Feat #5: choose additive or replacement import

tests/test_import_export_workflow.py

@@ -15,7 +15,12 @@ from hosts.core.import_export import (
 )
 from hosts.core.models import HostEntry, HostsFile
 from hosts.tui.app import HostsManagerApp
-from hosts.tui.import_export_modal import ExportModal, FileBrowserModal, ImportModal
+from hosts.tui.import_export_modal import (
+    ExportModal,
+    FileBrowserModal,
+    ImportModal,
+    ReplaceImportConfirmationModal,
+)
 
 
 @pytest.mark.asyncio
@@ -236,14 +241,45 @@ async def test_import_shortcut_requires_privileged_mode_and_surfaces_service_err
 
 
 @pytest.mark.asyncio
-async def test_successful_import_replaces_entries_and_saves_through_the_manager():
-    """A valid import reaches the persistence seam without a real Hosts File."""
+async def test_import_form_asks_how_to_apply_entries_at_minimum_supported_size():
+    """Both import actions remain visible and reachable at 100 by 30."""
+    app = HostsManagerApp()
+    app.edit_mode = True
+    app.manager.edit_mode = True
+    app.import_export_service = Mock()
+    app.import_export_service.get_supported_import_formats.return_value = list(
+        ImportFormat
+    )
+
+    async with app.run_test(size=(100, 30)) as pilot:
+        app.action_import_entries()
+        await pilot.pause()
+
+        assert isinstance(app.screen, ImportModal)
+        actions = app.screen.query_one("#import-mode-select", RadioSet)
+        assert [button.label.plain for button in actions.query(RadioButton)] == [
+            "Add to Hosts File",
+            "Replace Hosts File",
+        ]
+        assert app.screen.query_one("#mode-add", RadioButton).value
+        assert not app.screen.query_one("#mode-replace", RadioButton).value
+        container = app.screen.query_one("#format-container")
+        submit = app.screen.query_one("#import-button", Button)
+        assert submit.region.bottom <= container.region.bottom
+
+
+@pytest.mark.asyncio
+async def test_successful_import_adds_entries_and_saves_through_the_manager():
+    """The safe default appends imported Host Entries to the Hosts File."""
     app = HostsManagerApp()
     app.hosts_file = HostsFile(
-        entries=[HostEntry(ip_address="192.0.2.10", hostnames=["original.test"])]
+        entries=[HostEntry(ip_address="192.0.2.10", hostnames=["original.test"])],
+        header_comments=["existing header"],
+        footer_comments=["existing footer"],
     )
     app.edit_mode = True
     app.manager.edit_mode = True
+    app.load_hosts_file = Mock()
     app.save_mutation = Mock(return_value=True)
     app.import_export_service = Mock()
     app.import_export_service.get_supported_import_formats.return_value = list(
@@ -269,9 +305,74 @@ async def test_successful_import_replaces_entries_and_saves_through_the_manager(
         await pilot.pause()
 
         assert [entry.hostnames for entry in app.hosts_file.entries] == [
-            ["imported.test"]
+            ["original.test"],
+            ["imported.test"],
         ]
+        assert app.hosts_file.header_comments == ["existing header"]
+        assert app.hosts_file.footer_comments == ["existing footer"]
         app.save_mutation.assert_called_once()
-        assert "Imported and saved 1 Host Entries" in str(
+        assert "Added and saved 1 Host Entry" in str(
+            app.query_one("#message-rail", Static).render()
+        )
+
+
+@pytest.mark.asyncio
+async def test_replace_import_requires_explicit_destructive_confirmation():
+    """Replacement cannot mutate until the warning modal is confirmed."""
+    app = HostsManagerApp()
+    original = HostEntry(ip_address="192.0.2.10", hostnames=["original.test"])
+    imported = HostEntry(ip_address="198.51.100.3", hostnames=["imported.test"])
+    app.hosts_file = HostsFile(entries=[original])
+    app.edit_mode = True
+    app.manager.edit_mode = True
+    app.load_hosts_file = Mock()
+    app.save_mutation = Mock(return_value=True)
+    app.import_export_service = Mock()
+    app.import_export_service.get_supported_import_formats.return_value = list(
+        ImportFormat
+    )
+    app.import_export_service.import_json_format.return_value = ImportResult(
+        success=True,
+        entries=[imported],
+        errors=[],
+        warnings=[],
+        total_processed=1,
+        successfully_imported=1,
+    )
+
+    async with app.run_test(size=(120, 40)) as pilot:
+
+        async def request_replacement() -> None:
+            app.action_import_entries()
+            await pilot.pause()
+            app.screen.query_one("#path-input", Input).value = "/tmp/entries.json"
+            app.screen.query_one("#format-json", RadioButton).value = True
+            app.screen.query_one("#mode-replace", RadioButton).value = True
+            await pilot.click("#import-button")
+            await pilot.pause()
+
+        await request_replacement()
+
+        assert isinstance(app.screen, ReplaceImportConfirmationModal)
+        assert app.focused is app.screen.query_one("#cancel-button", Button)
+        assert "remove all 1 current Host Entry" in str(
+            app.screen.query_one("#replace-warning", Static).render()
+        )
+        assert app.hosts_file.entries == [original]
+        app.save_mutation.assert_not_called()
+
+        await pilot.click("#cancel-button")
+        await pilot.pause()
+        assert app.hosts_file.entries == [original]
+        app.save_mutation.assert_not_called()
+
+        await request_replacement()
+        await pilot.click("#replace-button")
+        await pilot.pause()
+        await pilot.pause()
+
+        assert app.hosts_file.entries == [imported]
+        app.save_mutation.assert_called_once()
+        assert "Replaced Hosts File with 1 imported Host Entry" in str(
             app.query_one("#message-rail", Static).render()
         )