/**
 * HelpTooltip - Displays help icons (?) next to section headers with multilingual popup explanations.
 * Loads help content from a JSON file and supports EN/VI/JA language switching.
 * Requirements: 28.1, 28.2, 28.3, 28.4, 28.5, 28.6, 28.7, 28.8, 28.9
 */

class HelpTooltip {
  /**
   * @param {Object} [options]
   * @param {string} [options.helpContentPath] - Path to help JSON file (default: './help/help-content.json')
   * @param {string} [options.defaultLang] - Default language code (default: 'en')
   * @param {string} [options.storageKey] - localStorage key for language (default: 'onnx_explorer_help_lang')
   */
  constructor(options = {}) {
    this._helpContentPath = options.helpContentPath || './help/help-content.json';
    this._defaultLang = options.defaultLang || 'en';
    this._storageKey = options.storageKey || 'onnx_explorer_help_lang';

    this._helpContent = null;
    this._currentLang = this._loadLanguage();
    this._currentPopup = null;
    this._currentIconSection = null;

    // Bound handler for closing popup on outside click
    this._onDocumentClick = this._onDocumentClick.bind(this);

    // Section key → display name mapping
    this._sectionNames = {
      metadata: 'Metadata',
      inputOutput: 'Inputs & Outputs',
      initializers: 'Initializers',
      layerStats: 'Layer Statistics',
      modelComplexity: 'Model Complexity',
      opsetCompatibility: 'Opset Compatibility',
      modelGraph: 'Model Graph',
      nodeDetails: 'Node Details'
    };

    // Section key → container selector + header text for lookup
    this._sectionMap = {
      metadata:           { selector: '#metadataContainer',       headerText: 'Metadata' },
      inputOutput:        { selector: '#inputOutputContainer',    headerText: 'Inputs & Outputs' },
      initializers:       { selector: '#initializerContainer',    headerText: 'Initializers' },
      layerStats:         { selector: '#layerStatsContainer',     headerText: 'Layer Statistics', noCard: true },
      modelComplexity:    { selector: '#modelComplexityContainer',headerText: 'Model Complexity', noCard: true },
      opsetCompatibility: { selector: '#opsetCheckerContainer',   headerText: 'Opset Compatibility', noCard: true },
      modelGraph:         { selector: null,                       headerText: 'Model Graph' },
      nodeDetails:        { selector: null,                       headerText: 'Node Details' }
    };
  }

  // ─── Public API ───────────────────────────────────────────────────────────

  /**
   * Initialize: load help content JSON, inject icons into section headers.
   * @returns {Promise<void>}
   */
  async init() {
    try {
      this._helpContent = await this.loadHelpContent();
    } catch (err) {
      console.warn('[HelpTooltip] Failed to load help content:', err);
      this._helpContent = null;
    }

    this._injectAllIcons();
    document.addEventListener('click', this._onDocumentClick);
  }

  /**
   * Fetch help content from JSON file.
   * @returns {Promise<Object>}
   */
  async loadHelpContent() {
    const response = await fetch(this._helpContentPath);
    if (!response.ok) {
      throw new Error(`HTTP ${response.status}: ${response.statusText}`);
    }
    return response.json();
  }

  /**
   * Inject a help icon (?) next to a section header element.
   * @param {string} sectionKey - Key of the section (e.g. 'metadata')
   * @param {HTMLElement} headerElement - The heading element to inject icon next to
   */
  injectIcon(sectionKey, headerElement) {
    if (!headerElement) return;
    // Avoid duplicate injection
    if (headerElement.querySelector('.help-icon')) return;

    const icon = document.createElement('span');
    icon.className = 'help-icon';
    icon.setAttribute('data-section', sectionKey);
    icon.setAttribute('title', 'Help');
    icon.setAttribute('role', 'button');
    icon.setAttribute('tabindex', '0');
    icon.setAttribute('aria-label', `Help for ${this._sectionNames[sectionKey] || sectionKey}`);
    icon.textContent = '?';

    icon.addEventListener('click', (e) => {
      e.stopPropagation();
      this.showPopup(sectionKey, icon);
    });
    icon.addEventListener('keydown', (e) => {
      if (e.key === 'Enter' || e.key === ' ') {
        e.preventDefault();
        e.stopPropagation();
        this.showPopup(sectionKey, icon);
      }
    });

    headerElement.appendChild(icon);
  }

  /**
   * Show a help popup positioned near the anchor icon.
   * @param {string} sectionKey - Key of the section
   * @param {HTMLElement} anchorElement - The icon element to position popup near
   */
  showPopup(sectionKey, anchorElement) {
    // Close any existing popup
    this.closePopup();

    this._currentIconSection = sectionKey;

    const popup = document.createElement('div');
    popup.className = 'help-popup';
    popup.setAttribute('role', 'dialog');
    popup.setAttribute('aria-label', `Help: ${this._sectionNames[sectionKey] || sectionKey}`);

    popup.innerHTML = this._buildPopupHTML(sectionKey);
    document.body.appendChild(popup);
    this._currentPopup = popup;

    // Position popup near the icon
    this._positionPopup(popup, anchorElement);

    // Attach language button handlers
    this._attachLangHandlers(popup, sectionKey);

    // Attach close button handler
    const closeBtn = popup.querySelector('.help-popup-close');
    if (closeBtn) {
      closeBtn.addEventListener('click', (e) => {
        e.stopPropagation();
        this.closePopup();
      });
    }

    // Prevent clicks inside popup from closing it
    popup.addEventListener('click', (e) => {
      e.stopPropagation();
    });
  }

  /**
   * Close the current popup.
   */
  closePopup() {
    if (this._currentPopup && this._currentPopup.parentNode) {
      this._currentPopup.parentNode.removeChild(this._currentPopup);
    }
    this._currentPopup = null;
    this._currentIconSection = null;
  }

  /**
   * Set the display language and persist to localStorage.
   * @param {string} lang - Language code ('en', 'vi', 'ja')
   */
  setLanguage(lang) {
    if (['en', 'vi', 'ja'].indexOf(lang) === -1) return;
    this._currentLang = lang;
    this._saveLanguage(lang);
  }

  /**
   * Get the current display language.
   * @returns {string}
   */
  getLanguage() {
    return this._currentLang;
  }

  /**
   * Destroy: remove event listeners, close popup, remove injected icons.
   */
  destroy() {
    this.closePopup();
    document.removeEventListener('click', this._onDocumentClick);

    // Remove all injected help icons
    const icons = document.querySelectorAll('.help-icon');
    icons.forEach((icon) => {
      if (icon.parentNode) {
        icon.parentNode.removeChild(icon);
      }
    });
  }

  // ─── Private ──────────────────────────────────────────────────────────────

  /**
   * Load saved language from localStorage, or return default.
   * @returns {string}
   */
  _loadLanguage() {
    try {
      const saved = localStorage.getItem(this._storageKey);
      if (saved && ['en', 'vi', 'ja'].indexOf(saved) !== -1) {
        return saved;
      }
    } catch (e) {
      // localStorage unavailable
    }
    return this._defaultLang;
  }

  /**
   * Save language to localStorage.
   * @param {string} lang
   */
  _saveLanguage(lang) {
    try {
      localStorage.setItem(this._storageKey, lang);
    } catch (e) {
      // localStorage unavailable
    }
  }

  /**
   * Inject help icons into all known section headers.
   */
  _injectAllIcons() {
    for (const sectionKey of Object.keys(this._sectionMap)) {
      const config = this._sectionMap[sectionKey];
      const headerEl = this._findHeaderElement(sectionKey, config);
      if (headerEl) {
        this.injectIcon(sectionKey, headerEl);
      }
    }

    // For sections without card wrappers, observe for dynamic content
    this._observeDynamicSections();
  }

  /**
   * Find the header element for a given section.
   * @param {string} sectionKey
   * @param {Object} config - { selector, headerText, noCard }
   * @returns {HTMLElement|null}
   */
  _findHeaderElement(sectionKey, config) {
    // For sections with a container selector and card wrapper
    if (config.selector) {
      const container = document.querySelector(config.selector);
      if (!container) return null;

      if (config.noCard) {
        // No card wrapper — look for a heading inside the container
        const heading = container.querySelector('h5, h6, .card-header h5, .card-header h6');
        if (heading) return heading;
        // Will be handled by MutationObserver
        return null;
      }

      // Find the .card-header ancestor and its h5/h6
      const card = container.closest('.card');
      if (card) {
        const header = card.querySelector('.card-header h5, .card-header h6');
        if (header) return header;
      }
    }

    // For sections without a selector (modelGraph, nodeDetails) — search by header text
    if (!config.selector || !document.querySelector(config.selector)) {
      const allHeaders = document.querySelectorAll('.card-header h5, .card-header h6');
      for (const h of allHeaders) {
        if (h.textContent.trim() === config.headerText) {
          return h;
        }
      }
    }

    return null;
  }

  /**
   * Observe dynamic sections (layerStats, modelComplexity, opsetCompatibility)
   * that render content after init. Inject icons when headings appear.
   */
  _observeDynamicSections() {
    const dynamicKeys = ['layerStats', 'modelComplexity', 'opsetCompatibility'];

    dynamicKeys.forEach((sectionKey) => {
      const config = this._sectionMap[sectionKey];
      if (!config.selector) return;

      const container = document.querySelector(config.selector);
      if (!container) return;

      // Already injected?
      if (container.querySelector('.help-icon')) return;

      const observer = new MutationObserver(() => {
        // Check if a heading appeared
        const heading = container.querySelector('h5, h6, .card-header h5, .card-header h6');
        if (heading && !heading.querySelector('.help-icon')) {
          this.injectIcon(sectionKey, heading);
          observer.disconnect();
        }
      });

      observer.observe(container, { childList: true, subtree: true });
    });
  }

  /**
   * Handle document click — close popup if click is outside popup and icon.
   * @param {Event} e
   */
  _onDocumentClick(e) {
    if (!this._currentPopup) return;

    // Check if click is inside popup
    if (this._currentPopup.contains(e.target)) return;

    // Check if click is on a help icon
    if (e.target.classList && e.target.classList.contains('help-icon')) return;

    this.closePopup();
  }

  /**
   * Build the inner HTML for the popup.
   * @param {string} sectionKey
   * @returns {string}
   */
  _buildPopupHTML(sectionKey) {
    const sectionName = this._sectionNames[sectionKey] || sectionKey;
    const bodyText = this._getHelpText(sectionKey);
    const langs = ['en', 'vi', 'ja'];
    const langLabels = { en: 'EN', vi: 'VI', ja: 'JA' };

    let langButtons = '';
    langs.forEach((lang) => {
      const active = lang === this._currentLang ? ' active' : '';
      langButtons += `<button class="help-lang-btn${active}" data-lang="${lang}" title="${langLabels[lang]}">${langLabels[lang]}</button>`;
    });

    return `
      <div class="help-popup-header">
        <span class="help-popup-title">${this._escapeHtml(sectionName)}</span>
        <button class="help-popup-close" title="Close" aria-label="Close">&times;</button>
      </div>
      <div class="help-popup-body">${this._escapeHtml(bodyText)}</div>
      <div class="help-popup-footer">${langButtons}</div>
    `;
  }

  /**
   * Get help text for a section in the current language.
   * @param {string} sectionKey
   * @returns {string}
   */
  _getHelpText(sectionKey) {
    if (!this._helpContent) {
      return 'Help content unavailable';
    }
    const section = this._helpContent[sectionKey];
    if (!section) {
      return 'Help content unavailable';
    }
    return section[this._currentLang] || section[this._defaultLang] || section['en'] || 'Help content unavailable';
  }

  /**
   * Position the popup near the anchor element, ensuring it stays within viewport.
   * @param {HTMLElement} popup
   * @param {HTMLElement} anchor
   */
  _positionPopup(popup, anchor) {
    const rect = anchor.getBoundingClientRect();
    const scrollX = window.pageXOffset || document.documentElement.scrollLeft;
    const scrollY = window.pageYOffset || document.documentElement.scrollTop;

    // Default: position below the icon
    let top = rect.bottom + scrollY + 6;
    let left = rect.left + scrollX;

    // Apply position so we can measure popup dimensions
    popup.style.position = 'absolute';
    popup.style.top = top + 'px';
    popup.style.left = left + 'px';

    // Adjust if popup overflows right edge
    const popupRect = popup.getBoundingClientRect();
    const viewportWidth = window.innerWidth;
    if (popupRect.right > viewportWidth - 10) {
      left = Math.max(10, viewportWidth - popupRect.width - 10 + scrollX);
      popup.style.left = left + 'px';
    }

    // Adjust if popup overflows bottom edge
    const viewportHeight = window.innerHeight;
    if (popupRect.bottom > viewportHeight - 10) {
      // Position above the icon instead
      top = rect.top + scrollY - popupRect.height - 6;
      if (top < scrollY + 10) {
        top = scrollY + 10;
      }
      popup.style.top = top + 'px';
    }
  }

  /**
   * Attach click handlers to language buttons inside the popup.
   * @param {HTMLElement} popup
   * @param {string} sectionKey
   */
  _attachLangHandlers(popup, sectionKey) {
    const buttons = popup.querySelectorAll('.help-lang-btn');
    buttons.forEach((btn) => {
      btn.addEventListener('click', (e) => {
        e.stopPropagation();
        const lang = btn.getAttribute('data-lang');
        this.setLanguage(lang);

        // Update body text
        const body = popup.querySelector('.help-popup-body');
        if (body) {
          body.textContent = this._getHelpText(sectionKey);
        }

        // Update active state on buttons
        buttons.forEach((b) => b.classList.remove('active'));
        btn.classList.add('active');
      });
    });
  }

  /**
   * Escape HTML special characters.
   * @param {string} str
   * @returns {string}
   */
  _escapeHtml(str) {
    const div = document.createElement('div');
    div.appendChild(document.createTextNode(String(str)));
    return div.innerHTML;
  }
}

window.HelpTooltip = HelpTooltip;