/**
 * @fileoverview Tests for TaskQueue
 *
 * Tests the priority queue functionality for managing tasks
 * including adding, removing, ordering, and dependency handling.
 */

import { describe, it, expect, beforeEach, vi } from 'vitest';

// Mock the state-store before importing task-queue
vi.mock('../src/state-store.js', () => ({
  getStore: vi.fn(() => ({
    getTasks: vi.fn(() => ({})),
    setTask: vi.fn(),
    removeTask: vi.fn(),
  })),
}));

// Import after mocking
import { TaskQueue, getTaskQueue } from '../src/task-queue.js';
import { Task } from '../src/task.js';

describe('TaskQueue', () => {
  let queue: TaskQueue;

  beforeEach(() => {
    // Create fresh queue for each test
    queue = new TaskQueue();
  });

  describe('addTask', () => {
    it('should add a task to the queue', () => {
      const task = queue.addTask({ prompt: 'Test prompt' });

      expect(task).toBeInstanceOf(Task);
      expect(task.prompt).toBe('Test prompt');
      expect(queue.getTask(task.id)).toBe(task);
    });

    it('should emit taskAdded event', () => {
      const handler = vi.fn();
      queue.on('taskAdded', handler);

      const task = queue.addTask({ prompt: 'Test prompt' });

      expect(handler).toHaveBeenCalledWith(task);
    });

    it('should accept optional parameters', () => {
      const task = queue.addTask({
        prompt: 'Test prompt',
        workingDir: '/tmp/test',
        priority: 5,
        dependencies: ['dep-1', 'dep-2'],
        completionPhrase: 'DONE',
        timeoutMs: 30000,
      });

      expect(task.prompt).toBe('Test prompt');
      expect(task.workingDir).toBe('/tmp/test');
      expect(task.priority).toBe(5);
      expect(task.dependencies).toEqual(['dep-1', 'dep-2']);
      expect(task.completionPhrase).toBe('DONE');
      expect(task.timeoutMs).toBe(30000);
    });
  });

  describe('getTask', () => {
    it('should return undefined for non-existent task', () => {
      expect(queue.getTask('non-existent')).toBeUndefined();
    });

    it('should return the correct task by ID', () => {
      const task1 = queue.addTask({ prompt: 'Task 1' });
      const task2 = queue.addTask({ prompt: 'Task 2' });

      expect(queue.getTask(task1.id)).toBe(task1);
      expect(queue.getTask(task2.id)).toBe(task2);
    });
  });

  describe('removeTask', () => {
    it('should remove a task from the queue', () => {
      const task = queue.addTask({ prompt: 'Test prompt' });

      const removed = queue.removeTask(task.id);

      expect(removed).toBe(true);
      expect(queue.getTask(task.id)).toBeUndefined();
    });

    it('should return false for non-existent task', () => {
      expect(queue.removeTask('non-existent')).toBe(false);
    });

    it('should emit taskRemoved event', () => {
      const handler = vi.fn();
      queue.on('taskRemoved', handler);

      const task = queue.addTask({ prompt: 'Test prompt' });
      queue.removeTask(task.id);

      expect(handler).toHaveBeenCalledWith(task.id);
    });
  });

  describe('updateTask', () => {
    it('should update a task and emit event', () => {
      const handler = vi.fn();
      queue.on('taskUpdated', handler);

      const task = queue.addTask({ prompt: 'Test prompt' });
      task.assign('session-1');
      queue.updateTask(task);

      expect(handler).toHaveBeenCalledWith(task);
      expect(queue.getTask(task.id)?.status).toBe('running');
    });
  });

  describe('getAllTasks', () => {
    it('should return empty array when no tasks', () => {
      expect(queue.getAllTasks()).toEqual([]);
    });

    it('should return all tasks', () => {
      const task1 = queue.addTask({ prompt: 'Task 1' });
      const task2 = queue.addTask({ prompt: 'Task 2' });
      const task3 = queue.addTask({ prompt: 'Task 3' });

      const tasks = queue.getAllTasks();

      expect(tasks).toHaveLength(3);
      expect(tasks).toContain(task1);
      expect(tasks).toContain(task2);
      expect(tasks).toContain(task3);
    });
  });

  describe('getPendingTasks', () => {
    it('should return only pending tasks', () => {
      const task1 = queue.addTask({ prompt: 'Task 1' });
      const task2 = queue.addTask({ prompt: 'Task 2' });
      task2.assign('session-1');

      const pending = queue.getPendingTasks();

      expect(pending).toHaveLength(1);
      expect(pending[0]).toBe(task1);
    });

    it('should sort by priority (higher first)', () => {
      const lowPriority = queue.addTask({ prompt: 'Low', priority: 1 });
      const highPriority = queue.addTask({ prompt: 'High', priority: 10 });
      const medPriority = queue.addTask({ prompt: 'Med', priority: 5 });

      const pending = queue.getPendingTasks();

      expect(pending[0]).toBe(highPriority);
      expect(pending[1]).toBe(medPriority);
      expect(pending[2]).toBe(lowPriority);
    });

    it('should sort by creation time when priority is equal', async () => {
      const first = queue.addTask({ prompt: 'First', priority: 5 });
      // Small delay to ensure different createdAt
      await new Promise((r) => setTimeout(r, 10));
      const second = queue.addTask({ prompt: 'Second', priority: 5 });

      const pending = queue.getPendingTasks();

      expect(pending[0]).toBe(first);
      expect(pending[1]).toBe(second);
    });
  });

  describe('getRunningTasks', () => {
    it('should return only running tasks', () => {
      const task1 = queue.addTask({ prompt: 'Task 1' });
      const task2 = queue.addTask({ prompt: 'Task 2' });
      task1.assign('session-1');

      const running = queue.getRunningTasks();

      expect(running).toHaveLength(1);
      expect(running[0]).toBe(task1);
    });
  });

  describe('getCompletedTasks', () => {
    it('should return only completed tasks', () => {
      const task1 = queue.addTask({ prompt: 'Task 1' });
      const task2 = queue.addTask({ prompt: 'Task 2' });
      task1.assign('session-1');
      task1.complete();

      const completed = queue.getCompletedTasks();

      expect(completed).toHaveLength(1);
      expect(completed[0]).toBe(task1);
    });
  });

  describe('getFailedTasks', () => {
    it('should return only failed tasks', () => {
      const task1 = queue.addTask({ prompt: 'Task 1' });
      const task2 = queue.addTask({ prompt: 'Task 2' });
      task1.assign('session-1');
      task1.fail('Some error');

      const failed = queue.getFailedTasks();

      expect(failed).toHaveLength(1);
      expect(failed[0]).toBe(task1);
    });
  });

  describe('hasNext and next', () => {
    it('should return false/null when no pending tasks', () => {
      expect(queue.hasNext()).toBe(false);
      expect(queue.next()).toBeNull();
    });

    it('should return true/task when pending tasks exist', () => {
      const task = queue.addTask({ prompt: 'Test' });

      expect(queue.hasNext()).toBe(true);
      expect(queue.next()).toBe(task);
    });

    it('should respect dependencies', () => {
      const dep = queue.addTask({ prompt: 'Dependency' });
      const dependent = queue.addTask({
        prompt: 'Dependent',
        dependencies: [dep.id],
      });

      // Should return dep first, not dependent
      expect(queue.next()).toBe(dep);

      // Complete the dependency
      dep.assign('session-1');
      dep.complete();
      queue.updateTask(dep);

      // Now dependent should be available
      expect(queue.next()).toBe(dependent);
    });

    it('should skip tasks with unsatisfied dependencies', () => {
      // Create dependency first but assign it so it's not pending
      const dep = queue.addTask({ prompt: 'Dependency' });
      dep.assign('session-1'); // Make it running, not pending

      const dependent = queue.addTask({
        prompt: 'Dependent',
        dependencies: [dep.id],
        priority: 100, // Higher priority but blocked
      });
      const independent = queue.addTask({ prompt: 'Independent', priority: 1 });

      // Should return independent even though dependent has higher priority
      // because dependent is blocked by unsatisfied dependency (dep is running, not completed)
      const next = queue.next();
      expect(next?.prompt).toBe('Independent');
    });
  });

  describe('getTasksBySession', () => {
    it('should return tasks assigned to a specific session', () => {
      const task1 = queue.addTask({ prompt: 'Task 1' });
      const task2 = queue.addTask({ prompt: 'Task 2' });
      const task3 = queue.addTask({ prompt: 'Task 3' });

      task1.assign('session-1');
      task2.assign('session-2');
      task3.assign('session-1');

      const session1Tasks = queue.getTasksBySession('session-1');

      expect(session1Tasks).toHaveLength(2);
      expect(session1Tasks).toContain(task1);
      expect(session1Tasks).toContain(task3);
    });
  });

  describe('getRunningTaskForSession', () => {
    it('should return the running task for a session', () => {
      const task1 = queue.addTask({ prompt: 'Task 1' });
      const task2 = queue.addTask({ prompt: 'Task 2' });

      task1.assign('session-1');
      task2.assign('session-2');

      expect(queue.getRunningTaskForSession('session-1')).toBe(task1);
      expect(queue.getRunningTaskForSession('session-2')).toBe(task2);
    });

    it('should return null if no running task for session', () => {
      expect(queue.getRunningTaskForSession('session-1')).toBeNull();
    });
  });

  describe('getCount', () => {
    it('should return correct counts', () => {
      const task1 = queue.addTask({ prompt: 'Pending' });
      const task2 = queue.addTask({ prompt: 'Running' });
      const task3 = queue.addTask({ prompt: 'Completed' });
      const task4 = queue.addTask({ prompt: 'Failed' });

      task2.assign('session-1');
      task3.assign('session-2');
      task3.complete();
      task4.assign('session-3');
      task4.fail('Error');

      const counts = queue.getCount();

      expect(counts.total).toBe(4);
      expect(counts.pending).toBe(1);
      expect(counts.running).toBe(1);
      expect(counts.completed).toBe(1);
      expect(counts.failed).toBe(1);
    });
  });

  describe('clearCompleted', () => {
    it('should remove all completed tasks', () => {
      const task1 = queue.addTask({ prompt: 'Completed 1' });
      const task2 = queue.addTask({ prompt: 'Completed 2' });
      const task3 = queue.addTask({ prompt: 'Pending' });

      task1.assign('session-1');
      task1.complete();
      task2.assign('session-2');
      task2.complete();

      const removed = queue.clearCompleted();

      expect(removed).toBe(2);
      expect(queue.getAllTasks()).toHaveLength(1);
      expect(queue.getTask(task3.id)).toBe(task3);
    });
  });

  describe('clearFailed', () => {
    it('should remove all failed tasks', () => {
      const task1 = queue.addTask({ prompt: 'Failed 1' });
      const task2 = queue.addTask({ prompt: 'Failed 2' });
      const task3 = queue.addTask({ prompt: 'Pending' });

      task1.assign('session-1');
      task1.fail('Error 1');
      task2.assign('session-2');
      task2.fail('Error 2');

      const removed = queue.clearFailed();

      expect(removed).toBe(2);
      expect(queue.getAllTasks()).toHaveLength(1);
      expect(queue.getTask(task3.id)).toBe(task3);
    });
  });

  describe('clearAll', () => {
    it('should remove all tasks', () => {
      queue.addTask({ prompt: 'Task 1' });
      queue.addTask({ prompt: 'Task 2' });
      queue.addTask({ prompt: 'Task 3' });

      const removed = queue.clearAll();

      expect(removed).toBe(3);
      expect(queue.getAllTasks()).toHaveLength(0);
    });
  });
});

describe('getTaskQueue singleton', () => {
  it('should return a TaskQueue instance', () => {
    const queue = getTaskQueue();
    expect(queue).toBeInstanceOf(TaskQueue);
  });
});