// src/lib/logger.ts
import winston from 'winston';

const logger = winston.createLogger({
  level: process.env.LOG_LEVEL || 'info',
  format: winston.format.combine(
    winston.format.timestamp(),
    winston.format.errors({ stack: true }),
    winston.format.json()
  ),
  defaultMeta: {
    service: 'my-app',
    environment: process.env.NODE_ENV,
  },
  transports: [
    // Console for development
    new winston.transports.Console({
      format: process.env.NODE_ENV === 'development'
        ? winston.format.combine(
            winston.format.colorize(),
            winston.format.simple()
          )
        : winston.format.json(),
    }),
  ],
});

// Add request context
export function createRequestLogger(requestId: string, userId?: string) {
  return logger.child({
    requestId,
    userId,
  });
}

export { logger };

// src/lib/logger.ts
import pino from 'pino';

export const logger = pino({
  level: process.env.LOG_LEVEL || 'info',
  transport: process.env.NODE_ENV === 'development'
    ? {
        target: 'pino-pretty',
        options: {
          colorize: true,
          translateTime: 'SYS:standard',
        },
      }
    : undefined,
  base: {
    service: 'my-app',
    env: process.env.NODE_ENV,
  },
  redact: {
    paths: ['password', 'token', 'apiKey', '*.password', '*.token'],
    censor: '[REDACTED]',
  },
});

// Request-scoped logger
export function requestLogger(requestId: string, userId?: string) {
  return logger.child({ requestId, userId });
}

// DO: Include context
logger.info('User signed up', {
  userId: user.id,
  email: user.email,
  plan: 'free',
  source: 'web',
});

// DO: Log errors with stack traces
logger.error('Payment failed', {
  error: err.message,
  stack: err.stack,
  userId: user.id,
  amount: 99.99,
  provider: 'stripe',
});

// DO: Use appropriate levels
logger.debug('Database query', {
  query: 'SELECT * FROM users WHERE id = ?',
  duration: 45,
  rows: 1,
});

// DON'T: Log sensitive data
// BAD: logger.info('Login', { password: user.password })

// DON'T: Use string concatenation
// BAD: logger.info('User ' + user.id + ' signed up')

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-- Query Postgres logs
SELECT *
FROM postgres_logs
WHERE timestamp > now() - interval '1 hour'
  AND error_severity = 'ERROR'
ORDER BY timestamp DESC
LIMIT 100;

-- Query auth logs
SELECT *
FROM auth.audit_log_entries
WHERE timestamp > now() - interval '24 hours'
  AND payload->>'action' = 'login'
ORDER BY timestamp DESC;

-- Find slow queries
SELECT
  query,
  calls,
  mean_exec_time,
  total_exec_time
FROM pg_stat_statements
ORDER BY mean_exec_time DESC
LIMIT 20;

// Error pattern analyzer
interface ErrorPattern {
  pattern: RegExp;
  category: string;
  severity: 'critical' | 'high' | 'medium' | 'low';
  suggestion: string;
}

const errorPatterns: ErrorPattern[] = [
  {
    pattern: /ECONNREFUSED|connection refused/i,
    category: 'connectivity',
    severity: 'critical',
    suggestion: 'Check if the target service is running and accessible',
  },
  {
    pattern: /timeout|ETIMEDOUT/i,
    category: 'timeout',
    severity: 'high',
    suggestion: 'Increase timeout or check for slow operations',
  },
  {
    pattern: /out of memory|heap|OOM/i,
    category: 'memory',
    severity: 'critical',
    suggestion: 'Increase memory allocation or fix memory leak',
  },
  {
    pattern: /rate.?limit|429|too many requests/i,
    category: 'rate-limiting',
    severity: 'medium',
    suggestion: 'Implement backoff strategy or increase rate limits',
  },
  {
    pattern: /unauthorized|401|invalid.?token/i,
    category: 'auth',
    severity: 'medium',
    suggestion: 'Check authentication credentials or token expiry',
  },
  {
    pattern: /not.?found|404/i,
    category: 'not-found',
    severity: 'low',
    suggestion: 'Verify resource exists or check URL',
  },
];

function categorizeError(message: string): ErrorPattern | null {
  for (const pattern of errorPatterns) {
    if (pattern.pattern.test(message)) {
      return pattern;
    }
  }
  return null;
}

// scripts/analyze-logs.ts
import * as readline from 'readline';
import * as fs from 'fs';

interface LogEntry {
  timestamp: string;
  level: string;
  message: string;
  error?: {
    message: string;
    code?: string;
  };
  [key: string]: any;
}

interface LogSummary {
  totalEntries: number;
  byLevel: Record<string, number>;
  errorMessages: Record<string, number>;
  timeRange: {
    start: string;
    end: string;
  };
}

async function analyzeLogs(filePath: string): Promise<LogSummary> {
  const summary: LogSummary = {
    totalEntries: 0,
    byLevel: {},
    errorMessages: {},
    timeRange: { start: '', end: '' },
  };

  const fileStream = fs.createReadStream(filePath);
  const rl = readline.createInterface({
    input: fileStream,
    crlfDelay: Infinity,
  });

  for await (const line of rl) {
    try {
      const entry: LogEntry = JSON.parse(line);
      summary.totalEntries++;

      // Count by level
      summary.byLevel[entry.level] = (summary.byLevel[entry.level] || 0) + 1;

      // Track error messages
      if (entry.level === 'error' && entry.error?.message) {
        const msg = entry.error.message.substring(0, 100);
        summary.errorMessages[msg] = (summary.errorMessages[msg] || 0) + 1;
      }

      // Track time range
      if (!summary.timeRange.start || entry.timestamp < summary.timeRange.start) {
        summary.timeRange.start = entry.timestamp;
      }
      if (!summary.timeRange.end || entry.timestamp > summary.timeRange.end) {
        summary.timeRange.end = entry.timestamp;
      }
    } catch {
      // Skip non-JSON lines
    }
  }

  return summary;
}

// Usage
analyzeLogs('logs.json').then(console.log);

// src/middleware.ts
import { NextResponse } from 'next/server';
import type { NextRequest } from 'next/server';
import { v4 as uuidv4 } from 'uuid';

export function middleware(request: NextRequest) {
  const requestId = request.headers.get('x-request-id') || uuidv4();

  const response = NextResponse.next();
  response.headers.set('x-request-id', requestId);

  return response;
}

// src/lib/tracing.ts
import { AsyncLocalStorage } from 'async_hooks';

interface TraceContext {
  requestId: string;
  userId?: string;
  startTime: number;
}

const asyncLocalStorage = new AsyncLocalStorage<TraceContext>();

export function withTrace<T>(
  context: TraceContext,
  fn: () => T | Promise<T>
): T | Promise<T> {
  return asyncLocalStorage.run(context, fn);
}

export function getTrace(): TraceContext | undefined {
  return asyncLocalStorage.getStore();
}

// Usage in logger
export function log(level: string, message: string, data?: object) {
  const trace = getTrace();
  console.log(JSON.stringify({
    timestamp: new Date().toISOString(),
    level,
    message,
    requestId: trace?.requestId,
    userId: trace?.userId,
    duration: trace ? Date.now() - trace.startTime : undefined,
    ...data,
  }));
}

// src/lib/sentry.ts
import * as Sentry from '@sentry/nextjs';

Sentry.init({
  dsn: process.env.SENTRY_DSN,
  environment: process.env.NODE_ENV,
  tracesSampleRate: 0.1, // 10% of transactions
  beforeSend(event, hint) {
    // Filter out specific errors
    const error = hint.originalException;
    if (error instanceof Error && error.message.includes('Network')) {
      return null;
    }
    return event;
  },
});

// Capture with context
export function captureError(error: Error, context?: Record<string, any>) {
  Sentry.withScope((scope) => {
    if (context) {
      scope.setExtras(context);
    }
    Sentry.captureException(error);
  });
}

// Usage
try {
  await riskyOperation();
} catch (error) {
  captureError(error, {
    userId: user.id,
    action: 'payment',
    amount: 99.99,
  });
  throw error;
}

// src/components/error-boundary.tsx
'use client';

import { useEffect } from 'react';
import * as Sentry from '@sentry/nextjs';

export default function Error({
  error,
  reset,
}: {
  error: Error & { digest?: string };
  reset: () => void;
}) {
  useEffect(() => {
    // Log to error tracking
    Sentry.captureException(error);

    // Log to console with context
    console.error('Client Error:', {
      message: error.message,
      digest: error.digest,
      stack: error.stack,
      url: window.location.href,
      userAgent: navigator.userAgent,
    });
  }, [error]);

  return (
    <div>
      <h2>Something went wrong!</h2>
      <button onClick={reset}>Try again</button>
    </div>
  );
}

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-- Using tools like clickhouse or DuckDB for log analysis

-- Error rate by hour
SELECT
  date_trunc('hour', timestamp) as hour,
  count(*) FILTER (WHERE level = 'error') as errors,
  count(*) as total,
  round(100.0 * count(*) FILTER (WHERE level = 'error') / count(*), 2) as error_rate
FROM logs
WHERE timestamp > now() - interval '24 hours'
GROUP BY 1
ORDER BY 1;

-- Top error messages
SELECT
  error_message,
  count(*) as occurrences,
  min(timestamp) as first_seen,
  max(timestamp) as last_seen
FROM logs
WHERE level = 'error'
  AND timestamp > now() - interval '24 hours'
GROUP BY error_message
ORDER BY occurrences DESC
LIMIT 10;

-- Slowest endpoints
SELECT
  path,
  count(*) as requests,
  avg(duration) as avg_duration,
  max(duration) as max_duration,
  percentile_cont(0.95) WITHIN GROUP (ORDER BY duration) as p95
FROM logs
WHERE timestamp > now() - interval '1 hour'
GROUP BY path
ORDER BY avg_duration DESC
LIMIT 10;

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// scripts/cleanup-logs.ts
import * as fs from 'fs';
import * as path from 'path';

const LOG_DIR = '/var/log/myapp';
const RETENTION_DAYS = 30;

function cleanupOldLogs() {
  const now = Date.now();
  const maxAge = RETENTION_DAYS * 24 * 60 * 60 * 1000;

  const files = fs.readdirSync(LOG_DIR);

  for (const file of files) {
    const filePath = path.join(LOG_DIR, file);
    const stats = fs.statSync(filePath);

    if (now - stats.mtime.getTime() > maxAge) {
      fs.unlinkSync(filePath);
      console.log(`Deleted: ${file}`);
    }
  }
}

cleanupOldLogs();