# Wasot Selector System Status Report
**Date:** January 2025  
**Author:** Development Team  
**Status:** Phase 3 Complete - Full Integration Achieved

## Executive Summary

The Wasot selector system has successfully completed Phase 3 of implementation, achieving full integration between the CSS-like selector parser and the event-based consumer system. The system now provides a robust, command-line accessible tool for querying and filtering Wasot documents using familiar CSS selector syntax.

## Implementation Phases Overview

### Phase 1: Parser Development ✅ Complete
- **Objective:** Parse selector strings into Abstract Syntax Tree (AST)
- **Location:** `src/parsers/selectors/`
- **Key Files:**
  - `parser.rs` - Pest-based parser implementation
  - `ast.rs` - AST type definitions
  - `selectors.pest` - Grammar definition
- **Status:** Fully functional parser supporting all planned selector types

### Phase 2: Stack-Based Matching ✅ Complete
- **Objective:** Implement selector matching against document stack
- **Location:** `src/consumers/selector_consumer.rs`
- **Key Achievement:** Stack tracking for hierarchical document structure
- **Status:** Core matching logic implemented and tested

### Phase 3: Integration ✅ Complete (Current Work)
- **Objective:** Connect parser with consumer for end-to-end functionality
- **Key Achievements:**
  - Modified `SelectorConsumer` to accept string selectors
  - Integrated AST parser for runtime selector parsing
  - Added CLI subcommand for user access
  - Created comprehensive examples and documentation

## Current Capabilities

### Fully Implemented Selectors

#### Basic Selectors
| Selector Type | Syntax | Example | Status |
|--------------|--------|---------|--------|
| Type | `element` | `paragraph` | ✅ Working |
| Universal | `*` | `*` | ✅ Working |
| ID | `#id` | `#intro` | ✅ Working |
| Class | `.class` | `.highlight` | ✅ Working |

#### Attribute Selectors
| Selector Type | Syntax | Example | Status |
|--------------|--------|---------|--------|
| Presence | `[attr]` | `[lang]` | ✅ Working |
| Negated Presence | `[!attr]` | `[!disabled]` | ✅ Working |
| Exact Match | `[attr=value]` | `[lang=en]` | ✅ Working |
| Negated Match | `[attr~=value]` | `[lang~=fr]` | ✅ Working |
| Starts With | `[attr^=value]` | `[href^=https]` | ✅ Working |
| Ends With | `[attr$=value]` | `[href$=.pdf]` | ✅ Working |
| Contains | `[attr*=value]` | `[title*=important]` | ✅ Working |

#### Combinators
| Combinator | Syntax | Example | Status |
|-----------|--------|---------|--------|
| Descendant | `A B` | `section paragraph` | ✅ Working |
| Child | `A > B` | `section > paragraph` | ✅ Working |
| Adjacent Sibling | `A + B` | `h1 + paragraph` | ⚠️ Parsed, not matched |
| General Sibling | `A ~ B` | `h1 ~ paragraph` | ⚠️ Parsed, not matched |

#### Grouping
| Feature | Syntax | Example | Status |
|---------|--------|---------|--------|
| OR Selector | `A, B` | `paragraph, quote` | ✅ Working (via multiple -s flags) |

### Partially Implemented Features

#### Pseudo-Classes
| Pseudo-Class | Status | Notes |
|-------------|--------|-------|
| `:first-child` | 🔨 Parsed only | AST support exists, matching not implemented |
| `:last-child` | 🔨 Parsed only | AST support exists, matching not implemented |
| `:nth-child(n)` | 🔨 Parsed only | AST support exists, matching not implemented |
| `:first-block` | 🔨 Parsed only | Wasot-specific, planned |
| `:last-block` | 🔨 Parsed only | Wasot-specific, planned |
| `:nth-block(n)` | 🔨 Parsed only | Wasot-specific, planned |
| `:not(selector)` | 🔨 Parsed only | AST support exists, matching not implemented |

## Architecture Overview

### Component Structure
```
┌─────────────────────────────────────────────┐
│              CLI Interface                   │
│         (wasot select command)               │
└─────────────────┬───────────────────────────┘
                  │
┌─────────────────▼───────────────────────────┐
│          SelectorConsumer                   │
│   - Parses selector strings to AST          │
│   - Maintains document stack                │
│   - Matches selectors against events        │
└─────────────────┬───────────────────────────┘
                  │
        ┌─────────┴─────────┐
        │                   │
┌───────▼────────┐ ┌────────▼────────┐
│ Selector Parser│ │  Event System   │
│  (Pest-based)  │ │  (Emitter/      │
│                │ │   Consumer)     │
└────────────────┘ └─────────────────┘
```

### Key Components

#### 1. Parser Module (`src/parsers/selectors/`)
- **Technology:** Pest parser generator
- **Grammar:** Comprehensive CSS-like selector syntax
- **AST Design:** Hierarchical representation supporting all selector types
- **Error Handling:** Graceful parsing with detailed error messages

#### 2. Consumer Module (`src/consumers/selector_consumer.rs`)
- **Design Pattern:** Event-driven consumer
- **Stack Management:** Tracks document hierarchy with `StackFrame`
- **Matching Engine:** Recursive matching for combinators
- **Performance:** Streaming processing with minimal memory overhead

#### 3. CLI Integration (`src/main.rs`)
- **Command:** `wasot select <file> -s <selector> [-s <selector>...]`
- **Multiple Selectors:** Supports OR logic via multiple `-s` flags
- **Output:** Prints matched elements to stdout

## Technical Implementation Details

### Wasot-Specific Considerations

#### Argument Handling
Wasot uses a unique syntax for arguments that required special consideration:
- **Separator:** Arguments must be separated from inline text using `..`
- **Format:** `.type Inline text .. arg1 arg2 key=value`
- **Classes:** Positional arguments starting with `.` (e.g., `.highlight`)
- **IDs:** Specified with `:` after type (e.g., `.paragraph :my-id`)

#### Stack-Based Matching
The implementation maintains a stack of `StackFrame` objects:
```rust
pub struct StackFrame {
    meta_line: MetaLine,
    child_index: usize, // For future pseudo-class support
}
```

This enables efficient hierarchical matching for descendant and child combinators.

### Performance Characteristics
- **Memory:** O(depth) where depth is document nesting level
- **Time Complexity:** O(n × m) where n = events, m = selectors
- **Streaming:** Processes documents without loading entire file into memory

## Usage Examples

### Command Line Interface
```bash
# Basic type selector
wasot select document.wasot -s "paragraph"

# ID selector
wasot select document.wasot -s "#intro"

# Class selector
wasot select document.wasot -s ".highlight"

# Attribute selector
wasot select document.wasot -s "[lang=en]"

# Descendant combinator
wasot select document.wasot -s "section paragraph"

# Child combinator
wasot select document.wasot -s "section > paragraph"

# Multiple selectors (OR)
wasot select document.wasot -s "quote" -s "blockquote"
```

### Programmatic Usage
```rust
use wasot_compiler::{SelectorConsumer, WasotFileEmitter};
use wasot_compiler::events::run;

let emitter = WasotFileEmitter::from_file("document.wasot");
let consumer = SelectorConsumer::new(vec![
    "paragraph".to_string(),
    "section > paragraph".to_string(),
]);
run(emitter, consumer)?;
```

## Testing and Validation

### Test Coverage
- **Unit Tests:** Parser and consumer components tested independently
- **Integration Tests:** End-to-end selector matching validation
- **Example Files:**
  - `examples/selector-showcase.wasot` - Comprehensive test document
  - `examples/selector-showcase-demo.sh` - Automated test script

### Quality Assurance
- All tests passing (`cargo test`)
- No compilation warnings (except intentional unused fields for future features)
- Code formatted with `cargo fmt`
- Clippy compliance verified

## Known Limitations

### Functional Limitations
1. **Sibling Combinators:** Parsed but not implemented in matching
2. **Pseudo-Classes:** Full AST support but matching not implemented
3. **Complex Selectors:** Combined attribute+class selectors may not work
4. **Regex Matching:** Not supported for attribute values

### Technical Debt
1. **Child Index Tracking:** Infrastructure in place but not utilized
2. **Sibling Tracking:** Would require significant architecture changes
3. **Performance Optimization:** Room for optimization in complex selector matching

## Future Roadmap

### Short Term (Phase 4)
- [ ] Implement `:first-child` pseudo-class
- [ ] Implement `:last-child` pseudo-class
- [ ] Add child index tracking for nth-child support
- [ ] Optimize matching performance for complex selectors

### Medium Term (Phase 5)
- [ ] Implement sibling combinators (`+`, `~`)
- [ ] Add `:not()` pseudo-class support
- [ ] Implement Wasot-specific pseudo-classes (`:first-block`, etc.)
- [ ] Add selector validation and optimization

### Long Term
- [ ] Regex support for attribute matching
- [ ] Custom pseudo-class extensions
- [ ] Selector result caching
- [ ] Parallel selector matching

## Conclusion

The Wasot selector system has achieved its primary goal of providing CSS-like selector functionality for Wasot documents. The implementation is robust, well-tested, and user-accessible through both CLI and programmatic interfaces. While some advanced features remain unimplemented, the current system provides substantial value and a solid foundation for future enhancements.

The successful integration of the Pest-based parser with the event-driven consumer architecture demonstrates the flexibility and extensibility of the Wasot compiler design. The system is ready for production use within its current capability boundaries.

## Recommendations

1. **Documentation:** Continue expanding user documentation with more examples
2. **Performance:** Consider benchmarking with large documents to identify optimization opportunities
3. **Testing:** Add property-based testing for selector parser
4. **Features:** Prioritize pseudo-class implementation based on user needs
5. **API:** Consider exposing a higher-level API for selector-based document transformation

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*Report generated based on codebase analysis as of January 2025*