const STATUS_LABELS = {
  pending: "待开始",
  "in-progress": "执行中",
  completed: "已完成",
  bug: "Bug",
};

function svgEl(tagName, attrs = {}) {
  const node = document.createElementNS("http://www.w3.org/2000/svg", tagName);
  Object.entries(attrs).forEach(([key, value]) => {
    if (value !== undefined && value !== null) node.setAttribute(key, String(value));
  });
  return node;
}

function truncate(text, max = 26) {
  if (!text) return "";
  if (text.length <= max) return text;
  return `${text.slice(0, max - 1)}…`;
}

function oneLine(text) {
  return String(text || "").replace(/\s+/g, " ").trim();
}

function toPrettyTime(isoValue) {
  if (!isoValue) return "-";
  const date = new Date(isoValue);
  if (Number.isNaN(date.getTime())) return "-";
  const y = date.getFullYear();
  const m = String(date.getMonth() + 1).padStart(2, "0");
  const d = String(date.getDate()).padStart(2, "0");
  const h = String(date.getHours()).padStart(2, "0");
  const min = String(date.getMinutes()).padStart(2, "0");
  return `${y}-${m}-${d} ${h}:${min}`;
}

function edgePath(from, to) {
  const c1x = from.x + 92;
  const c2x = to.x - 92;
  return `M ${from.x} ${from.y} C ${c1x} ${from.y}, ${c2x} ${to.y}, ${to.x} ${to.y}`;
}

export class ThoughtChainRenderer {
  constructor(params) {
    this.svg = params.svg;
    this.linksLayer = params.linksLayer;
    this.nodesLayer = params.nodesLayer;
  }

  renderEmpty() {
    this.linksLayer.innerHTML = "";
    this.nodesLayer.innerHTML = "";
    const text = svgEl("text", {
      x: 180,
      y: 200,
      class: "empty-state",
    });
    text.textContent = "当前会话暂无节点";
    this.nodesLayer.appendChild(text);
  }

  render(graph, layout, options = {}) {
    const nodes = Array.isArray(graph?.nodes) ? graph.nodes : [];
    if (!nodes.length) {
      this.renderEmpty();
      return;
    }

    const selectedNodeId = options.selectedNodeId || null;
    const onNodeClick = typeof options.onNodeClick === "function" ? options.onNodeClick : null;

    this.linksLayer.innerHTML = "";
    this.nodesLayer.innerHTML = "";

    for (const link of layout.links) {
      const path = svgEl("path", {
        class: `link-path status-${link.status} type-${link.type || "reference"}`,
        d: edgePath(link.from, link.to),
      });
      this.linksLayer.appendChild(path);
    }

    for (const node of nodes) {
      const pos = layout.positions.get(node.id);
      if (!pos) continue;

      const selectedClass = node.id === selectedNodeId ? " selected" : "";
      const group = svgEl("g", {
        class: `node-group status-${node.status}${selectedClass}`,
        transform: `translate(${pos.x} ${pos.y})`,
        "data-id": node.id,
      });

      if (node.status === "in-progress") {
        const ring = svgEl("rect", {
          class: "progress-ring",
          x: -146,
          y: -58,
          width: 292,
          height: 116,
          rx: 24,
        });
        group.appendChild(ring);
      }

      const card = svgEl("rect", {
        class: "node-card",
        x: -135,
        y: -50,
        width: 270,
        height: 100,
        rx: 18,
      });
      group.appendChild(card);

      const statusDot = svgEl("circle", {
        class: "node-status-dot",
        cx: -114,
        cy: -31,
        r: 7,
      });
      group.appendChild(statusDot);

      const title = svgEl("text", {
        class: "node-title",
        x: -98,
        y: -27,
      });
      title.textContent = truncate(oneLine(node.name), 22);
      group.appendChild(title);

      const line1 = svgEl("text", {
        class: "node-subtitle",
        x: -98,
        y: -5,
      });
      line1.textContent = `${STATUS_LABELS[node.status] || node.status} · ${node.nodeType}`;
      group.appendChild(line1);

      const line2 = svgEl("text", {
        class: "node-subtitle",
        x: -98,
        y: 16,
      });
      line2.textContent = toPrettyTime(node.timestamps?.created || node.createdAt);
      group.appendChild(line2);

      const line3 = svgEl("text", {
        class: "node-subtitle muted",
        x: -98,
        y: 36,
      });
      line3.textContent = truncate(oneLine(node.content || node.notes || ""), 28) || "无详细内容";
      group.appendChild(line3);

      if (onNodeClick) {
        group.addEventListener("click", (event) => {
          event.stopPropagation();
          onNodeClick(node.id);
        });
      }

      this.nodesLayer.appendChild(group);
    }
  }

  exportSvg(filename) {
    const cloned = this.svg.cloneNode(true);
    cloned.setAttribute("xmlns", "http://www.w3.org/2000/svg");
    cloned.setAttribute("width", String(this.svg.clientWidth || 1600));
    cloned.setAttribute("height", String(this.svg.clientHeight || 960));
    const source = new XMLSerializer().serializeToString(cloned);
    const blob = new Blob([source], { type: "image/svg+xml;charset=utf-8" });
    const url = URL.createObjectURL(blob);
    const link = document.createElement("a");
    link.href = url;
    link.download = filename;
    link.click();
    URL.revokeObjectURL(url);
  }
}