Add docs for the CLI module

src/cli.rs

@@ -1,3 +1,43 @@
+//! Payphone's main entry point, which initializes the bot and starts the event loop.
+//!
+//! This module is responsible for parsing command line arguments, nothing else.
+//!
+//! # Command Line Arguments
+//!
+//! The command line arguments are parsed using the [`clap`] crate, and can be found in the
+//! [`Args`] struct. The arguments are:
+//!
+//! - `--token` or `-t`: The Discord bot token to run the bot with. This is required.
+//! - `--logging` or `-l`: The minimum level logs have to be to be outputted into the console, or
+//!   off for no logs. Defaults to `info`.
+//! - `--database-addr` or `-d`: The address of the database to connect to, a Scylla node.
+//!
+//! The CLI also supports setting argument values via environment variables. The environment
+//! variables are prefixed with `PAYPHONE_`, so for example, the `--token` argument can be set
+//! using the `PAYPHONE_TOKEN` environment variable. The environment variables are used to
+//! override the command line arguments. `.env` files are also supported by default, so you can
+//! create a `.env` file in the root of the project with the following content:
+//!
+//! ```env
+//! PAYPHONE_TOKEN="your_discord_bot_token"
+//! PAYPHONE_LOGGING="info"
+//! PAYPHONE_DATABASE_ADDR="your_database_addr"
+//! ```
+//! 
+//! # Parsing Arguments
+//! 
+//! The arguments are parsed using the [`Args::parse`] method, which returns an instance of the
+//! [`Args`] struct. This struct contains the parsed values of the command line arguments, and
+//! can be used to initialize the bot and start the event loop.
+//! 
+//! ```
+//! // Read the environment variables from the `.env` file, if it exists, and load them as proper
+//! // env variables.
+//! dotenvy::dotenv().ok();
+//! 
+//! let args = Args::parse();
+//! ```
+
 #[derive(clap::Parser)]
 pub struct Args {
     /// The Discord bot token to run the bot with.
@@ -18,11 +58,11 @@ pub struct Args {
     #[arg(
         long,
         short,
-        env = "PAYPHONE_DATABASE_URL",
-        value_name = "URL",
+        env = "PAYPHONE_DATABASE_ADDR",
+        value_name = "ADDR",
         default_value_t = String::from("127.0.0.1:9042"))
     ]
-    pub database_url: String,
+    pub database_addr: String,
 }
 
 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, clap::ValueEnum)]