Feat: add in stdio read

following the tutorial for this.

src/bin/counter.rs

@@ -1,22 +1,42 @@
-use clap::Parser;
-use std::path::PathBuf;
+use clap::{CommandFactory, Parser};
+use std::{
+    fs::File,
+    io::{stdin, BufRead, BufReader, IsTerminal},
+    path::PathBuf,
+};
 
 /// Count the number of lines in a file
 #[derive(Parser)]
 #[command(arg_required_else_help = true)]
 struct Cli {
-    /// The path to the file to read
+    /// The path to the file to read, use - to read from stdin (must not be a tty)
     file: PathBuf,
 }
 
 fn main() {
     let args = Cli::parse();
-    let mut word_count = 0;
-    let file = args.file;
+    let word_count;
+    let mut file = args.file;
 
-    for line in std::fs::read_to_string(&file).unwrap().lines() {
-        word_count += line.split(' ').count();
+    if file == PathBuf::from("-") {
+        if stdin().is_terminal() {
+            Cli::command().print_help().unwrap();
+            ::std::process::exit(2);
+        }
+
+        file = PathBuf::from("<stdin>");
+        word_count = words_in_buf_reader(BufReader::new(stdin().lock()));
+    } else {
+        word_count = words_in_buf_reader(BufReader::new(File::open(&file).unwrap()));
     }
 
-    println!("Words in {}: {}", file.to_str().unwrap(), word_count)
+    println!("Words in {}: {}", file.to_string_lossy(), word_count)
+}
+
+fn words_in_buf_reader<R: BufRead>(buf_reader: R) -> usize {
+    let mut count = 0;
+    for line in buf_reader.lines() {
+        count += line.unwrap().split(' ').count()
+    }
+    count
 }