// @vitest-environment node

import { describe, expect, it } from 'vitest';
import type { PrepareConversationInput } from '../../electron/coding-runtime/contracts';
import {
  PiProcessBudget,
  PiWorkerPool,
  type PiConversationWorker,
  type PiWorkerOpenResult,
} from '../../electron/coding-runtime/pi/worker-pool';
import type { PiProcessError } from '../../electron/coding-runtime/pi/process-errors';
import { PiProcessError as PiProcessFailure } from '../../electron/coding-runtime/pi/process-errors';
import type { PiRpcCommand, PiRpcEvent } from '../../electron/coding-runtime/pi/rpc-client';
import type { PiRuntimeTelemetryEvent } from '../../electron/coding-runtime/pi/telemetry';

const MODEL = {
  model: {
    accountId: 'account-a',
    modelId: 'model-a',
    thinkingLevel: 'medium' as const,
  },
  modelResolution: 'resolved' as const,
};

function conversation(conversationId: string): PrepareConversationInput {
  return {
    conversationId,
    projectId: 'project-a',
    agentId: 'agent-a',
    title: conversationId,
    model: MODEL,
  };
}

function deferred(): { promise: Promise<void>; resolve(): void } {
  let resolve!: () => void;
  const promise = new Promise<void>((done) => { resolve = done; });
  return { promise, resolve };
}

class FakeWorker implements PiConversationWorker {
  readonly generation = 1;
  readonly requests: PiRpcCommand[] = [];
  stopped = false;
  private readonly eventListeners = new Set<(event: PiRpcEvent) => void>();
  private readonly invalidationListeners = new Set<(error: PiProcessError) => void>();

  constructor(readonly id: string) {}

  async request() {
    this.requests.push(arguments[0] as PiRpcCommand);
    return { type: 'response' as const, id: 'fake', success: true };
  }

  async send(command: PiRpcCommand): Promise<void> {
    this.requests.push(command);
  }

  subscribe(listener: (event: PiRpcEvent) => void): () => void {
    this.eventListeners.add(listener);
    return () => this.eventListeners.delete(listener);
  }

  subscribeInvalidation(listener: (error: PiProcessError) => void): () => void {
    this.invalidationListeners.add(listener);
    return () => this.invalidationListeners.delete(listener);
  }

  emit(event: PiRpcEvent): void {
    for (const listener of this.eventListeners) listener(event);
  }

  invalidate(error = new PiProcessFailure('PI_RPC_EXITED', 'fake worker crashed')): void {
    for (const listener of this.invalidationListeners) listener(error);
  }

  async stop() {
    this.stopped = true;
    return { mode: 'stdin-close' as const, code: 0, signal: null };
  }
}

describe('Pi worker pool', () => {
  it('single-flights prepare per Conversation and never shares its worker with another Conversation', async () => {
    const gate = deferred();
    const opened: string[] = [];
    const pool = new PiWorkerPool({
      openWorker: async ({ conversation: input }): Promise<PiWorkerOpenResult> => {
        opened.push(input.conversationId);
        await gate.promise;
        return {
          worker: new FakeWorker(`worker-${input.conversationId}`),
          session: {
            piSessionId: `session-${input.conversationId}`,
            sessionKey: `key-${input.conversationId}`,
          },
        };
      },
      maxIdle: 6,
    });

    const first = pool.prepare(conversation('conversation-a'));
    const duplicate = pool.prepare(conversation('conversation-a'));
    const other = pool.prepare(conversation('conversation-b'));
    await expect.poll(() => opened).toEqual(['conversation-a', 'conversation-b']);
    gate.resolve();

    const [firstState, duplicateState, otherState] = await Promise.all([first, duplicate, other]);
    expect(firstState).toEqual(duplicateState);
    expect(firstState).toMatchObject({
      conversationId: 'conversation-a',
      workerId: 'worker-conversation-a',
      state: 'ready',
      generation: 1,
    });
    expect(otherState).toMatchObject({
      conversationId: 'conversation-b',
      workerId: 'worker-conversation-b',
      state: 'ready',
      generation: 1,
    });
  });

  it('starts only four top-level runs and advances the remaining queue fairly on agent_settled', async () => {
    const workers = new Map<string, FakeWorker>();
    const pool = new PiWorkerPool({
      maxIdle: 6,
      openWorker: async ({ conversation: input }) => {
        const worker = new FakeWorker(`worker-${input.conversationId}`);
        workers.set(input.conversationId, worker);
        return {
          worker,
          session: {
            piSessionId: `session-${input.conversationId}`,
            sessionKey: `key-${input.conversationId}`,
          },
        };
      },
    });
    const ids = ['a', 'b', 'c', 'd', 'e', 'f'].map((id) => `conversation-${id}`);
    await Promise.all(ids.map((id) => pool.prepare(conversation(id))));

    const runs = ids.map((conversationId, index) => pool.startTopLevel({
      conversationId,
      runId: `run-${index + 1}`,
      command: { type: 'prompt', message: conversationId },
    }));

    expect(runs.map((run) => run.queuePosition)).toEqual([undefined, undefined, undefined, undefined, 1, 2]);
    await expect.poll(() => ids.map((id) => workers.get(id)!.requests.length))
      .toEqual([1, 1, 1, 1, 0, 0]);
    workers.get('conversation-a')!.emit({ type: 'agent_end' });
    expect(workers.get('conversation-e')!.requests).toHaveLength(0);

    workers.get('conversation-a')!.emit({ type: 'agent_settled' });
    await expect.poll(() => workers.get('conversation-e')!.requests.length).toBe(1);
    expect(workers.get('conversation-f')!.requests).toHaveLength(0);
    workers.get('conversation-b')!.emit({ type: 'agent_settled' });
    await expect.poll(() => workers.get('conversation-f')!.requests.length).toBe(1);
  });

  it('evicts only the least-recent idle worker and reopens it on demand', async () => {
    const workers = new Map<string, FakeWorker[]>();
    const pool = new PiWorkerPool({
      maxIdle: 2,
      openWorker: async ({ conversation: input }) => {
        const worker = new FakeWorker(`worker-${input.conversationId}-${(workers.get(input.conversationId)?.length ?? 0) + 1}`);
        workers.set(input.conversationId, [...(workers.get(input.conversationId) ?? []), worker]);
        return {
          worker,
          session: {
            piSessionId: `session-${input.conversationId}`,
            sessionKey: `key-${input.conversationId}`,
          },
        };
      },
    });

    await pool.prepare(conversation('conversation-a'));
    await pool.prepare(conversation('conversation-b'));
    await pool.prepare(conversation('conversation-c'));
    await expect.poll(() => workers.get('conversation-a')![0]!.stopped).toBe(true);
    expect(pool.getState('conversation-a')).toBeNull();
    expect(pool.getState('conversation-b')?.state).toBe('ready');
    expect(pool.getState('conversation-c')?.state).toBe('ready');

    const reopened = await pool.prepare(conversation('conversation-a'));
    expect(reopened).toMatchObject({
      workerId: 'worker-conversation-a-2',
      generation: 2,
      state: 'ready',
    });
  });

  it('shares a fair total-process budget and starts the next worker only after a lease is released', async () => {
    const processBudget = new PiProcessBudget(2);
    const opened: string[] = [];
    const pool = new PiWorkerPool({
      maxIdle: 3,
      processBudget,
      openWorker: async ({ conversation: input }) => {
        opened.push(input.conversationId);
        return {
          worker: new FakeWorker(`worker-${input.conversationId}`),
          session: {
            piSessionId: `session-${input.conversationId}`,
            sessionKey: `key-${input.conversationId}`,
          },
        };
      },
    });

    await Promise.all([
      pool.prepare(conversation('conversation-a')),
      pool.prepare(conversation('conversation-b')),
    ]);
    const third = pool.prepare(conversation('conversation-c'));
    await expect.poll(() => processBudget.waitingCount).toBe(1);
    expect(opened).toEqual(['conversation-a', 'conversation-b']);

    await pool.dispose('conversation-a');
    await expect(third).resolves.toMatchObject({ conversationId: 'conversation-c', state: 'ready' });
    expect(opened).toEqual(['conversation-a', 'conversation-b', 'conversation-c']);
    expect(processBudget.activeCount).toBe(2);

    await pool.shutdown();
    expect(processBudget.activeCount).toBe(0);
  });

  it('releases the process lease even when stopping an idle worker fails', async () => {
    const processBudget = new PiProcessBudget(1);
    const pool = new PiWorkerPool({
      processBudget,
      maxIdle: 1,
      openWorker: async ({ conversation: input }) => {
        const worker = new FakeWorker(`worker-${input.conversationId}`);
        worker.stop = async () => {
          worker.stopped = true;
          throw new Error('stop failed');
        };
        return {
          worker,
          session: {
            piSessionId: `session-${input.conversationId}`,
            sessionKey: `key-${input.conversationId}`,
          },
        };
      },
    });
    await pool.prepare(conversation('conversation-stop-failure'));

    await expect(pool.dispose('conversation-stop-failure')).rejects.toThrow('stop failed');
    expect(processBudget.activeCount).toBe(0);
    expect(processBudget.waitingCount).toBe(0);
  });

  it('never evicts a running worker when the warm-idle LRU exceeds its cap', async () => {
    const workers = new Map<string, FakeWorker>();
    const pool = new PiWorkerPool({
      maxIdle: 1,
      openWorker: async ({ conversation: input }) => {
        const worker = new FakeWorker(`worker-${input.conversationId}`);
        workers.set(input.conversationId, worker);
        return {
          worker,
          session: {
            piSessionId: `session-${input.conversationId}`,
            sessionKey: `key-${input.conversationId}`,
          },
        };
      },
    });
    await pool.prepare(conversation('conversation-running'));
    const running = pool.startTopLevel({
      conversationId: 'conversation-running',
      runId: 'run-running',
      command: { type: 'prompt', message: 'keep alive' },
    });
    await running.accepted;
    await pool.prepare(conversation('conversation-old-idle'));
    await pool.prepare(conversation('conversation-new-idle'));

    expect(workers.get('conversation-running')!.stopped).toBe(false);
    expect(pool.getState('conversation-running')).toMatchObject({ state: 'running' });
    expect(workers.get('conversation-old-idle')!.stopped).toBe(true);
    expect(pool.getState('conversation-new-idle')).toMatchObject({ state: 'ready' });
  });

  it('cleans only the crashed generation and releases its permit for the next Conversation', async () => {
    const workers = new Map<string, FakeWorker>();
    const pool = new PiWorkerPool({
      maxRunning: 2,
      maxIdle: 3,
      openWorker: async ({ conversation: input }) => {
        const worker = new FakeWorker(`worker-${input.conversationId}`);
        workers.set(input.conversationId, worker);
        return {
          worker,
          session: {
            piSessionId: `session-${input.conversationId}`,
            sessionKey: `key-${input.conversationId}`,
          },
        };
      },
    });
    await Promise.all(['a', 'b', 'c'].map((id) => pool.prepare(conversation(`conversation-${id}`))));
    pool.startTopLevel({ conversationId: 'conversation-a', runId: 'run-a', command: { type: 'prompt', message: 'a' } });
    pool.startTopLevel({ conversationId: 'conversation-b', runId: 'run-b', command: { type: 'prompt', message: 'b' } });
    pool.startTopLevel({ conversationId: 'conversation-c', runId: 'run-c', command: { type: 'prompt', message: 'c' } });
    await expect.poll(() => workers.get('conversation-a')!.requests.length).toBe(1);

    const cancelled: string[] = [];
    for (const kind of ['command', 'interaction', 'child'] as const) {
      pool.trackGenerationResource({
        conversationId: 'conversation-a',
        kind,
        id: `${kind}-a`,
        cancel: () => { cancelled.push(kind); },
      });
    }
    pool.trackGenerationResource({
      conversationId: 'conversation-b',
      kind: 'child',
      id: 'child-b',
      cancel: () => { cancelled.push('other'); },
    });

    workers.get('conversation-a')!.invalidate();

    expect(cancelled.sort()).toEqual(['child', 'command', 'interaction']);
    expect(pool.getState('conversation-a')).toMatchObject({ state: 'crashed', generation: 1 });
    expect(pool.getState('conversation-b')).toMatchObject({ state: 'running', generation: 1 });
    await expect.poll(() => workers.get('conversation-c')!.requests.length).toBe(1);
    expect(cancelled).not.toContain('other');
  });

  it('rebuilds stale idle workers before prompt and lets running workers settle first', async () => {
    const workers = new Map<string, FakeWorker[]>();
    const revisions: Array<{ conversationId: string; provider: number; resources: number }> = [];
    const pool = new PiWorkerPool({
      maxIdle: 4,
      openWorker: async ({ conversation: input, revision }) => {
        const worker = new FakeWorker(`worker-${input.conversationId}-${(workers.get(input.conversationId)?.length ?? 0) + 1}`);
        workers.set(input.conversationId, [...(workers.get(input.conversationId) ?? []), worker]);
        revisions.push({ conversationId: input.conversationId, ...revision });
        return {
          worker,
          session: {
            piSessionId: `session-${input.conversationId}`,
            sessionKey: `key-${input.conversationId}`,
          },
        };
      },
    });
    await Promise.all([
      pool.prepare(conversation('conversation-running')),
      pool.prepare(conversation('conversation-idle')),
    ]);
    pool.startTopLevel({
      conversationId: 'conversation-running',
      runId: 'run-running',
      command: { type: 'prompt', message: 'running' },
    });
    await expect.poll(() => workers.get('conversation-running')![0]!.requests.length).toBe(1);

    pool.markProviderStale();
    pool.startTopLevel({
      conversationId: 'conversation-idle',
      runId: 'run-idle',
      command: { type: 'prompt', message: 'idle' },
    });

    await expect.poll(() => workers.get('conversation-idle')?.length).toBe(2);
    expect(workers.get('conversation-idle')![0]!.stopped).toBe(true);
    await expect.poll(() => workers.get('conversation-idle')![1]!.requests.length).toBe(1);
    expect(workers.get('conversation-running')).toHaveLength(1);
    expect(workers.get('conversation-running')![0]!.stopped).toBe(false);

    workers.get('conversation-running')![0]!.emit({ type: 'agent_settled' });
    await expect.poll(() => workers.get('conversation-running')?.length).toBe(2);
    expect(workers.get('conversation-running')![0]!.stopped).toBe(true);
    expect(revisions).toEqual(expect.arrayContaining([
      { conversationId: 'conversation-idle', provider: 2, resources: 1 },
      { conversationId: 'conversation-running', provider: 2, resources: 1 },
    ]));
  });

  it('re-applies the idle LRU after a running stale worker rebuilds on settle', async () => {
    const workers = new Map<string, FakeWorker[]>();
    const pool = new PiWorkerPool({
      maxIdle: 1,
      openWorker: async ({ conversation: input, generation, existingSession }) => {
        const worker = new FakeWorker(`worker-${input.conversationId}-${generation}`);
        workers.set(input.conversationId, [...(workers.get(input.conversationId) ?? []), worker]);
        return {
          worker,
          session: existingSession ?? {
            piSessionId: `session-${input.conversationId}`,
            sessionKey: `key-${input.conversationId}`,
          },
        };
      },
    });
    await pool.prepare(conversation('conversation-running'));
    const running = pool.startTopLevel({
      conversationId: 'conversation-running',
      runId: 'run-running',
      command: { type: 'prompt', message: 'running' },
    });
    await running.accepted;
    await pool.prepare(conversation('conversation-idle'));
    pool.markProviderStale();

    workers.get('conversation-running')![0]!.emit({ type: 'agent_settled' });
    await expect.poll(() => workers.get('conversation-running')?.length).toBe(2);
    await expect.poll(() => workers.get('conversation-idle')![0]!.stopped).toBe(true);
    expect(pool.getState('conversation-idle')).toBeNull();
    expect(pool.getState('conversation-running')).toMatchObject({ state: 'ready', generation: 2 });
  });

  it('reuses an in-flight rebuild for recover and leaves no unowned replacement worker', async () => {
    const generationTwoGate = deferred();
    const workers: FakeWorker[] = [];
    const openedGenerations: number[] = [];
    const pool = new PiWorkerPool({
      maxIdle: 2,
      openWorker: async ({ conversation: input, generation, existingSession }) => {
        openedGenerations.push(generation);
        const worker = new FakeWorker(`worker-${input.conversationId}-${generation}`);
        workers.push(worker);
        if (generation === 2) await generationTwoGate.promise;
        return {
          worker,
          session: existingSession ?? {
            piSessionId: `session-${input.conversationId}`,
            sessionKey: `key-${input.conversationId}`,
          },
        };
      },
    });
    await pool.prepare(conversation('conversation-a'));
    pool.markProviderStale();
    const ticket = pool.startTopLevel({
      conversationId: 'conversation-a',
      runId: 'run-a',
      command: { type: 'prompt', message: 'do not replay' },
    });
    const ticketOutcome = ticket.accepted.then(
      () => 'resolved',
      (error: unknown) => error instanceof Error ? error.message : String(error),
    );
    await expect.poll(() => openedGenerations).toEqual([1, 2]);

    const recovered = pool.recover('conversation-a');
    await new Promise((resolve) => setTimeout(resolve, 10));
    expect(openedGenerations).toEqual([1, 2]);
    generationTwoGate.resolve();

    await expect(recovered).resolves.toMatchObject({ generation: 2, state: 'ready' });
    expect(await ticketOutcome).toMatch(/recovering|cancelled/);
    await pool.shutdown();
    expect(workers).toHaveLength(2);
    expect(workers.every((worker) => worker.stopped)).toBe(true);
  });

  it('rejects queued work and stops every parent worker during app shutdown', async () => {
    const workers: FakeWorker[] = [];
    const pool = new PiWorkerPool({
      maxRunning: 1,
      maxIdle: 3,
      openWorker: async ({ conversation: input }) => {
        const worker = new FakeWorker(`worker-${input.conversationId}`);
        workers.push(worker);
        return {
          worker,
          session: {
            piSessionId: `session-${input.conversationId}`,
            sessionKey: `key-${input.conversationId}`,
          },
        };
      },
    });
    await Promise.all(['a', 'b', 'c'].map((id) => pool.prepare(conversation(`conversation-${id}`))));
    pool.startTopLevel({ conversationId: 'conversation-a', runId: 'run-a', command: { type: 'prompt', message: 'a' } });
    const queued = pool.startTopLevel({
      conversationId: 'conversation-b',
      runId: 'run-b',
      command: { type: 'prompt', message: 'b' },
    });
    let childCancelled = false;
    pool.trackGenerationResource({
      conversationId: 'conversation-a',
      kind: 'child',
      id: 'child-a',
      cancel: () => { childCancelled = true; },
    });

    await pool.shutdown();

    await expect(queued.accepted).rejects.toThrow('shutting down');
    expect(childCancelled).toBe(true);
    expect(workers.every((worker) => worker.stopped)).toBe(true);
    expect(pool.getState('conversation-a')).toBeNull();
    await expect(pool.prepare(conversation('conversation-after-quit')))
      .rejects.toThrow('shutting down');
  });

  it('waits for an in-flight fork open and stops that process before shutdown completes', async () => {
    const forkGate = deferred();
    const workers: FakeWorker[] = [];
    let forkOpenStarted = false;
    const pool = new PiWorkerPool({
      maxIdle: 3,
      openWorker: async ({ conversation: input, existingSession }) => {
        if (input.conversationId === 'conversation-fork') {
          forkOpenStarted = true;
          await forkGate.promise;
        }
        const worker = new FakeWorker(`worker-${input.conversationId}`);
        workers.push(worker);
        return {
          worker,
          session: existingSession ?? {
            piSessionId: `session-${input.conversationId}`,
            sessionKey: `key-${input.conversationId}`,
          },
        };
      },
    });
    await pool.prepare(conversation('conversation-source'));
    const fork = pool.fork('conversation-source', conversation('conversation-fork'));
    await expect.poll(() => forkOpenStarted).toBe(true);
    const forkOutcome = fork.then(
      () => 'resolved',
      (error: unknown) => error instanceof Error ? error.message : String(error),
    );
    let shutdownCompleted = false;
    const shutdown = pool.shutdown().then(() => { shutdownCompleted = true; });
    await Promise.resolve();
    expect(shutdownCompleted).toBe(false);

    forkGate.resolve();
    await shutdown;
    expect(await forkOutcome).toContain('shutting down');
    expect(workers).toHaveLength(2);
    expect(workers.every((worker) => worker.stopped)).toBe(true);
  });

  it('recovers the target session with a new generation and disposes no sibling worker', async () => {
    const workers = new Map<string, FakeWorker[]>();
    const pool = new PiWorkerPool({
      maxIdle: 4,
      openWorker: async ({ conversation: input, existingSession }) => {
        const worker = new FakeWorker(`worker-${input.conversationId}-${(workers.get(input.conversationId)?.length ?? 0) + 1}`);
        workers.set(input.conversationId, [...(workers.get(input.conversationId) ?? []), worker]);
        return {
          worker,
          session: existingSession ?? {
            piSessionId: `session-${input.conversationId}`,
            sessionKey: `key-${input.conversationId}`,
          },
        };
      },
    });
    await Promise.all([
      pool.prepare(conversation('conversation-a')),
      pool.prepare(conversation('conversation-b')),
    ]);
    workers.get('conversation-a')![0]!.invalidate();

    const recovered = await pool.recover('conversation-a');
    expect(recovered).toMatchObject({
      workerId: 'worker-conversation-a-2',
      generation: 2,
      state: 'ready',
      session: { piSessionId: 'session-conversation-a', sessionKey: 'key-conversation-a' },
    });
    expect(workers.get('conversation-a')![0]!.stopped).toBe(true);
    expect(workers.get('conversation-b')![0]!.stopped).toBe(false);

    await pool.dispose('conversation-a');
    expect(workers.get('conversation-a')![1]!.stopped).toBe(true);
    expect(pool.getState('conversation-a')).toBeNull();
    expect(pool.getState('conversation-b')).toMatchObject({ state: 'ready', generation: 1 });
  });

  it('records privacy-safe queue wait and RPC prompt acceptance spans', async () => {
    let now = 0;
    const telemetry: PiRuntimeTelemetryEvent[] = [];
    const workers = new Map<string, FakeWorker>();
    const pool = new PiWorkerPool({
      maxRunning: 1,
      maxIdle: 2,
      now: () => now,
      onTelemetry: (event) => telemetry.push(event),
      openWorker: async ({ conversation: input }) => {
        const worker = new FakeWorker(`worker-${input.conversationId}`);
        workers.set(input.conversationId, worker);
        return {
          worker,
          session: {
            piSessionId: `session-${input.conversationId}`,
            sessionKey: `key-${input.conversationId}`,
          },
        };
      },
    });
    await Promise.all([
      pool.prepare(conversation('f47ac10b-58cc-4372-a567-0e02b2c3d479')),
      pool.prepare(conversation('8b1a9953-c461-4d88-9c3e-7e1f8f3f2c11')),
    ]);
    const first = pool.startTopLevel({
      conversationId: 'f47ac10b-58cc-4372-a567-0e02b2c3d479',
      runId: 'run-first-1234567890',
      command: { type: 'prompt', message: 'private first prompt' },
    });
    now = 5;
    const second = pool.startTopLevel({
      conversationId: '8b1a9953-c461-4d88-9c3e-7e1f8f3f2c11',
      runId: 'run-second-1234567890',
      command: { type: 'prompt', message: 'private second prompt' },
    });
    await first.accepted;
    now = 25;
    workers.get('f47ac10b-58cc-4372-a567-0e02b2c3d479')!.emit({ type: 'agent_settled' });
    await second.accepted;

    expect(telemetry.map(({ milestone }) => milestone)).toEqual([
      'prompt.accepted',
      'worker.queue_wait',
      'prompt.accepted',
    ]);
    expect(telemetry[1]).toMatchObject({ durationMs: 20, workerGeneration: 1, cold: true });
    const serialized = JSON.stringify(telemetry);
    expect(serialized).not.toContain('private first prompt');
    expect(serialized).not.toContain('private second prompt');
    expect(serialized).not.toContain('f47ac10b-58cc-4372-a567-0e02b2c3d479');
    expect(serialized).not.toContain('8b1a9953-c461-4d88-9c3e-7e1f8f3f2c11');
  });
});