/**
 * Unit tests for src/core/writer.ts
 *
 * All Postgres I/O is mocked — no real database required. The integration test
 * (task 1.10) covers byte-level round-trip including TimescaleDB hypertable.
 *
 * Covers:
 *  - Happy path: all records inserted (all appear in RETURNING rows)
 *  - Duplicate-key: ON CONFLICT DO NOTHING → records absent from RETURNING → 'duplicate'
 *  - Mixed: half new, half duplicate
 *  - Pool error: all records in the batch get 'failed'; error is attached
 *  - Chunking: batch larger than WRITE_BATCH_SIZE results in multiple queries
 *  - Bigint attribute is stringified before serialization
 *  - Buffer attribute is base64-encoded before serialization
 *  - Empty batch returns empty results
 *  - SQL parameter order: device_id, ts, latitude, longitude, altitude, angle,
 *    speed, satellites, priority, codec, attributes
 */

import { describe, it, expect, vi } from 'vitest';
import type { Logger } from 'pino';
import type { Pool } from 'pg';
import type { Config } from '../src/config/load.js';
import type { Metrics, Position } from '../src/core/types.js';
import type { ConsumedRecord } from '../src/core/consumer.js';
import { createWriter } from '../src/core/writer.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 {
  return {
    inc: vi.fn(),
    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,
  };
}

function makePosition(deviceId: string, overrides: Partial<Position> = {}): Position {
  return {
    device_id: deviceId,
    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 makeRecord(id: string, deviceId: string, overrides: Partial<Position> = {}): ConsumedRecord {
  return {
    id,
    position: makePosition(deviceId, overrides),
    codec: '8',
    ts: '2024-05-01T12:00:00.000Z',
  };
}

/**
 * Creates a mock pg.Pool whose query() returns the given rows.
 * Captures all SQL and params for assertion.
 */
function makeMockPool(
  queryResponses: Array<{ rows: unknown[] } | Error>,
): {
  pool: Pool;
  queryCalls: Array<{ sql: string; params: unknown[] }>;
} {
  const queryCalls: Array<{ sql: string; params: unknown[] }> = [];
  let callIndex = 0;

  const query = vi.fn(async (sql: string, params: unknown[] = []) => {
    queryCalls.push({ sql, params });
    const response = queryResponses[callIndex++];
    if (response instanceof Error) throw response;
    return response ?? { rows: [] };
  });

  return {
    pool: { query } as unknown as Pool,
    queryCalls,
  };
}

// ---------------------------------------------------------------------------
// Tests — happy path
// ---------------------------------------------------------------------------

describe('createWriter — happy path', () => {
  it('returns inserted for all records when all appear in RETURNING', async () => {
    const ts = new Date('2024-05-01T12:00:00.000Z');
    const records = [
      makeRecord('1-0', 'DEV001', { timestamp: ts }),
      makeRecord('1-1', 'DEV002', { timestamp: ts }),
    ];

    const { pool } = makeMockPool([
      {
        rows: [
          { device_id: 'DEV001', ts },
          { device_id: 'DEV002', ts },
        ],
      },
    ]);

    const writer = createWriter(pool, makeConfig(), makeSilentLogger(), makeMetrics());
    const results = await writer.write(records);

    expect(results).toHaveLength(2);
    expect(results[0]).toEqual({ id: '1-0', status: 'inserted' });
    expect(results[1]).toEqual({ id: '1-1', status: 'inserted' });
  });

  it('returns duplicate for records absent from RETURNING', async () => {
    const ts = new Date('2024-05-01T12:00:00.000Z');
    const records = [
      makeRecord('2-0', 'DEV003', { timestamp: ts }),
      makeRecord('2-1', 'DEV004', { timestamp: ts }),
    ];

    // Only DEV003 returned — DEV004 was a conflict
    const { pool } = makeMockPool([{ rows: [{ device_id: 'DEV003', ts }] }]);

    const writer = createWriter(pool, makeConfig(), makeSilentLogger(), makeMetrics());
    const results = await writer.write(records);

    expect(results).toHaveLength(2);
    expect(results.find((r) => r.id === '2-0')?.status).toBe('inserted');
    expect(results.find((r) => r.id === '2-1')?.status).toBe('duplicate');
  });

  it('handles mixed batch: some inserted, some duplicate', async () => {
    const ts = new Date('2024-05-01T12:00:00.000Z');
    const records = [
      makeRecord('3-0', 'DEV005', { timestamp: ts }),
      makeRecord('3-1', 'DEV006', { timestamp: ts }),
      makeRecord('3-2', 'DEV007', { timestamp: ts }),
      makeRecord('3-3', 'DEV008', { timestamp: ts }),
    ];

    // DEV005 and DEV007 are new; DEV006 and DEV008 are duplicates
    const { pool } = makeMockPool([
      {
        rows: [
          { device_id: 'DEV005', ts },
          { device_id: 'DEV007', ts },
        ],
      },
    ]);

    const writer = createWriter(pool, makeConfig(), makeSilentLogger(), makeMetrics());
    const results = await writer.write(records);

    expect(results.find((r) => r.id === '3-0')?.status).toBe('inserted');
    expect(results.find((r) => r.id === '3-1')?.status).toBe('duplicate');
    expect(results.find((r) => r.id === '3-2')?.status).toBe('inserted');
    expect(results.find((r) => r.id === '3-3')?.status).toBe('duplicate');
  });

  it('returns empty array for empty input', async () => {
    const { pool } = makeMockPool([]);
    const writer = createWriter(pool, makeConfig(), makeSilentLogger(), makeMetrics());
    const results = await writer.write([]);
    expect(results).toEqual([]);
  });
});

// ---------------------------------------------------------------------------
// Tests — failure handling
// ---------------------------------------------------------------------------

describe('createWriter — pool error', () => {
  it('returns failed for all records in the chunk when pool throws', async () => {
    const ts = new Date('2024-05-01T12:00:00.000Z');
    const records = [
      makeRecord('4-0', 'DEV009', { timestamp: ts }),
      makeRecord('4-1', 'DEV010', { timestamp: ts }),
    ];

    const dbError = new Error('connection terminated unexpectedly');
    const { pool } = makeMockPool([dbError]);

    const writer = createWriter(pool, makeConfig(), makeSilentLogger(), makeMetrics());
    const results = await writer.write(records);

    expect(results).toHaveLength(2);
    for (const result of results) {
      expect(result.status).toBe('failed');
      expect(result.error).toBeDefined();
      expect(result.error?.message).toBe('connection terminated unexpectedly');
    }
  });

  it('logs error and increments failed metric on pool error', async () => {
    const records = [makeRecord('5-0', 'DEV011')];
    const { pool } = makeMockPool([new Error('timeout')]);
    const logger = makeSilentLogger();
    const metrics = makeMetrics();

    const writer = createWriter(pool, makeConfig(), logger, metrics);
    await writer.write(records);

    expect(logger.error).toHaveBeenCalled();
    expect(metrics.inc).toHaveBeenCalledWith(
      'processor_position_writes_total',
      { status: 'failed' },
      records.length,
    );
  });
});

// ---------------------------------------------------------------------------
// Tests — chunking
// ---------------------------------------------------------------------------

describe('createWriter — chunking', () => {
  it('splits a batch larger than WRITE_BATCH_SIZE into multiple sequential queries', async () => {
    const writeBatchSize = 3;
    const config = makeConfig({ WRITE_BATCH_SIZE: writeBatchSize });
    const ts = new Date('2024-05-01T12:00:00.000Z');

    // 7 records → ceil(7/3) = 3 chunks: [3, 3, 1]
    const records = Array.from({ length: 7 }, (_, i) =>
      makeRecord(`6-${i}`, `DEV${100 + i}`, { timestamp: ts }),
    );

    const { pool, queryCalls } = makeMockPool([
      { rows: records.slice(0, 3).map((r) => ({ device_id: r.position.device_id, ts })) },
      { rows: records.slice(3, 6).map((r) => ({ device_id: r.position.device_id, ts })) },
      { rows: records.slice(6).map((r) => ({ device_id: r.position.device_id, ts })) },
    ]);

    const writer = createWriter(pool, config, makeSilentLogger(), makeMetrics());
    const results = await writer.write(records);

    // 3 separate queries issued
    expect(queryCalls).toHaveLength(3);
    // All 7 records should be returned
    expect(results).toHaveLength(7);
    for (const result of results) {
      expect(result.status).toBe('inserted');
    }
  });

  it('first chunk fails, second chunk succeeds — correct per-record status', async () => {
    const writeBatchSize = 2;
    const config = makeConfig({ WRITE_BATCH_SIZE: writeBatchSize });
    const ts = new Date('2024-05-01T12:00:00.000Z');

    const records = Array.from({ length: 4 }, (_, i) =>
      makeRecord(`7-${i}`, `DEV${200 + i}`, { timestamp: ts }),
    );

    const { pool } = makeMockPool([
      new Error('chunk 1 failed'),
      {
        rows: records.slice(2).map((r) => ({ device_id: r.position.device_id, ts })),
      },
    ]);

    const writer = createWriter(pool, config, makeSilentLogger(), makeMetrics());
    const results = await writer.write(records);

    expect(results[0]?.status).toBe('failed');
    expect(results[1]?.status).toBe('failed');
    expect(results[2]?.status).toBe('inserted');
    expect(results[3]?.status).toBe('inserted');
  });
});

// ---------------------------------------------------------------------------
// Tests — attribute serialization
// ---------------------------------------------------------------------------

describe('createWriter — attribute serialization', () => {
  it('serializes bigint attributes as decimal strings in the attributes JSON', async () => {
    const ts = new Date('2024-05-01T12:00:00.000Z');
    const u64Max = BigInt('18446744073709551615');
    const records = [
      makeRecord('8-0', 'DEV020', {
        timestamp: ts,
        attributes: { io_240: u64Max },
      }),
    ];

    let capturedParams: unknown[] = [];
    const query = vi.fn(async (sql: string, params: unknown[]) => {
      capturedParams = params;
      return { rows: [{ device_id: 'DEV020', ts }] };
    });
    const pool = { query } as unknown as Pool;

    const writer = createWriter(pool, makeConfig(), makeSilentLogger(), makeMetrics());
    await writer.write(records);

    // The attributes param is the 11th per row (index 10)
    const attributesParam = capturedParams[10] as string;
    expect(typeof attributesParam).toBe('string');
    const parsed = JSON.parse(attributesParam) as Record<string, unknown>;
    expect(parsed['io_240']).toBe('18446744073709551615');
    // Must be a string, not a bigint (JSON can't hold bigints)
    expect(typeof parsed['io_240']).toBe('string');
  });

  it('serializes Buffer attributes as base64 strings in the attributes JSON', async () => {
    const ts = new Date('2024-05-01T12:00:00.000Z');
    const rawBytes = Buffer.from([0xde, 0xad, 0xbe, 0xef]);
    const records = [
      makeRecord('9-0', 'DEV021', {
        timestamp: ts,
        attributes: { io_nx: rawBytes },
      }),
    ];

    let capturedParams: unknown[] = [];
    const query = vi.fn(async (sql: string, params: unknown[]) => {
      capturedParams = params;
      return { rows: [{ device_id: 'DEV021', ts }] };
    });
    const pool = { query } as unknown as Pool;

    const writer = createWriter(pool, makeConfig(), makeSilentLogger(), makeMetrics());
    await writer.write(records);

    const attributesParam = capturedParams[10] as string;
    expect(typeof attributesParam).toBe('string');
    const parsed = JSON.parse(attributesParam) as Record<string, unknown>;
    const b64 = parsed['io_nx'];
    expect(typeof b64).toBe('string');
    // Decode and verify byte equality
    const decoded = Buffer.from(b64 as string, 'base64');
    expect(decoded).toEqual(rawBytes);
  });

  it('serializes numeric attributes as-is in the attributes JSON', async () => {
    const ts = new Date('2024-05-01T12:00:00.000Z');
    const records = [
      makeRecord('10-0', 'DEV022', {
        timestamp: ts,
        attributes: { io_21: 42, io_1: 0 },
      }),
    ];

    let capturedParams: unknown[] = [];
    const query = vi.fn(async (sql: string, params: unknown[]) => {
      capturedParams = params;
      return { rows: [{ device_id: 'DEV022', ts }] };
    });
    const pool = { query } as unknown as Pool;

    const writer = createWriter(pool, makeConfig(), makeSilentLogger(), makeMetrics());
    await writer.write(records);

    const attributesParam = capturedParams[10] as string;
    const parsed = JSON.parse(attributesParam) as Record<string, unknown>;
    expect(parsed['io_21']).toBe(42);
    expect(parsed['io_1']).toBe(0);
  });
});

// ---------------------------------------------------------------------------
// Tests — SQL parameter ordering
// ---------------------------------------------------------------------------

describe('createWriter — SQL parameter ordering', () => {
  it('passes parameters in the correct column order', async () => {
    const ts = new Date('2024-05-01T12:00:00.000Z');
    const position: Position = {
      device_id: 'PARAMTEST001',
      timestamp: ts,
      latitude: 10.0,
      longitude: 20.0,
      altitude: 300,
      angle: 180,
      speed: 75,
      satellites: 9,
      priority: 2,
      attributes: { io_21: 99 },
    };
    const records: ConsumedRecord[] = [{ id: 'p-0', position, codec: '8E', ts: ts.toISOString() }];

    let capturedParams: unknown[] = [];
    const query = vi.fn(async (sql: string, params: unknown[]) => {
      capturedParams = params;
      return { rows: [{ device_id: 'PARAMTEST001', ts }] };
    });
    const pool = { query } as unknown as Pool;

    const writer = createWriter(pool, makeConfig(), makeSilentLogger(), makeMetrics());
    await writer.write(records);

    // Expected column order (11 params for row 0, 1-indexed in SQL, 0-indexed here):
    // $1  device_id
    // $2  ts
    // $3  latitude
    // $4  longitude
    // $5  altitude
    // $6  angle
    // $7  speed
    // $8  satellites
    // $9  priority
    // $10 codec
    // $11 attributes
    expect(capturedParams[0]).toBe('PARAMTEST001');
    expect(capturedParams[1]).toEqual(ts);
    expect(capturedParams[2]).toBe(10.0);
    expect(capturedParams[3]).toBe(20.0);
    expect(capturedParams[4]).toBe(300);
    expect(capturedParams[5]).toBe(180);
    expect(capturedParams[6]).toBe(75);
    expect(capturedParams[7]).toBe(9);
    expect(capturedParams[8]).toBe(2);
    expect(capturedParams[9]).toBe('8E');
    expect(typeof capturedParams[10]).toBe('string');
    const attrs = JSON.parse(capturedParams[10] as string) as Record<string, unknown>;
    expect(attrs['io_21']).toBe(99);
  });

  it('SQL contains ON CONFLICT DO NOTHING and RETURNING clause', async () => {
    const records = [makeRecord('q-0', 'DEV030')];
    let capturedSql = '';
    const query = vi.fn(async (sql: string, _params: unknown[]) => {
      capturedSql = sql;
      return { rows: [{ device_id: 'DEV030', ts: new Date() }] };
    });
    const pool = { query } as unknown as Pool;

    const writer = createWriter(pool, makeConfig(), makeSilentLogger(), makeMetrics());
    await writer.write(records);

    expect(capturedSql).toMatch(/ON CONFLICT.*DO NOTHING/i);
    expect(capturedSql).toMatch(/RETURNING/i);
    expect(capturedSql).toMatch(/device_id/);
    expect(capturedSql).toMatch(/ts/);
  });
});

// ---------------------------------------------------------------------------
// Tests — metrics
// ---------------------------------------------------------------------------

describe('createWriter — metrics', () => {
  it('emits inserted and duplicate counters after a successful write', async () => {
    const ts = new Date('2024-05-01T12:00:00.000Z');
    const records = [
      makeRecord('m-0', 'DEV040', { timestamp: ts }),
      makeRecord('m-1', 'DEV041', { timestamp: ts }),
    ];

    // Only DEV040 returned — DEV041 is duplicate
    const { pool } = makeMockPool([{ rows: [{ device_id: 'DEV040', ts }] }]);
    const metrics = makeMetrics();

    const writer = createWriter(pool, makeConfig(), makeSilentLogger(), metrics);
    await writer.write(records);

    expect(metrics.inc).toHaveBeenCalledWith('processor_position_writes_total', { status: 'inserted' }, 1);
    expect(metrics.inc).toHaveBeenCalledWith('processor_position_writes_total', { status: 'duplicate' }, 1);
    expect(metrics.observe).toHaveBeenCalledWith(
      'processor_position_write_duration_seconds',
      expect.any(Number),
    );
  });
});