/**
 * @file GET /api/workflows tool-to-tool transitions (`stats.topFlow`,
 * `toolFlow.transitions`): each tool event pairs with the NEXT tool event of the
 * same session, and the query stays linear in the session's event count — the
 * old correlated `MIN(id)` subquery went quadratic once `idx_events_session`
 * was dropped and froze the whole server on a large session.
 * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
 */

const { describe, it, before, after } = require("node:test");
const assert = require("node:assert/strict");
const fs = require("fs");
const os = require("os");
const path = require("path");

const TEST_DB = path.join(os.tmpdir(), `dashboard-toolflow-test-${Date.now()}-${process.pid}.db`);
process.env.DASHBOARD_DB_PATH = TEST_DB;

const { createApp, startServer } = require("../index");
const { db } = require("../db");

let server;
let BASE;

function addSession(id, tools) {
  db.prepare("INSERT INTO sessions (id, status) VALUES (?, 'completed')").run(id);
  const ins = db.prepare("INSERT INTO events (session_id, event_type, tool_name) VALUES (?, ?, ?)");
  db.transaction(() => {
    for (const t of tools) ins.run(id, t ? "PreToolUse" : "Stop", t);
  })();
}

before(async () => {
  // A: Read → (Stop, no tool) → Edit → Read ; B: Read → Edit
  addSession("flow-a", ["Read", null, "Edit", "Read"]);
  addSession("flow-b", ["Read", "Edit"]);
  server = await startServer(createApp(), 0);
  BASE = `http://127.0.0.1:${server.address().port}`;
});

after(() => {
  server?.close();
  try {
    db.close();
  } catch {}
  for (const s of ["", "-wal", "-shm"]) fs.rmSync(TEST_DB + s, { force: true });
});

describe("GET /api/workflows tool transitions", () => {
  it("pairs each tool event with the next tool event of its own session", async () => {
    const body = await (await fetch(`${BASE}/api/workflows`)).json();
    const flow = Object.fromEntries(
      body.toolFlow.transitions.map((t) => [`${t.source}>${t.target}`, t.value])
    );
    // Read>Edit twice (A skips its Stop, B), Edit>Read once; nothing crosses sessions.
    assert.deepEqual(flow, { "Read>Edit": 2, "Edit>Read": 1 });
    assert.deepEqual(body.stats.topFlow, { source: "Read", target: "Edit", count: 2 });
  });

  it("?sections= computes only the named parts, and refuses names it does not know", async () => {
    const body = await (await fetch(`${BASE}/api/workflows?sections=stats,toolFlow,bogus`)).json();
    assert.deepEqual(Object.keys(body), ["stats", "toolFlow"]);
    assert.equal(body.stats.topFlow.source, "Read");
    const bad = await fetch(`${BASE}/api/workflows?sections=bogus`);
    assert.equal(bad.status, 400);
    assert.equal((await bad.json()).error.code, "INVALID_SECTIONS");
  });

  it("stays fast on one large session", async () => {
    const tools = ["Read", "Edit", "Bash", "Grep"];
    addSession(
      "flow-big",
      Array.from({ length: 20000 }, (_, i) => tools[i % 4])
    );
    const t0 = Date.now();
    const res = await fetch(`${BASE}/api/workflows`);
    assert.equal(res.status, 200);
    await res.json();
    assert.ok(Date.now() - t0 < 3000, `took ${Date.now() - t0} ms`);
  });
});