notes(2025-03-02) Add architecture notes

Author: tony

notes/2025-03-02-architecture-plan.md

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+<think>Let me analyze the `snapshot.py` file for its architecture, typing, and implementation details, as well as identify any flaws or opportunities for improvement in its API.
+
+First, let's understand what this module is doing:
+
+1. This module implements a snapshot mechanism for tmux objects (Server, Session, Window, Pane)
+2. It uses frozen_dataclass_sealable to create immutable snapshots of these objects
+3. It provides utilities to filter snapshots, convert them to dictionaries, etc.
+
+Key classes in this module:
+- PaneSnapshot, WindowSnapshot, SessionSnapshot, ServerSnapshot - these create immutable snapshots of their respective tmux objects
+- Each snapshot class inherits from both the respective tmux class (Pane, Window, etc.) and Sealable
+- Each has a from_X factory method to create a snapshot from a live object
+
+Let's identify any architectural or typing issues:
+
+1. Type annotations: The module uses Python's typing system extensively, with TypeVars, Union types, etc.
+2. Immutability pattern: It uses frozen_dataclass_sealable to implement immutability
+3. Circular references: The snapshots can have circular references (e.g., a WindowSnapshot has SessionSnapshot which has the same WindowSnapshot)
+
+Now, let's look for flaws or areas for improvement:
+
+1. **Complex Inheritance**: Multiple inheritance from both tmux objects and Sealable might cause confusion
+2. **Code Duplication**: The from_X factory methods have a lot of duplicated logic
+3. **Excessive Type Annotations**: Some of the type annotations might be overly complex
+4. **Error Handling**: There's a mix of error suppression and re-raising
+5. **Memory Usage**: Snapshots might use a lot of memory, especially with capture_content=True
+
+API simplification opportunities:
+
+1. **Factory Method Consistency**: Consider simplifying the factory methods
+2. **Context Manager**: Consider adding a context manager for creating and using snapshots
+3. **Fluent Interface**: Consider making the filter and conversion methods chainable
+4. **Simplify Type Annotations**: Make type annotations more consistent and simpler where possible
+5. **Reduce Circular References**: Consider alternative designs to reduce circular references
+
+Let's discuss each of these in detail in the response.</think># Analysis of Snapshot Architecture
+
+After examining the `snapshot.py` module, I can provide an analysis of its architecture, typing approach, and potential areas for improvement.
+
+## Overall Architecture
+
+The module implements a hierarchical snapshot system for tmux objects with these key components:
+
+1. Four snapshot classes that mirror the tmux object hierarchy:
+   - `ServerSnapshot`
+   - `SessionSnapshot`
+   - `WindowSnapshot`
+   - `PaneSnapshot`
+
+2. Each class inherits from both:
+   - The corresponding tmux class (Server, Session, etc.)
+   - A `Sealable` base class to provide immutability
+
+3. Utility functions for:
+   - Filtering snapshots (`filter_snapshot`)
+   - Converting to dictionaries (`snapshot_to_dict`) 
+   - Creating active-only views (`snapshot_active_only`)
+
+## Typing Approach
+
+The module makes excellent use of Python's modern typing features:
+
+- Type variables with covariance (`PaneT = t.TypeVar("PaneT", bound=Pane, covariant=True)`)
+- Proper return type annotations with Union types
+- Type checking guards (`if t.TYPE_CHECKING:`)
+- Type casts for better type safety (`t.cast("ServerSnapshot", filtered)`)
+
+## Strengths
+
+1. **Immutability Pattern**: Using `frozen_dataclass_sealable` provides a robust way to create immutable snapshots
+2. **Complete Object Graph**: Snapshots maintain the full hierarchy of relationships
+3. **Type Safety**: Strong typing throughout the codebase
+
+## Potential Flaws
+
+1. **Complex Factory Methods**: The `from_X` methods contain complex logic for finding server references, with multiple fallback strategies:
+   ```python
+   if source_server is None and window_snapshot is not None:
+       source_server = window_snapshot.server
+   # ...more fallbacks...
+   ```
+
+2. **Circular References**: The bi-directional references (window_snapshot -> session_snapshot -> window_snapshot) could create complexity for serialization and garbage collection.
+
+3. **Error Handling Inconsistencies**: There's a mix of:
+   ```python
+   with contextlib.suppress(Exception):
+       # silent failure
+   ```
+   and explicit error raising:
+   ```python
+   if source_server is None:
+       error_msg = "Cannot create snapshot..."
+       raise ValueError(error_msg)
+   ```
+
+4. **Memory Overhead**: Snapshots duplicate a lot of data, especially with `capture_content=True`.
+
+5. **Attribute Access Pattern**: The code uses direct attribute access in some places but property methods in others.
+
+## API Simplification Opportunities
+
+1. **Unified Factory Method**: Consider a single entry point for snapshot creation:
+   ```python
+   def create_snapshot(tmux_object, capture_content=False, depth=None):
+       """Create a snapshot of a tmux object."""
+       # Dispatch to appropriate snapshot class based on type
+   ```
+
+2. **Context Manager Support**:
+   ```python
+   @contextlib.contextmanager
+   def tmux_snapshot(server, capture_content=False):
+       """Create a snapshot and yield it as a context manager."""
+       snapshot = ServerSnapshot.from_server(server, capture_content)
+       try:
+           yield snapshot
+       finally:
+           # Cleanup if needed
+   ```
+
+3. **Fluent Interface** for chaining operations:
+   ```python
+   snapshot = (
+       ServerSnapshot.from_server(server)
+       .filter(lambda obj: obj.name.startswith("dev"))
+       .active_only()
+       .to_dict()
+   )
+   ```
+
+4. **Focused Snapshot Classes**: The snapshots try to maintain compatibility with their tmux counterparts but override behaviors. Consider a cleaner separation with composition instead of inheritance.
+
+5. **More Targeted Snapshot Creation**: Allow for creating more targeted snapshots:
+   ```python
+   # Only capturing active session/window/pane hierarchy
+   snapshot = create_snapshot(server, include='active')
+   
+   # Capturing only specified sessions
+   snapshot = create_snapshot(server, include_sessions=['dev', 'prod'])
+   ```
+
+## Type Safety Improvements
+
+1. The use of `type: ignore[override]` comments suggests there might be a better way to handle property overrides in the typing system. Consider using Protocol classes or structural typing.
+
+2. The `filter_snapshot` function's return type is quite complex - it might be worth creating a generic type for this.
+
+Overall, the module is well-designed but could benefit from some API simplifications to make it more intuitive for users while maintaining its strong typing and immutability guarantees.