Make help a bit clearer

check_home_assistant_state.conf

@@ -1,45 +0,0 @@
-object CheckCommand "home_assistant_state" {
-  command = [ PluginContribDir + "/check_home_assistant_state/check_home_assistant_state.py" ]
-  arguments = {
-    "--token" = {
-      value = "$home_assistant_state_token$"
-      description = "API token for Home Assistant"
-    }
-    "--url" = {
-      value = "$home_assistant_state_url$"
-      description = "URL for Home Assistant"
-    }
-    "--device-class" = {
-      value = "$home_assistant_state_device_class$"
-      description = "Device class of entities to monitor"
-    }
-    "--warning" = {
-      value = "$home_assistant_state_warning$"
-      description = "Return warning if battery percentage is outside RANGE"
-    }
-    "--critical" = {
-      value = "$home_assistant_state_critical$"
-      description = "Return critical if battery percentage is outside RANGE"
-    }
-    "--min" = {
-      value = "$home_assistant_state_min$"
-      description = "Min for performance data"
-    }
-    "--max" = {
-      value = "$home_assistant_state_max$"
-      description = "Max for performance data"
-    }
-    "--attribute" = {
-      value = "$home_assistant_state_attribute$"
-      description = "Check attribute instead of value"
-    }
-    "--filter" = {
-      value = "$home_assistant_state_filter$"
-      description = "Filter by 'attribute=value' (can be an array)"
-    }
-    "--friendly" = {
-      set_if = "$home_assistant_state_friendly$"
-      description = "Use friendly name, when available"
-    }
-  }
-}

check_home_assistant_state.py

@@ -6,6 +6,7 @@ import logging
 import sys
 from urllib.parse import urljoin
 from typing import Optional
+from pathlib import Path
 
 import requests
 import nagiosplugin
@@ -83,23 +84,80 @@ def key_value(arg: str):
     return k, v
 
 
+class Icinga2ConfAction(argparse.Action):
+    def __init__(
+        self,
+        option_strings,
+        dest=argparse.SUPPRESS,
+        default=argparse.SUPPRESS,
+        help="Generate conf file for icinga2 CheckCommand",
+    ):
+        super().__init__(
+            option_strings=option_strings,
+            dest=dest,
+            default=default,
+            nargs=0,
+            help=help,
+        )
+
+    def __call__(
+        self, parser: argparse.ArgumentParser, namespace, values, option_string=None
+    ):
+        filename = Path(__file__).absolute()
+        command_name = filename.stem.removeprefix("check_")
+        # FIXME: assumes that script will be in a subdirectory of PluginContribDir
+        command_path = filename.relative_to(filename.parents[1])
+
+        print(f'object CheckCommand "{command_name}" {{')
+        print(f'  command = [ PluginContribDir + "/{command_path}" ]')
+        print("  arguments = {")
+        for action in parser._actions:
+            if action.dest in ["verbose", "help", self.dest]:
+                continue
+
+            arg_str = action.option_strings[-1]
+            icinga2_var = arg_str.lstrip("-").replace("-", "_")
+            print(f'    "{arg_str}" = {{')
+
+            if action.required:
+                print("      required = true")
+
+            if isinstance(action, argparse._StoreConstAction):
+                print(f'      set_if = "${command_name}_{icinga2_var}$"')
+            else:
+                print(f'      value = "${command_name}_{icinga2_var}$"')
+
+            print(f'      description = "{action.help}"')
+            print("    }")
+
+        print("  }\n}")
+        parser.exit()
+
+
 @nagiosplugin.guarded
 def main():
     argp = argparse.ArgumentParser(description=__doc__)
+
+    argp.add_argument("-v", "--verbose", action="count", default=0)
+    argp.add_argument("--make-icinga-conf", action=Icinga2ConfAction)
+
     argp.add_argument(
-        "-t", "--token", required=True, type=str, help="API token for Home Assistant"
+        "-t",
+        "--token",
+        required=True,
+        type=str,
+        help="token for Home Assistant REST API (see https://developers.home-assistant.io/docs/api/rest/)",
     )
     argp.add_argument(
         "-u", "--url", required=True, type=str, help="URL for Home Assistant"
     )
-    argp.add_argument("-v", "--verbose", action="count", default=0)
 
     argp.add_argument(
         "-d",
         "--device-class",
         type=str,
         required=True,
-        help="Device class of entities to monitor",
+        help="device class of entities to monitor",
     )
     argp.add_argument(
         "-w",
@@ -118,15 +176,15 @@ def main():
     argp.add_argument(
         "--min",
         type=float,
-        help="Min for performance data",
+        help="min for performance data",
     )
     argp.add_argument(
         "--max",
         type=float,
-        help="Max for performance data",
+        help="max for performance data",
     )
     argp.add_argument(
-        "-a", "--attribute", type=str, help="Check attribute instead of value"
+        "-a", "--attribute", type=str, help="check attribute instead of value"
     )
     argp.add_argument(
         "-f",
@@ -134,12 +192,12 @@ def main():
         type=key_value,
         default=[],
         nargs="*",
-        help="Filter by 'attribute=value'",
+        help="filter by 'attribute=value' (may be specified multiple times)",
     )
     argp.add_argument(
         "--friendly",
         action="store_true",
-        help="Use friendly name, when available",
+        help="use friendly name, when available",
     )
 
     args = argp.parse_args()