Allow CLI override PostgreSQL connection settings (#24)

src/pgcachewatch/cli.py

@@ -1,4 +1,5 @@
 import argparse
+import os
 import sys
 
 import asyncpg
@@ -38,6 +39,63 @@ def cliparser() -> argparse.Namespace:
         help="Commit changes to database.",
     )
 
+    common_arguments.add_argument(
+        "--pg-dsn",
+        help=(
+            "Connection string in the libpq URI format, including host, port, user, "
+            "database, password, passfile, and SSL options. Must be properly quoted; "
+            "IPv6 addresses must be in brackets. "
+            "Example: postgres://user:pass@host:port/database. Defaults to PGDSN "
+            "environment variable if set."
+        ),
+        default=os.environ.get("PGDSN"),
+    )
+
+    common_arguments.add_argument(
+        "--pg-host",
+        help=(
+            "Database host address, which can be an IP or domain name. "
+            "Defaults to PGHOST environment variable if set."
+        ),
+        default=os.environ.get("PGHOST"),
+    )
+
+    common_arguments.add_argument(
+        "--pg-port",
+        help=(
+            "Port number for the server host Defaults to PGPORT environment variable "
+            "or 5432 if not set."
+        ),
+        default=os.environ.get("PGPORT", "5432"),
+    )
+
+    common_arguments.add_argument(
+        "--pg-user",
+        help=(
+            "Database role for authentication. Defaults to PGUSER environment "
+            "variable if set."
+        ),
+        default=os.environ.get("PGUSER"),
+    )
+
+    common_arguments.add_argument(
+        "--pg-database",
+        help=(
+            "Name of the database to connect to. Defaults to PGDATABASE environment "
+            "variable if set."
+        ),
+        default=os.environ.get("PGDATABASE"),
+    )
+
+    common_arguments.add_argument(
+        "--pg-password",
+        help=(
+            "Password for authentication. Defaults to PGPASSWORD "
+            "environment variable if set"
+        ),
+        default=os.environ.get("PGPASSWORD"),
+    )
+
     parser = argparse.ArgumentParser(
         formatter_class=argparse.ArgumentDefaultsHelpFormatter,
         prog="pgcachewatch",
@@ -67,53 +125,63 @@ async def main() -> None:
     pg_fn_name = f"{parsed.function_name}_{parsed.channel_name}"
     pg_tg_name = f"{parsed.trigger_name}_{parsed.channel_name}"
 
-    match parsed.command:
-        case "install":
-            install = "\n".join(
-                [
-                    queries.create_notify_function(
-                        channel_name=parsed.channel_name,
-                        function_name=pg_fn_name,
-                    )
-                ]
-                + [
-                    queries.create_after_change_trigger(
-                        trigger_name=pg_tg_name,
-                        table_name=table,
-                        function_name=pg_fn_name,
-                    )
-                    for table in parsed.tables
-                ]
-            )
-
-            print(install, flush=True)
-
-            if parsed.commit:
-                await (await asyncpg.connect()).execute(install)
-            else:
-                print(
-                    "::: Use '--commit' to write changes to db. :::",
-                    file=sys.stderr,
+    async with asyncpg.create_pool(
+        parsed.pg_dsn,
+        database=parsed.pg_database,
+        password=parsed.pg_password,
+        port=parsed.pg_port,
+        user=parsed.pg_user,
+        host=parsed.pg_host,
+        min_size=0,
+        max_size=1,
+    ) as pool:
+        match parsed.command:
+            case "install":
+                install = "\n".join(
+                    [
+                        queries.create_notify_function(
+                            channel_name=parsed.channel_name,
+                            function_name=pg_fn_name,
+                        )
+                    ]
+                    + [
+                        queries.create_after_change_trigger(
+                            trigger_name=pg_tg_name,
+                            table_name=table,
+                            function_name=pg_fn_name,
+                        )
+                        for table in parsed.tables
+                    ]
                 )
 
-        case "uninstall":
-            trigger_names = await (await asyncpg.connect()).fetch(
-                queries.fetch_trigger_names(pg_tg_name),
-            )
-            combined = "\n".join(
-                (
-                    "\n".join(
-                        queries.drop_trigger(t["trigger_name"], t["table"])
-                        for t in trigger_names
-                    ),
-                    queries.drop_function(pg_fn_name),
+                print(install, flush=True)
+
+                if parsed.commit:
+                    await pool.execute(install)
+                else:
+                    print(
+                        "::: Use '--commit' to write changes to db. :::",
+                        file=sys.stderr,
+                    )
+
+            case "uninstall":
+                trigger_names = await pool.fetch(
+                    queries.fetch_trigger_names(pg_tg_name),
                 )
-            )
-            print(combined, flush=True)
-            if parsed.commit:
-                await (await asyncpg.connect()).execute(combined)
-            else:
-                print(
-                    "::: Use '--commit' to write changes to db. :::",
-                    file=sys.stderr,
+                combined = "\n".join(
+                    (
+                        "\n".join(
+                            queries.drop_trigger(t["trigger_name"], t["table"])
+                            for t in trigger_names
+                        ),
+                        queries.drop_function(pg_fn_name),
+                    )
                 )
+                print(combined, flush=True)
+                if parsed.commit:
+                    await pool.execute(combined)
+                else:
+                    print(
+                        "::: Use '--commit' to write changes to db. :::",
+                        file=sys.stderr,
+                    )