/**
 * mock 任务看板服务器：内存实现，语义严格对齐真实 Host v3 API：
 *   GET  全量文档；PUT 体内 revision 必须匹配（同时认 If-Match 头），
 *   冲突 409 并回带当前文档；成功 revision+1 返回新文档。
 * 可强制前 N 次 PUT 返回 409（forceConflicts），用于验证客户端重试。
 * 零依赖，仅供测试/演练。
 */
import { createServer } from "node:http";
import { randomUUID } from "node:crypto";

export function makeTask(overrides = {}) {
  const now = Date.now();
  return {
    id: overrides.id || `task-${now}-${Math.random().toString(36).slice(2, 7)}`,
    title: "示例任务",
    description: "",
    prompt: "在工作区创建 hello.txt",
    status: "todo",
    createdAt: now,
    updatedAt: now,
    executions: [],
    ...overrides,
  };
}

function initialState(seedTasks = []) {
  return {
    schemaVersion: 3,
    revision: 1,
    updatedAt: Date.now(),
    projects: [],
    tasks: seedTasks,
    evidences: [],
  };
}

export function startMockBoard({ port = 0, seedTasks = [], forceConflicts = 0 } = {}) {
  let state = initialState(seedTasks);
  let forcedLeft = forceConflicts;
  const conflictCount = { value: 0 };

  const server = createServer((req, res) => {
    if (req.url.endsWith("/events")) {
      res.writeHead(200, { "content-type": "text/event-stream" });
      res.write(`data: ${JSON.stringify({ type: "ready", revision: state.revision })}\n\n`);
      // 200ms 后主动断开，用于验证客户端 SSE 自动重连
      const t = setTimeout(() => res.end(), 200);
      req.on("close", () => {
        clearTimeout(t);
        res.end();
      });
      return;
    }

    if (req.method === "GET") {
      res.writeHead(200, { "content-type": "application/json" });
      res.end(JSON.stringify(state));
      return;
    }

    if (req.method === "PUT") {
      const chunks = [];
      req.on("data", (c) => chunks.push(c));
      req.on("end", () => {
        let body;
        try {
          body = JSON.parse(Buffer.concat(chunks).toString("utf8"));
        } catch {
          res.writeHead(400).end();
          return;
        }
        const forced = forcedLeft > 0;
        if (forced) forcedLeft -= 1;
        if (forced || body.revision !== state.revision) {
          conflictCount.value += 1;
          res.writeHead(409, { "content-type": "application/json" });
          res.end(
            JSON.stringify({ ok: false, code: "task-board-revision-conflict", document: state }),
          );
          return;
        }
        state = {
          schemaVersion: 3,
          revision: state.revision + 1,
          updatedAt: Date.now(),
          projects: body.projects ?? [],
          tasks: body.tasks ?? [],
          evidences: body.evidences ?? [],
        };
        res.writeHead(200, { "content-type": "application/json" });
        res.end(JSON.stringify(state));
      });
      return;
    }

    res.writeHead(405).end();
  });

  return new Promise((resolve) => {
    server.listen(port, "127.0.0.1", () => {
      const addr = server.address();
      resolve({
        url: `http://127.0.0.1:${addr.port}/api/dsh-task-board/v3`,
        port: addr.port,
        conflictCount,
        getState: () => structuredClone(state),
        close: () => new Promise((r) => server.close(r)),
      });
    });
  });
}

/** 可直接运行：node test/mock-board-server.js [port] */
if (import.meta.url === `file://${process.argv[1].replace(/\\/g, "/")}`) {
  const port = Number(process.argv[2]) || 32999;
  const seed = [
    makeTask({ id: "demo-todo", title: "演示待办", status: "todo" }),
    makeTask({ id: "demo-backlog", title: "演示 backlog", status: "backlog" }),
  ];
  const mock = await startMockBoard({ port, seedTasks: seed });
  console.log(`mock board: ${mock.url}（Ctrl+C 退出）`);
}