refactor(commands): model package queries explicitly

Introduce a PackageQuery type to group each command with its
description, metric, and accepted exit codes.

Move the static pacman queries into module-level constants and construct
only the update and optional AUR queries at runtime.

Use immutable command tuples throughout and rename success_codes to
accepted_exit_codes to better describe the command execution contract.

1 files changed, 74 insertions, 65 deletions

diff --git a/prometheus_pacman_exporter/__init__.py b/prometheus_pacman_exporter/__init__.py
index cb19032..73f0945 100644
--- a/prometheus_pacman_exporter/__init__.py
+++ b/prometheus_pacman_exporter/__init__.py
@@ -8,11 +8,11 @@ import os
 import shlex
 import subprocess
 from pathlib import Path
-from typing import cast
+from typing import NamedTuple, cast
 
 import click_extra as click
 from cloup.constraints import If, require_all
-from prometheus_client import write_to_textfile
+from prometheus_client import Gauge, write_to_textfile
 
 from . import metrics
 from .cli import FlexibleColorOption, debug, error, msg, verbose
@@ -25,6 +25,47 @@ AUTHOR = "Dennis Fink <me+coding@dennisfink.me>"
 LICENSE = "BSD-3-Clause"
 
 
+class PackageQuery(NamedTuple):
+    command: tuple[str, ...]
+    description: str
+    metric: Gauge
+    accepted_exit_codes: tuple[int, ...] = (0,)
+
+
+PACMAN_BASE_COMMAND = ("pacman", "--query")
+BASE_QUERIES: tuple[PackageQuery, ...] = (
+    PackageQuery(PACMAN_BASE_COMMAND, "installed packages", metrics.INSTALLED_PACKAGES),
+    PackageQuery(
+        (*PACMAN_BASE_COMMAND, "--explicit"),
+        "explicitly installed packages",
+        metrics.EXPLICIT_PACKAGES,
+    ),
+    PackageQuery(
+        (*PACMAN_BASE_COMMAND, "--deps"),
+        "packages installed as dependencies",
+        metrics.DEPENDS_PACKAGES,
+    ),
+    PackageQuery(
+        (*PACMAN_BASE_COMMAND, "--unrequired"),
+        "unrequired packages",
+        metrics.UNREQUIRED_PACKAGES,
+    ),
+    PackageQuery(
+        (*PACMAN_BASE_COMMAND, "--foreign"),
+        "foreign packages",
+        metrics.FOREIGN_PACKAGES,
+    ),
+    PackageQuery(
+        (*PACMAN_BASE_COMMAND, "--native"), "native packages", metrics.NATIVE_PACKAGES
+    ),
+    PackageQuery(
+        (*PACMAN_BASE_COMMAND, "--deps", "--unrequired"),
+        "orphan packages",
+        metrics.ORPHAN_PACKAGES,
+    ),
+)
+
+
 def print_version(
     ctx: click.Context, param: click.Parameter | None, value: bool
 ) -> None:
@@ -80,7 +121,9 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.""")
 
 @click.pass_context
 def run_command(
-    ctx: click.Context, command: list[str], success_codes: tuple[int, ...] = (0,)
+    ctx: click.Context,
+    command: tuple[str, ...],
+    accepted_exit_codes: tuple[int, ...] = (0,),
 ) -> subprocess.CompletedProcess[str]:
     """Run a shell command and return the result.
 
@@ -89,13 +132,13 @@ def run_command(
 
     :param ctx: Click context injected by :func:`click.pass_context`.
     :param command: Command and its arguments.
-    :param success_codes: Exit codes considered successful.
+    :param accepted_exit_codes: Exit codes considered successful.
     :return: Completed process with stdout and stderr captured.
     """
     debug("Running command", " ".join(command), err=True)
     result = subprocess.run(command, capture_output=True, encoding="utf-8", check=False)
 
-    if result.returncode not in success_codes:
+    if result.returncode not in accepted_exit_codes:
         error(
             f"Command ({' '.join(command)}) failed with exit code {result.returncode}"
         )
@@ -201,75 +244,41 @@ def prometheus_pacman_exporter(
     debug("  verbose:", str(verbose_flag), err=True)
     debug("  quiet:", str(quiet_flag), err=True)
 
-    pacman_base_command = ["pacman", "--query"]
-    queries = [
-        (
-            [*pacman_base_command],
-            "installed packages",
-            metrics.INSTALLED_PACKAGES,
-            (0,),
-        ),
-        (
-            [*pacman_base_command, "--explicit"],
-            "explicitly installed packages",
-            metrics.EXPLICIT_PACKAGES,
-            (0,),
-        ),
-        (
-            [*pacman_base_command, "--deps"],
-            "packages installed as dependencies",
-            metrics.DEPENDS_PACKAGES,
-            (0,),
-        ),
-        (
-            [*pacman_base_command, "--unrequired"],
-            "unrequired packages",
-            metrics.UNREQUIRED_PACKAGES,
-            (0,),
-        ),
-        (
-            [*pacman_base_command, "--foreign"],
-            "foreign packages",
-            metrics.FOREIGN_PACKAGES,
-            (0,),
-        ),
-        (
-            [*pacman_base_command, "--native"],
-            "native packages",
-            metrics.NATIVE_PACKAGES,
-            (0,),
-        ),
-        (
-            [*pacman_base_command, "--deps", "--unrequired"],
-            "orphan packages",
-            metrics.ORPHAN_PACKAGES,
-            (0,),
-        ),
-        (
-            ["checkupdates"]
-            if use_checkupdates_flag
-            else [*pacman_base_command, "--upgrades"],
-            "updateable packages",
-            metrics.UPDATEABLE_PACKAGES,
-            (0, 2) if use_checkupdates_flag else (0, 1),
-        ),
-    ]
+    queries: list[PackageQuery] = [*BASE_QUERIES]
+
+    if use_checkupdates_flag:
+        queries.append(
+            PackageQuery(
+                ("checkupdates",),
+                "updateable packages",
+                metrics.UPDATEABLE_PACKAGES,
+                (0, 2),
+            )
+        )
+    else:
+        queries.append(
+            PackageQuery(
+                (*PACMAN_BASE_COMMAND, "--upgrades"),
+                "updateable packages",
+                metrics.UPDATEABLE_PACKAGES,
+                (0, 1),
+            )
+        )
 
     if aur_flag:
         queries.append(
-            (
-                shlex.split(cast(str, aur_command)),
+            PackageQuery(
+                tuple(shlex.split(cast(str, aur_command))),
                 "AUR updateable packages",
                 metrics.AUR_UPDATEABLE_PACKAGES,
-                (0,),
             )
         )
 
-    for command, description, metric, success_codes in queries:
-        output = run_command(command, success_codes)
+    for query in queries:
+        output = run_command(query.command, query.accepted_exit_codes)
         value = len(output.stdout.splitlines())
-        verbose(f"Setting {description}:", str(value), err=True)
-        metric.set(value)
+        verbose(f"Setting {query.description}:", str(value), err=True)
+        query.metric.set(value)
 
     metrics_file = textfile_collector_dir / "pacman.prom"
     write_to_textfile(str(metrics_file.absolute()), metrics.REGISTRY)