/**
 * KamiDatePicker — 轻量日历弹窗，kami 暖纸风格。
 *
 * 用法:
 *   new KamiDatePicker(triggerEl, {
 *     value: '2025-06-09',        // 初始日期
 *     maxDate: '2025-06-09',      // 最晚可选
 *     minDate: '2024-01-01',      // 最早可选
 *     markedDates: ['2025-06-08'],// 有数据的日期（小圆点）
 *     onChange: function(dateStr) {},  // 选择回调
 *   });
 */
;(function () {
  'use strict';

  var INSTANCES = [];

  var WEEKDAYS = ['日', '一', '二', '三', '四', '五', '六'];

  function pad(n) {
    return n < 10 ? '0' + n : '' + n;
  }
  function isoDate(y, m, d) {
    return y + '-' + pad(m + 1) + '-' + pad(d);
  }
  function parseDate(s) {
    if (!s) return null;
    var parts = s.split('-');
    if (parts.length !== 3) return null;
    return new Date(+parts[0], +parts[1] - 1, +parts[2]);
  }
  function sameDay(a, b) {
    return a && b && a.getFullYear() === b.getFullYear() &&
      a.getMonth() === b.getMonth() && a.getDate() === b.getDate();
  }

  function KamiDatePicker(triggerEl, opts) {
    opts = opts || {};
    this.trigger = triggerEl;
    this.value = opts.value || null;
    this.maxDate = opts.maxDate ? parseDate(opts.maxDate) : null;
    this.minDate = opts.minDate ? parseDate(opts.minDate) : null;
    this.markedSet = {};
    if (opts.markedDates) {
      for (var i = 0; i < opts.markedDates.length; i++) {
        this.markedSet[opts.markedDates[i]] = true;
      }
    }
    this.onChange = opts.onChange || function () {};
    this.opened = false;

    // view state
    var initial = parseDate(this.value) || new Date();
    this.viewYear = initial.getFullYear();
    this.viewMonth = initial.getMonth();

    this._build();
    this._bind();
    INSTANCES.push(this);
  }

  KamiDatePicker.prototype._build = function () {
    // wrapper
    this.wrapper = document.createElement('div');
    this.wrapper.className = 'kami-date-picker-wrapper';
    this.trigger.parentNode.insertBefore(this.wrapper, this.trigger);
    this.wrapper.appendChild(this.trigger);

    // popup
    this.popup = document.createElement('div');
    this.popup.className = 'kami-date-popup';
    this.popup.innerHTML = this._renderHTML();
    this.wrapper.appendChild(this.popup);

    // make trigger look clickable
    this.trigger.style.cursor = 'pointer';
  };

  KamiDatePicker.prototype._bind = function () {
    var self = this;

    // toggle on trigger click
    this._triggerHandler = function (e) {
      e.preventDefault();
      e.stopPropagation();
      self.toggle();
    };
    this.trigger.addEventListener('click', this._triggerHandler);

    // popup internal clicks
    this.popup.addEventListener('click', function (e) {
      var target = e.target;

      // prev month
      if (target.closest('.kami-date-prev')) {
        e.stopPropagation();
        self.viewMonth--;
        if (self.viewMonth < 0) { self.viewMonth = 11; self.viewYear--; }
        self._update();
        return;
      }
      // next month
      if (target.closest('.kami-date-next')) {
        e.stopPropagation();
        self.viewMonth++;
        if (self.viewMonth > 11) { self.viewMonth = 0; self.viewYear++; }
        self._update();
        return;
      }
      // today link
      if (target.closest('.kami-date-today-link')) {
        e.stopPropagation();
        self.select(new Date());
        return;
      }
      // day cell
      var dayEl = target.closest('.kami-date-day');
      if (dayEl && !dayEl.classList.contains('muted')) {
        e.stopPropagation();
        var y = +dayEl.dataset.year;
        var m = +dayEl.dataset.month;
        var d = +dayEl.dataset.day;
        self.select(new Date(y, m, d));
      }
    });
  };

  KamiDatePicker.prototype._renderHTML = function () {
    var y = this.viewYear;
    var m = this.viewMonth;
    var today = new Date();
    var selected = parseDate(this.value);

    var html = '';

    // header
    html += '<div class="kami-date-header">';
    html += '<button type="button" class="kami-date-prev" title="上个月">‹</button>';
    html += '<span class="kami-date-label">' + y + ' 年 ' + (m + 1) + ' 月</span>';
    html += '<button type="button" class="kami-date-next" title="下个月">›</button>';
    html += '</div>';

    // weekdays
    html += '<div class="kami-date-weekdays">';
    for (var w = 0; w < 7; w++) {
      html += '<span>' + WEEKDAYS[w] + '</span>';
    }
    html += '</div>';

    // day grid
    var firstDay = new Date(y, m, 1).getDay(); // 0=Sun
    var daysInMonth = new Date(y, m + 1, 0).getDate();
    var daysInPrevMonth = new Date(y, m, 0).getDate();

    html += '<div class="kami-date-grid">';

    // prev month trailing days
    for (var p = firstDay - 1; p >= 0; p--) {
      var pd = daysInPrevMonth - p;
      var pm = m - 1;
      var py = y;
      if (pm < 0) { pm = 11; py--; }
      html += '<div class="kami-date-day muted" data-year="' + py + '" data-month="' + pm + '" data-day="' + pd + '">' + pd + '</div>';
    }

    // current month days
    for (var d = 1; d <= daysInMonth; d++) {
      var date = new Date(y, m, d);
      var iso = isoDate(y, m, d);
      var cls = 'kami-date-day';
      if (sameDay(date, today)) cls += ' today';
      if (sameDay(date, selected)) cls += ' selected';
      if (this.markedSet[iso]) cls += ' marked';
      if (this.maxDate && date > this.maxDate) cls += ' disabled';
      if (this.minDate && date < this.minDate) cls += ' disabled';
      html += '<div class="' + cls + '" data-year="' + y + '" data-month="' + m + '" data-day="' + d + '">' + d + '</div>';
    }

    // next month leading days
    var totalCells = firstDay + daysInMonth;
    var remaining = (7 - totalCells % 7) % 7;
    for (var n = 1; n <= remaining; n++) {
      var nm = m + 1;
      var ny = y;
      if (nm > 11) { nm = 0; ny++; }
      html += '<div class="kami-date-day muted" data-year="' + ny + '" data-month="' + nm + '" data-day="' + n + '">' + n + '</div>';
    }

    html += '</div>';

    // footer — "回到今天"
    html += '<div class="kami-date-footer">';
    html += '<a href="javascript:void(0)" class="kami-date-today-link">回到今天</a>';
    html += '</div>';

    return html;
  };

  KamiDatePicker.prototype._update = function () {
    this.popup.innerHTML = this._renderHTML();
  };

  KamiDatePicker.prototype.open = function () {
    // close other instances
    for (var i = 0; i < INSTANCES.length; i++) {
      if (INSTANCES[i] !== this && INSTANCES[i].opened) {
        INSTANCES[i].close();
      }
    }

    // sync view to current value
    var sel = parseDate(this.value);
    if (sel) {
      this.viewYear = sel.getFullYear();
      this.viewMonth = sel.getMonth();
    }
    this._update();
    this.popup.classList.add('open');
    this.opened = true;
    this._addGlobalListeners();
  };

  KamiDatePicker.prototype.close = function () {
    this.popup.classList.remove('open');
    this.opened = false;
    this._removeGlobalListeners();
  };

  KamiDatePicker.prototype.toggle = function () {
    if (this.opened) this.close();
    else this.open();
  };

  KamiDatePicker.prototype.select = function (date) {
    var iso = isoDate(date.getFullYear(), date.getMonth(), date.getDate());
    this.value = iso;
    this.close();
    this.onChange(iso);
  };

  KamiDatePicker.prototype.setValue = function (dateStr) {
    this.value = dateStr || null;
    var d = parseDate(dateStr);
    if (d) {
      this.viewYear = d.getFullYear();
      this.viewMonth = d.getMonth();
    }
    if (this.opened) this._update();
  };

  KamiDatePicker.prototype.getValue = function () {
    return this.value;
  };

  KamiDatePicker.prototype.destroy = function () {
    this.close();
    this.trigger.removeEventListener('click', this._triggerHandler);
    // move trigger back out of wrapper
    this.wrapper.parentNode.insertBefore(this.trigger, this.wrapper);
    this.wrapper.remove();
    var idx = INSTANCES.indexOf(this);
    if (idx > -1) INSTANCES.splice(idx, 1);
  };

  // ── Global listeners ──

  KamiDatePicker.prototype._addGlobalListeners = function () {
    var self = this;
    if (!this._docClickHandler) {
      this._docClickHandler = function (e) {
        if (self.wrapper.contains(e.target)) return;
        self.close();
      };
    }
    if (!this._keyHandler) {
      this._keyHandler = function (e) {
        if (e.key === 'Escape') self.close();
      };
    }
    document.addEventListener('click', this._docClickHandler);
    document.addEventListener('keydown', this._keyHandler);
  };

  KamiDatePicker.prototype._removeGlobalListeners = function () {
    if (this._docClickHandler) document.removeEventListener('click', this._docClickHandler);
    if (this._keyHandler) document.removeEventListener('keydown', this._keyHandler);
  };

  // expose
  window.KamiDatePicker = KamiDatePicker;
})();