# Parameter Extraction Feature - Implementation Summary

## Overview
Added parameter/argument name extraction to the FileIndex system, enabling storage of method and function parameter information for code completion, documentation, and analysis purposes.

## Files Modified

### 1. `src/client/javascript.js`
- **Added** `extractParameters()` helper function (lines 35-62)
  - Handles simple parameters: `method(a, b)`
  - Handles rest parameters: `method(...args)`
  - Handles default parameters: `method(x = 5)`
  - Handles object destructuring: `method({x, y})`
  - Handles array destructuring: `method([a, b])`
  
- **Modified** ClassMethod extraction (line 201)
  - Added `params: extractParameters(item.params)` field to method objects
  
- **Modified** FunctionDeclaration extraction (line 171)
  - Added `params: extractParameters(funcNode.params)` field to function objects

### 2. `test/javascript-params-test.js` (NEW)
- Comprehensive test suite with 17 tests
- Tests all parameter types for both class methods and functions
- Tests edge cases (no params, mixed types, static methods, getters/setters)
- All tests passing ✓

### 3. `demos/claude/test-params-in-db.js` (NEW)
- Test script for verifying parameters are stored in the database
- Can be used to inspect parameter data in live FileIndex
- Usage: `import script from "browse://demos/claude/test-params-in-db.js"; script.testParamsInDB()`

## Parameter Data Structure

Each parameter is stored as an object with:
```javascript
{
  name: string,      // Parameter name or pattern indicator
  type: string,      // 'simple' | 'rest' | 'default' | 'destructure' | 'unknown'
  defaultValue?: string,  // For default params (currently '...')
  properties?: string[]   // For object destructuring
}
```

## Examples

### Simple Method
```javascript
class Foo {
  method(a, b, c) {}
}
// Stored params: [{name: 'a', type: 'simple'}, {name: 'b', type: 'simple'}, {name: 'c', type: 'simple'}]
```

### Complex Method
```javascript
class FileIndex {
  async updateDirectory(baseURL, showProgress = false, {recursive, force}, ...options) {}
}
// Stored params:
// [
//   {name: 'baseURL', type: 'simple'},
//   {name: 'showProgress', type: 'default', defaultValue: '...'},
//   {name: '{...}', type: 'destructure', properties: ['recursive', 'force']},
//   {name: 'options', type: 'rest'}
// ]
```

## Database Schema

**No schema changes required!** Using Option A from the plan:
- Methods remain nested in class records
- Parameters are just additional fields in method objects
- Existing Dexie `*methods` index automatically handles the richer objects
- Functions table similarly stores params in function objects

## Usage Examples

### Query methods with their parameters:
```javascript
const fileIndex = FileIndex.current();

// Get all classes in a file
const classes = await fileIndex.db.classes
  .where("url").equals(someUrl)
  .toArray();

// Access method parameters
classes[0].methods.forEach(method => {
  console.log(`${method.name}(${method.params.map(p => p.name).join(', ')})`);
});
```

### Get function parameters:
```javascript
const functions = await fileIndex.db.functions
  .where("name").equals("myFunction")
  .toArray();

functions[0].params.forEach(param => {
  console.log(`${param.name} (${param.type})`);
});
```

## Migration Notes

- **Backward compatible**: Old indexed files without `params` field will still work
- **Re-indexing needed**: To get parameter data for existing files:
  - Files are automatically re-indexed when saved
  - Or manually: `FileIndex.current().updateFile(url)`
  - Or bulk: `FileIndex.current().updateAllModuleSemantics()`

## Test Results

```
JavaScript Parameter Extraction
  ClassMethod parameters
    ✔ extracts simple parameters
    ✔ extracts rest parameters
    ✔ extracts default parameters
    ✔ extracts destructured object parameters
    ✔ extracts destructured array parameters
    ✔ handles mixed parameter types
    ✔ handles methods with no parameters
    ✔ extracts parameters from static methods
    ✔ extracts parameters from getters and setters
    ✔ extracts parameters from constructor
  FunctionDeclaration parameters
    ✔ extracts simple parameters from functions
    ✔ extracts rest parameters from functions
    ✔ extracts default parameters from functions
    ✔ extracts destructured parameters from functions
    ✔ handles functions with no parameters
    ✔ handles multiple function declarations
  Real-world examples
    ✔ handles complex class with multiple methods

17 tests passing
```

## Benefits

✓ **Code completion**: Suggest correct parameter names when calling methods
✓ **Documentation**: Auto-generate accurate method signatures  
✓ **Refactoring**: Find methods with specific parameter patterns
✓ **Analysis**: Identify code smells (too many params, inconsistent naming)
✓ **Inspection**: Better developer tools and code browsers

## Next Steps (Optional Enhancements)

- [ ] Extract actual default values instead of '...'
- [ ] Add parameter type annotations (for TypeScript files)
- [ ] Create UI component to browse methods by parameter signature
- [ ] Add search capability to find methods by parameter names
- [ ] Generate method documentation from params + comments