# Twig Implementation Progress

## Completed Features

1. **Parser Improvements**
   - Added parser support for function syntax with arguments
   - Added parser support for new operators: 'is', 'is not', 'matches', 'starts with', 'ends with', 'not in'
   - Added parser support for test conditions ('is defined', 'is empty', etc.)
   - Added conditional expressions (ternary operators)
   - Added array literal support
   - Added evaluator implementations for the new node types

2. **Full Filter Support**
   - Fixed filter parsing and evaluation to properly handle the pipe (`|`) character in the tokenizer/parser
   - Ensured filter arguments are passed correctly to filter functions
   - Implemented support for chained filters (e.g., `var|filter1|filter2`)
   - Verified comprehensive set of standard Twig filters work correctly:
     - Text manipulation: `upper`, `lower`, `capitalize`, `trim`, etc.
     - Array manipulation: `join`, `split`, `slice`, `sort`, etc.
     - Type conversion: `length/count`, `keys`, etc.
     - Formatting: `date`, `number_format`, etc.
   - Added extensive tests for all filter functionality

3. **Documentation**
   - Updated README with filter information and examples
   - Added comprehensive test suite for filters with various use cases

## Recent Improvements

1. **Custom Filter and Function Registration**
   - Added `AddFilter()` method to easily register custom filters
   - Added `AddFunction()` method to easily register custom functions
   - Added `AddTest()` method to register custom tests
   - Created `CustomExtension` type for comprehensive extensions
   - Added `RegisterExtension()` method for registering extension bundles
   - Created example application demonstrating custom extensions

2. **Development Mode and Template Caching**
   - Added `SetDevelopmentMode()` method that sets appropriate debug/cache settings
   - Added `SetDebug()` and `SetCache()` methods for individual control
   - Improved template loading to respect cache settings
   - Templates are not cached when cache is disabled
   - Added tests to verify caching behavior

3. **Template Modification Checking**
   - Added `TimestampAwareLoader` interface for loaders that support modification time checking
   - Implemented modification time tracking in the `FileSystemLoader`
   - Added cache invalidation based on file modification times
   - Automatic template reloading when files change and auto-reload is enabled
   - Updated Template struct to track the source loader and modification time
   - Added comprehensive tests for file modification detection
   - Added example application demonstrating auto-reload in action

4. **Optimized Filter Chain Processing**
   - Implemented a specialized filter chain detection and evaluation algorithm
   - Added support for detecting and processing filter chains in a single pass
   - Reduced the number of intermediate allocations for chained filters
   - Improved performance for templates with multiple filters applied to the same value
   - Added tests and benchmarks to verify correctness and performance gains

## Future Improvements

1. **More Tests**
   - Add more comprehensive tests for edge cases
   - Add more benchmarks for different template scenarios

2. **Error Handling**
   - Improve error messages for filter-related issues
   - Add better debugging support

3. **Template Compilation**
   - Implement a compiled template format for even faster rendering
   - Add the ability to pre-compile templates for production use