// In-browser unit tests for the shell primitives. No server, no JS toolchain:
// globals (fetch, EventSource) are stubbed and the modules are exercised directly.
// Driven by tests/e2e/test_frontend_shell.py, which loads harness.html and reads
// window.__RESULTS__. Covers API errors + cancellation, store transitions,
// routing, and the SSE→polling event fallback (US02-05 acceptance).
import { createStore } from "../store.js";
import { parseHash, navigate } from "../router.js";
import { api, cancellable } from "../api.js";
import { subscribeJob } from "../events.js";

const cases = [];
function ok(name, cond) {
  cases.push({ name, ok: !!cond });
}
async function throws(name, fn, predicate) {
  try {
    await fn();
    cases.push({ name, ok: false });
  } catch (error) {
    cases.push({ name, ok: !!predicate(error) });
  }
}

const realFetch = window.fetch;
const realES = window.EventSource;
function jsonResponse(status, body) {
  return { ok: status < 400, status, statusText: "", json: async () => body };
}
const tick = (ms = 0) => new Promise((r) => setTimeout(r, ms));

async function run() {
  // ── store ────────────────────────────────────────────────────────────────
  {
    const store = createStore({ n: 0 });
    const seen = [];
    const off = store.subscribe((s) => seen.push(s.n));
    store.set({ n: 1 });
    store.set((s) => ({ n: s.n + 1 }));
    ok("store applies object and updater patches", store.get().n === 2);
    ok("store notifies each change", seen.length === 2 && seen[1] === 2);
    off();
    store.set({ n: 99 });
    ok("store unsubscribe stops notifications", seen.length === 2);
  }

  // ── router ───────────────────────────────────────────────────────────────
  {
    navigate("/inventory", { q: "beach", offset: 0, empty: "" });
    const { path, params } = parseHash();
    ok("router restores path", path === "/inventory");
    ok("router restores non-empty filters", params.q === "beach" && params.offset === "0");
    ok("router drops empty filters", !("empty" in params));
    location.hash = "";
    ok("router defaults to /inventory", parseHash().path === "/inventory");
  }

  // ── api errors + cancellation ────────────────────────────────────────────
  {
    window.fetch = async () =>
      jsonResponse(404, { error: { code: "not_found", message: "unknown job x" } });
    await throws(
      "api surfaces the error envelope",
      () => api.getJob("x"),
      (e) => e.status === 404 && e.code === "not_found" && e.message === "unknown job x"
    );

    window.fetch = async () => {
      const err = new Error("aborted");
      err.name = "AbortError";
      throw err;
    };
    const { signal, cancel } = cancellable();
    cancel();
    await throws(
      "api tags aborted requests as cancelled",
      () => api.getJob("x", { signal }),
      (e) => e.code === "cancelled"
    );
    window.fetch = realFetch;
  }

  // ── event fallback: polling when EventSource is unavailable ───────────────
  {
    window.EventSource = undefined;
    const pages = [
      jsonResponse(200, { state: "running", events: [{ seq: 1, type: "queued", message: null }] }),
      jsonResponse(200, {
        state: "succeeded",
        events: [{ seq: 2, type: "state:succeeded", message: null }],
      }),
    ];
    let call = 0;
    window.fetch = async () => pages[Math.min(call++, pages.length - 1)];
    const got = [];
    await new Promise((resolve) => {
      subscribeJob("job1", {
        pollMs: 1,
        onEvent: (e) => got.push(e.seq),
        onDone: resolve,
      });
    });
    ok("polling delivers events in order", got.join(",") === "1,2");
    ok("polling stops on terminal state", call >= 2);
    window.fetch = realFetch;
  }

  // ── event stream: SSE path, then done ─────────────────────────────────────
  {
    class FakeES {
      constructor() {
        this.listeners = {};
        setTimeout(() => {
          this.onmessage?.({ lastEventId: "5", data: JSON.stringify({ type: "state:running", message: "go" }) });
          this.listeners.done?.();
        }, 0);
      }
      addEventListener(type, fn) {
        this.listeners[type] = fn;
      }
      close() {
        this.closed = true;
      }
    }
    window.EventSource = FakeES;
    let polled = false;
    window.fetch = async () => {
      polled = true;
      return jsonResponse(200, { state: "succeeded", events: [] });
    };
    const got = [];
    await new Promise((resolve) => {
      subscribeJob("job2", { onEvent: (e) => got.push(e), onDone: resolve });
    });
    ok("SSE delivers event with seq from lastEventId", got.length === 1 && got[0].seq === 5);
    ok("SSE carries type from payload", got[0].type === "state:running");
    ok("SSE path does not poll", polled === false);
    window.fetch = realFetch;
    window.EventSource = realES;
  }

  await tick();
  const failed = cases.filter((c) => !c.ok);
  window.__RESULTS__ = { passed: cases.length - failed.length, failed: failed.length, cases };
  const pre = document.createElement("pre");
  pre.id = "results";
  pre.textContent = cases.map((c) => `${c.ok ? "PASS" : "FAIL"} ${c.name}`).join("\n");
  document.body.appendChild(pre);
}

run();