more error handling

src/processor.rs

@@ -1,31 +1,45 @@
+use std::error::Error;
+use std::fmt::Display;
 use std::hash::Hash;
 
 use crate::constants::{COMMENT, MINUS};
 use crate::tacview::{Coalition, CoalitionIDs};
 
-pub fn split_into_header_and_body<S: AsRef<str>>(lines: &[S]) -> (&[S], &[S]) {
+pub fn split_into_header_and_body<S, E>(lines: &[S]) -> Result<(&[S], &[S]), ProcessingError>
+where
+    S: AsRef<str>,
+{
     let mut i = 0;
     for line in lines {
-        if line.as_ref().chars().next().expect("malformed line") == COMMENT {
+        if line
+            .as_ref()
+            .chars()
+            .next()
+            .ok_or(ProcessingError::LineIsEmptyError)?
+            == COMMENT
+        {
             break;
         }
         i += 1;
     }
-    (&lines[..i], &lines[i..])
+    Ok((&lines[..i], &lines[i..]))
 }
 
-pub fn divide_body_by_coalition<S: AsRef<str> + Hash + Eq>(body: &[S]) -> Vec<Coalition> {
+pub fn divide_body_by_coalition<S>(body: &[S]) -> Result<Vec<Coalition>, Box<dyn Error>>
+where
+    S: AsRef<str> + Hash + Eq,
+{
     let mut result = vec![];
     let mut coalition_ids: CoalitionIDs = CoalitionIDs::new();
 
     let mut old_line = Line::default();
 
     for line_s in body {
-        let processed = Line::process_line(old_line, line_s, &mut coalition_ids);
+        let processed = Line::process_line(old_line, line_s, &mut coalition_ids)?;
         result.push(processed.coalition.clone());
         old_line = processed;
     }
-    result
+    Ok(result)
 }
 
 struct Line {
@@ -39,17 +53,19 @@ impl Line {
         old_line: Line,
         current_line: &'a S,
         coalition_ids: &mut CoalitionIDs<'a>,
-    ) -> Self {
+    ) -> Result<Self, ProcessingError> {
         let line_type = match old_line.continued {
             true => old_line.line_type,
-            false => LineType::find_type(current_line),
+            false => LineType::find_type(current_line)?,
         };
 
         match line_type {
-            LineType::Telemetry => Line::from_content(line_type, current_line, coalition_ids),
-            LineType::Timestamp => Line::new(line_type, false, Coalition::All),
-            LineType::Destruction => Line::from_content(line_type, current_line, coalition_ids),
-            LineType::Unknown => panic!(""),
+            LineType::Telemetry => Ok(Line::from_content(line_type, current_line, coalition_ids)?),
+            LineType::Timestamp => Ok(Line::new(line_type, false, Coalition::All)),
+            LineType::Destruction => {
+                Ok(Line::from_content(line_type, current_line, coalition_ids)?)
+            }
+            LineType::Unknown => Err(ProcessingError::UnknownLineType),
         }
     }
 
@@ -57,11 +73,11 @@ impl Line {
         line_type: LineType,
         current_line: &'a S,
         coalition_ids: &mut CoalitionIDs<'a>,
-    ) -> Self {
-        let id = Self::get_id_from_line(current_line);
+    ) -> Result<Self, ProcessingError> {
+        let id = Self::get_id_from_line(current_line)?;
         let continued = Self::will_line_continue(current_line);
         let coalition = Self::assign_id_to_coalitions(coalition_ids, current_line, id);
-        Line::new(line_type, continued, coalition)
+        Ok(Line::new(line_type, continued, coalition))
     }
 
     fn assign_id_to_coalitions<'a, S: AsRef<str>>(
@@ -82,8 +98,12 @@ impl Line {
         current_line.as_ref().ends_with('\\')
     }
 
-    fn get_id_from_line<S: AsRef<str>>(line: &S) -> &str {
-        line.as_ref().split_once(',').unwrap().0
+    fn get_id_from_line<S: AsRef<str>>(line: &S) -> Result<&str, ProcessingError> {
+        Ok(line
+            .as_ref()
+            .split_once(',')
+            .ok_or(ProcessingError::CannotGetIDFromLine)?
+            .0)
     }
 
     fn new(line_type: LineType, continued: bool, coalition: Coalition) -> Self {
@@ -93,7 +113,9 @@ impl Line {
             coalition,
         }
     }
+}
 
+impl Default for Line {
     fn default() -> Self {
         Self::new(LineType::Unknown, false, Coalition::Unknown)
     }
@@ -108,14 +130,41 @@ enum LineType {
 }
 
 impl LineType {
-    fn find_type<S: AsRef<str>>(line: &S) -> Self {
-        let first_char = line.as_ref().chars().next().unwrap();
+    fn find_type<S: AsRef<str>>(line: &S) -> Result<Self, ProcessingError> {
+        let first_char = line
+            .as_ref()
+            .chars()
+            .next()
+            .ok_or(ProcessingError::LineIsEmptyError)?;
         if first_char == COMMENT {
-            Self::Timestamp
+            Ok(Self::Timestamp)
         } else if first_char == MINUS {
-            Self::Destruction
+            Ok(Self::Destruction)
         } else {
-            LineType::Telemetry
+            Ok(LineType::Telemetry)
+        }
+    }
+}
+
+#[derive(Debug)]
+enum ProcessingError {
+    LineIsEmptyError,
+    UnknownLineType,
+    CannotSplitIntoHeaderAndBody,
+    CannotGetIDFromLine,
+}
+
+impl Error for ProcessingError {}
+
+impl Display for ProcessingError {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            Self::LineIsEmptyError => write!(f, "line in tacview file is empty"),
+            Self::UnknownLineType => write!(f, "unknown line type in tacview file"),
+            Self::CannotSplitIntoHeaderAndBody => {
+                write!(f, "cannot split the file into header and body")
+            }
+            Self::CannotGetIDFromLine => write!(f, "cannot get unit ID from line"),
         }
     }
 }