Add search functionality to Mail TUI with / keybinding

- Add reusable SearchScreen modal and ClearableSearchInput widget
- Implement filter_by_query in MessageStore for client-side filtering
- Search matches subject, sender name/email, recipient name/email
- Press / to open search, Escape to clear search filter
- Shows search query in list subtitle when filter is active

src/mail/app.py

@@ -11,6 +11,7 @@ from src.services.taskwarrior import client as taskwarrior_client
 from src.services.himalaya import client as himalaya_client
 from src.utils.shared_config import get_theme_name
 from src.utils.ipc import IPCListener, IPCMessage
+from src.utils.search import SearchScreen
 from textual.containers import Container, ScrollableContainer, Vertical, Horizontal
 from textual.timer import Timer
 from textual.binding import Binding
@@ -73,6 +74,7 @@ class EmailViewerApp(App):
     sort_order_ascending: Reactive[bool] = reactive(True)
     selected_messages: Reactive[set[int]] = reactive(set())
     main_content_visible: Reactive[bool] = reactive(True)
+    search_query: Reactive[str] = reactive("")  # Current search filter
 
     def get_system_commands(self, screen: Screen) -> Iterable[SystemCommand]:
         yield from super().get_system_commands(screen)
@@ -126,6 +128,7 @@ class EmailViewerApp(App):
             Binding("x", "toggle_selection", "Toggle selection", show=False),
             Binding("space", "toggle_selection", "Toggle selection"),
             Binding("escape", "clear_selection", "Clear selection"),
+            Binding("/", "search", "Search"),
         ]
     )
 
@@ -511,7 +514,13 @@ class EmailViewerApp(App):
 
         config = get_config()
 
-        for item in self.message_store.envelopes:
+        # Use filtered envelopes if search is active
+        if self.search_query:
+            display_envelopes = self.message_store.filter_by_query(self.search_query)
+        else:
+            display_envelopes = self.message_store.envelopes
+
+        for item in display_envelopes:
             if item and item.get("type") == "header":
                 # Use the new GroupHeader widget for date groupings
                 envelopes_list.append(ListItem(GroupHeader(label=item["label"])))
@@ -872,10 +881,17 @@ class EmailViewerApp(App):
             self._update_list_view_subtitle()
 
     def action_clear_selection(self) -> None:
-        """Clear all selected messages."""
+        """Clear all selected messages and search filter."""
+        if self.selected_messages:
             self.selected_messages.clear()
             self.refresh_list_view_items()  # Refresh all items to uncheck checkboxes
             self._update_list_view_subtitle()
+        elif self.search_query:
+            # Clear search if no selection
+            self.search_query = ""
+            self._populate_list_view()
+            self._update_list_view_subtitle()
+            self.show_status("Search cleared")
 
     def action_oldest(self) -> None:
         self.fetch_envelopes() if self.reload_needed else None
@@ -885,6 +901,40 @@ class EmailViewerApp(App):
         self.fetch_envelopes() if self.reload_needed else None
         self.show_message(self.message_store.get_newest_id())
 
+    def action_search(self) -> None:
+        """Open search dialog to filter messages."""
+
+        def handle_search_result(query: str | None) -> None:
+            if query is None:
+                return  # User cancelled
+            self.search_query = query
+            self._apply_search_filter()
+
+        self.push_screen(
+            SearchScreen(
+                title="Search Messages",
+                placeholder="Search by subject, sender, or recipient...",
+                initial_value=self.search_query,
+            ),
+            handle_search_result,
+        )
+
+    def _apply_search_filter(self) -> None:
+        """Apply the current search filter to the envelope list."""
+        self._populate_list_view()
+
+        # Update the title to show search status
+        if self.search_query:
+            self.query_one("#envelopes_list").border_subtitle = f"[{self.search_query}]"
+        else:
+            self._update_list_view_subtitle()
+
+        # Focus the list and select first message
+        self.query_one("#envelopes_list").focus()
+        envelopes_list = self.query_one("#envelopes_list", ListView)
+        if envelopes_list.children:
+            envelopes_list.index = 0
+
     def action_focus_1(self) -> None:
         self.query_one("#envelopes_list").focus()
 

src/mail/message_store.py

@@ -148,3 +148,64 @@ class MessageStore:
             self.total_messages = len(self.metadata_by_id)
         else:
             logging.warning(f"Invalid index {index} for message ID {message_id}")
+
+    def filter_by_query(self, query: str) -> List[Dict[str, Any]]:
+        """Filter envelopes by search query.
+
+        Searches subject, from name, from address, to name, and to address.
+        Returns a new list of filtered envelopes (with headers regenerated).
+        """
+        if not query or not query.strip():
+            return self.envelopes
+
+        query_lower = query.lower().strip()
+        filtered = []
+        current_month = None
+
+        for item in self.envelopes:
+            if item is None:
+                continue
+
+            # Skip headers - we'll regenerate them
+            if item.get("type") == "header":
+                continue
+
+            # Check if envelope matches query
+            subject = item.get("subject", "").lower()
+            from_info = item.get("from", {})
+            from_name = (
+                from_info.get("name", "").lower() if isinstance(from_info, dict) else ""
+            )
+            from_addr = (
+                from_info.get("addr", "").lower() if isinstance(from_info, dict) else ""
+            )
+            to_info = item.get("to", {})
+            to_name = (
+                to_info.get("name", "").lower() if isinstance(to_info, dict) else ""
+            )
+            to_addr = (
+                to_info.get("addr", "").lower() if isinstance(to_info, dict) else ""
+            )
+
+            if (
+                query_lower in subject
+                or query_lower in from_name
+                or query_lower in from_addr
+                or query_lower in to_name
+                or query_lower in to_addr
+            ):
+                # Regenerate month header if needed
+                date_str = item.get("date", "")
+                try:
+                    date = datetime.fromisoformat(date_str.replace("Z", "+00:00"))
+                    month_key = date.strftime("%B %Y")
+                except (ValueError, TypeError):
+                    month_key = "Unknown Date"
+
+                if month_key != current_month:
+                    current_month = month_key
+                    filtered.append({"type": "header", "label": month_key})
+
+                filtered.append(item)
+
+        return filtered

src/utils/search.py

@@ -0,0 +1,179 @@
+"""Reusable search input screen for TUI apps.
+
+A modal input dialog that can be used for search across all apps.
+"""
+
+from typing import Optional
+
+from textual.app import ComposeResult
+from textual.binding import Binding
+from textual.containers import Vertical, Horizontal
+from textual.screen import ModalScreen
+from textual.widgets import Input, Static, Label, Button
+
+
+class SearchScreen(ModalScreen[str | None]):
+    """A modal screen for search input.
+
+    Returns the search query string on submit, or None on cancel.
+    """
+
+    DEFAULT_CSS = """
+    SearchScreen {
+        align: center middle;
+    }
+    
+    SearchScreen > Vertical {
+        width: 60;
+        height: auto;
+        border: solid $primary;
+        background: $surface;
+        padding: 1 2;
+    }
+    
+    SearchScreen > Vertical > Label {
+        margin-bottom: 1;
+    }
+    
+    SearchScreen > Vertical > Input {
+        margin-bottom: 1;
+    }
+    
+    SearchScreen > Vertical > Horizontal {
+        height: auto;
+        align: right middle;
+    }
+    
+    SearchScreen > Vertical > Horizontal > Button {
+        margin-left: 1;
+    }
+    """
+
+    BINDINGS = [
+        Binding("escape", "cancel", "Cancel", show=True),
+    ]
+
+    def __init__(
+        self,
+        title: str = "Search",
+        placeholder: str = "Enter search query...",
+        initial_value: str = "",
+        name: Optional[str] = None,
+        id: Optional[str] = None,
+        classes: Optional[str] = None,
+    ) -> None:
+        super().__init__(name=name, id=id, classes=classes)
+        self._title = title
+        self._placeholder = placeholder
+        self._initial_value = initial_value
+
+    def compose(self) -> ComposeResult:
+        with Vertical():
+            yield Label(self._title)
+            yield Input(
+                placeholder=self._placeholder,
+                value=self._initial_value,
+                id="search-input",
+            )
+            with Horizontal():
+                yield Button("Search", variant="primary", id="search-btn")
+                yield Button("Cancel", variant="default", id="cancel-btn")
+
+    def on_mount(self) -> None:
+        """Focus the input on mount."""
+        self.query_one("#search-input", Input).focus()
+
+    def on_input_submitted(self, event: Input.Submitted) -> None:
+        """Handle Enter key in input."""
+        self.dismiss(event.value)
+
+    def on_button_pressed(self, event: Button.Pressed) -> None:
+        """Handle button presses."""
+        if event.button.id == "search-btn":
+            query = self.query_one("#search-input", Input).value
+            self.dismiss(query)
+        elif event.button.id == "cancel-btn":
+            self.dismiss(None)
+
+    def action_cancel(self) -> None:
+        """Cancel the search."""
+        self.dismiss(None)
+
+
+class ClearableSearchInput(Static):
+    """A search input widget with clear button for use in sidebars/headers.
+
+    Emits SearchInput.Submitted message when user submits a query.
+    Emits SearchInput.Cleared message when user clears the search.
+    """
+
+    DEFAULT_CSS = """
+    ClearableSearchInput {
+        height: 3;
+        padding: 0 1;
+    }
+    
+    ClearableSearchInput > Horizontal {
+        height: auto;
+    }
+    
+    ClearableSearchInput > Horizontal > Input {
+        width: 1fr;
+    }
+    
+    ClearableSearchInput > Horizontal > Button {
+        width: 3;
+        min-width: 3;
+    }
+    """
+
+    from textual.message import Message
+
+    class Submitted(Message):
+        """Search query was submitted."""
+
+        def __init__(self, query: str) -> None:
+            super().__init__()
+            self.query = query
+
+    class Cleared(Message):
+        """Search was cleared."""
+
+        pass
+
+    def __init__(
+        self,
+        placeholder: str = "Search...",
+        name: Optional[str] = None,
+        id: Optional[str] = None,
+        classes: Optional[str] = None,
+    ) -> None:
+        super().__init__(name=name, id=id, classes=classes)
+        self._placeholder = placeholder
+
+    def compose(self) -> ComposeResult:
+        with Horizontal():
+            yield Input(placeholder=self._placeholder, id="search-input")
+            yield Button("X", id="clear-btn", variant="error")
+
+    def on_input_submitted(self, event: Input.Submitted) -> None:
+        """Handle search submission."""
+        self.post_message(self.Submitted(event.value))
+
+    def on_button_pressed(self, event: Button.Pressed) -> None:
+        """Handle clear button."""
+        if event.button.id == "clear-btn":
+            input_widget = self.query_one("#search-input", Input)
+            input_widget.value = ""
+            input_widget.focus()
+            self.post_message(self.Cleared())
+
+    @property
+    def value(self) -> str:
+        """Get the current search value."""
+        return self.query_one("#search-input", Input).value
+
+    @value.setter
+    def value(self, new_value: str) -> None:
+        """Set the search value."""
+        self.query_one("#search-input", Input).value = new_value