import { describe, test, expect } from 'bun:test';
import { SubtleCryptoProvider } from '@shade/crypto-web';
import { sha256Once } from '@shade/streams';
import {
  TransferEngine,
  MemoryControlChannel,
  MemoryTransferTransport,
} from '../src/index.js';
import type { IncomingTransfer, TransferResult } from '../src/index.js';

const crypto = new SubtleCryptoProvider();

function hex(bytes: Uint8Array): string {
  return Array.from(bytes, (b) => b.toString(16).padStart(2, '0')).join('');
}

interface PairedEngines {
  sender: TransferEngine;
  receiver: TransferEngine;
}

function makePair(): PairedEngines {
  const { a: ctrlA, b: ctrlB } = MemoryControlChannel.linked('alice', 'bob');
  const { a: txA, b: txB } = MemoryTransferTransport.linked('alice', 'bob');

  const senderEngine = new TransferEngine({
    crypto,
    controlChannel: ctrlA,
    transport: txA,
    myAddress: 'alice',
  });
  const receiverEngine = new TransferEngine({
    crypto,
    controlChannel: ctrlB,
    transport: txB,
    myAddress: 'bob',
  });

  // Wire receiver-side transport to route chunks into receiver-engine.
  txB.setChunkHandler(async (from, streamId, laneId, seq, bytes) =>
    receiverEngine.receiveChunk(from, streamId, laneId, seq, bytes),
  );
  txB.setResumeProvider(async (from, streamId) =>
    receiverEngine.getResumeState(from, streamId),
  );

  return { sender: senderEngine, receiver: receiverEngine };
}

async function uploadAndAwait(
  pair: PairedEngines,
  input: Uint8Array,
  opts?: { lanes?: number; chunkSize?: number; partition?: 'auto' | 'range' | 'round-robin' },
): Promise<{ result: TransferResult; received: Uint8Array }> {
  // The handler accepts and PUBLISHES the receive-handle out-of-band so
  // it can return promptly (control channel awaits handler completion).
  let resolveReceiveHandle!: (h: import('../src/index.js').TransferHandle) => void;
  const receiveHandlePromise = new Promise<import('../src/index.js').TransferHandle>(
    (r) => { resolveReceiveHandle = r; },
  );
  const unsubscribe = pair.receiver.onIncomingTransfer(async (incoming: IncomingTransfer) => {
    const handle = await incoming.accept({ output: { kind: 'buffer' } });
    resolveReceiveHandle(handle);
  });

  const handle = await pair.sender.upload({
    to: 'bob',
    input,
    ...(opts?.lanes !== undefined ? { lanes: opts.lanes } : {}),
    ...(opts?.chunkSize !== undefined ? { chunkSize: opts.chunkSize } : {}),
    ...(opts?.partition !== undefined ? { partition: opts.partition } : {}),
    metadata: { name: 'test.bin', contentType: 'application/octet-stream' },
  });
  const recvHandle = await receiveHandlePromise;
  const [senderResult, receiverResult] = await Promise.all([handle.done(), recvHandle.done()]);
  unsubscribe();
  const bytes =
    (receiverResult as TransferResult & { bytes?: Uint8Array }).bytes ?? new Uint8Array(0);
  return { result: senderResult, received: bytes };
}

describe('TransferEngine (memory loopback)', () => {
  test('1 KiB upload — 1 lane (auto-degrade for small file)', async () => {
    const pair = makePair();
    const input = crypto.randomBytes(1024);
    const { result, received } = await uploadAndAwait(pair, input, { lanes: 4, chunkSize: 256 });
    expect(received).toEqual(input);
    expect(result.sha256).toBe(hex(sha256Once(input)));
  });

  test('256 KiB upload — 4 lanes range partition', async () => {
    const pair = makePair();
    const input = crypto.randomBytes(256 * 1024);
    const { result, received } = await uploadAndAwait(pair, input, {
      lanes: 4,
      chunkSize: 16 * 1024,
      partition: 'range',
    });
    expect(received).toEqual(input);
    expect(result.sha256).toBe(hex(sha256Once(input)));
  });

  test('1 MiB upload — 4 lanes round-robin partition', async () => {
    const pair = makePair();
    const input = crypto.randomBytes(1024 * 1024);
    const { result, received } = await uploadAndAwait(pair, input, {
      lanes: 4,
      chunkSize: 64 * 1024,
      partition: 'round-robin',
    });
    expect(received).toEqual(input);
    expect(result.sha256).toBe(hex(sha256Once(input)));
  });

  test('integrity: same sha256 across lane counts', async () => {
    const input = crypto.randomBytes(512 * 1024);
    const expected = hex(sha256Once(input));
    for (const lanes of [1, 2, 4, 8]) {
      const pair = makePair();
      const { result, received } = await uploadAndAwait(pair, input, { lanes, chunkSize: 8 * 1024 });
      expect(received).toEqual(input);
      expect(result.sha256).toBe(expected);
    }
  });

  test('upload with ReadableStream input → round-robin partition', async () => {
    const pair = makePair();
    const input = crypto.randomBytes(300 * 1024);
    const stream = new ReadableStream<Uint8Array>({
      start(controller) {
        for (let off = 0; off < input.length; off += 64 * 1024) {
          controller.enqueue(input.subarray(off, Math.min(off + 64 * 1024, input.length)));
        }
        controller.close();
      },
    });
    let resolveRecv!: (h: import('../src/index.js').TransferHandle) => void;
    const recvHandlePromise = new Promise<import('../src/index.js').TransferHandle>((r) => {
      resolveRecv = r;
    });
    const unsubscribe = pair.receiver.onIncomingTransfer(async (incoming) => {
      const h = await incoming.accept({ output: { kind: 'buffer' } });
      resolveRecv(h);
    });
    const handle = await pair.sender.upload({
      to: 'bob',
      input: stream,
      lanes: 4,
      chunkSize: 32 * 1024,
    });
    const recvHandle = await recvHandlePromise;
    const [, recvResult] = await Promise.all([handle.done(), recvHandle.done()]);
    unsubscribe();
    const bytes = (recvResult as TransferResult & { bytes?: Uint8Array }).bytes ?? new Uint8Array();
    expect(bytes).toEqual(input);
  });

  test('progress events fire and end with complete', async () => {
    const pair = makePair();
    const input = crypto.randomBytes(64 * 1024);
    const senderProgressSamples: number[] = [];
    const receiverEvents: string[] = [];

    let resolveRecv!: (h: import('../src/index.js').TransferHandle) => void;
    const recvHandlePromise = new Promise<import('../src/index.js').TransferHandle>((r) => {
      resolveRecv = r;
    });
    const unsub = pair.receiver.onIncomingTransfer(async (incoming) => {
      const h = await incoming.accept({
        output: { kind: 'buffer' },
        onEvent: (e) => {
          receiverEvents.push(e.type);
        },
      });
      resolveRecv(h);
    });

    const handle = await pair.sender.upload({
      to: 'bob',
      input,
      lanes: 2,
      chunkSize: 8 * 1024,
      onProgress: (p) => senderProgressSamples.push(p.bytesSent),
    });
    const recvHandle = await recvHandlePromise;
    await Promise.all([handle.done(), recvHandle.done()]);
    unsub();
    expect(senderProgressSamples.length).toBeGreaterThan(0);
    expect(senderProgressSamples[senderProgressSamples.length - 1]).toBe(64 * 1024);
    expect(receiverEvents).toContain('start');
    expect(receiverEvents).toContain('complete');
  });
});