/**
 * Unit tests for src/core/consumer.ts
 *
 * All Redis I/O is mocked — no real Redis required. The integration test
 * (task 1.10) covers the end-to-end round-trip.
 *
 * Covers:
 *  - Decodes a synthetic stream entry into a ConsumedRecord with the right shape
 *  - Calls sink with the decoded batch and ACKs only the IDs the sink returned
 *  - Partial ACK: sink returns subset of IDs; only those are ACKed
 *  - BUSYGROUP error from XGROUP CREATE is swallowed and continues
 *  - Malformed payload: increments metric, logs at error, does NOT ACK the entry
 *  - Missing payload field: logs at error, does NOT ACK the entry
 *  - stop() causes the loop to exit cleanly
 *  - XREADGROUP failure logs error and backs off without crashing
 */

import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest';
import type { MockedFunction } from 'vitest';
import type { Redis } from 'ioredis';
import type { Logger } from 'pino';
import type { Config } from '../src/config/load.js';
import type { Metrics, Position } from '../src/core/types.js';

// ---------------------------------------------------------------------------
// Helpers
// ---------------------------------------------------------------------------

function makeSilentLogger(): Logger {
  return {
    debug: vi.fn(),
    info: vi.fn(),
    warn: vi.fn(),
    error: vi.fn(),
    fatal: vi.fn(),
    child: vi.fn().mockReturnThis(),
    trace: vi.fn(),
    level: 'silent',
    silent: vi.fn(),
  } as unknown as Logger;
}

function makeMetrics(): Metrics & {
  incCalls: Array<{ name: string; labels?: Record<string, string> }>;
} {
  const incCalls: Array<{ name: string; labels?: Record<string, string> }> = [];
  return {
    incCalls,
    inc: (name: string, labels?: Record<string, string>) => {
      incCalls.push({ name, labels });
    },
    observe: vi.fn(),
  };
}

function makeConfig(overrides: Partial<Config> = {}): Config {
  return {
    NODE_ENV: 'test',
    INSTANCE_ID: 'test-processor',
    LOG_LEVEL: 'silent',
    REDIS_URL: 'redis://localhost:6379',
    POSTGRES_URL: 'postgres://localhost:5432/test',
    REDIS_TELEMETRY_STREAM: 'telemetry:t',
    REDIS_CONSUMER_GROUP: 'processor',
    REDIS_CONSUMER_NAME: 'test-consumer',
    METRICS_PORT: 9090,
    BATCH_SIZE: 10,
    BATCH_BLOCK_MS: 100,
    WRITE_BATCH_SIZE: 50,
    DEVICE_STATE_LRU_CAP: 1000,
    ...overrides,
  };
}

/**
 * Builds the JSON payload for a synthetic Position, mirroring tcp-ingestion's
 * serialization format (sentinel encoding for bigint/Buffer/Date).
 */
function buildPayload(overrides: Partial<Position> = {}): string {
  const position: Position = {
    device_id: 'TESTDEVICE001',
    timestamp: new Date('2024-05-01T12:00:00.000Z'),
    latitude: 54.6872,
    longitude: 25.2797,
    altitude: 100,
    angle: 90,
    speed: 50,
    satellites: 12,
    priority: 1,
    attributes: {},
    ...overrides,
  };

  function jsonReplacer(_key: string, value: unknown): unknown {
    if (typeof value === 'bigint') return { __bigint: value.toString() };
    if (value instanceof Uint8Array) return { __buffer_b64: Buffer.from(value).toString('base64') };
    if (value instanceof Date) return value.toISOString();
    return value;
  }

  return JSON.stringify(position, jsonReplacer);
}

/**
 * Builds a raw XREADGROUP response for a single entry.
 * ioredis returns: [[streamName, [[entryId, [field, value, ...]], ...]]]
 */
function buildXreadgroupResponse(
  stream: string,
  entries: Array<{ id: string; fields: Record<string, string> }>,
): [string, [string, string[]][]][] {
  return [
    [
      stream,
      entries.map(({ id, fields }) => [
        id,
        Object.entries(fields).flat(),
      ] as [string, string[]]),
    ],
  ];
}

// ---------------------------------------------------------------------------
// Mock ioredis
// ---------------------------------------------------------------------------

type MockRedis = {
  xgroup: MockedFunction<(...args: unknown[]) => Promise<string>>;
  xreadgroup: MockedFunction<(...args: unknown[]) => Promise<unknown>>;
  xack: MockedFunction<(...args: unknown[]) => Promise<number>>;
};

function makeMockRedis(): MockRedis {
  return {
    xgroup: vi.fn().mockResolvedValue('OK'),
    xreadgroup: vi.fn().mockResolvedValue(null), // default: BLOCK timeout
    xack: vi.fn().mockResolvedValue(1),
  };
}

// ---------------------------------------------------------------------------
// ensureConsumerGroup tests
// ---------------------------------------------------------------------------

import { ensureConsumerGroup } from '../src/core/consumer.js';

describe('ensureConsumerGroup', () => {
  it('calls XGROUP CREATE with MKSTREAM and $ start ID', async () => {
    const redis = makeMockRedis();
    const logger = makeSilentLogger();

    await ensureConsumerGroup(redis as unknown as Redis, 'telemetry:t', 'processor', logger);

    expect(redis.xgroup).toHaveBeenCalledWith('CREATE', 'telemetry:t', 'processor', '$', 'MKSTREAM');
    expect(logger.info).toHaveBeenCalledWith(
      expect.objectContaining({ stream: 'telemetry:t', group: 'processor' }),
      'consumer group created',
    );
  });

  it('swallows BUSYGROUP error and logs info', async () => {
    const redis = makeMockRedis();
    redis.xgroup.mockRejectedValue(new Error('BUSYGROUP Consumer Group name already exists'));
    const logger = makeSilentLogger();

    await expect(
      ensureConsumerGroup(redis as unknown as Redis, 'telemetry:t', 'processor', logger),
    ).resolves.toBeUndefined();

    expect(logger.info).toHaveBeenCalledWith(
      expect.objectContaining({ stream: 'telemetry:t', group: 'processor' }),
      'consumer group already exists',
    );
  });

  it('rethrows non-BUSYGROUP errors', async () => {
    const redis = makeMockRedis();
    redis.xgroup.mockRejectedValue(new Error('NOPERM no permissions'));
    const logger = makeSilentLogger();

    await expect(
      ensureConsumerGroup(redis as unknown as Redis, 'telemetry:t', 'processor', logger),
    ).rejects.toThrow('NOPERM no permissions');
  });
});

// ---------------------------------------------------------------------------
// createConsumer tests
// ---------------------------------------------------------------------------

import { createConsumer } from '../src/core/consumer.js';
import type { ConsumedRecord } from '../src/core/consumer.js';

describe('createConsumer — happy path', () => {
  afterEach(() => {
    vi.restoreAllMocks();
    vi.useRealTimers();
  });

  it('decodes a stream entry and passes a ConsumedRecord to the sink', async () => {
    const redis = makeMockRedis();
    const logger = makeSilentLogger();
    const metrics = makeMetrics();
    const config = makeConfig();

    const payload = buildPayload({ device_id: 'DEV001' });
    const stream = 'telemetry:t';
    const entryId = '1714488000000-0';

    // First call: return one entry. Subsequent calls: return null (BLOCK timeout).
    redis.xreadgroup
      .mockResolvedValueOnce(
        buildXreadgroupResponse(stream, [
          { id: entryId, fields: { ts: '2024-05-01T12:00:00.000Z', device_id: 'DEV001', codec: '8', payload } },
        ]),
      )
      .mockResolvedValue(null);

    const receivedRecords: ConsumedRecord[][] = [];
    let consumerRef: ReturnType<typeof createConsumer> | undefined;

    const sink = vi.fn(async (records: ConsumedRecord[]) => {
      receivedRecords.push(records);
      // Stop the consumer after processing the first batch so the loop exits.
      void consumerRef?.stop();
      return records.map((r) => r.id);
    });

    const consumer = createConsumer(
      redis as unknown as Redis,
      config,
      logger,
      metrics,
      sink,
    );
    consumerRef = consumer;

    await consumer.start();
    // Wait for the consumer to process and stop
    await consumer.stop();

    expect(receivedRecords.length).toBeGreaterThanOrEqual(1);
    const firstBatch = receivedRecords[0];
    expect(firstBatch).toBeDefined();
    expect(firstBatch!.length).toBe(1);

    const record = firstBatch![0]!;
    expect(record.id).toBe(entryId);
    expect(record.codec).toBe('8');
    expect(record.ts).toBe('2024-05-01T12:00:00.000Z');
    expect(record.position.device_id).toBe('DEV001');
    expect(record.position.latitude).toBe(54.6872);
  });

  it('ACKs only the IDs returned by the sink (partial ACK)', async () => {
    const redis = makeMockRedis();
    const logger = makeSilentLogger();
    const metrics = makeMetrics();
    const config = makeConfig();

    const stream = 'telemetry:t';
    const ids = ['1000-0', '1000-1', '1000-2'];

    const entries = ids.map((id) => ({
      id,
      fields: {
        ts: '2024-05-01T12:00:00.000Z',
        device_id: `DEV${id}`,
        codec: '8',
        payload: buildPayload({ device_id: `DEV${id}` }),
      },
    }));

    let consumerRef: ReturnType<typeof createConsumer> | undefined;

    redis.xreadgroup
      .mockResolvedValueOnce(buildXreadgroupResponse(stream, entries))
      .mockResolvedValue(null);

    // Sink returns only the first and third IDs — second stays pending
    const sink = vi.fn(async (records: ConsumedRecord[]) => {
      void consumerRef?.stop();
      return [records[0]!.id, records[2]!.id];
    });

    const consumer = createConsumer(
      redis as unknown as Redis,
      config,
      logger,
      metrics,
      sink,
    );
    consumerRef = consumer;

    await consumer.start();
    await consumer.stop();

    expect(redis.xack).toHaveBeenCalledWith(stream, 'processor', ids[0], ids[2]);
    // id[1] must NOT be in any xack call
    const xackCalls = redis.xack.mock.calls.flat();
    expect(xackCalls).not.toContain(ids[1]);
  });

  it('does not call xack when sink returns an empty array', async () => {
    const redis = makeMockRedis();
    const logger = makeSilentLogger();
    const metrics = makeMetrics();
    const config = makeConfig();

    const stream = 'telemetry:t';
    let consumerRef: ReturnType<typeof createConsumer> | undefined;

    redis.xreadgroup
      .mockResolvedValueOnce(
        buildXreadgroupResponse(stream, [
          {
            id: '2000-0',
            fields: {
              ts: '2024-05-01T12:00:00.000Z',
              device_id: 'DEV002',
              codec: '8',
              payload: buildPayload({ device_id: 'DEV002' }),
            },
          },
        ]),
      )
      .mockResolvedValue(null);

    const sink = vi.fn(async (_records: ConsumedRecord[]) => {
      void consumerRef?.stop();
      return [];
    });

    const consumer = createConsumer(
      redis as unknown as Redis,
      config,
      logger,
      metrics,
      sink,
    );
    consumerRef = consumer;

    await consumer.start();
    await consumer.stop();

    expect(redis.xack).not.toHaveBeenCalled();
  });
});

describe('createConsumer — decode errors', () => {
  afterEach(() => {
    vi.restoreAllMocks();
  });

  it('skips malformed payload: increments metric, logs error, does not ACK', async () => {
    const redis = makeMockRedis();
    const logger = makeSilentLogger();
    const metrics = makeMetrics();
    const config = makeConfig();

    const stream = 'telemetry:t';
    const badId = '3000-0';
    let consumerRef: ReturnType<typeof createConsumer> | undefined;

    redis.xreadgroup
      .mockResolvedValueOnce(
        buildXreadgroupResponse(stream, [
          {
            id: badId,
            fields: {
              ts: '2024-05-01T12:00:00.000Z',
              device_id: 'DEV003',
              codec: '8',
              payload: 'not valid json {{{',
            },
          },
        ]),
      )
      .mockResolvedValue(null);

    const sink = vi.fn(async (_records: ConsumedRecord[]) => {
      void consumerRef?.stop();
      return [];
    });

    const consumer = createConsumer(
      redis as unknown as Redis,
      config,
      logger,
      metrics,
      sink,
    );
    consumerRef = consumer;

    await consumer.start();
    await consumer.stop();

    // Decode error metric incremented
    expect(metrics.incCalls.some((c) => c.name === 'processor_decode_errors_total')).toBe(true);

    // Logged at error
    expect(logger.error).toHaveBeenCalled();

    // Sink was called with empty records (bad entry filtered out)
    expect(sink).toHaveBeenCalledWith([]);

    // No XACK for the bad entry
    expect(redis.xack).not.toHaveBeenCalledWith(stream, 'processor', badId);
  });

  it('skips entry with missing payload field: increments metric, logs error, does not ACK', async () => {
    const redis = makeMockRedis();
    const logger = makeSilentLogger();
    const metrics = makeMetrics();
    const config = makeConfig();

    const stream = 'telemetry:t';
    const badId = '3001-0';
    let consumerRef: ReturnType<typeof createConsumer> | undefined;

    redis.xreadgroup
      .mockResolvedValueOnce(
        buildXreadgroupResponse(stream, [
          {
            id: badId,
            // No payload field
            fields: { ts: '2024-05-01T12:00:00.000Z', device_id: 'DEV004', codec: '8' },
          },
        ]),
      )
      .mockResolvedValue(null);

    const sink = vi.fn(async (_records: ConsumedRecord[]) => {
      void consumerRef?.stop();
      return [];
    });

    const consumer = createConsumer(
      redis as unknown as Redis,
      config,
      logger,
      metrics,
      sink,
    );
    consumerRef = consumer;

    await consumer.start();
    await consumer.stop();

    expect(metrics.incCalls.some((c) => c.name === 'processor_decode_errors_total')).toBe(true);
    expect(logger.error).toHaveBeenCalled();
    expect(redis.xack).not.toHaveBeenCalled();
  });

  it('valid and invalid entries in the same batch: ACKs only valid ones', async () => {
    const redis = makeMockRedis();
    const logger = makeSilentLogger();
    const metrics = makeMetrics();
    const config = makeConfig();

    const stream = 'telemetry:t';
    const goodId = '4000-0';
    const badId = '4000-1';
    let consumerRef: ReturnType<typeof createConsumer> | undefined;

    redis.xreadgroup
      .mockResolvedValueOnce(
        buildXreadgroupResponse(stream, [
          {
            id: goodId,
            fields: {
              ts: '2024-05-01T12:00:00.000Z',
              device_id: 'DEV005',
              codec: '8',
              payload: buildPayload({ device_id: 'DEV005' }),
            },
          },
          {
            id: badId,
            fields: {
              ts: '2024-05-01T12:00:00.000Z',
              device_id: 'DEV005',
              codec: '8',
              payload: 'not json',
            },
          },
        ]),
      )
      .mockResolvedValue(null);

    const sink = vi.fn(async (records: ConsumedRecord[]) => {
      void consumerRef?.stop();
      return records.map((r) => r.id);
    });

    const consumer = createConsumer(
      redis as unknown as Redis,
      config,
      logger,
      metrics,
      sink,
    );
    consumerRef = consumer;

    await consumer.start();
    await consumer.stop();

    // Sink received only the good record
    expect(sink).toHaveBeenCalledWith(
      expect.arrayContaining([expect.objectContaining({ id: goodId })]),
    );
    expect(sink).toHaveBeenCalledWith(
      expect.not.arrayContaining([expect.objectContaining({ id: badId })]),
    );

    // ACK called for good entry only
    expect(redis.xack).toHaveBeenCalledWith(stream, 'processor', goodId);
    const xackArgs = redis.xack.mock.calls.flat();
    expect(xackArgs).not.toContain(badId);
  });
});

describe('createConsumer — XREADGROUP failure', () => {
  beforeEach(() => {
    vi.useFakeTimers();
  });

  afterEach(() => {
    vi.useRealTimers();
    vi.restoreAllMocks();
  });

  it('backs off and retries after XREADGROUP error', async () => {
    const redis = makeMockRedis();
    const logger = makeSilentLogger();
    const metrics = makeMetrics();
    const config = makeConfig({ BATCH_BLOCK_MS: 10 });

    let consumerRef: ReturnType<typeof createConsumer> | undefined;

    let callCount = 0;
    redis.xreadgroup.mockImplementation(async () => {
      callCount++;
      if (callCount === 1) {
        throw new Error('LOADING Redis is loading the dataset in memory');
      }
      // Stop consumer on second call
      void consumerRef?.stop();
      return null;
    });

    const sink = vi.fn(async () => []);

    const consumer = createConsumer(
      redis as unknown as Redis,
      config,
      logger,
      metrics,
      sink,
    );
    consumerRef = consumer;

    await consumer.start();

    // Advance timers past the 1000ms backoff
    await vi.advanceTimersByTimeAsync(1_100);
    await consumer.stop();

    expect(logger.error).toHaveBeenCalledWith(
      expect.objectContaining({ err: expect.anything() }),
      'XREADGROUP failed; backing off',
    );

    // Should have retried at least once
    expect(callCount).toBeGreaterThanOrEqual(2);
  });
});

describe('createConsumer — clean stop', () => {
  afterEach(() => {
    vi.restoreAllMocks();
  });

  it('stop() returns after current batch completes', async () => {
    const redis = makeMockRedis();
    const logger = makeSilentLogger();
    const metrics = makeMetrics();
    const config = makeConfig();

    // Return null immediately (BLOCK timeout) so the loop spins and we can stop it
    redis.xreadgroup.mockResolvedValue(null);

    const sink = vi.fn(async () => []);

    const consumer = createConsumer(
      redis as unknown as Redis,
      config,
      logger,
      metrics,
      sink,
    );

    await consumer.start();

    // stop() should resolve without hanging
    await expect(consumer.stop()).resolves.toBeUndefined();
  });
});