app.py: refactoring

* Every Command is now a Task.
* Introduce TaskList.
* This allows for shorter and more generic code.

1 files changed, 75 insertions, 95 deletions

diff --git a/app.py b/app.py
index dd3edfc..9ce527e 100755
--- a/app.py
+++ b/app.py
@@ -65,10 +65,6 @@ def split_by(xs, sep):
     yield group
 
 
-def hostname():
-    return socket.gethostname()
-
-
 class Response:
     DEFAULT_STATUS = http.server.HTTPStatus.OK
 
@@ -126,6 +122,32 @@ def run_do(*args, **kwargs):
     return output.stdout
 
 
+class Task(abc.ABC):
+    def complete(self):
+        self.run()
+        return Response(Response.body_from_json(self.result()))
+
+    @abc.abstractmethod
+    def run(self):
+        pass
+
+    @abc.abstractmethod
+    def result(self):
+        pass
+
+
+class TaskList(Task):
+    def __init__(self, tasks):
+        self.tasks = tasks
+
+    def run(self):
+        for task in self.tasks.values():
+            task.run()
+
+    def result(self):
+        return {name: task.result() for name, task in self.tasks.items()}
+
+
 pool = ThreadPoolExecutor()
 
 
@@ -133,13 +155,20 @@ def run(*args, **kwargs):
     return pool.submit(run_do, *args, **kwargs)
 
 
-class Command:
+class Command(Task):
     def __init__(self, *args):
         self.args = args
         self.env = None
 
     def run(self):
-        return run(*self.args, env=self.env)
+        self.task = run(*self.args, env=self.env)
+        return self.task
+
+    def result(self):
+        return self.task.result()
+
+    def now(self):
+        return self.run().result()
 
 
 class Systemd(Command):
@@ -202,31 +231,19 @@ class Loginctl(Systemd):
         super().__init__('loginctl', *args, '--full')
 
 
-class Task(abc.ABC):
-    def complete(self):
-        self.run()
-        return Response(Response.body_from_json(self.result()))
-
-    @abc.abstractmethod
+class Hostname(Task):
     def run(self):
         pass
 
-    @abc.abstractmethod
     def result(self):
-        pass
+        return socket.gethostname()
 
 
-class TopTask(Task):
+class Top(Command):
     COMMAND = None
 
     def __init__(self):
-        self.cmd = TopTask.get_command()
-
-    def run(self):
-        self.task = self.cmd.run()
-
-    def result(self):
-        return self.task.result()
+        super().__init__(*Top.get_command())
 
     @staticmethod
     def get_command():
@@ -234,66 +251,43 @@ class TopTask(Task):
         # from the command line (another option is the rc file, but that's too
         # complicated).  For that, we simply run `top -h` once, and check if
         # the output contains the flags we want to use.
-        if TopTask.COMMAND is not None:
-            return TopTask.COMMAND
+        if Top.COMMAND is not None:
+            return Top.COMMAND
         help_output = run_do('top', '-h')
         args = ['top', '-b', '-n', '1', '-w', '512']
         if 'Ee' in help_output:
             args += ['-E', 'm', '-e', 'm']
-        TopTask.COMMAND = Command(*args)
-        return TopTask.COMMAND
+        Top.COMMAND = args
+        return Top.COMMAND
 
 
-class RebootTask(Task):
+class Reboot(Command):
     def __init__(self):
-        self.cmd = Command('systemctl', 'reboot')
+        super().__init__('systemctl', 'reboot')
 
-    def run(self):
-        self.task = self.cmd.run()
 
-    def result(self):
-        return self.task.result()
-
-
-class PoweroffTask(Task):
+class Poweroff(Command):
     def __init__(self):
-        self.cmd = Command('systemctl', 'poweroff')
+        super().__init__('systemctl', 'poweroff')
 
-    def run(self):
-        self.task = self.cmd.run()
-
-    def result(self):
-        return self.task.result()
 
-
-class InstanceStatusTask(Task):
+class InstanceStatus(TaskList):
     def __init__(self, systemctl, journalctl):
-        self.overview_cmd = systemctl('status')
-        self.failed_cmd = systemctl('list-units', '--failed')
-        self.timers_cmd = systemctl('list-timers', '--all')
-        self.journal_cmd = journalctl('-b', '--lines=20')
-
-    def run(self):
-        self.overview_task = self.overview_cmd.run()
-        self.failed_task = self.failed_cmd.run()
-        self.timers_task = self.timers_cmd.run()
-        self.journal_task = self.journal_cmd.run()
-
-    def result(self):
-        return {
-            'overview': self.overview_task.result(),
-            'failed': self.failed_task.result(),
-            'timers': self.timers_task.result(),
-            'journal': self.journal_task.result(),
+        tasks = {
+            'overview': systemctl('status'),
+            'failed': systemctl('list-units', '--failed'),
+            'timers': systemctl('list-timers', '--all'),
+            'journal': journalctl('-b', '--lines=20'),
         }
+        super().__init__(tasks)
 
 
-class SystemInstanceStatusTask(InstanceStatusTask):
+class SystemStatus(InstanceStatus):
     def __init__(self):
         super().__init__(Systemctl.system, Journalctl.system)
 
 
-class UserInstanceStatusTask(InstanceStatusTask):
+class UserStatus(InstanceStatus):
     def __init__(self, systemctl=Systemctl.user, journalctl=Journalctl.user):
         super().__init__(systemctl, journalctl)
 
@@ -301,45 +295,31 @@ class UserInstanceStatusTask(InstanceStatusTask):
     def su(user):
         systemctl = lambda *args: Systemd.su(user, Systemctl.user(*args))
         journalctl = lambda *args: Systemd.su(user, Journalctl.user(*args))
-        return UserInstanceStatusTask(systemctl, journalctl)
+        return UserStatus(systemctl, journalctl)
 
 
-class UserInstanceStatusTaskList(Task):
+class UserStatusList(TaskList):
     def __init__(self):
         if running_as_root():
             # As root, we can query all the user instances.
-            self.tasks = {user.name: UserInstanceStatusTask.su(user) for user in systemd_users()}
+            tasks = {user.name: UserStatus.su(user) for user in systemd_users()}
         else:
             # As a regular user, we can only query ourselves.
-            self.tasks = {}
+            tasks = {}
             user = get_current_user()
             if user_instance_active(user):
-                self.tasks[user.name] = UserInstanceStatusTask()
-
-    def run(self):
-        for task in self.tasks.values():
-            task.run()
-
-    def result(self):
-        return {name: task.result() for name, task in self.tasks.items()}
+                tasks[user.name] = UserStatus()
+        super().__init__(tasks)
 
 
-class StatusTask(Task):
+class Status(TaskList):
     def __init__(self):
-        self.hostname = hostname()
-        self.system = SystemInstanceStatusTask()
-        self.user = UserInstanceStatusTaskList()
-
-    def run(self):
-        self.system.run()
-        self.user.run()
-
-    def result(self):
-        return {
-            'hostname': self.hostname,
-            'system': self.system.result(),
-            'user': self.user.result(),
+        tasks = {
+            'hostname': Hostname(),
+            'system': SystemStatus(),
+            'user': UserStatusList(),
         }
+        super().__init__(tasks)
 
 
 User = namedtuple('User', ['uid', 'name'])
@@ -373,7 +353,7 @@ def user_instance_active(user):
     unit_name = f'user@{user.uid}.service'
     cmd = Systemctl.system('is-active', unit_name, '--quiet')
     try:
-        cmd.run().result()
+        cmd.now()
         return True
     except Exception:
         return False
@@ -413,7 +393,7 @@ def human_users():
 # that were running a systemd instance.
 def systemd_users():
     def list_users():
-        output = Loginctl('list-users', '--no-legend').run().result()
+        output = Loginctl('list-users', '--no-legend').now()
         lines = output.splitlines()
         if not lines:
             return
@@ -432,7 +412,7 @@ def systemd_users():
             return None
         properties = 'UID', 'Name', 'RuntimePath'
         prop_args = (arg for prop in properties for arg in ('-p', prop))
-        output = Loginctl('show-user', *prop_args, '--value', *user_args).run().result()
+        output = Loginctl('show-user', *prop_args, '--value', *user_args).now()
         lines = output.splitlines()
         # Assuming that for muptiple users, the properties will be separated by
         # an empty string.
@@ -462,13 +442,13 @@ class Request(Enum):
 
     def process(self):
         if self is Request.STATUS:
-            return StatusTask().complete()
+            return Status().complete()
         if self is Request.TOP:
-            return TopTask().complete()
+            return Top().complete()
         if self is Request.REBOOT:
-            return RebootTask().complete()
+            return Reboot().complete()
         if self is Request.POWEROFF:
-            return PoweroffTask().complete()
+            return Poweroff().complete()
         raise NotImplementedError(f'unknown request: {self}')