import { createViewer } from './viewer.js';

const DEFAULT_VIEW = [0.86, -1.35, 0.98];
const MAX_FILE_BYTES = 512 * 1024;

const byId = (id) => document.getElementById(id);
const els = {
  runtime: byId('runtime'),
  runtimeText: byId('runtimeText'),
  loadBtn: byId('loadBtn'),
  fileInput: byId('fileInput'),
  exampleList: byId('exampleList'),
  exampleCount: byId('exampleCount'),
  fileName: byId('fileName'),
  fileState: byId('fileState'),
  revertBtn: byId('revertBtn'),
  runBtn: byId('runBtn'),
  editorWrap: byId('editorWrap'),
  cursorInfo: byId('cursorInfo'),
  objectCount: byId('objectCount'),
  autoBtn: byId('autoBtn'),
  resetBtn: byId('resetBtn'),
  canvasWrap: byId('canvasWrap'),
  view: byId('view'),
  canvasHint: byId('canvasHint'),
  loadingState: byId('loadingState'),
  loadingText: byId('loadingText'),
  emptyState: byId('emptyState'),
  emptyHint: byId('emptyHint'),
  errorState: byId('errorState'),
  errorText: byId('errorText'),
  dismissError: byId('dismissError'),
  toast: byId('toast'),
  dropOverlay: byId('dropOverlay'),
};

const state = {
  examples: [],
  current: null,
  mode: 'example',
  source: '',
  fileName: '未命名.py',
  dirty: false,
  scene: null,
  sceneSource: '',
  busy: false,
  pendingRun: null,
  uiSeq: 0,
  cm: null,
  viewer: null,
  toastTimer: null,
  hintTimer: null,
};

const RUNTIME_LABELS = {
  idle: 'Python 待命',
  loading: 'Python 載入中',
  ready: 'Python 就緒',
  busy: 'Python 執行中',
  error: 'Python 離線',
};

class PythonRuntime {
  constructor() {
    this.worker = null;
    this.ready = false;
    this.failed = false;
    this.shim = null;
    this.initPromise = null;
    this.seq = 0;
    this.pending = new Map();
    this.onState = () => {};
    this.lastError = '';
    this._readyResolve = null;
    this._readyReject = null;
    this._initTimer = null;
  }

  setState(name, detail = '') {
    this.state = name;
    this.onState(name, detail);
  }

  async loadShim() {
    if (this.shim) return this.shim;
    const response = await fetch('cadshim.py', { cache: 'no-cache' });
    if (!response.ok) {
      throw new Error(`無法載入 Python shim（HTTP ${response.status}）`);
    }
    const text = await response.text();
    if (!text.includes('__wfcad_runtime')) {
      throw new Error('Python shim 內容不正確');
    }
    this.shim = text;
    return text;
  }

  preload() {
    this.ensure().catch(() => {});
  }

  async ensure() {
    if (this.ready && this.worker) return;
    if (this.initPromise) return this.initPromise;
    this.initPromise = this.boot();
    try {
      await this.initPromise;
    } catch (error) {
      if (this.initPromise === null) throw error;
      this.initPromise = null;
      throw error;
    }
  }

  async boot() {
    this.setState('loading');
    let shim;
    try {
      shim = await this.loadShim();
    } catch (error) {
      this.fail(error);
      throw error;
    }

    let worker;
    try {
      worker = new Worker('worker.js');
    } catch (error) {
      this.fail(error);
      throw error;
    }
    this.worker = worker;
    worker.onmessage = (event) => this.handleMessage(event.data);
    worker.onerror = (event) => {
      this.fail(event.message || 'Python worker 發生錯誤');
    };

    const ready = new Promise((resolve, reject) => {
      this._readyResolve = resolve;
      this._readyReject = reject;
    });

    this._initTimer = setTimeout(() => {
      this.fail('Python 執行環境載入逾時，請檢查網路後重試。');
    }, 90000);

    worker.postMessage({ type: 'init', shim });
    await ready;
  }

  handleMessage(message) {
    if (!message) return;
    if (message.type === 'ready') {
      if (this._initTimer) {
        clearTimeout(this._initTimer);
        this._initTimer = null;
      }
      this.ready = true;
      this.failed = false;
      this.setState('ready');
      const resolve = this._readyResolve;
      this._readyResolve = null;
      this._readyReject = null;
      if (resolve) resolve();
      return;
    }
    if (message.type === 'fatal') {
      this.fail(message.error || 'Python 執行環境發生錯誤');
      return;
    }
    if (message.type === 'result' || message.type === 'error') {
      const pending = this.pending.get(message.id);
      if (!pending) return;
      this.pending.delete(message.id);
      if (message.type === 'result') {
        pending.resolve(message.result);
      } else {
        pending.reject(new Error(message.error || 'Python 執行失敗'));
      }
    }
  }

  fail(error) {
    const reason = error instanceof Error ? error.message : String(error || 'Python 執行環境發生錯誤');
    this.lastError = reason;
    this.ready = false;
    this.failed = true;
    if (this._initTimer) {
      clearTimeout(this._initTimer);
      this._initTimer = null;
    }
    if (this.worker) {
      this.worker.terminate();
      this.worker = null;
    }
    this.initPromise = null;
    const rejectReady = this._readyReject;
    this._readyResolve = null;
    this._readyReject = null;
    if (rejectReady) rejectReady(new Error(reason));
    for (const pending of [...this.pending.values()]) {
      pending.reject(new Error(reason));
    }
    this.pending.clear();
    this.setState('error', reason);
  }

  async run(code) {
    await this.ensure();
    if (!this.worker) throw new Error('Python 執行環境不在線');
    this.setState('busy');
    const id = ++this.seq;
    return new Promise((resolve, reject) => {
      const timer = setTimeout(() => {
        this.pending.delete(id);
        this.restart();
        reject(new Error('執行逾時。程式可能進入了無窮迴圈，已停止執行。'));
      }, 20000);
      this.pending.set(id, {
        resolve: (value) => {
          clearTimeout(timer);
          this.finishRun();
          resolve(value);
        },
        reject: (error) => {
          clearTimeout(timer);
          this.finishRun();
          reject(error);
        },
      });
      this.worker.postMessage({ type: 'run', id, code });
    });
  }

  finishRun() {
    if (this.ready) {
      this.setState('ready');
    } else if (this.failed) {
      this.setState('error', this.lastError);
    }
  }

  restart() {
    if (this.worker) {
      this.worker.terminate();
      this.worker = null;
    }
    this.ready = false;
    this.failed = false;
    this.initPromise = null;
    this.pending.clear();
    this.setState('idle');
  }
}

const runtime = new PythonRuntime();
runtime.onState = (name, detail) => {
  els.runtime.dataset.state = name;
  els.runtimeText.textContent = RUNTIME_LABELS[name] || 'Python';
  if (name === 'error') {
    els.runtime.title = detail || 'Python 執行環境無法載入';
  } else {
    els.runtime.title = 'Python 執行環境';
  }
};

// --------------------------------------------------------------------------
// small helpers
// --------------------------------------------------------------------------

function escapeHtml(value) {
  return String(value).replace(/[&<>"']/g, (char) => {
    const map = { '&': '&amp;', '<': '&lt;', '>': '&gt;', '"': '&quot;', "'": '&#39;' };
    return map[char];
  });
}

function cleanError(value) {
  let text = value instanceof Error ? value.stack || value.message : String(value || '未知錯誤');
  text = text.replace(/\u001b\[[0-9;]*m/g, '').trim();
  if (text.length > 7000) text = `${text.slice(0, 7000)}\n…`;
  return text || '未知錯誤';
}

function hideToast() {
  if (state.toastTimer) clearTimeout(state.toastTimer);
  state.toastTimer = null;
  els.toast.hidden = true;
}

function toast(message, tone = 'info') {
  hideToast();
  els.toast.textContent = message;
  els.toast.dataset.tone = tone;
  els.toast.hidden = false;
  state.toastTimer = setTimeout(() => {
    els.toast.hidden = true;
    state.toastTimer = null;
  }, tone === 'error' ? 4200 : 2800);
}

function showLoading(text) {
  hideToast();
  if (text) els.loadingText.textContent = text;
  els.loadingState.hidden = false;
  els.emptyState.hidden = true;
  els.errorState.hidden = true;
}

function showError(message) {
  hideToast();
  els.errorText.textContent = cleanError(message);
  els.errorState.hidden = false;
  els.loadingState.hidden = true;
  els.emptyState.hidden = true;
  els.canvasHint.classList.add('is-hidden');
  els.fileState.textContent = '錯誤';
  els.fileState.dataset.state = 'error';
}

function hideError() {
  if (!els.errorState.hidden) {
    els.errorState.hidden = true;
    updateFileUI();
  }
}

function updateCursor() {
  if (!state.cm) return;
  const cursor = state.cm.getCursor();
  els.cursorInfo.textContent = `Ln ${cursor.line + 1}, Col ${cursor.ch + 1}`;
}

function updateRunButton() {
  els.runBtn.disabled = state.busy;
  els.runBtn.setAttribute('aria-busy', String(state.busy));
  els.runBtn.classList.toggle('is-busy', state.busy);
}

function updateFileUI() {
  els.fileName.textContent = state.fileName || '未命名.py';
  document.title = `${state.fileName || 'WFreeCAD'} · WFreeCAD`;
  els.revertBtn.disabled = !(state.mode === 'example' && state.current);
  els.revertBtn.title = els.revertBtn.disabled ? '只有範例可以還原' : '回到範例程式';

  let label = '範例';
  let kind = 'example';
  if (state.mode === 'upload') {
    label = state.dirty ? '已修改' : '已載入';
    kind = state.dirty ? 'modified' : 'upload';
  } else if (state.dirty) {
    label = '已修改';
    kind = 'modified';
  }
  els.fileState.textContent = label;
  els.fileState.dataset.state = kind;
}

function updateActive(id) {
  const cards = els.exampleList.querySelectorAll('.example-card');
  for (const card of cards) {
    const active = card.dataset.id === id;
    card.classList.toggle('is-active', active);
    if (active) {
      card.setAttribute('aria-current', 'true');
    } else {
      card.removeAttribute('aria-current');
    }
  }
}

// --------------------------------------------------------------------------
// editor
// --------------------------------------------------------------------------

function initEditor() {
  state.cm = CodeMirror.fromTextArea(byId('editor'), {
    mode: 'python',
    lineNumbers: true,
    indentUnit: 4,
    tabSize: 4,
    indentWithTabs: false,
    lineWrapping: true,
    matchBrackets: true,
    autoCloseBrackets: true,
    styleActiveLine: true,
    viewportMargin: 40,
    extraKeys: {
      Tab: (editor) => {
        if (editor.somethingSelected()) {
          editor.indentSelection('add');
        } else {
          editor.replaceSelection('    ', 'end');
        }
      },
    },
  });
  state.cm.setSize('100%', '100%');
  state.cm.on('change', () => {
    const value = state.cm.getValue();
    state.dirty = value !== state.source;
    updateFileUI();
    updateCursor();
    if (!els.errorState.hidden) hideError();
  });
  state.cm.on('cursorActivity', updateCursor);
  state.cm.on('focus', () => runtime.preload());
  requestAnimationFrame(() => state.cm.refresh());
  updateCursor();
}

function setEditor(text, { mode, name } = {}) {
  state.source = text;
  if (mode) state.mode = mode;
  if (name) state.fileName = name;
  state.dirty = false;
  state.cm.setValue(text || '');
  state.cm.clearHistory();
  state.cm.setCursor({ line: 0, ch: 0 });
  updateFileUI();
  updateCursor();
  requestAnimationFrame(() => state.cm.refresh());
}

// --------------------------------------------------------------------------
// preview
// --------------------------------------------------------------------------

function showScene(scene, view) {
  if (!scene) {
    showError('沒有可顯示的場景');
    return { objects: 0, skipped: 0 };
  }
  const stats = state.viewer.setScene(scene, view || DEFAULT_VIEW);
  els.objectCount.textContent = `${stats.objects} 個物件`;
  els.loadingState.hidden = true;
  els.errorState.hidden = true;
  if (stats.objects === 0) {
    els.emptyState.hidden = false;
    if (stats.skipped > 0) {
      els.emptyHint.textContent = '場景中的幾何使用了尚未支援的 FreeCAD API';
    } else {
      els.emptyHint.innerHTML = '在程式裡呼叫 <code>Part.show(shape)</code>';
    }
  } else {
    els.emptyState.hidden = true;
  }
  return stats;
}

function presentScene(scene, view, { notify = false } = {}) {
  const stats = showScene(scene, view);
  const errors = (scene && scene.errors) || [];
  if (stats.objects === 0 && errors.length) {
    showError(errors.join('\n'));
  } else if (errors.length) {
    toast(`有 ${errors.length} 個物件計算失敗`, 'error');
  } else if (stats.objects === 0) {
    // Empty state already visible.
  } else if (stats.skipped > 0) {
    toast(`已顯示 ${stats.objects} 個物件，${stats.skipped} 個未支援`, 'error');
  } else if (notify) {
    toast('執行完成');
  }
  return stats;
}

// --------------------------------------------------------------------------
// examples
// --------------------------------------------------------------------------

async function loadExamples() {
  const indexResponse = await fetch('examples/index.json', { cache: 'no-cache' });
  if (!indexResponse.ok) {
    throw new Error(`無法載入範例索引（HTTP ${indexResponse.status}）`);
  }
  const index = await indexResponse.json();
  const examples = await Promise.all(
    index.map(async (item) => {
      const [codeResponse, sceneResponse] = await Promise.all([
        fetch(`examples/${item.code}`, { cache: 'no-cache' }),
        fetch(`scenes/${item.scene}`, { cache: 'no-cache' }),
      ]);
      if (!codeResponse.ok || !sceneResponse.ok) {
        throw new Error(`無法載入 ${item.id} 的範例檔`);
      }
      return {
        ...item,
        codeText: await codeResponse.text(),
        sceneData: await sceneResponse.json(),
      };
    }),
  );
  state.examples = examples;
  els.exampleCount.textContent = String(examples.length).padStart(2, '0');
  renderExamples();
  return examples;
}

function renderExamples() {
  els.exampleList.innerHTML = '';
  const fragment = document.createDocumentFragment();
  state.examples.forEach((item, index) => {
    const button = document.createElement('button');
    button.type = 'button';
    button.className = 'example-card';
    button.dataset.id = item.id;
    button.innerHTML = `
      <span class="example-thumb">
        <img src="thumbs/${encodeURIComponent(item.thumb)}" alt="" loading="lazy" draggable="false">
      </span>
      <span class="example-meta">
        <span class="example-title">${escapeHtml(item.title || item.id)}</span>
        <span class="example-sub">${escapeHtml(item.subtitle || item.code)}</span>
      </span>
      <span class="example-index">${String(index + 1).padStart(2, '0')}</span>
      <span class="example-chev" aria-hidden="true">
        <svg viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="1.8" stroke-linecap="round" stroke-linejoin="round">
          <path d="m9 6 6 6-6 6"/>
        </svg>
      </span>
    `;
    button.addEventListener('click', () => loadExample(item));
    fragment.appendChild(button);
  });
  els.exampleList.appendChild(fragment);
}

function loadExample(item, { initial = false } = {}) {
  if (!item) return;
  hideToast();
  state.uiSeq += 1;
  state.pendingRun = null;
  state.current = item;
  state.mode = 'example';
  state.fileName = item.code;
  state.source = item.codeText;
  state.dirty = false;
  state.scene = item.sceneData;
  state.sceneSource = item.codeText;
  setEditor(item.codeText, { mode: 'example', name: item.code });
  updateActive(item.id);
  hideError();
  presentScene(item.sceneData, item.view);
  if (initial) {
    els.canvasHint.classList.remove('is-hidden');
    if (state.hintTimer) clearTimeout(state.hintTimer);
    state.hintTimer = setTimeout(() => els.canvasHint.classList.add('is-hidden'), 9000);
  }
}

// --------------------------------------------------------------------------
// running
// --------------------------------------------------------------------------

async function runCode(code) {
  if (state.busy) {
    state.pendingRun = { code };
    toast('正在執行，完成後會接著執行');
    return;
  }
  state.busy = true;
  updateRunButton();
  const uiSeq = state.uiSeq;
  showLoading(runtime.ready ? '正在解析 Part 指令…' : 'Python 執行環境載入中…（首次約 10 MB）');
  runtime.preload();
  try {
    const result = await runtime.run(code);
    if (uiSeq !== state.uiSeq) return;
    if (!result || !result.ok) {
      showError((result && result.error) || '執行失敗');
      return;
    }
    state.scene = result.scene;
    state.sceneSource = code;
    presentScene(result.scene, state.current ? state.current.view : DEFAULT_VIEW, { notify: true });
  } catch (error) {
    if (uiSeq !== state.uiSeq) return;
    showError(error && error.message ? error.message : error);
  } finally {
    state.busy = false;
    updateRunButton();
    if (state.pendingRun) {
      const pending = state.pendingRun;
      state.pendingRun = null;
      runCode(pending.code);
    }
  }
}

function requestRun(code) {
  runtime.preload();
  if (state.busy) {
    state.pendingRun = { code };
    toast('正在執行，完成後會接著執行');
    return;
  }
  runCode(code);
}

function runCurrent() {
  const code = state.cm.getValue();
  if (state.mode === 'example' && state.current && !state.dirty && state.current.sceneData) {
    state.uiSeq += 1;
    presentScene(state.current.sceneData, state.current.view);
    if (els.errorState.hidden) toast('已重新載入範例預覽');
    return;
  }
  requestRun(code);
}

// --------------------------------------------------------------------------
// files
// --------------------------------------------------------------------------

async function loadFile(file) {
  if (!file) return;
  if (!/\.(py|txt)$/i.test(file.name)) {
    toast('請選擇 .py 檔', 'error');
    return;
  }
  if (file.size > MAX_FILE_BYTES) {
    toast('檔案太大（上限 512 KB）', 'error');
    return;
  }
  try {
    const text = await file.text();
    state.uiSeq += 1;
    state.pendingRun = null;
    state.current = null;
    state.mode = 'upload';
    state.fileName = file.name;
    state.source = text;
    state.dirty = false;
    state.scene = null;
    state.sceneSource = '';
    setEditor(text, { mode: 'upload', name: file.name });
    updateActive(null);
    hideError();
    requestRun(text);
  } catch (error) {
    showError(error && error.message ? error.message : error);
  }
}

// --------------------------------------------------------------------------
// ui events
// --------------------------------------------------------------------------

function bindUI() {
  els.loadBtn.addEventListener('click', () => {
    runtime.preload();
    els.fileInput.click();
  });

  els.fileInput.addEventListener('change', () => {
    const file = els.fileInput.files && els.fileInput.files[0];
    if (file) loadFile(file);
    els.fileInput.value = '';
  });

  els.runBtn.addEventListener('click', runCurrent);

  els.revertBtn.addEventListener('click', () => {
    if (!state.current) return;
    state.uiSeq += 1;
    state.pendingRun = null;
    loadExample(state.current);
    toast('已回到範例程式');
  });

  els.dismissError.addEventListener('click', hideError);

  els.autoBtn.addEventListener('click', () => {
    const enabled = !state.viewer.isAutoRotate();
    state.viewer.setAutoRotate(enabled);
    els.autoBtn.classList.toggle('is-on', enabled);
    els.autoBtn.setAttribute('aria-pressed', String(enabled));
    els.autoBtn.title = enabled ? '自動旋轉' : '自動旋轉（已暫停）';
  });

  els.resetBtn.addEventListener('click', () => {
    state.viewer.resetView();
    els.canvasHint.classList.add('is-hidden');
  });

  els.view.addEventListener(
    'pointerdown',
    () => {
      els.canvasHint.classList.add('is-hidden');
    },
    { once: true },
  );

  window.addEventListener('keydown', (event) => {
    if ((event.metaKey || event.ctrlKey) && event.key === 'Enter') {
      event.preventDefault();
      runCurrent();
    } else if (event.key === 'Escape') {
      hideError();
      els.dropOverlay.hidden = true;
    }
  });

  let dragDepth = 0;
  const hasFiles = (event) => {
    const types = event.dataTransfer && event.dataTransfer.types;
    return Boolean(types && Array.from(types).includes('Files'));
  };
  window.addEventListener('dragenter', (event) => {
    if (!hasFiles(event)) return;
    event.preventDefault();
    dragDepth += 1;
    els.dropOverlay.hidden = false;
  });
  window.addEventListener('dragover', (event) => {
    if (!hasFiles(event)) return;
    event.preventDefault();
    if (event.dataTransfer) event.dataTransfer.dropEffect = 'copy';
  });
  window.addEventListener('dragleave', (event) => {
    if (!hasFiles(event)) return;
    dragDepth = Math.max(0, dragDepth - 1);
    if (dragDepth === 0) els.dropOverlay.hidden = true;
  });
  window.addEventListener('drop', (event) => {
    event.preventDefault();
    dragDepth = 0;
    els.dropOverlay.hidden = true;
    const file = event.dataTransfer && event.dataTransfer.files && event.dataTransfer.files[0];
    if (file) loadFile(file);
  });

  let resizeTimer = null;
  window.addEventListener('resize', () => {
    if (resizeTimer) clearTimeout(resizeTimer);
    resizeTimer = setTimeout(() => {
      if (state.cm) state.cm.refresh();
    }, 120);
  });
}

function schedulePreload() {
  const connection =
    navigator.connection || navigator.mozConnection || navigator.webkitConnection;
  if (connection && (connection.saveData || /2g/.test(connection.effectiveType || ''))) {
    return;
  }
  setTimeout(() => runtime.preload(), 5000);
}

async function init() {
  state.viewer = createViewer(els.view, { autoRotate: true });
  initEditor();
  bindUI();
  updateFileUI();
  showLoading('正在載入範例…');
  try {
    const examples = await loadExamples();
    if (examples.length > 0) {
      loadExample(examples[0], { initial: true });
    } else {
      showError('找不到任何範例。');
    }
  } catch (error) {
    showError(error && error.message ? error.message : error);
  }
  schedulePreload();
}

init().catch((error) => {
  console.error(error);
  showError(error && error.message ? error.message : error);
});