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

import {
  RedisTaskRepository,
  TaskAlreadyExistsError,
  TaskTransitionError,
  type RedisTaskClient,
  type RedisTaskTransaction,
} from '../src/task-repository.js';

class NoopRedisTransaction implements RedisTaskTransaction {
  private readonly operations: (
    | {
        readonly type: 'set';
        readonly key: string;
        readonly value: string;
        readonly mode?: 'NX' | 'XX';
      }
    | {
        readonly type: 'sadd';
        readonly key: string;
        readonly member: string;
      }
  )[] = [];

  public constructor(
    private readonly kv: Map<string, string>,
    private readonly sets: Map<string, Set<string>>,
  ) {}

  public set(key: string, value: string, mode?: 'NX' | 'XX'): RedisTaskTransaction {
    this.operations.push({
      type: 'set',
      key,
      value,
      mode,
    });
    return this;
  }

  public sadd(key: string, member: string): RedisTaskTransaction {
    this.operations.push({
      type: 'sadd',
      key,
      member,
    });
    return this;
  }

  public exec(): Promise<readonly (readonly [Error | null, unknown])[] | null> {
    const results: (readonly [Error | null, unknown])[] = [];

    for (const operation of this.operations) {
      if (operation.type === 'set') {
        const exists = this.kv.has(operation.key);

        if (operation.mode === 'NX' && exists) {
          results.push([null, null]);
          continue;
        }

        if (operation.mode === 'XX' && !exists) {
          results.push([null, null]);
          continue;
        }

        this.kv.set(operation.key, operation.value);
        results.push([null, 'OK']);
        continue;
      }

      const values = this.sets.get(operation.key) ?? new Set<string>();
      const beforeSize = values.size;

      values.add(operation.member);
      this.sets.set(operation.key, values);
      results.push([null, values.size === beforeSize ? 0 : 1]);
    }

    return Promise.resolve(results);
  }
}

class InMemoryRedisClient implements RedisTaskClient {
  private readonly kv = new Map<string, string>();
  private readonly sets = new Map<string, Set<string>>();

  public get(key: string): Promise<string | null> {
    return Promise.resolve(this.kv.get(key) ?? null);
  }

  public mget(...keys: string[]): Promise<(string | null)[]> {
    return Promise.resolve(keys.map((key) => this.kv.get(key) ?? null));
  }

  public set(
    key: string,
    value: string,
    mode?: 'NX' | 'XX',
  ): Promise<'OK' | null> {
    const exists = this.kv.has(key);

    if (mode === 'NX' && exists) {
      return Promise.resolve(null);
    }

    if (mode === 'XX' && !exists) {
      return Promise.resolve(null);
    }

    this.kv.set(key, value);
    return Promise.resolve('OK');
  }

  public smembers(key: string): Promise<string[]> {
    return Promise.resolve([...(this.sets.get(key) ?? new Set<string>())]);
  }

  public sadd(key: string, member: string): Promise<number> {
    const values = this.sets.get(key) ?? new Set<string>();
    const beforeSize = values.size;

    values.add(member);
    this.sets.set(key, values);

    return Promise.resolve(values.size === beforeSize ? 0 : 1);
  }

  public watch(): Promise<'OK'> {
    return Promise.resolve('OK');
  }

  public unwatch(): Promise<'OK'> {
    return Promise.resolve('OK');
  }

  public multi(): RedisTaskTransaction {
    return new NoopRedisTransaction(this.kv, this.sets);
  }
}

class MgetTrackingRedisClient extends InMemoryRedisClient {
  public getCalls = 0;
  public mgetCalls = 0;
  public lastMgetKeys: string[] = [];

  public override get(key: string): Promise<string | null> {
    this.getCalls += 1;
    return super.get(key);
  }

  public override mget(...keys: string[]): Promise<(string | null)[]> {
    this.mgetCalls += 1;
    this.lastMgetKeys = [...keys];
    return super.mget(...keys);
  }
}

describe('RedisTaskRepository CRUD', () => {
  it('creates and fetches a task with defaults', async () => {
    const repository = new RedisTaskRepository({
      client: new InMemoryRedisClient(),
      now: () => 1_700_000_000_000,
    });

    const created = await repository.create({
      project: 'queue',
      mission: 'phase1',
      taskId: 'MQ-003',
      title: 'Implement task CRUD',
    });

    const fetched = await repository.get('MQ-003');

    expect(created.id).toBe('MQ-003');
    expect(created.status).toBe('pending');
    expect(created.priority).toBe('medium');
    expect(created.lane).toBe('any');
    expect(created.dependencies).toEqual([]);
    expect(created.createdAt).toBe(1_700_000_000_000);
    expect(fetched).toEqual(created);
  });

  it('throws when creating a duplicate task id', async () => {
    const repository = new RedisTaskRepository({
      client: new InMemoryRedisClient(),
    });

    await repository.create({
      project: 'queue',
      mission: 'phase1',
      taskId: 'MQ-003',
      title: 'First task',
    });

    await expect(
      repository.create({
        project: 'queue',
        mission: 'phase1',
        taskId: 'MQ-003',
        title: 'Duplicate',
      }),
    ).rejects.toBeInstanceOf(TaskAlreadyExistsError);
  });

  it('lists tasks and filters by project, mission, and status', async () => {
    const repository = new RedisTaskRepository({
      client: new InMemoryRedisClient(),
    });

    await repository.create({
      project: 'queue',
      mission: 'phase1',
      taskId: 'MQ-003A',
      title: 'Pending task',
    });

    await repository.create({
      project: 'queue',
      mission: 'phase2',
      taskId: 'MQ-003B',
      title: 'Claimed task',
    });

    await repository.claim('MQ-003B', {
      agentId: 'agent-a',
      ttlSeconds: 60,
    });

    const byProject = await repository.list({
      project: 'queue',
    });
    const byMission = await repository.list({
      mission: 'phase2',
    });
    const byStatus = await repository.list({
      status: 'claimed',
    });

    expect(byProject).toHaveLength(2);
    expect(byMission.map((task) => task.taskId)).toEqual(['MQ-003B']);
    expect(byStatus.map((task) => task.taskId)).toEqual(['MQ-003B']);
  });

  it('lists 3+ tasks with a single mget call', async () => {
    const client = new MgetTrackingRedisClient();
    const repository = new RedisTaskRepository({
      client,
    });

    await repository.create({
      project: 'queue',
      mission: 'phase-list',
      taskId: 'MQ-MGET-001',
      title: 'Task one',
    });
    await repository.create({
      project: 'queue',
      mission: 'phase-list',
      taskId: 'MQ-MGET-002',
      title: 'Task two',
    });
    await repository.create({
      project: 'queue',
      mission: 'phase-list',
      taskId: 'MQ-MGET-003',
      title: 'Task three',
    });

    const tasks = await repository.list();

    expect(tasks).toHaveLength(3);
    expect(client.mgetCalls).toBe(1);
    expect(client.getCalls).toBe(0);
    expect(client.lastMgetKeys).toHaveLength(3);
  });

  it('updates mutable fields and preserves immutable fields', async () => {
    const repository = new RedisTaskRepository({
      client: new InMemoryRedisClient(),
      now: () => 1_700_000_000_001,
    });

    await repository.create({
      project: 'queue',
      mission: 'phase1',
      taskId: 'MQ-003',
      title: 'Original title',
      description: 'Original description',
    });

    const updated = await repository.update('MQ-003', {
      title: 'Updated title',
      description: 'Updated description',
      priority: 'high',
      lane: 'coding',
      dependencies: ['MQ-002'],
      metadata: {
        source: 'unit-test',
      },
    });

    expect(updated.title).toBe('Updated title');
    expect(updated.description).toBe('Updated description');
    expect(updated.priority).toBe('high');
    expect(updated.lane).toBe('coding');
    expect(updated.dependencies).toEqual(['MQ-002']);
    expect(updated.metadata).toEqual({ source: 'unit-test' });
    expect(updated.project).toBe('queue');
    expect(updated.taskId).toBe('MQ-003');
    expect(updated.updatedAt).toBe(1_700_000_000_001);
  });

  it('rejects status transitions through update()', async () => {
    const repository = new RedisTaskRepository({
      client: new InMemoryRedisClient(),
    });

    await repository.create({
      project: 'queue',
      mission: 'phase1',
      taskId: 'MQ-003-TRANSITION',
      title: 'Transition guard',
    });

    await expect(
      repository.update('MQ-003-TRANSITION', {
        status: 'completed',
      }),
    ).rejects.toBeInstanceOf(TaskTransitionError);
  });
});