Refactor and cleanup (#3)

* Update main.rs

* Update main.rs

* fmt

* update dockerfile

Dockerfile

@@ -4,8 +4,7 @@
 FROM rust:latest AS builder
 
 RUN rustup target add x86_64-unknown-linux-musl
-RUN apt update && apt install -y musl-tools musl-dev binutils upx
-RUN update-ca-certificates
+RUN apt update && apt install -y musl-tools musl-dev binutils
 
 # Create appuser
 ENV USER=rust
@@ -20,7 +19,6 @@ RUN adduser \
     --uid "${UID}" \
     "${USER}"
 
-
 WORKDIR /rust-percentage-change-calculator
 
 COPY ./ .
@@ -29,7 +27,9 @@ RUN cargo build --target x86_64-unknown-linux-musl --release
 
 RUN strip target/x86_64-unknown-linux-musl/release/rust-percentage-change-calculator
 
-RUN upx --best --lzma target/x86_64-unknown-linux-musl/release/rust-percentage-change-calculator
+# Download upx binary
+ADD https://github.com/upx/upx/releases/download/v4.2.2/upx-4.2.2-amd64_linux.tar.xz /tmp/upx.tar.xz
+RUN tar -xvf /tmp/upx.tar.xz -C /tmp && cp /tmp/upx-4.2.2-amd64_linux/upx /usr/local/bin/upx
 
 ####################################################################################################
 ## Final Image

src/main.rs

@@ -1,47 +1,68 @@
-use std::env::args;
+use std::env;
 
 fn main() {
-    let first = get_input(1);
-    let second = get_input(2);
-    let percentage_change = calculate_percentage_change(first, second);
-    println!("{}", percentage_change);
+    let args: Vec<String> = env::args().collect();
+    if args.len() != 3 {
+        eprintln!("Usage: {} <first_value> <second_value>", args[0]);
+        std::process::exit(1);
+    }
+
+    let first = parse_input(&args[1]);
+    let second = parse_input(&args[2]);
+    match (first, second) {
+        (Ok(first), Ok(second)) => match calculate_percentage_change(first, second) {
+            Ok(percentage_change) => println!("{}", percentage_change),
+            Err(err) => {
+                eprintln!("{}", err);
+                std::process::exit(1);
+            }
+        },
+        (Err(err), _) | (_, Err(err)) => {
+            eprintln!("{}", err);
+            std::process::exit(1);
+        }
+    }
 }
 
-pub fn get_input(index: usize) -> f32 {
-    let args: Vec<String> = args().collect();
-    let result: f32 = match args[index].trim().parse() {
-        Ok(num) => num,
-        Err(_) => panic!(
-            "Failed to read value \"{}\", we were expecting a u32 or f32!",
-            args[index].trim()
-        ),
-    };
-    result
+fn parse_input(input: &str) -> Result<f32, String> {
+    input
+        .trim()
+        .parse()
+        .map_err(|_| format!("Failed to parse value: {}", input))
 }
 
-pub fn calculate_percentage_change(first: f32, second: f32) -> String {
-    if first < second {
-        return format!("+{}%", (second - first) / first * 100.0);
-    }
-    if first > second {
-        format!("-{}%", (first - second) / first * 100.0)
-    } else {
-        "0%".to_string()
-    }
+fn calculate_percentage_change(first: f32, second: f32) -> Result<String, String> {
+    let percentage_change = match (first, second) {
+        (f, s) if f < s => format!("+{}%", ((s - f) / f * 100.0)),
+        (f, s) if f > s => format!("-{}%", ((f - s) / f * 100.0)),
+        (_, _) => "0%".to_string(),
+    };
+    Ok(percentage_change)
 }
 
 #[cfg(test)]
 mod tests {
-
     use super::*;
 
     #[test]
     fn test_calculate_percentage_change() {
-        assert_eq!(calculate_percentage_change(1_f32, 2_f32), "+100%");
-        assert_eq!(calculate_percentage_change(2_f32, 1_f32), "-50%");
-        assert_eq!(calculate_percentage_change(1_f32, 1_f32), "0%");
-        assert_eq!(calculate_percentage_change(1.2, 2.4), "+100%");
-        assert_eq!(calculate_percentage_change(2.4, 1.2), "-50%");
-        assert_eq!(calculate_percentage_change(1.1, 1.1), "0%");
+        assert_eq!(
+            calculate_percentage_change(1.0, 2.0),
+            Ok("+100%".to_string())
+        );
+        assert_eq!(
+            calculate_percentage_change(2.0, 1.0),
+            Ok("-50%".to_string())
+        );
+        assert_eq!(calculate_percentage_change(1.0, 1.0), Ok("0%".to_string()));
+        assert_eq!(
+            calculate_percentage_change(1.2, 2.4),
+            Ok("+100%".to_string())
+        );
+        assert_eq!(
+            calculate_percentage_change(2.4, 1.2),
+            Ok("-50%".to_string())
+        );
+        assert_eq!(calculate_percentage_change(1.1, 1.1), Ok("0%".to_string()));
     }
 }