update: add --force option

also collapse multiple consecutive separators into one underscore.

Cargo.toml

@@ -1,12 +1,10 @@
 [package]
 name = "snakify"
-version = "1.0.0"
+version = "1.1.0"
 edition = "2021"
 
-authors = ["m-hgn"]
+authors = ["mxhagen"]
 description = "Quickly snake-caseify any input text"
 
 license = "GPL-3.0"
 readme = "README.md"
-
-[dependencies]

src/main.rs

@@ -1,22 +1,78 @@
-#![feature(iter_intersperse)]
-fn main() {
-    let args = std::env::args();
-    let separators: Vec<char> = vec!['-', '_', ' '];
+use Flag::*;
 
-    let input: String = args.skip(1).intersperse(" ".to_string()).collect();
-
-    let output: String = input
-        .chars()
-        .map(|c| {
-            if separators.contains(&c) {
-                '_'
-            } else {
-                c.to_lowercase().next().unwrap_or_else(|| {
-                    panic!("Error: couldn't convert character to lowercase: `{}`", c)
-                })
-            }
-        })
-        .collect();
-
-    println!("{}", output);
+#[derive(PartialEq, Eq, Debug)]
+enum Flag {
+    Force,
+    Help,
+    Version,
+}
+
+fn main() {
+    let (appname, version) = (env!("CARGO_BIN_NAME"), env!("CARGO_PKG_VERSION"));
+    let (flag, arg_start) = std::env::args()
+        .enumerate()
+        .skip(1)
+        .next()
+        .map(|(i, arg)| match arg.as_str() {
+            "-f" | "--force" => (Some(Force), i),
+            "-h" | "--help" => (Some(Help), i),
+            "-V" | "--version" => (Some(Version), i),
+            _ => (None, 0),
+        })
+        .unwrap_or_default();
+
+    if flag == Some(Help) {
+        println!("Convert space-separated strings to `snake_case` and print to stdout.");
+        println!("If input contains invalid symbols, exits with code 1.");
+        println!("");
+        println!("Usage: {appname} [Option] [<string>...]");
+        println!("");
+        println!("Arguments:");
+        println!("  [<string>...]  One or more strings treated as a single input");
+        println!("");
+        println!("Options:");
+        println!("  -f, --force    Force successful conversion, ignoring invalid chars");
+        println!("  -h, --help     Print this usage information");
+        println!("  -V, --version  Print version information");
+        std::process::exit(0);
+    } else if flag == Some(Version) {
+        println!("{appname} {version}");
+        std::process::exit(0);
+    }
+
+    let mut arg_warned = false;
+    let mut output = String::new();
+    for arg in std::env::args().skip(1 + arg_start) {
+        if !arg_warned
+            && matches!(
+                arg.as_str(),
+                "-f" | "--force" | "-h" | "--help" | "-V" | "--version"
+            )
+        {
+            eprintln!("Warning: You might have passed an option where input was expected.");
+            eprintln!("         If this was unintentional: pass options *before* input.");
+            eprintln!("");
+            arg_warned = true;
+        }
+
+        let last_was_separator = output.bytes().last().map(|x| x == b'_').unwrap_or(true);
+        for c in arg.chars() {
+            match c {
+                ' ' | '-' | '_' if last_was_separator => {}
+                ' ' | '-' | '_' => output.push('_'),
+
+                'a'..='z' | 'A'..='Z' | '0'..='9' => output.push(c.to_ascii_lowercase()),
+                _ if flag == Some(Force) => output.push(c),
+
+                _ => {
+                    eprintln!("Error: Invalid snake_case character: `{c}`");
+                    std::process::exit(1);
+                }
+            }
+        }
+        output.push('_')
+    }
+    output.pop();
+
+    println!("{output}");
 }