From ef70bc1cc0847a01af5e07b32b89cafbce358c76 Mon Sep 17 00:00:00 2001
From: Araozu <fernando@araozu.dev>
Date: Tue, 2 Jan 2024 06:31:27 -0500
Subject: [PATCH] Minimal error display for syntax error

---
 CHANGELOG.md                       |  4 ++--
 src/error_handling/syntax_error.rs | 33 +++++++++++++++++++++++++-----
 2 files changed, 30 insertions(+), 7 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 6e76821..e9c1219 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -24,8 +24,8 @@
 
 - [x] Hand-make CLI, remove clap
 - [x] Compile a single file
-- [ ] Display error messages during compilation instead of panicking
-- [ ] Improve errror messages
+- [x] Display error messages during compilation instead of panicking
+- [x] Improve error messages
 - [ ] Implement code generation for ast nodes implemented as of now
 
 
diff --git a/src/error_handling/syntax_error.rs b/src/error_handling/syntax_error.rs
index 656a298..b7a846d 100644
--- a/src/error_handling/syntax_error.rs
+++ b/src/error_handling/syntax_error.rs
@@ -1,22 +1,29 @@
-use std::collections::VecDeque;
-
 use super::{PrintableError, SyntaxError};
+use std::collections::VecDeque;
 
 impl PrintableError for SyntaxError {
     fn get_error_str(&self, chars: &Vec<char>) -> String {
         let (line, before, length) = get_line(chars, self.error_start, self.error_end);
 
+        let line_number = get_line_number(chars, self.error_start);
+        let line_number_whitespace = " ".repeat(line_number.to_string().len());
+
         let whitespace = vec![' '; before].iter().collect::<String>();
         let indicator = vec!['^'; length].iter().collect::<String>();
+        let reason = &self.reason;
 
         format!(
-            "\n{}\n{}{}\n\n{}{}{}\n{}",
-            line, whitespace, indicator, "Syntax error at pos ", self.error_start, ":", self.reason
+            r#"
+{line_number_whitespace} |
+{line_number           } | {line}
+{line_number_whitespace} | {whitespace}{indicator}
+
+{reason} at line {line_number}:{before}"#,
         )
     }
 }
 
-/// Extracts a lin e of code
+/// Extracts a line of code
 ///
 /// - `chars`: Input where to extract the line from
 /// - `start_position`: Position where the erroneous code starts
@@ -90,6 +97,22 @@ fn get_line(
     )
 }
 
+fn get_line_number(chars: &Vec<char>, target_pos: usize) -> usize {
+    let mut count = 1;
+
+    for (pos, char) in chars.iter().enumerate() {
+        if pos >= target_pos {
+            break;
+        }
+
+        if *char == '\n' {
+            count += 1;
+        }
+    }
+
+    count
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;