import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest';
import { mkdtempSync, rmSync, existsSync } from 'node:fs';
import { join } from 'node:path';
import { tmpdir } from 'node:os';
import { initDatabaseAsync, closeDatabase } from '../db/index';
import { runMigrations } from '../db/migrate';
import { createChannel } from '../db/repositories/channel-repository';
import {
  createContentItem,
  getContentItemById,
} from '../db/repositories/content-repository';
import {
  getQueueItemById,
  updateQueueItemStatus,
  createQueueItem,
  countQueueItemsByStatus,
} from '../db/repositories/queue-repository';
import { getHistoryEvents } from '../db/repositories/history-repository';
import { QueueService } from '../services/queue';
import type { ContentItem, Channel } from '../types/index';

// ── Test Helpers ──

let tmpDir: string;
let db: Awaited<ReturnType<typeof initDatabaseAsync>>;
let testChannel: Channel;
let contentItems: ContentItem[];

/** Create a mock DownloadService with a controllable downloadItem. */
function createMockDownloadService() {
  return {
    downloadItem: vi.fn().mockResolvedValue(undefined),
  };
}

async function setupDb(): Promise<void> {
  tmpDir = mkdtempSync(join(tmpdir(), 'tubearr-qs-test-'));
  const dbPath = join(tmpDir, 'test.db');
  db = await initDatabaseAsync(dbPath);
  await runMigrations(dbPath);

  testChannel = await createChannel(db, {
    name: 'Queue Service Test Channel',
    platform: 'youtube',
    platformId: 'UC_qs_test',
    url: 'https://www.youtube.com/channel/UC_qs_test',
    imageUrl: null,
    formatProfileId: null,
    monitoringEnabled: true,
    checkInterval: 360,
    metadata: null,
  });

  // Pre-create a batch of content items for tests
  contentItems = [];
  for (let i = 1; i <= 6; i++) {
    const item = await createContentItem(db, {
      channelId: testChannel.id,
      title: `QS Test Video ${i}`,
      platformContentId: `vid_qs_${i}`,
      url: `https://www.youtube.com/watch?v=qs${i}`,
      contentType: 'video',
      duration: 300 + i * 60,
      status: 'monitored',
    });
    contentItems.push(item!);
  }
}

function cleanup(): void {
  closeDatabase();
  try {
    if (tmpDir && existsSync(tmpDir)) {
      rmSync(tmpDir, { recursive: true, force: true });
    }
  } catch {
    // Windows cleanup best-effort
  }
}

/** Wait for async queue processing to settle. */
async function tick(ms = 50): Promise<void> {
  await new Promise((resolve) => setTimeout(resolve, ms));
}

// ── Tests ──

describe('QueueService', () => {
  let mockDownloadService: ReturnType<typeof createMockDownloadService>;

  beforeEach(async () => {
    await setupDb();
    mockDownloadService = createMockDownloadService();
  });

  afterEach(() => {
    cleanup();
  });

  // ── Enqueue ──

  describe('enqueue', () => {
    it('creates queue item with pending status', async () => {
      const qs = new QueueService(db, mockDownloadService as any, 0); // concurrency=0 to prevent auto-processing
      qs.stop();

      const queueItem = await qs.enqueue(contentItems[0].id);

      expect(queueItem).toBeDefined();
      expect(queueItem.contentItemId).toBe(contentItems[0].id);
      expect(queueItem.status).toBe('pending');
      expect(queueItem.priority).toBe(0);
      expect(queueItem.attempts).toBe(0);
    });

    it('updates content status to queued', async () => {
      const qs = new QueueService(db, mockDownloadService as any, 0);
      qs.stop();

      await qs.enqueue(contentItems[0].id);

      const updated = await getContentItemById(db, contentItems[0].id);
      expect(updated!.status).toBe('queued');
    });

    it('records grabbed history event', async () => {
      const qs = new QueueService(db, mockDownloadService as any, 0);
      qs.stop();

      await qs.enqueue(contentItems[0].id);

      const { items } = await getHistoryEvents(db);
      expect(items.length).toBe(1);
      expect(items[0].eventType).toBe('grabbed');
      expect(items[0].contentItemId).toBe(contentItems[0].id);
      expect(items[0].channelId).toBe(testChannel.id);
      expect(items[0].status).toBe('pending');
    });

    it('respects priority parameter', async () => {
      const qs = new QueueService(db, mockDownloadService as any, 0);
      qs.stop();

      const queueItem = await qs.enqueue(contentItems[0].id, 5);
      expect(queueItem.priority).toBe(5);
    });

    it('throws on duplicate enqueue for pending item', async () => {
      const qs = new QueueService(db, mockDownloadService as any, 0);
      qs.stop();

      await qs.enqueue(contentItems[0].id);
      await expect(qs.enqueue(contentItems[0].id)).rejects.toThrow(
        /already in the queue/
      );
    });

    it('throws for non-existent content item', async () => {
      const qs = new QueueService(db, mockDownloadService as any, 0);
      qs.stop();

      await expect(qs.enqueue(99999)).rejects.toThrow(/not found/);
    });
  });

  // ── Process ──

  describe('processItem', () => {
    it('transitions item through downloading to completed', async () => {
      const qs = new QueueService(db, mockDownloadService as any, 1);

      await qs.enqueue(contentItems[0].id);
      await tick(100);

      const queueItem = await getQueueItemById(db, 1);
      expect(queueItem!.status).toBe('completed');
      expect(queueItem!.completedAt).not.toBeNull();

      // Verify downloadItem was called
      expect(mockDownloadService.downloadItem).toHaveBeenCalledOnce();
      const [calledContentItem, calledChannel] = mockDownloadService.downloadItem.mock.calls[0];
      expect(calledContentItem.id).toBe(contentItems[0].id);
      expect(calledChannel.id).toBe(testChannel.id);
    });

    it('records downloaded history event on success', async () => {
      const qs = new QueueService(db, mockDownloadService as any, 1);

      await qs.enqueue(contentItems[0].id);
      await tick(100);

      const { items } = await getHistoryEvents(db);
      const downloadedEvent = items.find((e) => e.eventType === 'downloaded');
      expect(downloadedEvent).toBeDefined();
      expect(downloadedEvent!.contentItemId).toBe(contentItems[0].id);
      expect(downloadedEvent!.status).toBe('completed');
    });

    it('retries on failure — sets status to pending with incremented attempts', async () => {
      // Only fail once, then stop to prevent retry loop
      let callCount = 0;
      mockDownloadService.downloadItem.mockImplementation(() => {
        callCount++;
        if (callCount === 1) {
          return Promise.reject(new Error('network timeout'));
        }
        // On retry, return a deferred that never resolves so we can inspect state
        return new Promise(() => {});
      });

      const qs = new QueueService(db, mockDownloadService as any, 1);

      await qs.enqueue(contentItems[0].id);
      // Wait for first attempt to fail and item to be reset to pending,
      // then the retry attempt starts (downloading)
      await tick(150);
      qs.stop();

      // After the first failure, the item was reset to pending, then picked up again
      // Since we stopped, let's check the call count
      expect(callCount).toBeGreaterThanOrEqual(1);

      // After first failure, attempts should have been incremented to 1
      // The item may have been picked up again (status=downloading), so check via history
      const { items } = await getHistoryEvents(db);
      const failedEvents = items.filter((e) => e.eventType === 'failed');
      expect(failedEvents.length).toBeGreaterThanOrEqual(1);
      expect(failedEvents[0].details).toHaveProperty('error', 'network timeout');
      expect(failedEvents[0].details).toHaveProperty('attempt', 1);
    });

    it('records failed history event with error details', async () => {
      // Use a deferred to control exactly when the download completes
      let rejectFn: (err: Error) => void;
      mockDownloadService.downloadItem.mockImplementationOnce(() => {
        return new Promise<void>((_, reject) => {
          rejectFn = reject;
        });
      });

      const qs = new QueueService(db, mockDownloadService as any, 1);
      qs.stop();
      await qs.enqueue(contentItems[0].id);
      qs.start();
      await tick(50);

      // Now reject the download — this triggers the failure path
      rejectFn!(new Error('network timeout'));
      await tick(50);
      qs.stop();

      const { items } = await getHistoryEvents(db);
      const failedEvent = items.find((e) => e.eventType === 'failed');
      expect(failedEvent).toBeDefined();
      expect(failedEvent!.details).toHaveProperty('error', 'network timeout');
      expect(failedEvent!.details).toHaveProperty('attempt', 1);
      expect(failedEvent!.details).toHaveProperty('exhausted', false);
    });

    it('marks as failed when max attempts exhausted', async () => {
      mockDownloadService.downloadItem.mockRejectedValue(new Error('permanent failure'));

      const qs = new QueueService(db, mockDownloadService as any, 1);
      qs.stop();

      // Enqueue, then manually set attempts to maxAttempts - 1
      await qs.enqueue(contentItems[0].id);
      await updateQueueItemStatus(db, 1, 'pending', { attempts: 2 }); // maxAttempts defaults to 3

      qs.start();
      await tick(100);
      qs.stop();

      const queueItem = await getQueueItemById(db, 1);
      expect(queueItem!.status).toBe('failed');
      expect(queueItem!.attempts).toBe(3);

      // Content status should be set to failed
      const contentItem = await getContentItemById(db, contentItems[0].id);
      expect(contentItem!.status).toBe('failed');

      // History event should indicate exhaustion
      const { items } = await getHistoryEvents(db);
      const failedEvent = items.find(
        (e) => e.eventType === 'failed' && (e.details as any)?.exhausted === true
      );
      expect(failedEvent).toBeDefined();
    });
  });

  // ── Concurrency ──

  describe('concurrency', () => {
    it('limits simultaneous downloads to concurrency value', async () => {
      // Track how many downloads are running simultaneously
      let concurrentCount = 0;
      let maxConcurrentCount = 0;

      const deferreds: Array<{ resolve: () => void; reject: (err: Error) => void }> = [];

      mockDownloadService.downloadItem.mockImplementation(() => {
        return new Promise<void>((resolve, reject) => {
          concurrentCount++;
          maxConcurrentCount = Math.max(maxConcurrentCount, concurrentCount);
          deferreds.push({
            resolve: () => { concurrentCount--; resolve(); },
            reject: (err: Error) => { concurrentCount--; reject(err); },
          });
        });
      });

      const qs = new QueueService(db, mockDownloadService as any, 2);

      // Enqueue 4 items
      await qs.enqueue(contentItems[0].id);
      await qs.enqueue(contentItems[1].id);
      await qs.enqueue(contentItems[2].id);
      await qs.enqueue(contentItems[3].id);

      // Wait for processNext to fire
      await tick(100);

      // At most 2 should be downloading
      expect(maxConcurrentCount).toBe(2);
      expect(concurrentCount).toBe(2);

      // Resolve first two downloads
      deferreds[0].resolve();
      await tick(50);
      deferreds[1].resolve();
      await tick(150);

      // Remaining items should have been picked up and completed or still in-flight
      // Resolve any remaining deferreds
      for (let i = 2; i < deferreds.length; i++) {
        deferreds[i].resolve();
        await tick(50);
      }
      await tick(100);

      // All 4 should be completed
      const counts = await countQueueItemsByStatus(db);
      expect(counts.completed).toBe(4);
      expect(counts.pending).toBe(0);
      // Most important: never exceeded concurrency limit of 2
      expect(maxConcurrentCount).toBe(2);
    });
  });

  // ── Retry ──

  describe('retryItem', () => {
    it('resets failed item to pending and triggers processing', async () => {
      const qs = new QueueService(db, mockDownloadService as any, 0);
      qs.stop();

      // Create and manually fail a queue item
      await qs.enqueue(contentItems[0].id);
      await updateQueueItemStatus(db, 1, 'failed', { attempts: 1, error: 'test error' });

      const retried = await qs.retryItem(1);
      expect(retried.status).toBe('pending');
      expect(retried.error).toBeNull();

      // Content status should be reset to queued
      const contentItem = await getContentItemById(db, contentItems[0].id);
      expect(contentItem!.status).toBe('queued');
    });

    it('throws for non-failed item', async () => {
      const qs = new QueueService(db, mockDownloadService as any, 0);
      qs.stop();

      await qs.enqueue(contentItems[0].id);

      await expect(qs.retryItem(1)).rejects.toThrow(/expected 'failed'/);
    });

    it('throws when attempts exhausted', async () => {
      const qs = new QueueService(db, mockDownloadService as any, 0);
      qs.stop();

      await qs.enqueue(contentItems[0].id);
      await updateQueueItemStatus(db, 1, 'failed', { attempts: 3 }); // maxAttempts defaults to 3

      await expect(qs.retryItem(1)).rejects.toThrow(/attempts.*>=.*maxAttempts/);
    });

    it('throws for non-existent item', async () => {
      const qs = new QueueService(db, mockDownloadService as any, 0);
      await expect(qs.retryItem(99999)).rejects.toThrow(/not found/);
    });
  });

  // ── Cancel ──

  describe('cancelItem', () => {
    it('cancels a pending item', async () => {
      const qs = new QueueService(db, mockDownloadService as any, 0);
      qs.stop();

      await qs.enqueue(contentItems[0].id);

      const cancelled = await qs.cancelItem(1);
      expect(cancelled.status).toBe('cancelled');
    });

    it('cancels a failed item', async () => {
      const qs = new QueueService(db, mockDownloadService as any, 0);
      qs.stop();

      await qs.enqueue(contentItems[0].id);
      await updateQueueItemStatus(db, 1, 'failed', { attempts: 1, error: 'err' });

      const cancelled = await qs.cancelItem(1);
      expect(cancelled.status).toBe('cancelled');
    });

    it('throws for downloading item', async () => {
      const qs = new QueueService(db, mockDownloadService as any, 0);
      qs.stop();

      await qs.enqueue(contentItems[0].id);
      await updateQueueItemStatus(db, 1, 'downloading');

      await expect(qs.cancelItem(1)).rejects.toThrow(/must be 'pending' or 'failed'/);
    });

    it('throws for completed item', async () => {
      const qs = new QueueService(db, mockDownloadService as any, 0);
      qs.stop();

      await qs.enqueue(contentItems[0].id);
      await updateQueueItemStatus(db, 1, 'completed');

      await expect(qs.cancelItem(1)).rejects.toThrow(/must be 'pending' or 'failed'/);
    });

    it('throws for non-existent item', async () => {
      const qs = new QueueService(db, mockDownloadService as any, 0);
      await expect(qs.cancelItem(99999)).rejects.toThrow(/not found/);
    });
  });

  // ── Restart Recovery ──

  describe('recoverOnStartup', () => {
    it('resets downloading items to pending', async () => {
      const qs = new QueueService(db, mockDownloadService as any, 0);
      qs.stop();

      // Directly insert items in 'downloading' status (simulating a crash)
      await createQueueItem(db, { contentItemId: contentItems[0].id });
      await updateQueueItemStatus(db, 1, 'downloading', { startedAt: '2026-01-01T00:00:00Z' });

      await createQueueItem(db, { contentItemId: contentItems[1].id });
      await updateQueueItemStatus(db, 2, 'downloading', { startedAt: '2026-01-01T00:00:00Z' });

      // Also create one pending item — should not be affected
      await createQueueItem(db, { contentItemId: contentItems[2].id });

      const recovered = await qs.recoverOnStartup();
      expect(recovered).toBe(2);

      const item1 = await getQueueItemById(db, 1);
      expect(item1!.status).toBe('pending');
      expect(item1!.startedAt).toBeNull();

      const item2 = await getQueueItemById(db, 2);
      expect(item2!.status).toBe('pending');

      // Pending item should remain unchanged
      const item3 = await getQueueItemById(db, 3);
      expect(item3!.status).toBe('pending');
    });

    it('returns 0 when no items are stuck', async () => {
      const qs = new QueueService(db, mockDownloadService as any, 0);
      const recovered = await qs.recoverOnStartup();
      expect(recovered).toBe(0);
    });
  });

  // ── Stop / Start ──

  describe('stop/start', () => {
    it('stop prevents new items from being picked up', async () => {
      const qs = new QueueService(db, mockDownloadService as any, 2);
      qs.stop();

      await qs.enqueue(contentItems[0].id);
      await tick(100);

      // Item should still be pending — processNext is a no-op while stopped
      const item = await getQueueItemById(db, 1);
      expect(item!.status).toBe('pending');
      expect(mockDownloadService.downloadItem).not.toHaveBeenCalled();
    });

    it('start resumes processing', async () => {
      const qs = new QueueService(db, mockDownloadService as any, 2);
      qs.stop();

      await qs.enqueue(contentItems[0].id);
      await tick(50);

      // Verify still pending
      let item = await getQueueItemById(db, 1);
      expect(item!.status).toBe('pending');

      // Resume
      qs.start();
      await tick(100);

      item = await getQueueItemById(db, 1);
      expect(item!.status).toBe('completed');
      expect(mockDownloadService.downloadItem).toHaveBeenCalledOnce();
    });
  });

  // ── Pause ──

  describe('pauseItem', () => {
    it('pauses a pending item', async () => {
      const qs = new QueueService(db, mockDownloadService as any, 0);
      qs.stop();

      await qs.enqueue(contentItems[0].id);

      const paused = await qs.pauseItem(1);
      expect(paused.status).toBe('paused');
    });

    it('pauses a downloading item by aborting the active download', async () => {
      // Use a deferred so we can control when the download completes
      let rejectFn: (err: Error) => void;
      mockDownloadService.downloadItem.mockImplementationOnce(() => {
        return new Promise<void>((_resolve, reject) => {
          rejectFn = reject;
        });
      });

      const qs = new QueueService(db, mockDownloadService as any, 1);

      await qs.enqueue(contentItems[0].id);
      await tick(50); // Let it transition to downloading

      // Item should be downloading
      let item = await getQueueItemById(db, 1);
      expect(item!.status).toBe('downloading');

      // Pause it — this should abort the download
      const paused = await qs.pauseItem(1);
      expect(paused.status).toBe('paused');

      // Simulate the abort rejection (in real code, the AbortController signal kills yt-dlp)
      rejectFn!(new Error('aborted'));
      await tick(50);

      // Item should remain paused (not retried as failed)
      item = await getQueueItemById(db, 1);
      expect(item!.status).toBe('paused');
    });

    it('throws for completed item', async () => {
      const qs = new QueueService(db, mockDownloadService as any, 0);
      qs.stop();

      await qs.enqueue(contentItems[0].id);
      await updateQueueItemStatus(db, 1, 'completed');

      await expect(qs.pauseItem(1)).rejects.toThrow(/Cannot pause/);
    });

    it('throws for cancelled item', async () => {
      const qs = new QueueService(db, mockDownloadService as any, 0);
      qs.stop();

      await qs.enqueue(contentItems[0].id);
      await updateQueueItemStatus(db, 1, 'cancelled');

      await expect(qs.pauseItem(1)).rejects.toThrow(/Cannot pause/);
    });

    it('throws for non-existent item', async () => {
      const qs = new QueueService(db, mockDownloadService as any, 0);
      await expect(qs.pauseItem(99999)).rejects.toThrow(/not found/);
    });
  });

  // ── Resume ──

  describe('resumeItem', () => {
    it('resumes a paused item back to pending', async () => {
      const qs = new QueueService(db, mockDownloadService as any, 0);
      qs.stop();

      await qs.enqueue(contentItems[0].id);
      await qs.pauseItem(1);

      const resumed = await qs.resumeItem(1);
      expect(resumed.status).toBe('pending');
      expect(resumed.error).toBeNull();

      // Content status should be reset to queued
      const contentItem = await getContentItemById(db, contentItems[0].id);
      expect(contentItem!.status).toBe('queued');
    });

    it('throws for non-paused item', async () => {
      const qs = new QueueService(db, mockDownloadService as any, 0);
      qs.stop();

      await qs.enqueue(contentItems[0].id);

      await expect(qs.resumeItem(1)).rejects.toThrow(/expected 'paused'/);
    });

    it('throws for non-existent item', async () => {
      const qs = new QueueService(db, mockDownloadService as any, 0);
      await expect(qs.resumeItem(99999)).rejects.toThrow(/not found/);
    });

    it('triggers processNext after resume', async () => {
      // After resuming, the item should get picked up and processed
      const qs = new QueueService(db, mockDownloadService as any, 1);

      // Enqueue and pause
      qs.stop();
      await qs.enqueue(contentItems[0].id);
      await qs.pauseItem(1);

      // Resume — processNext should fire and download
      qs.start();
      await qs.resumeItem(1);
      await tick(100);

      const item = await getQueueItemById(db, 1);
      expect(item!.status).toBe('completed');
      expect(mockDownloadService.downloadItem).toHaveBeenCalledOnce();
    });
  });

  // ── getState ──

  describe('getState', () => {
    it('returns correct counts by status', async () => {
      const qs = new QueueService(db, mockDownloadService as any, 0);
      qs.stop();

      await qs.enqueue(contentItems[0].id);
      await qs.enqueue(contentItems[1].id);
      await qs.enqueue(contentItems[2].id);

      // Manually set some statuses
      await updateQueueItemStatus(db, 2, 'completed');
      await updateQueueItemStatus(db, 3, 'failed');

      const state = await qs.getState();
      expect(state.pending).toBe(1);
      expect(state.completed).toBe(1);
      expect(state.failed).toBe(1);
      expect(state.downloading).toBe(0);
      expect(state.cancelled).toBe(0);
      expect(state.paused).toBe(0);
    });

    it('returns all zeros when queue is empty', async () => {
      const qs = new QueueService(db, mockDownloadService as any, 0);

      const state = await qs.getState();
      expect(state).toEqual({
        pending: 0,
        downloading: 0,
        completed: 0,
        failed: 0,
        cancelled: 0,
        paused: 0,
      });
    });
  });

  // ── Integration: full lifecycle ──

  describe('full lifecycle', () => {
    it('enqueue → process → complete lifecycle works end-to-end', async () => {
      const qs = new QueueService(db, mockDownloadService as any, 2);

      // Enqueue two items
      const q1 = await qs.enqueue(contentItems[0].id);
      const q2 = await qs.enqueue(contentItems[1].id, 5);

      // Wait for processing
      await tick(150);

      // Both should be completed
      const item1 = await getQueueItemById(db, q1.id);
      const item2 = await getQueueItemById(db, q2.id);
      expect(item1!.status).toBe('completed');
      expect(item2!.status).toBe('completed');

      // Download service should have been called twice
      expect(mockDownloadService.downloadItem).toHaveBeenCalledTimes(2);

      // Should have history events: 2 grabbed + 2 downloaded
      const { items: history } = await getHistoryEvents(db);
      const grabbed = history.filter((e) => e.eventType === 'grabbed');
      const downloaded = history.filter((e) => e.eventType === 'downloaded');
      expect(grabbed.length).toBe(2);
      expect(downloaded.length).toBe(2);

      // State should reflect completed
      const state = await qs.getState();
      expect(state.completed).toBe(2);
      expect(state.pending).toBe(0);
    });
  });
});