Add backends CLI command (#18)

Author: shinaji

src/schnee/controllers/cli/commands.py

@@ -2,13 +2,29 @@
 
 from typing import TYPE_CHECKING
 
+from schnee.controllers.cli.errors import exit_for_service_error
+from schnee.controllers.cli.output import echo_text
+from schnee.services.backend import ListBackendNamesService
+from schnee.services.base import ServiceError
+
 if TYPE_CHECKING:
     import typer
 
 
-def register_commands(_app: typer.Typer) -> None:
+def register_commands(app: typer.Typer) -> None:
     """Register CLI commands."""
 
-    @_app.callback(invoke_without_command=True)
+    @app.callback(invoke_without_command=True)
     def root() -> None:
         """NFC/RFID tag authentication and encryption tools."""
+
+    @app.command("backends")
+    def backends() -> None:
+        """List selectable backend names."""
+        try:
+            names = ListBackendNamesService.call(ListBackendNamesService.Request())
+        except ServiceError as exc:
+            exit_for_service_error(exc)
+
+        for name in names:
+            echo_text(name)

tests/schnee/controllers/cli/test_backends.py

@@ -0,0 +1,94 @@
+"""Tests for the backends CLI command."""
+
+from __future__ import annotations
+
+from pathlib import Path
+from typing import TYPE_CHECKING, ClassVar
+
+from typer.testing import CliRunner
+
+from schnee.controllers.cli.errors import SERVICE_ERROR_EXIT_CODE
+from schnee.controllers.cli.main import app
+from schnee.services.base import ServiceError
+
+if TYPE_CHECKING:
+    import pytest
+
+
+class ExampleServiceError(ServiceError):
+    """Service error used by backends command tests."""
+
+    msg: ClassVar[str] = "backend names unavailable"
+
+
+def test_backends_command_prints_service_backend_names(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    """The backends command delegates backend discovery to the service layer."""
+    requests: list[object] = []
+
+    class FakeListBackendNamesService:
+        class Request:
+            """Request marker used to verify CLI delegation."""
+
+        @classmethod
+        def call(cls, req: object) -> list[str]:
+            requests.append(req)
+            return ["pcsc", "pcsc:Reader A"]
+
+    monkeypatch.setattr(
+        "schnee.controllers.cli.commands.ListBackendNamesService",
+        FakeListBackendNamesService,
+    )
+
+    result = CliRunner().invoke(app, ["backends"], prog_name="schnee")
+
+    assert result.exit_code == 0, "backends command should exit successfully"
+    assert result.output == "pcsc\npcsc:Reader A\n", (
+        "backends command should print each selectable backend name"
+    )
+    assert len(requests) == 1, "backends command should call the service once"
+    assert isinstance(requests[0], FakeListBackendNamesService.Request), (
+        "backends command should pass the service request type"
+    )
+
+
+def test_backends_command_uses_cli_error_handler_for_service_errors(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    """Service-level failures are rendered through the CLI error handler."""
+
+    class FakeListBackendNamesService:
+        class Request:
+            """Request marker used by the fake service."""
+
+        @classmethod
+        def call(cls, req: object) -> list[str]:
+            _ = req
+            raise ExampleServiceError
+
+    monkeypatch.setattr(
+        "schnee.controllers.cli.commands.ListBackendNamesService",
+        FakeListBackendNamesService,
+    )
+
+    result = CliRunner().invoke(app, ["backends"], prog_name="schnee")
+
+    assert result.exit_code == SERVICE_ERROR_EXIT_CODE, (
+        "service errors should terminate with the configured CLI error code"
+    )
+    assert ExampleServiceError.msg in result.stderr, (
+        "service errors should be rendered by the CLI error handler"
+    )
+
+
+def test_cli_code_does_not_import_adapter_layer() -> None:
+    """CLI modules must not import adapter-layer implementation details."""
+    cli_dir = Path("src/schnee/controllers/cli")
+    imported_adapters = [
+        path
+        for path in cli_dir.glob("*.py")
+        if "schnee.adapters" in path.read_text(encoding="utf-8")
+    ]
+
+    assert imported_adapters == [], "CLI code should not import schnee.adapters.*"