feat: add quick-switch to previous session

.github/workflows/ci.yml

@@ -21,7 +21,7 @@ jobs:
         uses: actions-rust-lang/setup-rust-toolchain@v1
 
       - name: Run tests
-        run: cargo test
+        run: cargo test --target x86_64-unknown-linux-gnu
 
   build-wasm:
     runs-on: ubuntu-latest

.planning/codebase/ARCHITECTURE.md

@@ -0,0 +1,174 @@
+# Architecture
+
+**Analysis Date:** 2026-01-13
+
+## Pattern Overview
+
+**Overall:** Plugin-based architecture with layered state management and event-driven processing
+
+**Key Characteristics:**
+- Zellij plugin using WASM (WebAssembly) with WASI sandbox
+- Event-driven: Zellij sends events → Plugin processes → State updates → UI renders
+- Single executable with two-screen UI (Main list, NewSession creation)
+- Stateless request handling within plugin instance
+
+## Layers
+
+**Plugin Layer:**
+- Purpose: Zellij plugin trait implementation, event dispatcher
+- Contains: `ZellijPlugin` trait methods (`load`, `update`, `pipe`, `render`)
+- Location: `src/main.rs`
+- Depends on: State layer for coordination
+- Used by: Zellij runtime
+
+**State Layer:**
+- Purpose: Central state management, business logic coordination
+- Contains: `PluginState` struct, key handlers, item combination logic
+- Location: `src/state.rs`
+- Depends on: Config, Session, Zoxide, NewSessionInfo, UI modules
+- Used by: Plugin layer
+
+**Session Layer:**
+- Purpose: Zellij session operations, lifecycle management, stability tracking
+- Contains: `SessionManager`, `SessionItem`, `SessionAction`
+- Location: `src/session/manager.rs`, `src/session/types.rs`
+- Depends on: No internal dependencies (isolated)
+- Used by: State layer
+
+**Zoxide Layer:**
+- Purpose: Directory discovery and fuzzy search
+- Contains: `ZoxideDirectory`, `SearchEngine`
+- Location: `src/zoxide/directory.rs`, `src/zoxide/search.rs`
+- Depends on: Session types (for `SessionItem`)
+- Used by: State layer
+
+**UI Layer:**
+- Purpose: Terminal rendering
+- Contains: `PluginRenderer`, `Theme`, `Colors`, components
+- Location: `src/ui/renderer.rs`, `src/ui/theme.rs`, `src/ui/components.rs`
+- Depends on: Session types, State for display data
+- Used by: Plugin layer (render method)
+
+**Configuration Layer:**
+- Purpose: Zellij layout-based configuration parsing
+- Contains: `Config` struct
+- Location: `src/config.rs`
+- Depends on: None
+- Used by: State layer
+
+## Data Flow
+
+**Plugin Initialization:**
+
+1. `ZellijPlugin::load()` in `src/main.rs:16` → Registers plugin with Zellij
+2. Requests permissions (RunCommands, ReadApplicationState, ChangeApplicationState, MessageAndLaunchOtherPlugins)
+3. Subscribes to events (ModeUpdate, SessionUpdate, Key, RunCommandResult, PermissionRequestResult)
+
+**Permission Grant & Zoxide Query:**
+
+1. User receives PermissionRequestResult → `update()` in `src/main.rs:50`
+2. `fetch_zoxide_directories()` runs `zoxide query -l -s` command
+3. Results returned via RunCommandResult event
+
+**Zoxide Output Processing:**
+
+1. `process_zoxide_output()` in `src/main.rs:161` parses score+path lines
+2. `generate_smart_session_names()` creates context-aware names (`src/main.rs:197-235`)
+3. Names conflict-resolved with parent context and truncated to 29 chars
+4. `update_zoxide_directories()` in `src/state.rs:102` stores directories
+
+**Session Updates:**
+
+1. Zellij sends SessionUpdate event with current and resurrectable sessions
+2. `update_sessions()` in `src/state.rs:57` uses stability tracking (MISSING_THRESHOLD=3)
+3. Prevents UI flickering from Zellij's inconsistent event timing
+
+**User Interaction:**
+
+1. Key event in `update()` → `handle_key()` in `src/state.rs:108`
+2. Routes to main screen or new session screen handlers
+3. Actions trigger session switches, deletions, or new session creation
+
+**State Management:**
+- File-based state for previous session: `/tmp/zsm-previous-session`
+- Each plugin instance has isolated state (per Zellij session)
+- State does not transfer between sessions automatically
+
+## Key Abstractions
+
+**SessionManager:**
+- Purpose: Orchestrates Zellij session operations with stability tracking
+- Examples: `update_sessions_stable()`, `execute_action()`, `generate_incremented_name()`
+- Location: `src/session/manager.rs`
+- Pattern: Stability threshold (MISSING_THRESHOLD=3) prevents UI flicker from inconsistent Zellij events
+
+**SessionItem:**
+- Purpose: Represents displayable items in the session list
+- Examples: `ExistingSession`, `ResurrectableSession`, `Directory`
+- Location: `src/session/types.rs`
+- Pattern: Enum with variant data
+
+**SearchEngine:**
+- Purpose: Fuzzy matching for search functionality
+- Examples: `search()`, `update_search()`, `get_results()`
+- Location: `src/zoxide/search.rs`
+- Pattern: Uses `SkimMatcherV2` from `fuzzy-matcher` crate
+
+**PluginState:**
+- Purpose: Central orchestrator holding all plugin state
+- Examples: `combined_items()`, `display_items()`, `handle_key()`
+- Location: `src/state.rs`
+- Pattern: Singleton state container, coordinates between all layers
+
+## Entry Points
+
+**Plugin Entry:**
+- Location: `src/main.rs:13` - `register_plugin!(PluginState)` macro
+- Triggers: Zellij loads plugin WASM binary
+- Responsibilities: Register plugin with Zellij runtime
+
+**ZellijPlugin Implementation:**
+- Location: `src/main.rs:15-152`
+- Triggers: Zellij events (permissions, keys, session updates)
+- Responsibilities: Event dispatch, zoxide command execution, rendering
+
+**Renderer Entry:**
+- Location: `src/ui/renderer.rs:14`
+- Triggers: Zellij render call
+- Responsibilities: Determine active screen, render UI, display overlays
+
+## Error Handling
+
+**Strategy:** Uses `Option<T>` for nullable values, UI error display for user feedback
+
+**Patterns:**
+- Validation errors shown via `.set_error()` method (`src/state.rs:26`)
+- Error cleared on next keypress
+- Permission denial shows error, prevents zoxide fetch
+- Invalid session names blocked with descriptive messages
+
+## Cross-Cutting Concerns
+
+**Logging:**
+- Plugin logs to Zellij's plugin log output
+- No external logging framework
+
+**Validation:**
+- Session name validation at creation time (`src/state.rs:614-622`)
+- Max 108 bytes, no `/` characters
+- Path validation for zoxide results
+
+**Smart Session Naming:**
+- Complex algorithm spanning `src/main.rs:197-502`
+- Conflict detection, context-aware naming, truncation to 29 chars
+- Respects Unix socket path limits
+
+**WASM Sandbox Handling:**
+- Direct filesystem writes use sandboxed paths
+- Shelling out via `run_command` for persistent file operations
+- Inter-plugin communication via `pipe_message_to_plugin`
+
+---
+
+*Architecture analysis: 2026-01-13*
+*Update when major patterns change*

.planning/codebase/CONCERNS.md

@@ -0,0 +1,165 @@
+# Codebase Concerns
+
+**Analysis Date:** 2026-01-13
+
+## Tech Debt
+
+**Code Duplication - Range Calculation:**
+- Issue: Duplicate range-to-render logic
+- Location: `src/new_session_info.rs:271` - TODO comment: "merge with similar function in zoxide_directories"
+- Why: Rapid development, similar patterns emerged independently
+- Impact: Maintenance burden, risk of divergent behavior
+- Fix approach: Extract shared utility function
+
+**Complex Smart Naming Algorithm:**
+- Issue: 300+ lines of interrelated functions for session name generation
+- Location: `src/main.rs:197-502` - `generate_smart_session_names`, `generate_context_aware_name`, `normalize_path`, `apply_smart_truncation`, `abbreviate_segment`
+- Why: Feature complexity (conflict detection, context-awareness, truncation limits)
+- Impact: Difficult to test, maintain, and debug
+- Fix approach: Extract to dedicated module, add comprehensive unit tests
+
+## Known Bugs
+
+**None identified during analysis.**
+
+The codebase appears stable with no obvious bugs. Session stability tracking specifically addresses Zellij's inconsistent event behavior.
+
+## Security Considerations
+
+**Shell Command Injection (Medium Risk):**
+- Risk: Session names interpolated into shell commands without escaping
+- Location: `src/state.rs:675-686` (write_previous_session function)
+- Code: `format!("echo '{}' > /tmp/zsm-previous-session", session_name)`
+- Current mitigation: Session name validation blocks `/` characters (`src/state.rs:619-621`)
+- Recommendations: Use shell-safe escaping, or write directly if WASM sandbox permits
+
+**World-Writable Temp File:**
+- Risk: `/tmp/zsm-previous-session` is world-readable/writable
+- Location: `src/state.rs:675, 690`
+- Current mitigation: File only contains session name (low sensitivity)
+- Recommendations: Use user-specific path or XDG_RUNTIME_DIR
+
+## Performance Bottlenecks
+
+**None identified.**
+
+The codebase handles small datasets (typically <100 directories/sessions). No performance issues expected at current scale.
+
+**Potential Future Concern - Combined Items Rebuild:**
+- Location: `src/state.rs:524-529` (update_search_if_needed)
+- Pattern: `combined_items()` rebuilds full list on every search update
+- Impact: Low with current dataset sizes
+- Improvement path: Cache combined items, use incremental updates
+
+## Fragile Areas
+
+**Smart Session Naming Algorithm:**
+- Location: `src/main.rs:197-502`
+- Why fragile: Complex interdependent functions, many edge cases (Unicode, symlinks, deep paths)
+- Common failures: Edge cases with unusual path structures
+- Safe modification: Add comprehensive unit tests before changes
+- Test coverage: **None** - HIGH RISK
+
+**WASM Sandbox Limitations:**
+- Location: `src/state.rs:675-702` (file I/O workarounds)
+- Why fragile: Relies on shelling out to bypass WASM restrictions
+- Common failures: File persistence issues, race conditions between plugin instances
+- Safe modification: Understand WASM sandbox constraints before changes
+- Test coverage: Cannot test in isolation (WASM-specific)
+
+## Scaling Limits
+
+**Not applicable.**
+
+Plugin runs locally with user's directory history. No cloud services or shared resources.
+
+## Dependencies at Risk
+
+**All dependencies current (as of Jan 2026):**
+- `zellij-tile 0.43.1` - Actively maintained with Zellij
+- `zellij-utils 0.43.1` - Same lifecycle as zellij-tile
+- `serde 1.0.164` - Stable, widely used
+- `fuzzy-matcher 0.3.7` - Stable, minimal updates expected
+- `uuid 1.8.0` - Stable, widely used
+- `humantime 2.2.0` - Stable, low update frequency
+
+No immediate risks identified.
+
+## Missing Critical Features
+
+**None identified.**
+
+The plugin provides complete session/directory management functionality as designed.
+
+## Test Coverage Gaps
+
+**Smart Naming Algorithm (HIGH PRIORITY):**
+- What's not tested: 503 lines of logic in `src/main.rs` - conflict detection, context naming, truncation
+- Location: `src/main.rs:197-502`
+- Risk: Naming bugs affect user experience, edge cases unknown
+- Priority: HIGH
+- Difficulty to test: Medium - need to mock or construct path data
+
+**State Coordination Logic:**
+- What's not tested: 709 lines in `src/state.rs` - display logic, selection, item combination
+- Location: `src/state.rs`
+- Risk: State management bugs could cause UI issues
+- Priority: Medium
+- Difficulty to test: Medium - need to simulate events
+
+**Fuzzy Search Engine:**
+- What's not tested: 204 lines in `src/zoxide/search.rs`
+- Location: `src/zoxide/search.rs`
+- Risk: Search ranking issues
+- Priority: Low (uses well-tested fuzzy-matcher crate)
+- Difficulty to test: Low - pure function logic
+
+**UI Rendering:**
+- What's not tested: 431 lines in `src/ui/renderer.rs`
+- Location: `src/ui/renderer.rs`
+- Risk: Display issues
+- Priority: Low (visual verification during development)
+- Difficulty to test: High - Zellij rendering API
+
+## Minor Issues
+
+**Error Messages Clear on Any Keypress:**
+- Location: `src/state.rs:108-113`
+- Behavior: Any keypress clears error, even if user didn't read it
+- UX impact: Users might miss validation errors
+- Recommendation: Only clear errors on meaningful actions
+
+**Unicode Truncation Edge Case:**
+- Location: `src/main.rs:343-344`
+- Problem: `.len()` counts bytes, not characters; multibyte UTF-8 could truncate mid-character
+- Impact: Low probability (requires non-ASCII paths)
+- Recommendation: Use `.chars().count()` or check byte boundaries
+
+**Configuration Delimiter Fragility:**
+- Location: `src/config.rs:43-51`
+- Issue: `base_paths` uses `|` delimiter with no escape mechanism
+- Impact: Cannot use `|` in paths (edge case)
+- Recommendation: Document limitation or add escape support
+
+---
+
+## Summary
+
+**Overall Assessment:** Clean, well-structured codebase with no critical issues.
+
+**Priorities:**
+1. **HIGH**: Add unit tests for smart naming algorithm (`src/main.rs:197-502`)
+2. **MEDIUM**: Address shell command injection concern in session persistence
+3. **LOW**: Extract duplicate range calculation logic
+
+**Positive Notes:**
+- No `unsafe` blocks
+- No unchecked `unwrap()` or `expect()` calls
+- Good inline documentation
+- CI/CD properly configured with tests, clippy, and fmt checks
+- Error handling is defensive and informative
+
+---
+
+*Concerns audit: 2026-01-13*
+*Update as issues are fixed or new ones discovered*