/* 白板：Canvas 绘画 + WebSocket 实时同步 + 心跳。
   - 笔画以 {points:[[x,y],...], color, width} 表示，增量广播。
   - 心跳 3s 一次 ping；服务端 15s 无心跳判失活会主动断连，前端据此重连。
   - 收到他人 stroke 增量重绘该笔；收到 cleared 清空本地画布。
   - 兼容鼠标 + 触摸：统一用 pointer events，touch-action:none 防滚动缩放。 */
(function () {
  "use strict";
  const { el, toast, copyText } = window.ZK;

  // ---------- 从 URL 解析 board_id ----------
  // 路径形如 /whiteboard/{id}；id 为 [a-zA-Z0-9_-]{1,64}
  const m = location.pathname.match(/^\/whiteboard\/([^/]+)\/?$/);
  let boardId = m ? decodeURIComponent(m[1]) : "default";
  // 合法性兜底：前端非法字符直接回退到 default，真正校验在服务端
  if (!/^[a-zA-Z0-9_-]{1,64}$/.test(boardId)) boardId = "default";
  document.getElementById("boardId").textContent = boardId;

  // ---------- DOM ----------
  const canvas = document.getElementById("canvas");
  const ctx = canvas.getContext("2d");
  const colorInput = document.getElementById("color");
  const widthInput = document.getElementById("width");
  const widthVal = document.getElementById("widthVal");
  const clearBtn = document.getElementById("clearBtn");
  const copyBtn = document.getElementById("copyBtn");
  const statusEl = document.getElementById("status");
  const onlineEl = document.getElementById("online");

  // ---------- 状态 ----------
  let strokes = [];          // 已确认的笔画
  let current = null;        // 正在画的笔画（本地未提交）
  let drawing = false;
  let ws = null;
  let clientId = localStorage.getItem("wb_cid") || "";
  if (!clientId) {
    clientId = "c_" + Math.random().toString(36).slice(2, 10);
    localStorage.setItem("wb_cid", clientId);
  }
  let heartbeatTimer = null;
  let reconnectTimer = null;
  let connected = false;

  // ---------- 画布尺寸 ----------
  function resize() {
    const dpr = window.devicePixelRatio || 1;
    const w = canvas.clientWidth;
    const h = canvas.clientHeight;
    canvas.width = Math.max(1, Math.floor(w * dpr));
    canvas.height = Math.max(1, Math.floor(h * dpr));
    ctx.setTransform(dpr, 0, 0, dpr, 0, 0);
    redraw();
  }
  window.addEventListener("resize", resize);

  // ---------- 绘制 ----------
  function drawStroke(s) {
    if (!s || !s.points || s.points.length < 1) return;
    ctx.strokeStyle = s.color || "#1565c0";
    ctx.lineWidth = Number(s.width) || 3;
    ctx.lineCap = "round";
    ctx.lineJoin = "round";
    const pts = s.points;
    ctx.beginPath();
    ctx.moveTo(pts[0][0], pts[0][1]);
    if (pts.length === 1) {
      // 单点：画一个小圆点
      ctx.arc(pts[0][0], pts[0][1], (ctx.lineWidth || 3) / 2, 0, Math.PI * 2);
      ctx.fillStyle = ctx.strokeStyle;
      ctx.fill();
      return;
    }
    for (let i = 1; i < pts.length; i++) ctx.lineTo(pts[i][0], pts[i][1]);
    ctx.stroke();
  }

  function redraw() {
    ctx.clearRect(0, 0, canvas.width, canvas.height);
    for (const s of strokes) drawStroke(s);
    if (current) drawStroke(current);
  }

  // ---------- 指针事件 ----------
  function pos(e) {
    const r = canvas.getBoundingClientRect();
    return [e.clientX - r.left, e.clientY - r.top];
  }

  canvas.addEventListener("pointerdown", (e) => {
    if (!connected) { flashStatus("未连接，正在重连…"); return; }
    e.preventDefault();
    canvas.setPointerCapture(e.pointerId);
    drawing = true;
    current = { points: [pos(e)], color: colorInput.value, width: Number(widthInput.value) };
    drawStroke(current);
  });
  canvas.addEventListener("pointermove", (e) => {
    if (!drawing) return;
    e.preventDefault();
    const p = pos(e);
    const last = current.points[current.points.length - 1];
    // 跳过过近的点，减少数据量
    if (Math.hypot(p[0] - last[0], p[1] - last[1]) < 1.5) return;
    current.points.push(p);
    // 增量画最后一段
    ctx.strokeStyle = current.color;
    ctx.lineWidth = current.width;
    ctx.lineCap = "round"; ctx.lineJoin = "round";
    ctx.beginPath();
    ctx.moveTo(last[0], last[1]);
    ctx.lineTo(p[0], p[1]);
    ctx.stroke();
  });
  function endStroke(e) {
    if (!drawing) return;
    drawing = false;
    if (e && e.pointerId !== undefined) {
      try { canvas.releasePointerCapture(e.pointerId); } catch {}
    }
    if (current && current.points.length) {
      strokes.push(current);
      send({ type: "stroke", stroke: current });
    }
    current = null;
  }
  canvas.addEventListener("pointerup", endStroke);
  canvas.addEventListener("pointercancel", endStroke);
  canvas.addEventListener("pointerleave", (e) => {
    // 仅在抬起时结束；离开但按住不放不结束（pointer capture 已处理）
    if (!drawing) return;
    if (e.buttons === 0) endStroke(e);
  });

  widthInput.addEventListener("input", () => (widthVal.textContent = widthInput.value));

  clearBtn.addEventListener("click", () => {
    if (!connected) { flashStatus("未连接"); return; }
    if (!confirm("确定清空白板？所有人的内容都会被清除。")) return;
    send({ type: "clear" });
  });

  copyBtn.addEventListener("click", async () => {
    const url = `${location.origin}/whiteboard/${boardId}`;
    const ok = await copyText(url);
    toast(ok ? "链接已复制" : "复制失败");
  });

  // ---------- WebSocket ----------
  function wsUrl() {
    const proto = location.protocol === "https:" ? "wss:" : "ws:";
    return `${proto}//${location.host}/ws/whiteboard/${encodeURIComponent(boardId)}`;
  }

  function connect() {
    setStatus("连接中…");
    try {
      ws = new WebSocket(wsUrl());
    } catch (e) {
      scheduleReconnect();
      return;
    }
    ws.onopen = () => {
      connected = true;
      setStatus("已连接", true);
      onlineEl.classList.remove("off");
      send({ type: "hello", client_id: clientId });
      startHeartbeat();
    };
    ws.onmessage = (ev) => onMessage(ev.data);
    ws.onclose = () => onLost("连接已关闭");
    ws.onerror = () => { /* close 会跟进 */ };
  }

  function onMessage(raw) {
    let msg;
    try { msg = JSON.parse(raw); } catch { return; }
    switch (msg.type) {
      case "init":
        strokes = Array.isArray(msg.strokes) ? msg.strokes : [];
        redraw();
        setStatus(`已同步 ${strokes.length} 笔`, true);
        break;
      case "pong":
        // 心跳回声，保持连接
        break;
      case "stroke":
        if (msg.client_id === clientId) break; // 自己的，已本地画
        strokes.push(msg.stroke);
        drawStroke(msg.stroke);
        break;
      case "cleared":
        strokes = [];
        current = null;
        redraw();
        flashStatus(msg.client_id === clientId ? "已清空" : "对方清空了白板");
        break;
      case "error":
        flashStatus(msg.msg || "错误", true);
        break;
    }
  }

  function send(obj) {
    if (ws && ws.readyState === WebSocket.OPEN) {
      try { ws.send(JSON.stringify(obj)); } catch {}
    }
  }

  function startHeartbeat() {
    stopHeartbeat();
    heartbeatTimer = setInterval(() => send({ type: "ping" }), 3000);
  }
  function stopHeartbeat() {
    if (heartbeatTimer) { clearInterval(heartbeatTimer); heartbeatTimer = null; }
  }

  function onLost(reason) {
    connected = false;
    stopHeartbeat();
    onlineEl.classList.add("off");
    setStatus(reason + "，重连中…", true);
    scheduleReconnect();
  }

  function scheduleReconnect() {
    if (reconnectTimer) return;
    reconnectTimer = setTimeout(() => {
      reconnectTimer = null;
      connect();
    }, 2000);
  }

  function setStatus(text, isErr) {
    statusEl.textContent = text;
    statusEl.classList.add("show");
    statusEl.classList.toggle("err", !!isErr);
  }
  let statusTimer = null;
  function flashStatus(text, isErr) {
    setStatus(text, isErr);
    clearTimeout(statusTimer);
    statusTimer = setTimeout(() => statusEl.classList.remove("show"), 1600);
  }

  // ---------- 启动 ----------
  // 先 GET /whiteboard/{id} 确保白板存在（不存在则服务端新建），再连 WS
  fetch(`/whiteboard/${encodeURIComponent(boardId)}`, { headers: { accept: "application/json" } })
    .then((r) => r.ok ? r.json() : null)
    .then((body) => {
      if (body && Array.isArray(body.strokes)) {
        strokes = body.strokes;
        redraw();
      }
      resize();
      connect();
    })
    .catch(() => { resize(); connect(); });

  // 页面隐藏时不发心跳可被服务端判失活；重新可见时主动重连
  document.addEventListener("visibilitychange", () => {
    if (document.visibilityState === "visible" && (!ws || ws.readyState !== WebSocket.OPEN)) {
      if (reconnectTimer) { clearTimeout(reconnectTimer); reconnectTimer = null; }
      connect();
    }
  });

  window.addEventListener("beforeunload", () => {
    stopHeartbeat();
    if (reconnectTimer) clearTimeout(reconnectTimer);
    try { ws && ws.close(); } catch {}
  });
})();