)', columns(
        data.byHour.map((x) => ({ label: String(x.hour), value: x.count, tick: x.hour % 6 === 0 })),
        'Alerts by hour of day')),
      card('Alerts by day', columns(
        data.byDay.map((x) => ({ label: x.day_name.slice(0, 3), value: x.count, tick: true })),
        'Alerts by day of week')));
  }
  clear(view(), h('div', {}, chips, body));
}

// A missing mean means nothing has been acknowledged or resolved yet.
const mean = (s) => (s == null ? '—' : duration(s * 1000));

function tiles(s) {
  const tile = (label, value, cls = '') => h('div', { class: `stat-tile ${cls}` },
    h('div', { class: 'stat-value', text: String(value) }),
    h('div', { class: 'stat-label', text: label }));
  return h('div', { class: 'stat-tiles' },
    tile('Incidents', s.total),
    tile('Triggered', s.triggered, 'st-triggered'),
    tile('Acknowledged', s.acknowledged, 'st-acknowledged'),
    tile('Resolved', s.resolved, 'st-resolved'),
    tile('Mean time to acknowledge', mean(s.mtta_seconds)),
    tile('Mean time to resolve', mean(s.mttr_seconds)));
}

function card(title, content) {
  return h('section', { class: 'chart-card card card-pad' },
    h('h3', { class: 'chart-title', text: title }), content);
}

// Ranked names with a bar scaled to the busiest one.
function topAlerts(items) {
  const max = Math.max(...items.map((x) => x.count), 1);
  return h('ol', { class: 'hbars' }, items.map((x) => {
    const fill = h('span', { class: 'hbar-fill' });
    fill.style.width = `${Math.max(2, (x.count / max) * 100)}%`;
    return h('li', { class: 'hbar' },
      h('span', { class: 'hbar-name', title: x.name, text: x.name }),
      h('span', { class: 'hbar-track' }, fill),
      h('span', { class: 'hbar-count', text: String(x.count) }));
  }));
}

const SVG_NS = 'http://www.w3.org/2000/svg';

function svg(tag, attrs = {}, text) {
  const el = document.createElementNS(SVG_NS, tag);
  for (const [k, v] of Object.entries(attrs)) el.setAttribute(k, String(v));
  if (text != null) el.textContent = text;
  return el;
}

// A column chart: one bar per item, the value in a tooltip, and a label under
// the items marked `tick`.
function columns(items, label) {
  const W = 480;
  const H = 140;
  const base = H - 18;
  const step = W / items.length;
  const max = Math.max(...items.map((x) => x.value), 1);
  const root = svg('svg', {
    class: 'columns', viewBox: `0 0 ${W} ${H}`, role: 'img', 'aria-label': label,
  });
  root.appendChild(svg('line', { class: 'axis', x1: 0, x2: W, y1: base, y2: base }));
  items.forEach((it, i) => {
    const bh = it.value ? Math.max(2, (it.value / max) * (base - 6)) : 0;
    const x = i * step + step * 0.15;
    const g = svg('g', { class: 'col' });
    g.appendChild(svg('title', {}, `${it.label}: ${it.value}`));
    // A full-height transparent hit area, so a tiny bar is still hoverable.
    g.appendChild(svg('rect', { class: 'col-hit', x: i * step, y: 0, width: step, height: base }));
    if (bh) g.appendChild(svg('rect', { class: 'col-bar', x, y: base - bh, width: step * 0.7, height: bh, rx: 2 }));
    root.appendChild(g);
    if (it.tick) {
      root.appendChild(svg('text', { class: 'col-label', x: i * step + step / 2, y: H - 4, 'text-anchor': 'middle' }, it.label));
    }
  });
  return root;
}