feat: add dingo link

__network/dingo/src/cli.rs

@@ -0,0 +1,83 @@
+use std::{
+    net::{Ipv4Addr, SocketAddr, SocketAddrV4},
+    process::exit,
+};
+
+use ascii::AsciiString;
+
+use crate::dns_types::RecordType;
+
+const HELP: &str = "\
+dingo -- domain information gatherer, obviously
+USAGE:
+  dingo [OPTIONS] --record-type TYPE NAME
+FLAGS:
+  -h, --help                Prints help information
+OPTIONS:
+  -t, --record-type TYPE    Choose the DNS record type (currently only supports A, CNAME, SOA and AAAA)
+  -r, --resolver IP         Which DNS resolver to query (default is 1.1.1.1:53)
+ARGS:
+  NAME A domain name to look up. Remember, these must be ASCII.
+";
+
+/// Values derived from the CLI arguments.
+#[derive(Debug)]
+pub struct AppArgs {
+    pub record_type: RecordType,
+    pub name: String,
+    pub resolver: SocketAddr,
+}
+
+impl AppArgs {
+    pub fn parse() -> Result<Self, pico_args::Error> {
+        let mut pargs = pico_args::Arguments::from_env();
+
+        // Help has a higher priority and should be handled separately.
+        if pargs.contains(["-h", "--help"]) {
+            print!("{}", HELP);
+            std::process::exit(0);
+        }
+
+        let record_type = match pargs
+            .opt_value_from_str("--record-type")?
+            .xor(pargs.opt_value_from_str("-t")?)
+        {
+            Some(rt) => rt,
+            None => {
+                eprintln!("You must supply exactly one of either -t or --record-type");
+                print!("{}", HELP);
+                std::process::exit(1);
+            }
+        };
+
+        // I asked some coworkers and they suggested this DNS resolver
+        let default_resolver = SocketAddr::V4(SocketAddrV4::new(Ipv4Addr::new(1, 1, 1, 1), 53));
+        let resolver = pargs
+            .opt_value_from_str("--resolver")?
+            .or(pargs.opt_value_from_str("-r")?)
+            .unwrap_or(default_resolver);
+
+        let mut name: String = pargs.free_from_str()?;
+        use std::str::FromStr;
+        if AsciiString::from_str(&name).is_err() {
+            eprintln!("DNS names must be ASCII, and {name} is not.");
+            exit(1);
+        }
+        if !name.ends_with('.') {
+            name.push('.');
+        }
+
+        let args = AppArgs {
+            record_type,
+            name,
+            resolver,
+        };
+
+        let remaining = pargs.finish();
+        if !remaining.is_empty() {
+            eprintln!("Warning: unused arguments left: {:?}.", remaining);
+        }
+
+        Ok(args)
+    }
+}