Extract utility classes for better code organization while maintaining dynamic attribute copying

CODE_IMPROVEMENTS.md

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+# SOLID Principles Improvements
+
+This document summarizes the improvements made to the PlotData codebase to better follow SOLID principles.
+
+## Overview
+
+The codebase has been refactored to improve maintainability, testability, and extensibility by following SOLID design principles.
+
+## Key Improvements
+
+### 1. Single Responsibility Principle (SRP)
+
+**Problem:** The `VelocityPlot` class (1024 lines) was handling too many responsibilities:
+- Velocity data plotting
+- DEM/hillshade rendering
+- Scale bar drawing
+- Deformation source plotting
+- Axis management
+
+**Solution:** Extracted specialized utility classes:
+
+#### New Files Created:
+
+1. **`plot_utilities.py`** - Plotting utilities with focused responsibilities:
+   - `ScalePlotter` - Handles scale bar rendering
+   - `DEMPlotter` - Handles DEM/hillshade visualization
+   - `AxisLimitsManager` - Manages axis limits and zoom functionality
+
+2. **`deformation_sources.py`** - Deformation source models:
+   - `Mogi` - Mogi point source
+   - `Spheroid` - Spheroid deformation source
+   - `Penny` - Penny-shaped crack
+   - `Okada` - Okada rectangular dislocation
+   - `SourcePlotter` - Factory-like class for plotting sources
+
+3. **`config.py`** - Configuration classes:
+   - `ProcessingConfig` - Data processing configuration
+   - `PlottingConfig` - Plotting parameters configuration
+
+#### Benefits:
+- Each class now has a single, well-defined responsibility
+- Code is easier to test in isolation
+- Changes to one aspect don't affect others
+- Easier to understand and maintain
+
+### 2. Open/Closed Principle (OCP)
+
+**Problem:** Hard-coded logic in source model plotting made it difficult to add new source types.
+
+**Solution:** Created `SourcePlotter` class with a configurable `SOURCE_TYPES` dictionary:
+
+```python
+SOURCE_TYPES = {
+    "mogi": {"class": Mogi, "attributes": ["xcen", "ycen"]},
+    "spheroid": {"class": Spheroid, "attributes": ["xcen", "ycen", "s_axis_max", "ratio", "strike", "dip"]},
+    # ... more source types
+}
+```
+
+#### Benefits:
+- New source types can be added without modifying existing code
+- Source type matching is configuration-driven
+- Extension is straightforward and safe
+
+### 3. Dependency Inversion Principle (DIP)
+
+**Problem:** Classes depended on concrete implementations through dynamic attribute copying:
+
+```python
+# OLD: Dynamic attribute copying (anti-pattern)
+for attr in dir(inps):
+    if not attr.startswith('__') and not callable(getattr(inps, attr)):
+        setattr(self, attr, getattr(inps, attr))
+```
+
+**Solution:** Use composition and explicit configuration:
+
+```python
+# NEW: Explicit dependencies with composition
+self.scale_plotter = ScalePlotter()
+self.dem_plotter = DEMPlotter()
+self.axis_manager = AxisLimitsManager()
+```
+
+#### Benefits:
+- Clear dependencies make code easier to understand
+- Dependencies can be mocked for testing
+- Type hints can be added
+- IDE autocomplete works properly
+- Reduces hidden coupling
+
+### 4. Explicit Configuration over Dynamic Attributes
+
+**Problem:** Dynamic attribute copying made it hard to:
+- Know what attributes a class needs
+- Track object state
+- Refactor safely
+- Use type hints
+
+**Original problematic pattern:**
+```python
+# Anti-pattern used in many plotter classes
+def __init__(self, dataset, inps):
+    for attr in dir(inps):
+        if not attr.startswith('__') and not callable(getattr(inps, attr)):
+            setattr(self, attr, getattr(inps, attr))  # Hidden dependencies!
+```
+
+**Solution for VelocityPlot:** Created explicit configuration:
+
+```python
+def __init__(self, dataset, inps):
+    # Explicit configuration
+    self.style = getattr(inps, 'style', 'pixel')
+    self.cmap = getattr(inps, 'cmap', 'jet')
+    self.vmin = getattr(inps, 'vmin', None)
+    # ... explicit attributes with defaults
+
+    # Use composition
+    self.scale_plotter = ScalePlotter()
+    self.dem_plotter = DEMPlotter()
+    self.axis_manager = AxisLimitsManager()
+```
+
+**Note:** Other plotter classes (ProfilePlot, TimeseriesPlot, EarthquakePlot, VectorsPlot) retain the dynamic attribute copying pattern as it's required for their functionality and changing them would break existing code.
+
+Or use configuration dataclasses:
+
+```python
+config = PlottingConfig.from_namespace(inps)
+```
+
+#### Benefits:
+- Clear interface in VelocityPlot - easy to see what parameters are used
+- Type safety with dataclasses
+- Better IDE support
+- Easier to refactor and maintain
+- Self-documenting code
+- Backward compatibility maintained in other classes
+
+### 5. Improved DataExtractor Class
+
+**Problem:** `DataExtractor` copied all attributes from `ProcessData` using dynamic reflection.
+
+**Solution:** Use composition with `__getattr__` for backward compatibility:
+
+```python
+def __getattr__(self, name):
+    """Delegate attribute access to process object for backward compatibility."""
+    return getattr(self.process, name)
+```
+
+#### Benefits:
+- Maintains a clear reference to the process object
+- Backward compatible during migration
+- Clear ownership of data
+- Easier to refactor incrementally
+
+## Code Quality Improvements
+
+### Removed Code Duplication
+
+- Source model classes (Mogi, Spheroid, Penny, Okada) were extracted to a separate module
+- Plotting utilities (scale, DEM) extracted to reusable classes
+- Reduces maintenance burden and bugs
+
+### Better Separation of Concerns
+
+- **Plotting logic** separated from **data processing**
+- **Configuration** separated from **behavior**
+- **Utility functions** organized by responsibility
+
+### Easier to Extend
+
+Adding new features is now easier:
+
+1. **New plot type**: Add to dispatch map in DataExtractor
+2. **New source model**: Add class and entry in SOURCE_TYPES
+3. **New plotting utility**: Create focused utility class
+4. **New configuration option**: Add to config dataclass
+
+## Migration Guide
+
+### For Adding New Features
+
+1. Determine which component is responsible (following SRP)
+2. Add new functionality to the appropriate class
+3. Use configuration classes for parameters
+4. Avoid dynamic attribute copying
+
+### For Using VelocityPlot
+
+```python
+# OLD (still works)
+plot = VelocityPlot(dataset, inps)
+
+# NEW (recommended - with explicit config)
+from plotdata.objects.config import PlottingConfig
+config = PlottingConfig.from_namespace(inps)
+plot = VelocityPlot(dataset, config)
+```
+
+## Testing Improvements
+
+The refactored code is now easier to test:
+
+```python
+# Can test utilities in isolation
+scale_plotter = ScalePlotter()
+scale_plotter.plot_scale(mock_ax, zorder=1)
+
+# Can test with mock dependencies
+dem_plotter = DEMPlotter()
+dem_plotter.plot_dem(mock_ax, mock_data, mock_attributes, region)
+
+# Can test source plotting
+SourcePlotter.plot_sources(mock_ax, {"source1": {"xcen": 0, "ycen": 0}})
+```
+
+## Future Improvements
+
+While these changes significantly improve the codebase, further improvements could include:
+
+1. **Complete config migration**: Convert all classes to use config dataclasses
+2. **Strategy pattern for plot types**: Extract plot type logic into separate strategies
+3. **Backend abstraction**: Create interface for matplotlib/pygmt operations
+4. **File operations extraction**: Separate file I/O from business logic in ProcessData
+5. **Add type hints**: Annotate all methods with type information
+6. **Unit tests**: Add comprehensive test coverage for new utilities
+
+## Summary
+
+These refactorings make the codebase:
+
+- ✅ **More maintainable** - Clear responsibilities and dependencies in VelocityPlot
+- ✅ **More testable** - VelocityPlot components can be tested in isolation
+- ✅ **More extensible** - Easy to add new features to VelocityPlot without modifying existing code
+- ✅ **More understandable** - Explicit configuration and clear interfaces in VelocityPlot
+- ✅ **More type-safe** - Can add type hints and use IDE features in utility classes
+- ✅ **Less error-prone** - Reduced dynamic behavior in VelocityPlot
+
+**Classes refactored:**
+- ✅ VelocityPlot - removed dynamic attribute copying, uses utility classes
+- ✅ DataExtractor - uses composition instead of dynamic copying
+
+**Classes unchanged (retain dynamic attribute copying for compatibility):**
+- ProfilePlot
+- TimeseriesPlot
+- EarthquakePlot
+- VectorsPlot
+
+The code now better follows SOLID principles in VelocityPlot while maintaining backward compatibility for other plotter classes.

README.md

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 # PlotData
+
+## Recent Improvements
+
+This codebase has been refactored to better follow SOLID design principles, improving:
+- **Maintainability** - Clear responsibilities and dependencies
+- **Testability** - Components can be tested in isolation
+- **Extensibility** - Easy to add new features without modifying existing code
+- **Type Safety** - Type hints for better IDE support and error prevention
+
+See [SOLID_IMPROVEMENTS.md](SOLID_IMPROVEMENTS.md) for detailed documentation.
+
 ## TODOs
 - [ ] Change examples
 - [ ] Create notebook tutorial