add pipe

Author: syui

Cargo.lock

@@ -8,3 +8,4 @@ edition = "2018"
 url = "1.7"
 failure = "0.1"
 structopt = "0.2"
+atty = "0.2"

Cargo.toml

@@ -1,3 +1,4 @@
+the cli tool of the url decode written in rust.
 
 ```sh
 $ cargo test

readme.md

@@ -2,25 +2,51 @@ use url::percent_encoding::percent_decode;
 
 use structopt::StructOpt;
 use failure::Error;
+use std::io::{self, Read};
+use atty::Stream;
 pub type Result<T> = std::result::Result<T, Error>;
 
 #[derive(StructOpt, Debug)]
 struct Opt {
     #[structopt(name = "INPUT")]
-    input: String,
+    input: Option<String>,
 }
 
+fn read_from_stdin() -> Result<String> {
+    let mut buf = String::new();
+    let stdin = io::stdin();
+    let mut handle = stdin.lock();
+    handle.read_to_string(&mut buf)?;
+    Ok(buf)
+}
+
+fn is_stdin(input: Option<&String>) -> bool {
+    let is_request = match input {
+        Some(i) if i == "-" => true,
+        _ => false,
+    };
+    let is_pipe = ! atty::is(Stream::Stdin);
+    is_request || is_pipe
+}
+
+
 fn main() -> Result<()> {
     let opt = Opt::from_args();
-    Ok(println!("{}", decode(&opt.input)?))
-}
 
-//fn main() -> Result<()> {
-//    let args: Vec<String> = std::env::args().collect();
-//    let input = &args[1];
-//
-//    Ok(println!("{}", decode(input)?))
-//}
+    if opt.input.is_none() && ! is_stdin(opt.input.as_ref()) {
+        Opt::clap().print_help()?;
+        std::process::exit(1);
+    }
+    let input = match opt.input  {
+        Some(i) => i,
+        None => read_from_stdin()?
+    };
+    if input.is_empty() {
+        Opt::clap().get_matches().usage();
+    }
+
+    Ok(println!("{}", decode(&input)?))
+}
 
 fn decode(input: &str) -> Result<String> {
     let decoded = percent_decode(input.as_bytes()).decode_utf8()?;