pkgs/cli: Add dynamic completer for tags

Add a dynamic completer for `tags`.

Queries tag information from:
- the keys of the computed/static tags (inventory tags)
- the services tags
- the machines tags

pkgs/clan-cli/clan_cli/completions.py

@@ -300,6 +300,111 @@ def complete_target_host(
     return providers_dict
 
 
+def complete_tags(
+    prefix: str, parsed_args: argparse.Namespace, **kwargs: Any
+) -> Iterable[str]:
+    """
+    Provides completion functionality for tags inside the inventory
+    """
+    tags: list[str] = []
+    threads = []
+
+    def run_computed_tags_cmd() -> None:
+        try:
+            if (clan_dir_result := clan_dir(None)) is not None:
+                flake = clan_dir_result
+            else:
+                flake = "."
+            computed_tags_result = json.loads(
+                run(
+                    nix_eval(
+                        flags=[
+                            f"{flake}#clanInternals.inventory.tags",
+                            "--apply",
+                            "builtins.attrNames",
+                        ],
+                    ),
+                ).stdout.strip()
+            )
+
+            tags.extend(computed_tags_result)
+        except subprocess.CalledProcessError:
+            pass
+
+    def run_services_tags_cmd() -> None:
+        services_tags: list[str] = []
+        try:
+            if (clan_dir_result := clan_dir(None)) is not None:
+                flake = clan_dir_result
+            else:
+                flake = "."
+            services_tags_result = json.loads(
+                run(
+                    nix_eval(
+                        flags=[
+                            f"{flake}#clanInternals.inventory.services",
+                        ],
+                    ),
+                ).stdout.strip()
+            )
+            for service in services_tags_result.values():
+                for environment in service.values():
+                    roles = environment.get("roles", {})
+                    for role_details in roles.values():
+                        services_tags += role_details.get("tags", [])
+
+            tags.extend(services_tags)
+
+        except subprocess.CalledProcessError:
+            pass
+
+    def run_machines_tags_cmd() -> None:
+        machine_tags: list[str] = []
+        try:
+            if (clan_dir_result := clan_dir(None)) is not None:
+                flake = clan_dir_result
+            else:
+                flake = "."
+            machine_tags_result = json.loads(
+                run(
+                    nix_eval(
+                        flags=[
+                            f"{flake}#clanInternals.inventory.machines",
+                        ],
+                    ),
+                ).stdout.strip()
+            )
+
+            for machine in machine_tags_result.values():
+                machine_tags.extend(machine.get("tags", []))
+
+            tags.extend(machine_tags)
+        except subprocess.CalledProcessError:
+            pass
+
+    def start_thread(target_function: Callable) -> threading.Thread:
+        thread = threading.Thread(target=target_function)
+        thread.start()
+        return thread
+
+    functions_to_run = [
+        run_computed_tags_cmd,
+        run_services_tags_cmd,
+        run_machines_tags_cmd,
+    ]
+
+    threads = [start_thread(func) for func in functions_to_run]
+
+    for thread in threads:
+        thread.join(timeout=COMPLETION_TIMEOUT)
+
+    if any(thread.is_alive() for thread in threads):
+        return iter([])
+
+    providers_dict = {name: "tag" for name in tags}
+    return providers_dict
+
+
 def add_dynamic_completer(
     action: argparse.Action,
     completer: Callable[..., Iterable[str]],