/**
 * Customer analytics — engagement overview (active vs. silent customers,
 * top communication). Reads the global ticket snapshot aggregated server-side.
 */
import { getJson } from '/js/core/app-http.js';
import { resolveHost } from '/js/core/app-dom.js';

const EMPTY_API = Object.freeze({ destroy: () => {} });

const resolveContainer = (root) => {
  const host = resolveHost(root);
  if (host instanceof HTMLElement && host.matches('.app-details-container[data-app-component="helpdesk-analytics"]')) {
    return host;
  }
  return host.querySelector('.app-details-container[data-app-component="helpdesk-analytics"]');
};

export function initHelpdeskAnalytics(root = document) {
  const container = resolveContainer(root);
  if (!container) {
    return EMPTY_API;
  }

  const listenerController = new AbortController();
  const requestController = new AbortController();
  const on = (target, type, handler, options = {}) => {
    if (!target || typeof target.addEventListener !== 'function') {
      return;
    }
    target.addEventListener(type, handler, { ...options, signal: listenerController.signal });
  };

  const dataUrl = container.dataset.analyticsUrl;
  const debitorBaseUrl = container.dataset.debitorBaseUrl || '';
  const d = (key, fallback) => container.dataset[key] || fallback;

  const elLoading = document.getElementById('analytics-loading');
  const elError = document.getElementById('analytics-error');
  const elTruncated = document.getElementById('analytics-truncated');
  const elContent = document.getElementById('analytics-content');
  const elTiles = document.getElementById('analytics-tiles');
  const elSilentTable = document.getElementById('analytics-silent-table');
  const elSilentBody = document.getElementById('analytics-silent-body');
  const elSilentEmpty = document.getElementById('analytics-silent-empty');
  const elTopTable = document.getElementById('analytics-top-table');
  const elTopBody = document.getElementById('analytics-top-body');
  const elTopEmpty = document.getElementById('analytics-top-empty');
  const elRefresh = container.querySelector('button[name="analytics-refresh"]');
  const periodSelector = document.getElementById('analytics-period-selector');

  let currentPeriod = 90;

  const showState = (state) => {
    if (elLoading) elLoading.hidden = state !== 'loading';
    if (elError) elError.hidden = state !== 'error';
    if (elContent) elContent.hidden = state !== 'success';
  };

  const h = (tag, cls, text) => {
    const element = document.createElement(tag);
    if (cls) element.className = cls;
    if (text !== undefined) element.textContent = text;
    return element;
  };

  const customerCell = (row) => {
    const td = h('td');
    const name = row.customer_name || row.customer_no;
    if (debitorBaseUrl && row.customer_no) {
      const link = h('a', '', name);
      link.href = debitorBaseUrl + encodeURIComponent(row.customer_no);
      td.appendChild(link);
    } else {
      td.textContent = name;
    }
    if (row.customer_name && row.customer_no) {
      td.appendChild(h('span', 'helpdesk-analytics-cust-no', ` ${row.customer_no}`));
    }
    return td;
  };

  const lastContactText = (row) => {
    if (row.days_since_contact === null || row.days_since_contact === undefined) {
      return d('labelNeverShort', 'never');
    }
    if (row.days_since_contact === 0) {
      return row.last_contact_iso || '';
    }
    return `${row.last_contact_iso || ''} · ${row.days_since_contact} ${d('labelDaysAgo', 'days ago')}`;
  };

  // Mirror templates/partials/app-tile.phtml so the .app-tile CSS applies, but
  // render a non-navigating <div> — these are stat tiles, not links.
  const buildTile = ({ icon, tone, count, label }) => {
    const tile = h('div', 'app-tile helpdesk-analytics-tile');
    if (tone) tile.dataset.tone = tone;
    const iconWrap = h('span', 'app-tile-icon');
    iconWrap.appendChild(h('i', `bi ${icon}`));
    tile.appendChild(iconWrap);
    tile.appendChild(h('span', 'app-tile-count', String(count)));
    tile.appendChild(h('span', 'app-tile-label', label));
    return tile;
  };

  const renderTiles = (summary) => {
    if (!elTiles) return;
    elTiles.replaceChildren();
    elTiles.appendChild(buildTile({
      icon: 'bi-people', tone: 'blue',
      count: summary.total_customers || 0, label: d('labelTotal', 'Customers'),
    }));
    elTiles.appendChild(buildTile({
      icon: 'bi-chat-dots', tone: 'emerald',
      count: summary.active || 0, label: d('labelActive', 'Active'),
    }));
    elTiles.appendChild(buildTile({
      icon: 'bi-exclamation-triangle', tone: 'amber',
      count: summary.silent || 0, label: d('labelSilent', 'No contact'),
    }));
    elTiles.appendChild(buildTile({
      icon: 'bi-question-circle', tone: 'neutral',
      count: summary.no_contact_ever || 0, label: d('labelNever', 'Never in contact'),
    }));
  };

  const renderSilent = (rows) => {
    if (!elSilentBody || !elSilentTable || !elSilentEmpty) return;
    elSilentBody.replaceChildren();
    if (!rows || rows.length === 0) {
      elSilentTable.hidden = true;
      elSilentEmpty.hidden = false;
      return;
    }
    elSilentEmpty.hidden = true;
    elSilentTable.hidden = false;
    for (const row of rows) {
      const tr = h('tr');
      tr.appendChild(customerCell(row));
      const contactTd = h('td', '', lastContactText(row));
      if (row.status === 'no_contact_ever') {
        contactTd.classList.add('helpdesk-analytics-never');
      }
      tr.appendChild(contactTd);
      tr.appendChild(h('td', 'num', String(row.ticket_count_period || 0)));
      elSilentBody.appendChild(tr);
    }
  };

  const renderTop = (rows) => {
    if (!elTopBody || !elTopTable || !elTopEmpty) return;
    elTopBody.replaceChildren();
    if (!rows || rows.length === 0) {
      elTopTable.hidden = true;
      elTopEmpty.hidden = false;
      return;
    }
    elTopEmpty.hidden = true;
    elTopTable.hidden = false;
    for (const row of rows) {
      const tr = h('tr');
      tr.appendChild(customerCell(row));
      tr.appendChild(h('td', 'num', String(row.ticket_count_period || 0)));
      tr.appendChild(h('td', '', lastContactText(row)));
      elTopBody.appendChild(tr);
    }
  };

  const fetchData = async (refresh = false) => {
    showState('loading');
    if (elTruncated) elTruncated.hidden = true;

    const params = new URLSearchParams({ periodDays: String(currentPeriod) });
    if (refresh) params.set('refresh', '1');

    try {
      const json = await getJson(`${dataUrl}?${params.toString()}`, {
        signal: requestController.signal,
      });
      if (!json.ok) { showState('error'); return; }

      renderTiles(json.summary || {});
      renderSilent(json.silent || []);
      renderTop(json.top_communication || []);
      showState('success');

      if (json.meta && json.meta.truncated && elTruncated) {
        elTruncated.hidden = false;
      }
    } catch (error) {
      if (error instanceof Error && error.name === 'AbortError') {
        return;
      }
      showState('error');
    }
  };

  on(periodSelector, 'change', (event) => {
    const radio = event.target.closest('input[name="analytics-period"]');
    if (!radio) return;
    const period = parseInt(radio.value, 10);
    if (!period || period === currentPeriod) return;
    currentPeriod = period;
    void fetchData();
  });

  on(elRefresh, 'click', () => {
    void fetchData(true);
  });

  void fetchData();

  return {
    destroy: () => {
      listenerController.abort();
      requestController.abort();
    },
  };
}