/**
 * S-09 — multi-session CRUD routes.
 *
 * POST   /sessions              → { id, name, state, lastOutputAt }
 * GET    /sessions              → [{ id, name, description, state, lastOutputAt }]
 * PATCH  /sessions/:id          → updates @description
 * DELETE /sessions/:id          → kills tmux session, optionally clears buffer
 * GET    /sessions/:id/thumbnail → text/plain capture-pane (40×12)
 *
 * Owner: T-1.6
 */

import type { IncomingMessage, ServerResponse } from "node:http";
import { BufferWriter } from "../../buffer/writer.js";
import {
  getSession,
  killSession,
  listSessions,
  setDescription,
  spawnSession,
} from "../../tmux/manager.js";
import { captureThumbnail } from "../../tmux/snapshot.js";
import { readBody, sendJson } from "../util.js";

export async function handleSessions(
  req: IncomingMessage,
  res: ServerResponse,
  sessionId?: string,
  sub?: string,
): Promise<void> {
  const method = req.method?.toUpperCase();

  // GET /sessions/:id/thumbnail
  if (sessionId && sub === "thumbnail" && method === "GET") {
    const session = await getSession(sessionId).catch(() => null);
    if (!session) {
      sendJson(res, 404, { error: "session_not_found" });
      return;
    }
    const text = await captureThumbnail(sessionId).catch(() => "");
    res.writeHead(200, { "Content-Type": "text/plain; charset=utf-8" });
    res.end(text);
    return;
  }

  // /sessions/:id — PATCH / DELETE
  if (sessionId && !sub) {
    if (method === "PATCH") {
      await handlePatch(req, res, sessionId);
      return;
    }
    if (method === "DELETE") {
      await handleDelete(req, res, sessionId);
      return;
    }
    sendJson(res, 405, { error: "method_not_allowed" });
    return;
  }

  // /sessions — GET / POST
  if (!sessionId) {
    if (method === "GET") {
      await handleList(res);
      return;
    }
    if (method === "POST") {
      await handleCreate(req, res);
      return;
    }
    sendJson(res, 405, { error: "method_not_allowed" });
    return;
  }

  sendJson(res, 404, { error: "not_found" });
}

async function handleList(res: ServerResponse): Promise<void> {
  try {
    const sessions = await listSessions();
    const payload = sessions.map((s) => ({
      id: s.id,
      name: s.name,
      description: s.description,
      state: "idle", // T-1.4 events will feed real state in Phase 2
      lastOutputAt: s.lastActivityAt,
    }));
    sendJson(res, 200, payload);
  } catch (err) {
    sendJson(res, 500, { error: "internal_error", message: String(err) });
  }
}

async function handleCreate(
  req: IncomingMessage,
  res: ServerResponse,
): Promise<void> {
  let body: Record<string, unknown> = {};
  try {
    const raw = await readBody(req);
    if (raw.trim()) body = JSON.parse(raw) as Record<string, unknown>;
  } catch {
    sendJson(res, 400, { error: "bad_request", message: "Invalid JSON" });
    return;
  }

  const name =
    typeof body.name === "string" && body.name.trim()
      ? body.name.trim()
      : `session-${Date.now()}`;

  try {
    const id = await spawnSession({ name });
    // Include state + lastOutputAt to match the GET /sessions response shape
    // so iOS clients can decode the response with the same type.
    sendJson(res, 201, { id, name, state: "idle", lastOutputAt: "" });
  } catch (err) {
    sendJson(res, 500, { error: "internal_error", message: String(err) });
  }
}

async function handlePatch(
  req: IncomingMessage,
  res: ServerResponse,
  sessionId: string,
): Promise<void> {
  const session = await getSession(sessionId).catch(() => null);
  if (!session) {
    sendJson(res, 404, { error: "session_not_found" });
    return;
  }

  let body: Record<string, unknown> = {};
  try {
    const raw = await readBody(req);
    if (raw.trim()) body = JSON.parse(raw) as Record<string, unknown>;
  } catch {
    sendJson(res, 400, { error: "bad_request", message: "Invalid JSON" });
    return;
  }

  if (typeof body.description === "string") {
    await setDescription(sessionId, body.description);
  }

  sendJson(res, 200, { id: sessionId, description: body.description });
}

async function handleDelete(
  _req: IncomingMessage,
  res: ServerResponse,
  sessionId: string,
): Promise<void> {
  const session = await getSession(sessionId).catch(() => null);
  if (!session) {
    sendJson(res, 404, { error: "session_not_found" });
    return;
  }

  try {
    await killSession(sessionId);
    // Optionally clear buffer
    const writer = new BufferWriter(sessionId);
    await writer.delete().catch(() => {}); // best-effort
    res.writeHead(204).end();
  } catch (err) {
    sendJson(res, 500, { error: "internal_error", message: String(err) });
  }
}