feat: Implement CLI and TUI for Fountain Pen Tracker

- Added CLI functionality for adding, editing, viewing, and deleting fountain pens.
- Introduced TUI using Textual for a more interactive experience.
- Created Pen and PenTracker classes to manage pen data and CSV storage.
- Implemented input validation for date fields.
- Added export functionality to JSON format.
- Updated project version to 0.2.0.
- Added unit tests for PenTracker functionality.

build/lib/pen_tracker/tui.py

@@ -0,0 +1,159 @@
+from textual.app import App, ComposeResult
+from textual.screen import Screen
+from textual.widgets import Label, Input, Button, Header, Footer, DataTable
+from textual.containers import Vertical, Horizontal
+from textual.binding import Binding
+from .engine import PenTracker, Pen
+# --- TUI SCREENS ---
+
+class PenFormScreen(Screen):
+    """A screen for adding or editing a pen."""
+    
+    def __init__(self, tracker, existing_pen=None):
+        super().__init__()
+        self.tracker = tracker
+        self.existing_pen = existing_pen
+
+    def compose(self) -> ComposeResult:
+        with Vertical(id="form-container"):
+            yield Label("📝 NEW PEN" if not self.existing_pen else "✏️ EDIT PEN")
+            
+            for header in self.tracker.headers:
+                field = self.tracker.key_map.get(header, header)
+                val = getattr(self.existing_pen, field) if self.existing_pen else ""
+                yield Input(value=val, placeholder=header, id=header)
+
+            with Horizontal():
+                yield Button("Save", variant="success", id="save_cmd")
+                yield Button("Cancel", variant="error", id="cancel_cmd")
+
+    def on_button_pressed(self, event: Button.Pressed) -> None:
+        if event.button.id == "cancel_cmd":
+            self.dismiss()
+            return
+
+        new_data = {}
+        for header in self.tracker.headers:
+            try:
+                input_widget = self.query_one(f"#{header}", Input)
+                new_data[header] = input_widget.value if input_widget.value.strip() else "N/A"
+            except Exception:
+                new_data[header] = "N/A"
+
+        # Map to Pen fields
+        mapped_data = {self.tracker.key_map.get(k, k): v for k, v in new_data.items()}
+        new_pen = Pen(**mapped_data)
+
+        if self.existing_pen is not None and self.existing_pen in self.tracker.pens:
+            idx = self.tracker.pens.index(self.existing_pen)
+            self.tracker.pens[idx] = new_pen
+        else:
+            self.tracker.pens.append(new_pen)
+        
+        # save_data() handles the sorting internally
+        self.tracker.save_data()
+        self.dismiss(new_pen)
+
+class PenTrackerApp(App):
+    """The Main TUI Application."""
+    
+    CSS = """
+    #form-container {
+        width: 60%;
+        height: auto;
+        border: heavy white;
+        padding: 1 2;
+        margin: 5 10;
+        background: $panel;
+    }
+    Label {
+        width: 100%;
+        text-align: center;
+        text-style: bold;
+        margin-bottom: 1;
+    }
+    Input {
+        margin-bottom: 1;
+    }
+    Horizontal {
+        align: center middle;
+        height: auto;
+    }
+    Button {
+        margin: 0 1;
+    }
+    DataTable {
+        height: 1fr;
+    }
+    """
+
+    BINDINGS = [
+        Binding("d", "delete_selected", "Delete Selected"),
+        Binding("a", "add_new", "Add New Pen"),
+        Binding("q", "quit", "Quit"),
+    ]
+
+    def compose(self) -> ComposeResult:
+        yield Header()
+        yield DataTable(id="pen_table")
+        yield Footer()
+
+    def on_mount(self) -> None:
+        self.tracker = PenTracker('Pens.csv')
+        self._refresh_table()
+
+    def _refresh_table(self):
+        table = self.query_one("#pen_table", DataTable)
+        table.clear(columns=True)
+        
+        display_cols = ['Make', 'Model', 'Nib', 'Nib-Material', 'Body','Cap', 'Current-Ink', 'Inked-date', 'Notes']
+        table.add_columns(*display_cols)
+
+        for idx, pen in enumerate(self.tracker.pens):
+            row_values = [getattr(pen, c.replace('-','_')) for c in display_cols]
+            # We use the index as the row key to track items accurately 
+            table.add_row(*row_values, key=str(idx))
+
+    def action_add_new(self) -> None:
+        form = PenFormScreen(self.tracker)
+        self.push_screen(form, self.handle_form_result)
+
+    def action_edit_selected(self, index_str: str):
+        try:
+            idx = int(index_str)
+            existing_pen = self.tracker.pens[idx]
+            form = PenFormScreen(self.tracker, existing_pen=existing_pen)
+            self.push_screen(form, self.handle_form_result)
+        except (ValueError, IndexError):
+            pass
+
+    def handle_form_result(self, updated_pen_data) -> None:
+        if updated_pen_data:
+            self._refresh_table()
+            self.notify("Collection Updated & Sorted!", title="Success")
+
+    def action_delete_selected(self) -> None:
+        table = self.query_one("#pen_table", DataTable)
+        try:
+            # Accessing via the table's current cursor
+            table = self.query_one("#pen_table", DataTable)
+            row_node = table.get_row_at_cursor()
+            idx = int(row_node.key.value)
+            removed = self.tracker.pens.pop(idx)
+            self.tracker.save_data()
+            self._refresh_table()
+            self.notify(f"Deleted {removed.Make}", title="Removed")
+        except Exception:
+            self.notify("No pen selected to delete", title="Error", severity="error")
+
+    def on_data_table_cell_selected(self, event: DataTable.CellSelected) -> None:
+        try:
+            idx = int(event.cell_key.row_key.value)
+            self.action_edit_selected(str(idx))
+        except (AttributeError, ValueError):
+            self.notify("Error selecting row", title="Error", severity="error")
+
+def main():
+    # This is the entry point defined in pyproject.toml
+    app = PenTrackerApp()
+    app.run()