/**
 * End-to-end test of `WebRtcTransferTransport` against the manager + memory
 * factory. Exercises the same `ITransferTransport` API the engine calls
 * (`probe`, `sendChunk`, `fetchResumeState`).
 */
import { afterEach, describe, expect, it } from 'bun:test';
import { MemoryRtcFactory } from '../src/memory-rtc.js';
import { MemoryShadeBridge, WebRtcSignalingChannel } from '../src/signaling.js';
import { WebRtcConnectionManager } from '../src/manager.js';
import {
  DEFAULT_MAX_DATACHANNEL_MESSAGE,
  WebRtcTransferTransport,
} from '../src/transport.js';
import { streamIdBytesToString } from '../src/wire.js';

afterEach(() => {
  MemoryRtcFactory.reset();
});

function paired(opts: {
  bobReceiver: import('../src/connection.js').WebRtcReceiverHooks;
}): {
  alice: WebRtcConnectionManager;
  bob: WebRtcConnectionManager;
  aliceTransport: WebRtcTransferTransport;
} {
  const factory = new MemoryRtcFactory();
  const { a, b } = MemoryShadeBridge.linked('alice', 'bob');
  const aliceSig = new WebRtcSignalingChannel(a);
  const bobSig = new WebRtcSignalingChannel(b);
  const alice = new WebRtcConnectionManager({ factory, signaling: aliceSig });
  const bob = new WebRtcConnectionManager({
    factory,
    signaling: bobSig,
    receiver: opts.bobReceiver,
  });
  const aliceTransport = new WebRtcTransferTransport({ manager: alice });
  return { alice, bob, aliceTransport };
}

function makeStreamId(): string {
  const b = new Uint8Array(16);
  globalThis.crypto.getRandomValues(b);
  return streamIdBytesToString(b);
}

describe('WebRtcTransferTransport', () => {
  it('probe opens the peer connection', async () => {
    const { alice, bob, aliceTransport } = paired({
      bobReceiver: {
        async onChunk() {
          return { lastSeq: 0 };
        },
        async onResumeQuery() {
          return null;
        },
      },
    });
    await aliceTransport.probe('bob');
    expect(alice.isConnected('bob')).toBe(true);
    alice.destroy();
    bob.destroy();
  });

  it('sendChunk routes envelope to receiver and returns the ack', async () => {
    let received: { laneId: number; seq: bigint; bytes: number } | null = null;
    const { alice, bob, aliceTransport } = paired({
      bobReceiver: {
        async onChunk(_from, _streamId, laneId, seq, envelope) {
          received = { laneId, seq, bytes: envelope.length };
          return { lastSeq: Number(seq), bytesReceived: envelope.length };
        },
        async onResumeQuery() {
          return null;
        },
      },
    });

    const streamId = makeStreamId();
    const envelope = new Uint8Array(2048);
    envelope.fill(0x42);
    const ack = await aliceTransport.sendChunk('bob', streamId, 1, 5n, envelope);
    expect(ack.lastSeq).toBe(5);
    expect(ack.bytesReceived).toBe(2048);
    expect(received).not.toBeNull();
    expect(received!.laneId).toBe(1);
    expect(received!.seq).toBe(5n);
    expect(received!.bytes).toBe(2048);

    alice.destroy();
    bob.destroy();
  });

  it('rejects oversized envelopes that would exceed the data channel cap', async () => {
    const { alice, bob, aliceTransport } = paired({
      bobReceiver: {
        async onChunk() {
          return { lastSeq: 0 };
        },
        async onResumeQuery() {
          return null;
        },
      },
    });
    const streamId = makeStreamId();
    const huge = new Uint8Array(DEFAULT_MAX_DATACHANNEL_MESSAGE + 1);
    await expect(aliceTransport.sendChunk('bob', streamId, 0, 0n, huge)).rejects.toThrow(
      /frame too large/,
    );
    alice.destroy();
    bob.destroy();
  });

  it('fetchResumeState returns parsed state when the receiver knows the stream', async () => {
    const { alice, bob, aliceTransport } = paired({
      bobReceiver: {
        async onChunk() {
          return { lastSeq: 0 };
        },
        async onResumeQuery(_from, streamId) {
          return {
            streamId,
            lanes: [
              { laneId: 0, lastSeqAcked: 11 },
              { laneId: 1, lastSeqAcked: 4 },
            ],
          };
        },
      },
    });
    const sid = makeStreamId();
    const state = await aliceTransport.fetchResumeState('bob', sid);
    expect(state).not.toBeNull();
    expect(state!.streamId).toBe(sid);
    expect(state!.lanes[0]!.lastSeqAcked).toBe(11);
    expect(state!.lanes[1]!.lastSeqAcked).toBe(4);
    alice.destroy();
    bob.destroy();
  });

  it('fetchResumeState returns null when the peer reports not found', async () => {
    const { alice, bob, aliceTransport } = paired({
      bobReceiver: {
        async onChunk() {
          return { lastSeq: 0 };
        },
        async onResumeQuery() {
          return null;
        },
      },
    });
    const state = await aliceTransport.fetchResumeState('bob', makeStreamId());
    expect(state).toBeNull();
    alice.destroy();
    bob.destroy();
  });

  it('multiple in-flight requests interleave correctly via requestId correlation', async () => {
    let inflight = 0;
    let maxInflight = 0;
    const { alice, bob, aliceTransport } = paired({
      bobReceiver: {
        async onChunk(_from, _streamId, _laneId, seq) {
          inflight++;
          if (inflight > maxInflight) maxInflight = inflight;
          // Stagger response so request ordering doesn't trivially match
          // response ordering.
          await new Promise<void>((resolve) =>
            setTimeout(resolve, Number(seq % 5n) * 5),
          );
          inflight--;
          return { lastSeq: Number(seq), bytesReceived: 0 };
        },
        async onResumeQuery() {
          return null;
        },
      },
    });
    const streamId = makeStreamId();
    const acks = await Promise.all(
      Array.from({ length: 12 }, (_, i) =>
        aliceTransport.sendChunk('bob', streamId, i % 4, BigInt(i), new Uint8Array(8)),
      ),
    );
    // Each ack matches its request seq (round-trip via requestId).
    for (let i = 0; i < acks.length; i++) {
      expect(acks[i]!.lastSeq).toBe(i);
    }
    expect(maxInflight).toBeGreaterThan(1);
    alice.destroy();
    bob.destroy();
  });
});