Add Support for Customizing Log Elements While Keeping Log Levels Mandatory

[Copilot]

Summary

This PR implements customizable log elements functionality, allowing users to control which components are included in log output while maintaining log levels as mandatory elements. This addresses the need for flexible log formatting in different deployment environments while preserving essential debugging information.

Key Features

✅ Customizable Timestamp Elements: Users can now control ISO timestamp and local time inclusion
✅ Mandatory Log Levels: Log levels always remain visible regardless of configuration (as required)
✅ Backward Compatible: Default behavior unchanged - existing code works without modifications
✅ Type Safe: Full TypeScript support with new LogFormatConfig interface
✅ Comprehensive Testing: 17 new tests covering all scenarios (272 total tests passing)

Usage Examples

import { LogEngine, LogMode } from '@wgtechlabs/log-engine';

// Default format (backward compatible)
LogEngine.configure({ mode: LogMode.DEBUG });
LogEngine.info('Server started');
// Output: [2025-05-29T16:57:45.678Z][4:57PM][INFO]: Server started

// Only ISO timestamp
LogEngine.configure({ 
  mode: LogMode.DEBUG,
  format: {
    includeIsoTimestamp: true,
    includeLocalTime: false
  }
});
LogEngine.info('Database connected');
// Output: [2025-05-29T16:57:45.678Z][INFO]: Database connected

// Minimal format (no timestamps)
LogEngine.configure({ 
  mode: LogMode.DEBUG,
  format: {
    includeIsoTimestamp: false,
    includeLocalTime: false
  }
});
LogEngine.error('Connection failed');
// Output: [ERROR]: Connection failed

Implementation Details

Changes Made

1. New Types (src/types/index.ts):

   • Added LogFormatConfig interface with includeIsoTimestamp and includeLocalTime options
   • Extended LoggerConfig interface with optional format property

2. Enhanced MessageFormatter (src/formatter/message-formatter.ts):

   • Updated format() method to accept optional LogFormatConfig parameter
   • Implemented conditional timestamp formatting logic
   • Updated formatSystemMessage() for consistency
   • Maintained backward compatibility when no format config is provided

3. Updated Logger Core (src/logger/core.ts):

   • Modified all logging methods to pass format configuration to MessageFormatter
   • Ensured configuration flows through both standard and raw logging methods

4. Comprehensive Testing (src/__tests__/format-customization.test.ts):

   • 17 new tests covering all format combinations
   • Backward compatibility validation
   • Edge cases and error handling
   • LogEngine integration testing

5. Documentation (README.md):

   • Added complete section on log element customization
   • Usage examples for all format combinations
   • Benefits and use cases explained

Technical Approach

• Minimal Changes: Surgical implementation touching only essential files
• Default Behavior: Uses spread operator to maintain defaults when no config provided
• Performance: Conditional timestamp generation only when needed
• Type Safety: Full TypeScript support with proper interfaces

Use Cases

• 🎯 Reduced Verbosity: Remove timestamps in containerized environments where external logging systems add timestamps
• 📱 Space Efficiency: Minimize log line length for mobile or constrained display environments
• 🔧 Integration Ready: Match existing log format requirements in infrastructure
• ⚡ Performance: Slightly reduced formatting overhead when timestamps are disabled

Testing

All existing tests continue to pass, ensuring no breaking changes:

• 272 total tests passing (255 existing + 17 new)
• 100% backward compatibility verified
• All linting rules passed
• Manual validation confirms expected behavior

Breaking Changes

None - This is a fully backward-compatible addition. Existing code continues to work without any modifications.

Related Issues

Closes #[issue-number] - Add Support for Customizing Log Elements

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