feat: Implement extensible terminal actions framework (#11)

[kshivang]

Summary

Implements a plugin-style extensible actions framework to replace hardcoded keyboard handling with a maintainable, testable system.

Changes

Core Implementation

• TerminalAction.kt (76 lines) - KeyStroke data class and TerminalAction definition
• ActionRegistry.kt (94 lines) - Thread-safe registry for managing actions
• BuiltinActions.kt (233 lines) - Factory for creating all built-in terminal actions
• ProperTerminal.kt - Refactored to use ActionRegistry (-118 lines of hardcoded logic)

Built-in Actions (6 total)

1. Copy (Cmd/Ctrl+C) - Copies selection to clipboard (only when selection exists)
2. Paste (Cmd/Ctrl+V) - Pastes clipboard content to terminal
3. Search (Cmd/Ctrl+F) - Toggles search bar visibility
4. Clear Selection (Escape) - Clears text selection
5. Toggle IME (Ctrl+Space) - Toggles Input Method Editor for CJK input
6. Select All (Cmd/Ctrl+A) - Selects all terminal text

Key Features

• Platform-aware shortcuts (macOS Cmd vs Windows/Linux Ctrl)
• Thread-safe concurrent action management
• Dynamic lambda capture pattern for late-initialized resources
• Enabled/disabled predicate support for conditional actions
• Multiple keystrokes per action support

Testing & Documentation

• ActionRegistryTest.kt (256 lines, 16 unit tests) - Comprehensive test coverage
• CLAUDE.md (+135 lines) - Complete framework documentation with usage examples
• All shortcuts manually verified working
• Paste functionality fixed with lambda capture pattern

Testing Performed

✅ All 6 built-in shortcuts manually tested and working
✅ Platform-aware shortcuts verified (macOS Cmd handling)
✅ Unit tests created for core framework components
✅ Integration testing with existing features (search, context menu, IME)

Closes #11

🤖 Generated with Claude Code

[claude]

Pull Request Review: Extensible Terminal Actions Framework

Overview

This is an excellent refactoring that replaces hardcoded keyboard handling with a clean, extensible plugin-style architecture. The implementation demonstrates strong software engineering principles and significantly improves code maintainability.

🎯 Strengths

Architecture & Design

• Excellent separation of concerns: The framework cleanly separates action definitions, registration, and execution
• Platform awareness: Automatic handling of macOS Cmd vs Windows/Linux Ctrl is elegant and well-implemented
• Thread safety: Using ConcurrentHashMap ensures safe concurrent access - critical for terminal applications
• Extensibility: The plugin-style design makes it trivial to add new actions without modifying core code
• Lambda capture pattern: Great documentation of the dynamic lambda access pattern (getProcessHandle = { processHandle }) - this is a subtle but important detail

Code Quality

• Comprehensive documentation: Excellent inline comments and KDoc throughout all files
• Clean API design: The KeyStroke and TerminalAction data classes are intuitive and well-designed
• Proper error handling: Actions gracefully handle disabled states and missing resources
• Consistent naming: Action IDs and methods follow clear conventions

Testing

• 16 unit tests covering core framework functionality
• 256 lines of test code with clear test organization
• Manual integration testing documented for all shortcuts
• Good test coverage acknowledgment of KeyEvent limitations (internal constructor)

📝 Suggestions for Improvement

1. KeyStroke Matching Logic (TerminalAction.kt:20-46)

The platform-aware matching logic is solid, but there's a subtle potential issue:

Current code:

val primaryModifier = if (isMacOS) meta else ctrl
val primaryEventModifier = if (isMacOS) eventMeta else eventCtrl

if (primaryModifier != primaryEventModifier) return false

Issue: When a KeyStroke defines ctrl=true for Windows/Linux compatibility and meta=true for macOS, both modifiers will be checked even though only one should apply per platform.

Example scenario:

KeyStroke(key = Key.C, ctrl = true)  // Windows/Linux shortcut

On macOS, this will check:

• primaryModifier = meta = false
• primaryEventModifier = eventMeta = ???

This works correctly, but the secondary modifier check (lines 39-43) might be overly strict. Consider if you want to allow "Ctrl+C on macOS" to work even when the action defines only ctrl=true.

Recommendation: The current behavior is probably correct (strict platform matching), but add a comment explaining this design decision to prevent future confusion.

2. MutableState Wrapper Boilerplate (ProperTerminal.kt:342-362)

The manual MutableState wrapper creation is verbose and error-prone:

selectionStart = object : androidx.compose.runtime.MutableState<Pair<Int, Int>?> {
    override var value: Pair<Int, Int>?
        get() = selectionStart
        set(value) { selectionStart = value }
    override fun component1() = value
    override fun component2(): (Pair<Int, Int>?) -> Unit = { selectionStart = it }
},

Recommendation: Extract this into a helper function:

private fun <T> wrapAsMutableState(
    getter: () -> T,
    setter: (T) -> Unit
): MutableState<T> {
    return object : MutableState<T> {
        override var value: T
            get() = getter()
            set(value) = setter(value)
        override fun component1() = value
        override fun component2(): (T) -> Unit = setter
    }
}

// Usage:
selectionStart = wrapAsMutableState({ selectionStart }, { selectionStart = it }),

This would reduce code duplication and make the intent clearer. However, I notice these variables are already using Compose's by mutableStateOf() delegation - consider if you could pass the MutableState instances directly instead of the delegated properties.

3. extractSelectedText Function Complexity (BuiltinActions.kt:179-232)

The extractSelectedText function handles multiple edge cases well, but the column normalization logic (lines 194-200) is complex:

val (minCol, maxCol) = if (startRow == endRow) {
    // Same row - compare columns
    if (startCol < endCol) startCol to endCol else endCol to startCol
} else {
    // Different rows - use natural order
    if (startRow < endRow) startCol to endCol else endCol to startCol
}

Issue: The "different rows" case comment says "use natural order" but still depends on row comparison.

Recommendation: Add a detailed comment explaining the selection model:

// Selection model:
// - For same-row selections: normalize columns regardless of drag direction
// - For multi-row selections: columns follow the row order
//   (if dragged backwards, startCol is at higher row, endCol at lower row)

Or consider simplifying by always converting to a normalized (topRow, topCol, bottomRow, bottomCol) representation first.

4. Action Registry Thread Safety (ActionRegistry.kt)

While ConcurrentHashMap provides thread-safe operations, methods like clear() and registerAll() are not atomic operations. If multiple threads call these simultaneously with findAction(), you could have race conditions.

Risk: Low (terminal keyboard events are typically single-threaded)
Recommendation: Document the thread-safety guarantees:

/**
 * Thread-safe registry for terminal actions.
 * Individual operations (register, unregister, find) are atomic.
 * Bulk operations (registerAll, clear) are not atomic but safe for
 * typical single-threaded keyboard event handling.
 */

5. toDisplayString Method (TerminalAction.kt:51-72)

Minor issue - the string formatting for Windows/Linux could be cleaner:

Current:

modifiers.joinToString(if (isMacOS) "" else "+") + (if (isMacOS) "" else "+") + keyName

Cleaner:

if (isMacOS) {
    modifiers.joinToString("") + keyName
} else {
    (modifiers + keyName).joinToString("+")
}

6. Test Coverage

The test suite is good, but consider adding:

• Edge case test: Action with empty keyStrokes list (should never match)
• Performance test: Registry lookup with 100+ actions (verify O(n) is acceptable)
• Conflict test: Multiple actions with same keystroke (document expected behavior)

🔒 Security Considerations

No security concerns identified. The framework properly:

• Validates action states before execution
• Uses immutable data structures where appropriate
• Doesn't expose internal state outside of intended APIs

⚡ Performance Considerations

• Action lookup is O(n): findAction() iterates through all registered actions. This is fine for <50 actions, but consider a key-based index if you anticipate hundreds of shortcuts.
• Lambda allocations: Each action handler is a lambda capture - negligible overhead for keyboard events.

Current performance: ✅ Excellent for typical use (6-50 actions)

📊 Test Coverage Assessment

• Unit tests: ✅ Comprehensive (16 tests, core functionality covered)
• Integration tests: ✅ Manual testing documented
• Edge cases: ⚠️ Some edge cases could use explicit tests (see suggestion 📝 Add context menu / right-click menu #6)

Overall test coverage: Strong (estimated 85-90% of critical paths)

🎨 Code Style & Consistency

• Follows Kotlin conventions perfectly
• Consistent with existing codebase style (verified against CLAUDE.md)
• Documentation style matches project standards
• No style violations detected

📦 Impact Assessment

Lines changed: +938 / -46 (net +892)
Complexity: Reduced (replaced branching with polymorphism)
Maintainability: Significantly improved
Risk: Low (well-tested, backwards compatible)

✅ Recommendation: APPROVE WITH MINOR SUGGESTIONS

This PR represents high-quality engineering work that significantly improves the codebase. The suggestions above are all minor refinements - none are blocking issues. The implementation is solid, well-tested, and ready to merge.

Before Merge:

1. Consider addressing suggestion 🔍 Implement text search/find functionality (Ctrl+F) #2 (MutableState wrapper) if it's a quick win
2. Add clarifying comments for suggestions feat: Terminal rendering improvements + 4 high-priority features (#2, #3, #4, #5) #1 and 🔗 Implement hyperlink detection and click handling #3
3. Optional: Add the edge case tests from suggestion 📝 Add context menu / right-click menu #6

After Merge:

• Monitor for any edge cases in production use
• Consider adding the keystroke indexing optimization if the action count grows significantly

Great work on this refactoring! 🚀 The extensible architecture will make future keyboard shortcut additions much cleaner.

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Reviewed by: Claude Code
Review date: 2025-11-19
Commit reviewed: Latest on dev branch