Implement scarf length wrapper type

crates/save/src/lib.rs

@@ -2,6 +2,7 @@ mod companion;
 mod glyphs;
 mod level;
 mod murals;
+mod scarf;
 mod symbol;
 mod test;
 
@@ -14,6 +15,7 @@ use std::path::{Path, PathBuf};
 use binrw::{until_eof, BinRead, BinReaderExt, BinWriterExt};
 use chrono::{DateTime, NaiveDateTime, Utc};
 use level::Level;
+use scarf::Scarf;
 use symbol::Symbol;
 
 use crate::companion::{CompanionSymbols, CompanionWithId, Companions};
@@ -39,6 +41,15 @@ pub enum Error {
     #[error("Level name was not found")]
     LevelNameNotFound,
 
+    #[error("Scarf already at maximum length")]
+    ScarfMaxLength,
+
+    #[error("Scarf already at minimum length")]
+    ScarfMinLength,
+
+    #[error("Scarf can be at most 30 long")]
+    ScarfTooLong,
+
     #[error("Symbol id is out of range")]
     SymbolIdOutOfRange,
 
@@ -77,7 +88,7 @@ pub struct Savefile {
 
     pub symbol: Symbol,
 
-    pub scarf_length: u32,
+    pub scarf_length: Scarf,
 
     #[br(count = 4)]
     _unknown1: Vec<u8>,

crates/save/src/scarf.rs

@@ -0,0 +1,58 @@
+use core::fmt;
+
+use binrw::{BinRead, BinWrite};
+
+use crate::{Error, Result};
+
+
+const MAX_LENGTH: u32 = 30;
+
+
+#[derive(Debug, Clone, BinRead, BinWrite)]
+pub struct Scarf {
+    #[br(assert(length <= MAX_LENGTH))]
+    length: u32,
+}
+
+impl Scarf {
+    pub fn set_length(&mut self, length: u32) -> Result<()> {
+        if length > MAX_LENGTH {
+            return Err(Error::ScarfTooLong);
+        }
+
+        self.length = length;
+
+        Ok(())
+    }
+
+    pub fn increase_length(&mut self) -> Result<()> {
+        let length = self.length + 1;
+        if length > MAX_LENGTH {
+            return Err(Error::ScarfMaxLength);
+        }
+
+        self.length = length;
+
+        Ok(())
+    }
+
+    pub fn decrease_length(&mut self) -> Result<()> {
+        let length = self.length.checked_sub(1).ok_or(Error::ScarfMinLength)?;
+
+        self.length = length;
+
+        Ok(())
+    }
+}
+
+impl fmt::Display for Scarf {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "{}", self.length)
+    }
+}
+
+impl AsRef<u32> for Scarf {
+    fn as_ref(&self) -> &u32 {
+        &self.length
+    }
+}

crates/save/src/test.rs

@@ -17,7 +17,7 @@ fn general_info() {
     assert_eq!(savefile.robe_tier(), 4);
 
     assert_eq!(savefile.symbol.as_ref(), &7);
-    assert_eq!(savefile.scarf_length, 27);
+    assert_eq!(savefile.scarf_length.as_ref(), &27);
     assert_eq!(savefile.current_level.as_ref(), &1);
     assert_eq!(savefile.total_collected_symbols, 107);
     assert_eq!(savefile.collected_symbols, 21);

crates/wayfarer/src/edit.rs

@@ -55,7 +55,7 @@ fn edit_file(cur_savefile: &Savefile, args: &Args) -> Result<Savefile> {
     let mut savefile = cur_savefile.clone();
 
     if let Some(val) = args.scarf_length {
-        savefile.scarf_length = val;
+        savefile.scarf_length.set_length(val)?;
     }
 
     if let Some(val) = &args.current_level {

crates/wayfarer/src/tui/state.rs

@@ -173,14 +173,7 @@ impl State {
             2 => savefile.total_collected_symbols = value.parse()?,
             3 => savefile.current_level.set_by_name(value)?,
             4 => savefile.companions_met = value.parse()?,
-            5 => {
-                let new_length = value.parse()?;
-                if new_length > 30 {
-                    bail!("Max length exceeded");
-                }
-
-                savefile.scarf_length = new_length;
-            }
+            5 => savefile.scarf_length.set_length(value.parse()?)?,
             6 => savefile.symbol.set_by_id(value.parse()?)?,
             7 => {
                 let new_color = match value {
@@ -218,11 +211,7 @@ impl State {
             2 => savefile.total_collected_symbols += 1,
             3 => savefile.current_level = savefile.current_level.wrapping_next(),
             4 => savefile.companions_met += 1,
-            5 => {
-                if savefile.scarf_length < 30 {
-                    savefile.scarf_length += 1;
-                }
-            }
+            5 => savefile.scarf_length.increase_length()?,
             6 => savefile.symbol = savefile.symbol.wrapping_next(),
             7 => {
                 savefile.set_robe_color(match savefile.robe_color() {
@@ -264,11 +253,7 @@ impl State {
             }
             3 => savefile.current_level = savefile.current_level.wrapping_previous(),
             4 => savefile.companions_met = savefile.companions_met.saturating_sub(1),
-            5 => {
-                if savefile.scarf_length > 0 {
-                    savefile.scarf_length = savefile.scarf_length.saturating_sub(1);
-                }
-            }
+            5 => savefile.scarf_length.decrease_length()?,
             6 => savefile.symbol = savefile.symbol.wrapping_previous(),
             7 => {
                 savefile.set_robe_color(match savefile.robe_color() {