// MarkLite — Core Module: state, DOM refs, settings, utilities, init orchestration
(function () {
  'use strict';

  // ===== Shared Namespace =====
  const ML = {};
  window.MarkLite = ML;

  // ===== DOM Elements =====
  ML.editor = document.getElementById('editor');
  ML.preview = document.getElementById('preview');
  ML.lineNumbers = document.getElementById('line-numbers');
  ML.welcomeScreen = document.getElementById('welcome-screen');
  ML.dropOverlay = document.getElementById('drop-overlay');
  ML.modifiedBanner = document.getElementById('modified-banner');
  ML.statusText = document.getElementById('status-text');
  ML.statusCursor = document.getElementById('status-cursor');
  ML.statusSize = document.getElementById('status-size');
  ML.statusSizeDivider = document.querySelector('.status-size-divider');
  ML.resizer = document.getElementById('resizer');
  ML.editorPanel = document.getElementById('editor-panel');
  ML.previewPanel = document.getElementById('preview-panel');
  ML.mainContent = document.getElementById('main-content');
  ML.contentWrapper = document.getElementById('content-wrapper');
  ML.tabList = document.getElementById('tab-list');

  // Sidebar
  ML.sidebar = document.getElementById('sidebar');
  ML.sidebarTree = document.getElementById('sidebar-tree');
  ML.btnOpenFolder = document.getElementById('btn-open-folder');

  // Search
  ML.searchBar = document.getElementById('search-bar');
  ML.searchInput = document.getElementById('search-input');
  ML.replaceInput = document.getElementById('replace-input');
  ML.searchCount = document.getElementById('search-count');
  ML.replaceRow = document.getElementById('replace-row');
  ML.btnCase = document.getElementById('btn-case');
  ML.btnRegex = document.getElementById('btn-regex');
  ML.btnNext = document.getElementById('btn-next');
  ML.btnPrev = document.getElementById('btn-prev');
  ML.btnSearchClose = document.getElementById('btn-search-close');
  ML.btnReplace = document.getElementById('btn-replace');
  ML.btnReplaceAll = document.getElementById('btn-replace-all');

  // Buttons
  ML.btnOpen = document.getElementById('btn-open');
  ML.btnSave = document.getElementById('btn-save');
  ML.btnSplit = document.getElementById('btn-split');
  ML.btnEditor = document.getElementById('btn-editor');
  ML.btnPreview = document.getElementById('btn-preview');
  ML.btnWelcomeOpen = document.getElementById('btn-welcome-open');
  ML.btnWelcomeNew = document.getElementById('btn-welcome-new');
  ML.btnDark = document.getElementById('btn-dark');
  ML.btnReload = document.getElementById('btn-reload');
  ML.btnDismiss = document.getElementById('btn-dismiss');
  ML.btnNewTab = document.getElementById('btn-new-tab');

  // ===== Shared State =====
  ML.viewMode = 'split';
  ML.updateTimer = null;
  ML.lineCountCache = 0;
  ML.currentRootPath = null;
  ML.MAX_FILE_SIZE = 20 * 1024 * 1024;

  // ===== Settings =====
  ML.loadSettings = function () {
    try { return JSON.parse(localStorage.getItem('marklite-settings') || '{}'); }
    catch { return {}; }
  };
  ML.saveSetting = function (key, value) {
    try {
      const s = ML.loadSettings();
      s[key] = value;
      localStorage.setItem('marklite-settings', JSON.stringify(s));
    } catch { /* ignore */ }
  };

  // ===== Utilities =====
  ML.getFileName = function (filePath) {
    return filePath.split(/[/\\]/).pop();
  };

  ML.formatBytes = function (bytes) {
    if (bytes < 1024) return bytes + ' B';
    if (bytes < 1024 * 1024) return (bytes / 1024).toFixed(1) + ' KB';
    return (bytes / (1024 * 1024)).toFixed(1) + ' MB';
  };

  // Character width measurement
  var _charWidthCanvas = document.createElement('canvas');
  var _charWidthCtx = _charWidthCanvas.getContext('2d');
  var _cachedCharWidth = null;
  ML.getCharWidth = function () {
    if (_cachedCharWidth !== null) return _cachedCharWidth;
    var style = getComputedStyle(ML.editor);
    _charWidthCtx.font = style.fontSize + ' ' + style.fontFamily;
    _cachedCharWidth = _charWidthCtx.measureText('M').width;
    return _cachedCharWidth;
  };
  new MutationObserver(function () { _cachedCharWidth = null; })
    .observe(document.documentElement, { attributes: true, attributeFilter: ['class'] });

  // Toast notification
  ML.showToast = function (message, duration) {
    duration = duration || 3000;
    var toast = document.getElementById('toast-notification');
    if (!toast) {
      toast = document.createElement('div');
      toast.id = 'toast-notification';
      document.getElementById('app').appendChild(toast);
    }
    toast.textContent = message;
    toast.classList.add('show');
    clearTimeout(toast._timer);
    toast._timer = setTimeout(function () { toast.classList.remove('show'); }, duration);
  };

  // ===== Dark Mode =====
  ML.initDarkMode = function () {
    var settings = ML.loadSettings();
    var iconDark = document.getElementById('icon-dark');
    var iconLight = document.getElementById('icon-light');
    function apply(isDark) {
      document.documentElement.classList.toggle('dark', isDark);
      iconDark.style.display = isDark ? 'none' : '';
      iconLight.style.display = isDark ? '' : 'none';
    }
    var prefersDark = window.matchMedia('(prefers-color-scheme: dark)').matches;
    apply(settings.darkMode !== undefined ? !!settings.darkMode : prefersDark);
    ML.btnDark.addEventListener('click', function () {
      var isDark = !document.documentElement.classList.contains('dark');
      apply(isDark);
      ML.saveSetting('darkMode', isDark);
    });
  };

  // ===== File Operations =====
  ML.handleOpenFile = async function () {
    if (typeof window.electronAPI !== 'undefined') {
      var result = await window.electronAPI.openFile();
      if (result && !result.error) {
        ML.createNewTab(result.filePath, result.content);
      }
    } else {
      var input = document.createElement('input');
      input.type = 'file';
      input.accept = '.md,.markdown,.txt';
      input.multiple = true;
      input.onchange = function (e) {
        Array.from(e.target.files).forEach(function (file) {
          var ext = file.name.substring(file.name.lastIndexOf('.')).toLowerCase();
          if (!['.md', '.markdown', '.txt'].includes(ext)) return;
          if (file.size > ML.MAX_FILE_SIZE) {
            alert('"' + file.name + '" 过大（' + ML.formatBytes(file.size) + '），暂不支持超过 20MB 的文件');
            return;
          }
          var reader = new FileReader();
          reader.onload = function (ev) { ML.createNewTab(file.name, ev.target.result); };
          reader.readAsText(file);
        });
      };
      input.click();
    }
  };

  ML.handleSave = async function () {
    var tab = ML.getActiveTab();
    if (!tab) return;
    if (typeof window.electronAPI !== 'undefined') {
      var result = await window.electronAPI.saveFile({ filePath: tab.filePath, content: ML.editor.value });
      if (result.success) {
        tab.filePath = result.filePath;
        tab.content = ML.editor.value;
        tab.isModified = false;
        ML.renderTabBar();
        ML.updateTitle();
        ML.updateSidebarHighlight();
        ML.statusText.textContent = '已保存';
        setTimeout(function () { ML.updateTitle(); }, 2000);
      }
    } else {
      var blob = new Blob([ML.editor.value], { type: 'text/markdown' });
      var a = document.createElement('a');
      a.href = URL.createObjectURL(blob);
      a.download = tab.filePath || 'untitled.md';
      a.click();
      setTimeout(function () { URL.revokeObjectURL(a.href); }, 1000);
      tab.isModified = false;
      ML.renderTabBar();
      ML.updateTitle();
    }
  };

  ML.handleSaveAs = async function () {
    var tab = ML.getActiveTab();
    if (!tab) return;
    if (typeof window.electronAPI !== 'undefined') {
      var result = await window.electronAPI.saveFileAs({ content: ML.editor.value });
      if (result.success) {
        tab.filePath = result.filePath;
        tab.content = ML.editor.value;
        tab.isModified = false;
        ML.renderTabBar();
        ML.updateTitle();
        ML.updateSidebarHighlight();
        ML.statusText.textContent = '已保存';
        setTimeout(function () { ML.updateTitle(); }, 2000);
      }
    } else {
      ML.handleSave();
    }
  };

  // ===== View Mode =====
  ML.setViewMode = function (mode) {
    ML.viewMode = mode;
    var app = document.getElementById('app');
    app.classList.remove('mode-editor', 'mode-preview');
    ML.btnSplit.classList.remove('active');
    ML.btnEditor.classList.remove('active');
    ML.btnPreview.classList.remove('active');
    switch (mode) {
      case 'split': ML.btnSplit.classList.add('active'); break;
      case 'editor': ML.btnEditor.classList.add('active'); app.classList.add('mode-editor'); break;
      case 'preview': ML.btnPreview.classList.add('active'); app.classList.add('mode-preview'); ML.renderMarkdown(ML.editor.value); break;
    }
    ML.saveSetting('viewMode', mode);
  };

  // ===== Resizer =====
  ML.initResizer = function () {
    var settings = ML.loadSettings();
    if (settings.splitRatio) {
      ML.editorPanel.style.flex = '0 0 ' + settings.splitRatio + '%';
      ML.previewPanel.style.flex = '0 0 ' + (100 - settings.splitRatio) + '%';
    }
    var isResizing = false;
    ML.resizer.addEventListener('mousedown', function (e) {
      isResizing = true;
      ML.resizer.classList.add('active');
      document.body.style.cursor = 'col-resize';
      document.body.style.userSelect = 'none';
      e.preventDefault();
    });
    document.addEventListener('mousemove', function (e) {
      if (!isResizing) return;
      var rect = ML.contentWrapper.getBoundingClientRect();
      var pct = Math.max(20, Math.min(80, ((e.clientX - rect.left) / rect.width) * 100));
      ML.editorPanel.style.flex = '0 0 ' + pct + '%';
      ML.previewPanel.style.flex = '0 0 ' + (100 - pct) + '%';
      ML.saveSetting('splitRatio', pct);
    });
    document.addEventListener('mouseup', function () {
      if (isResizing) {
        isResizing = false;
        ML.resizer.classList.remove('active');
        document.body.style.cursor = '';
        document.body.style.userSelect = '';
      }
    });
  };

  // ===== Drag & Drop =====
  ML.initDragDrop = function () {
    var dragCounter = 0;
    var allowedExts = ['.md', '.markdown', '.txt'];
    document.addEventListener('dragenter', function (e) { e.preventDefault(); e.stopPropagation(); dragCounter++; ML.dropOverlay.classList.remove('hidden'); });
    document.addEventListener('dragleave', function (e) { e.preventDefault(); e.stopPropagation(); dragCounter--; if (dragCounter === 0) ML.dropOverlay.classList.add('hidden'); });
    document.addEventListener('dragover', function (e) { e.preventDefault(); e.stopPropagation(); });
    document.addEventListener('drop', async function (e) {
      e.preventDefault(); e.stopPropagation(); dragCounter = 0; ML.dropOverlay.classList.add('hidden');
      var files = e.dataTransfer.files;
      var rejected = 0;
      for (var _i = 0; _i < files.length; _i++) {
        var file = files[_i];
        var filePath = file.path;
        var ext = filePath ? filePath.substring(filePath.lastIndexOf('.')).toLowerCase() : '';
        if (!allowedExts.includes(ext)) { rejected++; continue; }
        if (file.size > ML.MAX_FILE_SIZE) { ML.showToast('"' + file.name + '" 过大（' + ML.formatBytes(file.size) + '），暂不支持超过 20MB 的文件'); continue; }
        if (filePath && typeof window.electronAPI !== 'undefined') {
          var result = await window.electronAPI.readFile(filePath);
          if (result.success) ML.createNewTab(filePath, result.content);
        } else {
          var reader = new FileReader();
          reader.onload = function (ev) { ML.createNewTab(file.name, ev.target.result); };
          reader.readAsText(file);
        }
      }
      if (rejected > 0) ML.showToast('仅支持 .md / .markdown / .txt 文件，已忽略 ' + rejected + ' 个文件');
    });
  };

  // ===== Keyboard Shortcuts =====
  ML.initKeyboard = function () {
    document.addEventListener('keydown', function (e) {
      if (e.ctrlKey && e.key === 'o') { e.preventDefault(); ML.handleOpenFile(); }
      if (e.ctrlKey && e.key === 's' && !e.shiftKey) { e.preventDefault(); ML.handleSave(); }
      if (e.ctrlKey && e.shiftKey && e.key === 'S') { e.preventDefault(); ML.handleSaveAs(); }
      if (e.ctrlKey && e.key === '1') { e.preventDefault(); ML.setViewMode('split'); }
      if (e.ctrlKey && e.key === '2') { e.preventDefault(); ML.setViewMode('editor'); }
      if (e.ctrlKey && e.key === '3') { e.preventDefault(); ML.setViewMode('preview'); }
      if (e.ctrlKey && e.key === 't') { e.preventDefault(); ML.createNewTab(null, ''); }
      if (e.ctrlKey && e.key === 'w') { e.preventDefault(); if (ML.activeTabId) ML.closeTab(ML.activeTabId); }
      if (e.ctrlKey && e.key === 'Tab') {
        e.preventDefault();
        if (ML.tabs.length > 1) {
          if (e.shiftKey) {
            if (ML.mruTabStack.length > 0) {
              var targetId = ML.mruTabStack.shift();
              if (ML.tabs.find(function (t) { return t.id === targetId; })) ML.switchToTab(targetId);
            }
          } else {
            var idx = ML.getTabIndex(ML.activeTabId);
            var next = (idx + 1) % ML.tabs.length;
            ML.switchToTab(ML.tabs[next].id);
          }
        }
      }
      if (e.ctrlKey && e.key === 'f') { e.preventDefault(); ML.openSearch(false); }
      if (e.ctrlKey && e.key === 'h') { e.preventDefault(); ML.openSearch(true); }
      if (e.key === 'Escape' && !ML.searchBar.classList.contains('hidden')) { e.preventDefault(); ML.closeSearch(); }
      if (e.key === 'Enter' && document.activeElement === ML.searchInput) { e.preventDefault(); e.shiftKey ? ML.findPrev() : ML.findNext(); }
      if (e.altKey && e.key === 'c') { e.preventDefault(); ML.toggleSearchOption('case'); }
      if (e.altKey && e.key === 'r') { e.preventDefault(); ML.toggleSearchOption('regex'); }
      if (e.ctrlKey && e.shiftKey && e.key === 'H') { e.preventDefault(); ML.replaceAll(); }
      if (e.ctrlKey && e.shiftKey && e.key === 'G') { e.preventDefault(); ML.replaceCurrent(); }
    });
  };

  // ===== Tab Key Support =====
  ML.initEditorTab = function () {
    ML.editor.addEventListener('keydown', function (e) {
      if (e.key === 'Tab') {
        e.preventDefault();
        var start = ML.editor.selectionStart;
        var end = ML.editor.selectionEnd;
        if (start !== end) {
          var lines = ML.editor.value.substring(start, end).split('\n');
          var indented = lines.map(function (line) { return '    ' + line; }).join('\n');
          ML.editor.setRangeText(indented, start, end, 'end');
        } else {
          ML.editor.setRangeText('    ', start, end, 'end');
        }
        ML.scheduleUpdate();
      }
    });
  };

  // ===== External File Modification =====
  ML.initFileWatch = function () {
    if (typeof window.electronAPI === 'undefined') return;
    window.electronAPI.onExternalModification(function (filePath) {
      var tab = ML.getActiveTab();
      if (tab && tab.filePath === filePath) ML.modifiedBanner.classList.remove('hidden');
    });
    ML.btnReload.addEventListener('click', async function () {
      var tab = ML.getActiveTab();
      if (!tab || !tab.filePath) return;
      var result = await window.electronAPI.reloadFile();
      if (result.success) {
        ML.editor.value = result.content;
        tab.content = result.content;
        tab.isModified = false;
        ML.lineCountCache = 0;
        ML.updateLineNumbers();
        ML.renderMarkdown(result.content);
        ML.updateCursorPosition();
        ML.updateFileSize();
        ML.cachePreviewPositions();
        ML.renderTabBar();
        ML.updateTitle();
      }
      ML.modifiedBanner.classList.add('hidden');
    });
    ML.btnDismiss.addEventListener('click', function () { ML.modifiedBanner.classList.add('hidden'); });
  };

  // ===== Unsaved Changes Warning =====
  ML.initUnsavedWarning = function () {
    var hasUnsaved = function () { return ML.tabs.some(function (t) { return t.isModified; }); };
    if (typeof window.electronAPI === 'undefined') {
      window.addEventListener('beforeunload', function (e) { if (hasUnsaved()) { e.preventDefault(); e.returnValue = ''; } });
      return;
    }
    window.electronAPI.onConfirmClose(function () {
      if (!hasUnsaved()) { window.electronAPI.forceClose(); return; }
      var shouldClose = confirm('有文件尚未保存，确定要关闭吗？');
      if (shouldClose) window.electronAPI.forceClose();
      else window.electronAPI.cancelClose();
    });
  };

  // ===== Event Listeners =====
  ML.initEventListeners = function () {
    ML.editor.addEventListener('input', function () {
      var tab = ML.getActiveTab();
      if (tab) { tab.isModified = true; tab.content = ML.editor.value; ML.setModified(true); }
      ML.scheduleUpdate();
    });
    ML.editor.addEventListener('scroll', function () {
      ML.syncScroll();
      ML.lineNumbers.scrollTop = ML.editor.scrollTop;
      if (ML.lineCountCache > 2000) ML.renderVirtualLineNumbers(ML.lineCountCache);
    });
    ML.editor.addEventListener('click', ML.updateCursorPosition);
    ML.editor.addEventListener('keyup', ML.updateCursorPosition);
    ML.editor.addEventListener('select', ML.updateCursorPosition);

    ML.btnOpen.addEventListener('click', ML.handleOpenFile);
    ML.btnSave.addEventListener('click', ML.handleSave);
    ML.btnSplit.addEventListener('click', function () { ML.setViewMode('split'); });
    ML.btnEditor.addEventListener('click', function () { ML.setViewMode('editor'); });
    ML.btnPreview.addEventListener('click', function () { ML.setViewMode('preview'); });
    ML.btnNewTab.addEventListener('click', function () { ML.createNewTab(null, ''); });
    ML.btnWelcomeOpen.addEventListener('click', ML.handleOpenFile);
    ML.btnWelcomeNew.addEventListener('click', function () { ML.createNewTab(null, ''); });

    if (typeof window.electronAPI !== 'undefined') {
      window.electronAPI.removeAllListeners('file:openInTab');
      window.electronAPI.removeAllListeners('menu:save');
      window.electronAPI.removeAllListeners('menu:saveAs');
      window.electronAPI.removeAllListeners('menu:viewMode');
      window.electronAPI.onFileOpenInTab(function (data) { ML.createNewTab(data.filePath, data.content); });
      window.electronAPI.onMenuSave(function () { ML.handleSave(); });
      window.electronAPI.onMenuSaveAs(function () { ML.handleSaveAs(); });
      window.electronAPI.onViewModeChange(function (mode) { ML.setViewMode(mode); });
    }
  };

  // ===== Init =====
  ML.init = function () {
    ML.initMarked();
    ML.initDarkMode();
    ML.initResizer();
    ML.initDragDrop();
    ML.initKeyboard();
    ML.initEditorTab();
    ML.initPreviewLinks();
    ML.initEventListeners();
    ML.initFileWatch();
    ML.initUnsavedWarning();
    ML.initSidebar();
    ML.initSearchBar();
    var settings = ML.loadSettings();
    ML.setViewMode(settings.viewMode || 'split');
  };

  if (document.readyState === 'loading') {
    document.addEventListener('DOMContentLoaded', ML.init);
  } else {
    ML.init();
  }
})();