import type { Router } from "express";
import { z } from "zod";
import { getLocalAgentContext } from "../context/localContext.js";
import { readPurpose, type SessionMetadataStore } from "../sessions/metadataStore.js";

const nameSchema = z.object({ name: z.string().trim().min(1).max(80) }).strict();
const membershipSchema = z.object({ topic_id: z.string().uuid().nullable() }).strict();

export function registerChatTopicRoutes(router: Router, sessions: SessionMetadataStore) {
  router.get("/topics", async (req, res) => {
    res.json({ topics: await sessions.topics.list(getLocalAgentContext(req)) });
  });
  router.post("/topics", async (req, res) => {
    const parsed = nameSchema.safeParse(req.body);
    if (!parsed.success) { res.status(400).json({ message: "主题名称须为 1 至 80 个字符" }); return; }
    res.status(201).json(await sessions.topics.create(getLocalAgentContext(req), parsed.data.name));
  });
  router.patch("/topics/:topic_id", async (req, res) => {
    const parsed = nameSchema.safeParse(req.body);
    if (!parsed.success) { res.status(400).json({ message: "主题名称须为 1 至 80 个字符" }); return; }
    const topic = await sessions.topics.rename(getLocalAgentContext(req), req.params.topic_id, parsed.data.name);
    if (!topic) { res.status(404).json({ message: "主题不存在" }); return; }
    res.json(topic);
  });
  router.delete("/topics/:topic_id", async (req, res) => {
    // Removing a grouping never deletes conversations. Old IDs resolve as unclassified.
    const removed = await sessions.topics.remove(getLocalAgentContext(req), req.params.topic_id);
    if (!removed) { res.status(404).json({ message: "主题不存在" }); return; }
    res.status(204).end();
  });
  router.patch("/session/:session_id/topic", async (req, res) => {
    const parsed = membershipSchema.safeParse(req.body);
    if (!parsed.success) { res.status(400).json({ message: "invalid topic membership" }); return; }
    const context = getLocalAgentContext(req);
    const record = await sessions.get(context, req.params.session_id);
    if (!record || readPurpose(record) === "task_execution") { res.status(404).json({ message: "session not found" }); return; }
    if (parsed.data.topic_id && !await sessions.topics.get(context, parsed.data.topic_id)) {
      res.status(404).json({ message: "主题不存在" }); return;
    }
    await sessions.touch(record, { topicId: parsed.data.topic_id });
    res.json({ session_id: record.sessionId, topic_id: parsed.data.topic_id });
  });
}