var WEEKDAYS = ["Пн", "Вт", "Ср", "Чт", "Пт", "Сб", "Вс"];
var MONTHS = [
  "Январь", "Февраль", "Март", "Апрель", "Май", "Июнь",
  "Июль", "Август", "Сентябрь", "Октябрь", "Ноябрь", "Декабрь"
];

var now = new Date();
var view = { year: now.getFullYear(), month: now.getMonth() };
var openDate = null;
var allByDate = {};

var gridEl = document.getElementById("grid");
var monthNameEl = document.getElementById("monthName");
var panelBody = document.getElementById("panelBody");
var panelEmpty = document.getElementById("panelEmpty");
var panelDateEl = document.getElementById("panelDate");
var notesEl = document.getElementById("notes");
var countEl = document.getElementById("count");

function pad(n) { return (n < 10 ? "0" : "") + n; }

function fmt(d) {
  return pad(d.getDate()) + "." + pad(d.getMonth() + 1) + "." + d.getFullYear();
}
function iso(date) {
  return date.getFullYear() + "-" + pad(date.getMonth() + 1) + "-" + pad(date.getDate());
}
function escapeHtml(s) {
  return String(s).replace(/[&<>"']/g, function (c) {
    return { "&": "&amp;", "<": "&lt;", ">": "&gt;", '"': "&quot;", "'": "&#39;" }[c];
  });
}

function renderWeekdays() {
  document.getElementById("weekdays").innerHTML =
    WEEKDAYS.map(function (w) { return "<span>" + w + "</span>"; }).join("");
}

function render() {
  monthNameEl.textContent = MONTHS[view.month] + " " + view.year;

  var first = new Date(view.year, view.month, 1);
  var startPad = (first.getDay() + 6) % 7;
  var daysInMonth = new Date(view.year, view.month + 1, 0).getDate();
  var prevDays = new Date(view.year, view.month, 0).getDate();
  var html = "";

  for (var i = startPad - 1; i >= 0; i--) {
    html += '<div class="day empty">' + (prevDays - i) + "</div>";
  }

  for (var d = 1; d <= daysInMonth; d++) {
    var date = new Date(view.year, view.month, d);
    var key = iso(date);
    var cls = "day";

    var isToday =
      date.getFullYear() === now.getFullYear() &&
      date.getMonth() === now.getMonth() &&
      date.getDate() === now.getDate();
    if (isToday) cls += " today";
    if (openDate === key) cls += " selected";

    var has = (allByDate[key] || []).length > 0;
    var dot = has ? '<span class="dot"></span>' : '<span class="dot" style="visibility:hidden"></span>';

    html += '<div class="' + cls + '" data-key="' + key + '">' + d + dot + "</div>";
  }

  var endPad = 7 - ((startPad + daysInMonth) % 7);
  if (endPad < 7) {
    for (var j = 1; j <= endPad; j++) {
      html += '<div class="day empty">' + j + "</div>";
    }
  }

  gridEl.innerHTML = html;
}

function changeMonth(delta) {
  view.month += delta;
  if (view.month < 0) { view.month = 11; view.year--; }
  if (view.month > 11) { view.month = 0; view.year++; }
  render();
}

function goToday() {
  now = new Date();
  view = { year: now.getFullYear(), month: now.getMonth() };
  render();
}

function api(url, opts) {
  return fetch(url, opts).then(function (r) {
    if (!r.ok) throw new Error("Ошибка сервера " + r.status);
    return r.json();
  });
}

function loadAll() {
  return api("/api/notes").then(function (list) {
    allByDate = {};
    list.forEach(function (n) {
      (allByDate[n.date] = allByDate[n.date] || []).push(n);
    });
    render();
    if (openDate) renderPanel();
  });
}

function renderPanel() {
  var list = allByDate[openDate] || [];
  notesEl.innerHTML = list.map(function (n) {
    return (
      '<li class="note' + (n.done ? " done" : "") + '" data-id="' + n.id + '">' +
      '<button class="chk' + (n.done ? " on" : "") + '" title="Отметить">' + (n.done ? "✓" : "") + "</button>" +
      '<span class="note-text">' + escapeHtml(n.text) + "</span>" +
      '<button class="del" title="Удалить">×</button>' +
      "</li>"
    );
  }).join("");
  countEl.textContent = list.length ? "Дела: " + list.length : "";
}

function openDay(key) {
  openDate = key;
  panelEmpty.classList.add("hidden");
  panelBody.classList.remove("hidden");
  var parts = key.split("-");
  var date = new Date(parts[0], +parts[1] - 1, +parts[2]);
  panelDateEl.textContent = fmt(date);
  render();
  renderPanel();
}

function closePanel() {
  openDate = null;
  panelBody.classList.add("hidden");
  panelEmpty.classList.remove("hidden");
  render();
}

function addNote(text) {
  return api("/api/notes", {
    method: "POST",
    headers: { "Content-Type": "application/json" },
    body: JSON.stringify({ date: openDate, text: text })
  }).then(loadAll);
}

function toggleNote(id, done) {
  return api("/api/notes", {
    method: "PATCH",
    headers: { "Content-Type": "application/json" },
    body: JSON.stringify({ id: id, done: done })
  }).then(loadAll);
}

function deleteNote(id) {
  return api("/api/notes/" + id, { method: "DELETE" }).then(loadAll);
}

gridEl.addEventListener("click", function (e) {
  var day = e.target.closest(".day");
  if (!day || day.classList.contains("empty")) return;
  openDay(day.dataset.key);
});

notesEl.addEventListener("click", function (e) {
  var li = e.target.closest(".note");
  if (!li) return;
  var id = +li.dataset.id;
  var item = (allByDate[openDate] || []).find(function (n) { return n.id === id; });
  if (!item) return;

  if (e.target.classList.contains("del")) {
    if (confirm("Удалить это дело?")) deleteNote(id);
    return;
  }
  if (e.target.classList.contains("chk")) {
    toggleNote(id, !item.done);
  }
});

document.getElementById("addForm").addEventListener("submit", function (e) {
  e.preventDefault();
  var input = document.getElementById("noteText");
  var text = input.value.trim();
  if (!text || !openDate) return;
  addNote(text);
  input.value = "";
});

document.getElementById("prev").addEventListener("click", function () { changeMonth(-1); });
document.getElementById("next").addEventListener("click", function () { changeMonth(1); });
document.getElementById("today").addEventListener("click", goToday);
document.getElementById("closePanel").addEventListener("click", closePanel);

renderWeekdays();
render();
loadAll();