error handling for Item

src/game.rs

@@ -221,7 +221,13 @@ impl Game {
                     sprites.push(sprite);
                 }
             } else if segment.starts_with("ITM ") {
-                items.push(Item::from(segment));
+                let result = Item::from_str(&segment);
+
+                if let Ok(item) = result {
+                    items.push(item);
+                } else {
+                    warnings.push(result.unwrap_err());
+                }
             } else if segment.starts_with("DLG ") {
                 let result = Dialogue::from_str(&segment);
 

src/item.rs

@@ -1,5 +1,6 @@
 use crate::{optional_data_line, AnimationFrames, Image};
 use crate::image::animation_frames_from_str;
+use std::fmt;
 
 #[derive(Clone, Debug, Eq, PartialEq)]
 pub struct Item {
@@ -22,11 +23,13 @@ impl Item {
     fn colour_line(&self) -> String {
         optional_data_line("COL", self.colour_id.as_ref())
     }
-}
 
-impl From<String> for Item {
-    fn from(string: String) -> Item {
-        let mut lines: Vec<&str> = string.lines().collect();
+    pub fn from_str(str: &str) -> Result<Item, crate::Error> {
+        let mut lines: Vec<&str> = str.lines().collect();
+
+        if lines.is_empty() || !lines[0].starts_with("ITM ") {
+            return Err(crate::Error::Item);
+        }
 
         let id = lines[0].replace("ITM ", "");
         let mut name = None;
@@ -52,19 +55,14 @@ impl From<String> for Item {
             &lines[1..].join("\n")
         );
 
-        Item {
-            id,
-            name,
-            animation_frames,
-            dialogue_id,
-            colour_id,
-        }
+        Ok(Item { id, name, animation_frames, dialogue_id, colour_id })
     }
 }
 
-impl ToString for Item {
-    fn to_string(&self) -> String {
-        format!(
+impl fmt::Display for Item {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(
+            f,
             "ITM {}\n{}{}{}{}",
             self.id,
             self.animation_frames.to_string(),
@@ -81,7 +79,7 @@ mod test {
 
     #[test]
     fn item_from_string() {
-        let output = Item::from(include_str!("test-resources/item").to_string());
+        let output = Item::from_str(include_str!("test-resources/item")).unwrap();
         let expected = mock::item();
         assert_eq!(output, expected);
     }