allow multiple inputs to -s and -u

shuffle3rs/Cargo.lock

@@ -85,8 +85,15 @@ dependencies = [
  "lazy_static",
  "rand",
  "rand_chacha",
+ "smallvec",
 ]
 
+[[package]]
+name = "smallvec"
+version = "1.6.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "fe0f37c9e8f3c5a4a66ad655a93c74daac4ad00c441533bf5c6e7990bb42604e"
+
 [[package]]
 name = "wasi"
 version = "0.10.2+wasi-snapshot-preview1"

shuffle3rs/Cargo.toml

@@ -27,6 +27,7 @@ deferred-drop = []
 cfg-if = "1.0.0"
 lazy_static = "1.4.0"
 rand = "0.8.3"
+smallvec = "1.6.1"
 
 [dev-dependencies]
-rand_chacha = "0.3.0"
+rand_chacha = "0.3.0"

shuffle3rs/src/arg.rs

@@ -1,4 +1,7 @@
+use super::*;
 
+use std::{fmt, error};
+use std::path::PathBuf;
 
 /// The executable program name
 pub fn program_name() -> &'static str
@@ -36,3 +39,84 @@ pub fn usage()
 
     std::process::exit(2)
 }
+
+pub enum Mode
+{
+    Help,
+    ShuffleInPlace(MaybeVec<PathBuf>),
+    UnshuffleInPlace(MaybeVec<PathBuf>),
+}
+
+/// Parse the `argv` of this process.
+#[inline] pub fn parse_args() -> Result<Mode, Error>
+{
+    parse(std::env::args().skip(1))
+}
+
+fn parse<I: IntoIterator<Item = String>>(args: I) -> Result<Mode, Error>
+{
+    #[inline] fn validate_file(p: impl Into<PathBuf>) -> Result<PathBuf, Error>
+    {
+	let p = p.into();
+	if p.is_file()
+	{
+	    Ok(p)
+	} else {
+	    Err(Error::FileNotFound(p))
+	}
+    }
+    
+    let mut args = args.into_iter();
+
+    let farg = args.next();
+    match farg
+    {
+	Some(yes) => {
+	    match yes.trim()
+	    {		
+		"-h" => Ok(Mode::Help),
+		"-s" => {
+		    Ok(Mode::ShuffleInPlace(
+			args
+			    .map(|file| validate_file(file)).collect::<Result<MaybeVec<_>, Error>>()
+			    .and_then(|v| if v.len() == 0 { Err(Error::InvalidUseArg("-s"))} else {Ok(v)})?))
+		},
+		"-u" => {
+		    Ok(Mode::UnshuffleInPlace(
+			args
+			    .map(|file| validate_file(file)).collect::<Result<MaybeVec<_>, Error>>()
+			    .and_then(|v| if v.len() == 0 { Err(Error::InvalidUseArg("-u"))} else {Ok(v)})?))
+
+		},
+		_ => Err(Error::UnknownOpt(yes))
+	    }
+	}
+	None => Err(Error::NoOpt),
+    }
+}
+
+/// Arg parsing error
+#[derive(Debug)]
+#[non_exhaustive]
+pub enum Error
+{
+    InvalidUseArg(&'static str),
+    NoOpt,
+    
+    UnknownOpt(String),
+    FileNotFound(PathBuf),
+}
+
+impl error::Error for Error{}
+impl fmt::Display for Error
+{
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result
+    {
+	match self {
+	    Self::NoOpt => write!(f, "No options specified"),
+	    Self::UnknownOpt(opt) => write!(f, "Unknown option {:?}", opt),
+	    Self::FileNotFound(file) => write!(f, "File {:?} not found", file),
+	    Self::InvalidUseArg(string) => write!(f, "Argument {:?} expects a parameter", string),
+	}
+    }
+}

shuffle3rs/src/ext.rs

@@ -4,6 +4,8 @@ use std::iter::{FusedIterator, DoubleEndedIterator};
 use rand::Rng;
 use crate::shuffle;
 
+pub type MaybeVec<T> = smallvec::SmallVec<[T; 1]>;
+
 pub trait SliceElementExt<T>
 {
     fn random_element<R: Rng + ?Sized>(&self, rng: &mut R) -> &T;

shuffle3rs/src/main.rs

@@ -10,9 +10,24 @@
 mod shuffle;
 mod arg;
 
+use arg::Mode;
 
 fn main() {
-    arg::help();
+    match arg::parse_args()
+    {
+	Ok(Mode::Help) => arg::usage(),
+	Ok(Mode::ShuffleInPlace(file)) => {
+	    todo!()  
+	},
+	Ok(Mode::UnshuffleInPlace(file)) => {
+	    todo!()
+	},
+	Err(err) => {
+	    eprintln!("Error: {}", err);
+	    eprintln!("\nTry passing `-h`");
+	    std::process::exit(1)
+	}
+    }
 }
 
 #[cfg(test)] mod test;