From 1c6fa97eae3cbdee46c0878737d951f50061a316 Mon Sep 17 00:00:00 2001
From: Marco Thomas <github@marcothms.de>
Date: Tue, 22 Apr 2025 10:49:38 +0900
Subject: [PATCH] ft: add error type instead of plain panic

---
 src/interpret.rs | 21 +++++++++++++++------
 src/main.rs      |  5 ++++-
 2 files changed, 19 insertions(+), 7 deletions(-)

diff --git a/src/interpret.rs b/src/interpret.rs
index 54acefd..743baec 100644
--- a/src/interpret.rs
+++ b/src/interpret.rs
@@ -1,6 +1,13 @@
 use std::io::{self, Read};
 
-pub fn interpret(code: &str) -> Vec<u8> {
+#[derive(Debug)]
+pub enum BrainFuckError {
+    BracketMissing,
+    UserInput,
+    EmptyStack,
+}
+
+pub fn interpret(code: &str) -> Result<Vec<u8>, BrainFuckError> {
     let mut memory = [0 as u8; 10_000];
     let mut head = 0 as usize;
     let mut pc = 0 as usize;
@@ -25,6 +32,8 @@ pub fn interpret(code: &str) -> Vec<u8> {
                 let mut input_buf = [0u8; 1];
                 if io::stdin().read_exact(&mut input_buf).is_ok() {
                     memory[head] = input_buf[0];
+                } else {
+                    return Err(BrainFuckError::UserInput);
                 }
                 log::debug!("Read user input: {}", input_buf[0]);
             }
@@ -37,7 +46,7 @@ pub fn interpret(code: &str) -> Vec<u8> {
                     while count_brackets > 0 {
                         pc += 1;
                         if pc >= code_bytes.len() {
-                            panic!("Missing closing loop!");
+                            return Err(BrainFuckError::BracketMissing);
                         }
                         match code_bytes[pc] as char {
                             // closing current loop
@@ -62,7 +71,7 @@ pub fn interpret(code: &str) -> Vec<u8> {
                     if let Some(start_pc) = loop_stack.last() {
                         pc = *start_pc;
                     } else {
-                        panic!("Loop stack empty, but still called!")
+                        return Err(BrainFuckError::EmptyStack);
                     }
                 // loop done, continue normally
                 } else {
@@ -76,7 +85,7 @@ pub fn interpret(code: &str) -> Vec<u8> {
         pc += 1;
     }
     print!("\n");
-    return out;
+    Ok(out)
 }
 
 #[cfg(test)]
@@ -86,14 +95,14 @@ mod tests {
     #[test]
     fn test_h() {
         let code = "+++++++++[>++++++++<-]>.";
-        let out = interpret(code);
+        let out = interpret(code).unwrap();
         assert_eq!(std::str::from_utf8(&out).unwrap(), "H");
     }
 
     #[test]
     fn test_hello() {
         let code = "++++++++[>++++[>++>+++>+++>+<<<<-]>+>+>->>+[<]<-]>>.>---.+++++++..+++.>>.<-.<.+++.------.--------.>>+.>++.";
-        let out = interpret(code);
+        let out = interpret(code).unwrap();
         assert_eq!(std::str::from_utf8(&out).unwrap(), "Hello World!\n");
     }
 }
diff --git a/src/main.rs b/src/main.rs
index ec41f64..62b3205 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -18,5 +18,8 @@ fn main() {
     });
 
     println!("Running file {} with program {}", filename, code);
-    interpret(&code);
+    match interpret(&code) {
+        Ok(_) => {}
+        Err(err) => panic!("{:?}", err),
+    }
 }