/**
 * On-demand page loader for Babel/JSX scripts.
 *
 * Instead of loading ALL pages as <script type="text/babel"> upfront
 * (which forces Babel to parse ~580KB of JSX at once), this loader
 * fetches individual page scripts only when the user navigates to them,
 * then transforms with Babel and evaluates the result.
 *
 * Must be loaded as a plain <script> BEFORE any page scripts.
 */
(function() {
  'use strict';

  window.GDD = window.GDD || {};

  var _cache = {};      // pageId -> true (loaded)
  var _loading = {};    // pageId -> Promise
  var _scriptCache = {}; // src -> transformed code

  var PAGE_SCRIPTS = {
    'overview':       'js/pages/overview.js',
    'architecture':   'js/pages/architecture.js',
    'techstack':      'js/pages/techstack.js',
    'backend':        'js/pages/backend.js',
    'agents':         'js/pages/agents.js',
    'gameplay':       'js/pages/gameplay.js',
    'ships':          'js/pages/ships.js',
    'economy':        'js/pages/economy.js',
    'social':         'js/pages/social.js',
    'ship-ai':        'js/pages/ship-ai.js',
    'roadmap':        'js/pages/roadmap.js',
    'risks':          'js/pages/risks.js',
    'demo-gallery':   'js/pages/demo-gallery.js',
    'demo-starmap':    'js/demos/starmap.js',
    'demo-movement':   'js/demos/movement.js',
    'demo-combat':     'js/demos/combat.js',
    'demo-market':     'js/demos/market.js',
    'demo-fitting':    'js/demos/fitting.js',
    'demo-refining':   'js/demos/refining.js',
    'demo-progression':'js/demos/progression.js',
    'demo-bounty':     'js/demos/bounty.js',
    'demo-gamehud':    'js/demos/gamehud.js',
    'demo-chat':       'js/demos/chat.js',
    'demo-zora':       'js/demos/zora.js',
    'demo-galaxy':     'js/demos/galaxy.js',
  };

  // Component name map — mirrors the one in app.js
  var PAGE_COMP_NAMES = {
    'overview':       'OverviewPage',
    'architecture':   'ArchitecturePage',
    'techstack':      'TechStackPage',
    'backend':        'BackendPage',
    'agents':         'AgentsPage',
    'gameplay':       'GameplayPage',
    'ships':          'ShipsPage',
    'economy':        'EconomyPage',
    'social':         'SocialPage',
    'ship-ai':        'ShipAIPage',
    'roadmap':        'RoadmapPage',
    'risks':          'RisksPage',
    'demo-gallery':   'DemoGalleryPage',
    'demo-starmap':    'StarMapDemo',
    'demo-movement':   'ShipMovementDemo',
    'demo-combat':     'CombatDemo',
    'demo-market':     'MarketDemo',
    'demo-fitting':    'FittingDemo',
    'demo-refining':   'RefiningDemo',
    'demo-progression':'ProgressionDemo',
    'demo-bounty':     'BountyDemo',
    'demo-gamehud':   'GameHudDemo',
    'demo-chat':       'ChatDemo',
    'demo-zora':       'ZoraDemo',
    'demo-galaxy':     'GalaxyDemo',
  };

  var _isFileProtocol = (window.location.protocol === 'file:');

  function fetchAndTransform(src) {
    // Check memory cache first
    if (_scriptCache[src]) {
      return Promise.resolve(_scriptCache[src]);
    }

    // On file:// protocol, fetch() is blocked by the browser.
    // Try injecting a <script type="text/babel" src> tag instead —
    // Babel standalone's MutationObserver will pick it up.
    if (_isFileProtocol) {
      return new Promise(function(resolve, reject) {
        // Check if component appeared (Babel may have processed it
        // from a previously injected tag)
        var compName = PAGE_COMP_NAMES[Object.keys(PAGE_SCRIPTS).filter(
          function(k) { return PAGE_SCRIPTS[k] === src; }
        )[0]];
        if (compName && window.GDD[compName]) {
          resolve('');
          return;
        }
        reject(new Error(
          'Cannot load page from file:// protocol. ' +
          'Serve this folder via HTTP for full navigation. ' +
          'Run: python3 -m http.server 8000 (then open http://localhost:8000)'
        ));
      });
    }

    return fetch(src)
      .then(function(r) {
        if (!r.ok) throw new Error('HTTP ' + r.status + ' loading ' + src);
        return r.text();
      })
      .then(function(code) {
        // Transform JSX → JS using Babel standalone
        var transformed = Babel.transform(code, {
          presets: ['react'],
          plugins: [],
        }).code;

        _scriptCache[src] = transformed;
        return transformed;
      });
  }

  /**
   * Load a page script on demand. Returns a Promise.
   */
  window.GDD.loadPage = function loadPage(pageId) {
    if (_cache[pageId]) return Promise.resolve();
    if (_loading[pageId]) return _loading[pageId];

    // Check if component was already registered by an inline <script type="text/babel">
    var compName = PAGE_COMP_NAMES[pageId];
    if (compName && window.GDD[compName]) {
      _cache[pageId] = true;
      return Promise.resolve();
    }

    var src = PAGE_SCRIPTS[pageId];
    if (!src) return Promise.resolve();

    var promise = fetchAndTransform(src)
      .then(function(code) {
        // Execute in global scope so window.GDD assignments work
        (0, eval)(code);
        _cache[pageId] = true;
        delete _loading[pageId];
      })
      .catch(function(err) {
        delete _loading[pageId];
        console.error('[loader] Failed to load page:', pageId, err);
        throw err;
      });

    _loading[pageId] = promise;
    return promise;
  };

  /**
   * Preload a page in the background (no-op if already loaded/loading).
   */
  window.GDD.preloadPage = function preloadPage(pageId) {
    if (_cache[pageId] || _loading[pageId]) return;
    setTimeout(function() { window.GDD.loadPage(pageId); }, 200);
  };

  /**
   * Check if a page is loaded and its component is available.
   */
  window.GDD.isPageLoaded = function isPageLoaded(pageId) {
    return !!_cache[pageId];
  };
})();