import { strict as assert } from "node:assert";
import { test } from "node:test";
import {
  loadWithCurrentTrainFallback,
  mergeCurrentTrainFallback,
  RequestCoordinator,
} from "../lib/requestCoordinator";
import { carryForwardOfficialPositionMetadata } from "../lib/currentTrainMetadata";

const deferred = <T>() => {
  let resolve!: (value: T) => void;
  let reject!: (error: unknown) => void;
  const promise = new Promise<T>((promiseResolve, promiseReject) => {
    resolve = promiseResolve;
    reject = promiseReject;
  });
  return { promise, resolve, reject };
};

test("same-source polling skips a second in-flight request", async () => {
  const coordinator = new RequestCoordinator();
  const firstResult = deferred<string>();
  let calls = 0;

  const first = coordinator.start("primary", () => {
    calls += 1;
    return firstResult.promise;
  });
  if (!first) throw new Error("first request was not started");

  const duplicate = coordinator.start("primary", () => {
    calls += 1;
    return "duplicate";
  });
  assert.equal(duplicate, null);
  assert.equal(calls, 0, "operations start on the next microtask");

  firstResult.resolve("first");
  assert.equal(await first.promise, "first");
  await Promise.resolve();
  assert.equal(calls, 1);

  const next = coordinator.start("primary", () => {
    calls += 1;
    return "next";
  });
  if (!next) throw new Error("next polling request was not started");
  assert.equal(await next.promise, "next");
  assert.equal(calls, 2);
});

test("source switch aborts the old request and only the newest response commits", async () => {
  const coordinator = new RequestCoordinator();
  const oldResult = deferred<string>();
  const commits: string[] = [];

  const oldRequest = coordinator.start("primary", () => oldResult.promise);
  if (!oldRequest) throw new Error("old request was not started");

  const newRequest = coordinator.start("mock", () => "new");
  if (!newRequest) throw new Error("new request was not started");
  assert.equal(oldRequest.signal.aborted, true);

  const newResult = await newRequest.promise;
  if (coordinator.isCurrent(newRequest.token)) commits.push(newResult);

  oldResult.resolve("old");
  const oldValue = await oldRequest.promise;
  if (coordinator.isCurrent(oldRequest.token)) commits.push(oldValue);

  assert.deepEqual(commits, ["new"]);
  assert.equal(coordinator.isCurrent(oldRequest.token), false);
});

test("dispose aborts an in-flight request and rejects late commits", async () => {
  const coordinator = new RequestCoordinator();
  const result = deferred<string>();
  const request = coordinator.start("primary", () => result.promise);
  if (!request) throw new Error("request was not started");

  coordinator.dispose();
  assert.equal(request.signal.aborted, true);
  result.resolve("late");
  await request.promise;
  assert.equal(coordinator.isCurrent(request.token), false);
});

test("cancel aborts polling without disposing the coordinator", async () => {
  const coordinator = new RequestCoordinator();
  const result = deferred<string>();
  const request = coordinator.start("primary", () => result.promise);
  if (!request) throw new Error("request was not started");

  coordinator.cancel();
  assert.equal(request.signal.aborted, true);
  result.resolve("late");
  await request.promise;
  assert.equal(coordinator.isCurrent(request.token), false);

  const next = coordinator.start("primary", () => "next");
  if (!next) throw new Error("next request was not started");
  assert.equal(await next.promise, "next");
});

test("primary success does not call the fallback", async () => {
  let fallbackCalls = 0;
  const result = await loadWithCurrentTrainFallback({
    signal: new AbortController().signal,
    primary: async () => "primary",
    fallback: async () => {
      fallbackCalls += 1;
      return "fallback";
    },
  });
  assert.deepEqual(result, { data: "primary", source: "primary" });
  assert.equal(fallbackCalls, 0);
});

test("primary failure keeps the GAS fallback path", async () => {
  let fallbackCalls = 0;
  const result = await loadWithCurrentTrainFallback({
    signal: new AbortController().signal,
    primary: async () => {
      throw new Error("primary unavailable");
    },
    fallback: async () => {
      fallbackCalls += 1;
      return "fallback";
    },
  });
  assert.deepEqual(result, { data: "fallback", source: "gas_fallback" });
  assert.equal(fallbackCalls, 1);
});

test("fallback failure remains an error", async () => {
  await assert.rejects(
    loadWithCurrentTrainFallback({
      signal: new AbortController().signal,
      primary: async () => {
        throw new Error("primary unavailable");
      },
      fallback: async () => {
        throw new Error("fallback unavailable");
      },
    }),
    /fallback unavailable/,
  );
});

test("aborted primary does not start the fallback", async () => {
  const controller = new AbortController();
  controller.abort();
  let fallbackCalls = 0;

  await assert.rejects(
    loadWithCurrentTrainFallback({
      signal: controller.signal,
      primary: async () => {
        throw new Error("aborted");
      },
      fallback: async () => {
        fallbackCalls += 1;
        return "fallback";
      },
    }),
    /aborted/,
  );
  assert.equal(fallbackCalls, 0);
});

test("partial fallback preserves fields from the last complete response", () => {
  const previous = [
    { num: "D01", Pos: "高松", Direction: 1, Line: "dosan" },
    { num: "D02", Pos: "坂出", Direction: 0, Line: "yosan" },
  ];
  const fallback = [{ num: "D01", Pos: "多度津" }, { num: "D03", Pos: "琴平" }];

  assert.deepEqual(mergeCurrentTrainFallback(fallback, previous), [
    { num: "D01", Pos: "多度津", Direction: 1, Line: "dosan" },
    { num: "D03", Pos: "琴平" },
  ]);
});

test("recording and mock requests remain separate sources", async () => {
  const coordinator = new RequestCoordinator();
  const recording = coordinator.start("recording", () => "recorded");
  if (!recording) throw new Error("recording request was not started");
  assert.equal(await recording.promise, "recorded");

  const mock = coordinator.start("mock", () => "mocked");
  if (!mock) throw new Error("mock request was not started");
  assert.equal(await mock.promise, "mocked");
});

test("ambiguous fallback keeps every previous line-specific row", () => {
  const previous = [
    { num: "363D", Pos: "高松", PosNum: 279, Line: "yosan" },
    { num: "363D", Pos: "高松", PosNum: 279, Line: "koutoku" },
  ];
  const fallback = [
    { num: "363D", Pos: "高松" },
    { num: "363D", Pos: "高松" },
  ];

  assert.deepEqual(mergeCurrentTrainFallback(fallback, previous), previous);
});

test("line-aware fallback merges only the matching previous row", () => {
  const previous = [
    { num: "363D", Pos: "高松", PosNum: 279, Line: "yosan", delay: 0 },
    { num: "363D", Pos: "高松", PosNum: 279, Line: "koutoku", delay: 0 },
  ];
  const fallback = [{ num: "363D", Pos: "高松", Line: "koutoku", delay: 3 }];

  assert.deepEqual(mergeCurrentTrainFallback(fallback, previous), [
    { num: "363D", Pos: "高松", PosNum: 279, Line: "koutoku", delay: 3 },
  ]);
});

test("refresh keeps official position metadata for the unchanged position tuple", () => {
  const officialPosition = {
    positionId: "position-yosan-takamatsu",
    pos: "高松",
    line: "yosan",
    posNum: "279",
    positionType: "station",
    platform: "4",
    track: "4",
    note: null,
    enrichmentStatus: "reviewed",
    firstSeenAt: null,
    lastSeenAt: null,
    revision: 1,
  } as const;
  const previous = [
    {
      num: "1007M",
      Pos: "高松",
      PosNum: "279",
      Line: "yosan",
      officialPosition,
    },
    {
      num: "1007M",
      Pos: "高松",
      PosNum: "279",
      Line: "koutoku",
    },
  ];
  const next = [
    { num: "1007M", Pos: "高松", PosNum: "279", Line: "yosan" },
    { num: "1007M", Pos: "高松", PosNum: "279", Line: "koutoku" },
    { num: "1007M", Pos: "坂出", PosNum: "280", Line: "yosan" },
  ];

  const result = carryForwardOfficialPositionMetadata(next, previous);

  assert.equal(result[0]?.officialPosition, officialPosition);
  assert.equal(result[1]?.officialPosition, undefined);
  assert.equal(result[2]?.officialPosition, undefined);
});