/**
 * Calendar grid and events-by-date mapping.
 */

import { getCalendarEl, getMonthTitleEl, state } from "./dom.js";
import { monthName, t } from "./i18n.js";
import { escapeHtml } from "./utils.js";
import {
  localDateString,
  firstDayOfMonth,
  lastDayOfMonth,
  getMonday,
  dateKeyToDDMM
} from "./dateUtils.js";

/**
 * Build { localDateKey -> array of summary strings }. API date is UTC YYYY-MM-DD; map to local.
 * @param {object[]} events - Calendar events with date, summary
 * @returns {Record<string, string[]>}
 */
export function calendarEventsByDate(events) {
  const byDate = {};
  (events || []).forEach((e) => {
    const utcMidnight = new Date(e.date + "T00:00:00Z");
    const key = localDateString(utcMidnight);
    if (!byDate[key]) byDate[key] = [];
    if (e.summary) byDate[key].push(e.summary);
  });
  return byDate;
}

/** Max days to iterate per duty; prevents infinite loop on corrupted API data (end_at < start_at). */
const MAX_DAYS_PER_DUTY = 366;

/**
 * Group duties by local date (start_at/end_at are UTC).
 * @param {object[]} duties - Duties with start_at, end_at
 * @returns {Record<string, object[]>}
 */
export function dutiesByDate(duties) {
  const byDate = {};
  duties.forEach((d) => {
    const start = new Date(d.start_at);
    const end = new Date(d.end_at);
    if (end < start) return;
    const endLocal = localDateString(end);
    let cursor = new Date(start);
    let iterations = 0;
    while (iterations <= MAX_DAYS_PER_DUTY) {
      const key = localDateString(cursor);
      if (!byDate[key]) byDate[key] = [];
      byDate[key].push(d);
      if (key === endLocal) break;
      cursor.setDate(cursor.getDate() + 1);
      iterations++;
    }
  });
  return byDate;
}

/**
 * Render calendar grid for given month with duties and calendar events.
 * @param {number} year
 * @param {number} month - 0-based
 * @param {Record<string, object[]>} dutiesByDateMap
 * @param {Record<string, string[]>} calendarEventsByDateMap
 */
export function renderCalendar(
  year,
  month,
  dutiesByDateMap,
  calendarEventsByDateMap
) {
  const calendarEl = getCalendarEl();
  const monthTitleEl = getMonthTitleEl();
  if (!calendarEl || !monthTitleEl) return;
  const first = firstDayOfMonth(new Date(year, month, 1));
  const last = lastDayOfMonth(new Date(year, month, 1));
  const start = getMonday(first);
  const today = localDateString(new Date());
  const calendarEventsByDate = calendarEventsByDateMap || {};

  calendarEl.innerHTML = "";
  let d = new Date(start);
  const cells = 42;
  for (let i = 0; i < cells; i++) {
    const key = localDateString(d);
    const isOther = d.getMonth() !== month;
    const dayDuties = dutiesByDateMap[key] || [];
    const dutyList = dayDuties.filter((x) => x.event_type === "duty");
    const unavailableList = dayDuties.filter((x) => x.event_type === "unavailable");
    const vacationList = dayDuties.filter((x) => x.event_type === "vacation");
    const hasAny = dayDuties.length > 0;
    const isToday = key === today;
    const eventSummaries = calendarEventsByDate[key] || [];
    const hasEvent = eventSummaries.length > 0;

    const showIndicator = !isOther;
    const cell = document.createElement("div");
    cell.className =
      "day" +
      (isOther ? " other-month" : "") +
      (isToday ? " today" : "") +
      (showIndicator && hasAny ? " has-duty" : "") +
      (showIndicator && hasEvent ? " holiday" : "");

    cell.setAttribute("data-date", key);
    if (showIndicator) {
      const dayPayload = dayDuties.map((x) => ({
        event_type: x.event_type,
        full_name: x.full_name,
        start_at: x.start_at,
        end_at: x.end_at
      }));
      cell.setAttribute("data-day-duties", JSON.stringify(dayPayload));
      cell.setAttribute("data-day-events", JSON.stringify(eventSummaries));
    }

    const ariaParts = [];
    ariaParts.push(dateKeyToDDMM(key));
    if (hasAny || hasEvent) {
      const counts = [];
      const lang = state.lang;
      if (dutyList.length) counts.push(dutyList.length + " " + t(lang, "event_type.duty"));
      if (unavailableList.length) counts.push(unavailableList.length + " " + t(lang, "event_type.unavailable"));
      if (vacationList.length) counts.push(vacationList.length + " " + t(lang, "event_type.vacation"));
      if (hasEvent) counts.push(t(lang, "hint.events"));
      ariaParts.push(counts.join(", "));
    } else {
      ariaParts.push(t(state.lang, "aria.day_info"));
    }
    cell.setAttribute("role", "button");
    cell.setAttribute("tabindex", "0");
    cell.setAttribute("aria-label", ariaParts.join("; "));

    let indicatorHtml = "";
    if (showIndicator && (hasAny || hasEvent)) {
      indicatorHtml = '<div class="day-indicator">';
      if (dutyList.length) indicatorHtml += '<span class="day-indicator-dot duty"></span>';
      if (unavailableList.length) indicatorHtml += '<span class="day-indicator-dot unavailable"></span>';
      if (vacationList.length) indicatorHtml += '<span class="day-indicator-dot vacation"></span>';
      if (hasEvent) indicatorHtml += '<span class="day-indicator-dot events"></span>';
      indicatorHtml += "</div>";
    }

    cell.innerHTML =
      '<span class="num">' + d.getDate() + "</span>" + indicatorHtml;
    calendarEl.appendChild(cell);
    d.setDate(d.getDate() + 1);
  }

  monthTitleEl.textContent = monthName(state.lang, month) + " " + year;
}