sb-core: DomainError + signature conversions (WI-2, issue #2)

crates/sb-core/src/character.rs

@@ -1,4 +1,5 @@
 use crate::constants;
+use crate::error::DomainError;
 use crate::spells;
 use sb_shared::{Character, CharacterStats, Class, Race};
 
@@ -351,17 +352,17 @@ pub fn level_up_cost(level: i32) -> i32 {
     constants::LEVEL_UP_GOLD_PER_LEVEL * level
 }
 
-pub fn level_up(char: &mut Character) -> Result<i32, &'static str> {
+pub fn level_up(char: &mut Character) -> Result<i32, DomainError> {
     if char.level >= MAX_LEVEL {
-        return Err("already at max level");
+        return Err(DomainError::AlreadyAtMaxLevel);
     }
     let next_level = char.level + 1;
     if char.xp < xp_for_level(next_level) {
-        return Err("not enough XP");
+        return Err(DomainError::NotEnoughXp);
     }
     let cost = level_up_cost(next_level);
     if char.gold < cost {
-        return Err("not enough gold");
+        return Err(DomainError::NotEnoughGold);
     }
     char.gold -= cost;
     char.level = next_level;
@@ -483,7 +484,7 @@ mod tests {
         c.level = MAX_LEVEL;
         c.xp = i64::MAX;
         c.gold = i32::MAX;
-        assert_eq!(level_up(&mut c), Err("already at max level"));
+        assert_eq!(level_up(&mut c), Err(DomainError::AlreadyAtMaxLevel));
     }
 
     #[test]
@@ -512,7 +513,7 @@ mod tests {
         let mut c = base_char();
         c.xp = 100;
         c.gold = 10000;
-        assert_eq!(level_up(&mut c), Err("not enough XP"));
+        assert_eq!(level_up(&mut c), Err(DomainError::NotEnoughXp));
         assert_eq!(c.level, 1);
         assert_eq!(c.gold, 10000);
     }
@@ -522,7 +523,7 @@ mod tests {
         let mut c = base_char();
         c.xp = 1800;
         c.gold = 0;
-        assert_eq!(level_up(&mut c), Err("not enough gold"));
+        assert_eq!(level_up(&mut c), Err(DomainError::NotEnoughGold));
         assert_eq!(c.level, 1);
     }
 

crates/sb-core/src/error.rs

@@ -0,0 +1,23 @@
+#[derive(Debug, Clone, Copy, PartialEq, Eq, thiserror::Error)]
+pub enum DomainError {
+    #[error("character is incapacitated")]
+    CharacterIncapacitated,
+    #[error("not enough nerve")]
+    NotEnoughNerve,
+    #[error("not enough energy")]
+    NotEnoughEnergy,
+    #[error("not enough gold")]
+    NotEnoughGold,
+    #[error("not enough XP")]
+    NotEnoughXp,
+    #[error("already at max level")]
+    AlreadyAtMaxLevel,
+    #[error("invalid stat name")]
+    InvalidStat,
+    #[error("item not in inventory")]
+    ItemNotInInventory,
+    #[error("nothing equipped in slot")]
+    NothingEquippedInSlot,
+    #[error("encounter references unknown enemy")]
+    UnknownEncounterEnemy,
+}

crates/sb-core/src/lib.rs

@@ -4,6 +4,7 @@ pub mod character;
 pub mod combat;
 pub mod constants;
 pub mod data;
+pub mod error;
 pub mod items;
 pub mod services;
 pub mod songs;

crates/sb-core/src/services.rs

@@ -1,4 +1,5 @@
 use crate::data::{EncounterEntry, EnemyDef};
+use crate::error::DomainError;
 use rand::Rng;
 use sb_shared::{AttackType, Character, Item};
 
@@ -6,8 +7,11 @@ pub fn pick_enemy(
     rng: &mut impl Rng,
     encounters: &[EncounterEntry],
     enemies: &[EnemyDef],
-) -> EnemyDef {
+) -> Result<EnemyDef, DomainError> {
     let total_weight: i32 = encounters.iter().map(|e| e.weight).sum();
+    if encounters.is_empty() || total_weight <= 0 {
+        return Err(DomainError::UnknownEncounterEnemy);
+    }
     let roll: i32 = rng.random_range(0..total_weight);
     let mut remaining = roll;
     for enc in encounters {
@@ -16,15 +20,18 @@ pub fn pick_enemy(
             return enemies
                 .iter()
                 .find(|e| e.id == enc.enemy_id)
-                .expect("encounter references valid enemy")
-                .clone();
+                .cloned()
+                .ok_or(DomainError::UnknownEncounterEnemy);
         }
     }
+    let last = encounters
+        .last()
+        .ok_or(DomainError::UnknownEncounterEnemy)?;
     enemies
         .iter()
-        .find(|e| e.id == encounters.last().unwrap().enemy_id)
-        .expect("encounter references valid enemy")
-        .clone()
+        .find(|e| e.id == last.enemy_id)
+        .cloned()
+        .ok_or(DomainError::UnknownEncounterEnemy)
 }
 
 pub fn equipped_attack_type(
@@ -72,12 +79,12 @@ pub fn total_defense(
     total
 }
 
-pub fn equip_item(char: &mut Character, item: &Item, item_id: &str) -> Result<(), &'static str> {
+pub fn equip_item(char: &mut Character, item: &Item, item_id: &str) -> Result<(), DomainError> {
     let inv_pos = char
         .inventory
         .iter()
         .position(|id| id == item_id)
-        .ok_or("item not in inventory")?;
+        .ok_or(DomainError::ItemNotInInventory)?;
 
     char.inventory.remove(inv_pos);
     let slot = item.slot.clone();
@@ -88,20 +95,20 @@ pub fn equip_item(char: &mut Character, item: &Item, item_id: &str) -> Result<()
     Ok(())
 }
 
-pub fn unequip_item(char: &mut Character, slot: &str) -> Result<String, &'static str> {
+pub fn unequip_item(char: &mut Character, slot: &str) -> Result<String, DomainError> {
     let prev = char
         .equipment
         .insert(slot.to_string(), None)
         .flatten()
-        .ok_or("nothing equipped in slot")?;
+        .ok_or(DomainError::NothingEquippedInSlot)?;
 
     char.inventory.push(prev.clone());
     Ok(prev)
 }
 
-pub fn train_stat(char: &mut Character, stat: &str) -> Result<i64, &'static str> {
+pub fn train_stat(char: &mut Character, stat: &str) -> Result<i64, DomainError> {
     if char.energy < crate::constants::TRAINING_ENERGY_COST {
-        return Err("not enough energy");
+        return Err(DomainError::NotEnoughEnergy);
     }
     let current = match stat {
         "strength" => char.stats.strength,
@@ -109,11 +116,11 @@ pub fn train_stat(char: &mut Character, stat: &str) -> Result<i64, &'static str>
         "dexterity" => char.stats.dexterity,
         "constitution" => char.stats.constitution,
         "luck" => char.stats.luck,
-        _ => return Err("invalid stat"),
+        _ => return Err(DomainError::InvalidStat),
     };
     let cost = super::character::training_cost(current);
     if char.gold < cost {
-        return Err("not enough gold");
+        return Err(DomainError::NotEnoughGold);
     }
     char.energy -= crate::constants::TRAINING_ENERGY_COST;
     char.gold -= cost;
@@ -135,7 +142,7 @@ pub fn train_stat(char: &mut Character, stat: &str) -> Result<i64, &'static str>
         "dexterity" => char.stats.dexterity,
         "constitution" => char.stats.constitution,
         "luck" => char.stats.luck,
-        _ => return Err("invalid stat"),
+        _ => return Err(DomainError::InvalidStat),
     };
     Ok(new_val)
 }
@@ -225,20 +232,29 @@ mod tests {
     fn train_stat_fails_without_energy() {
         let mut c = base_char();
         c.energy = 0;
-        assert_eq!(train_stat(&mut c, "strength"), Err("not enough energy"));
+        assert_eq!(
+            train_stat(&mut c, "strength"),
+            Err(DomainError::NotEnoughEnergy)
+        );
     }
 
     #[test]
     fn train_stat_fails_without_gold() {
         let mut c = base_char();
         c.gold = 0;
-        assert_eq!(train_stat(&mut c, "strength"), Err("not enough gold"));
+        assert_eq!(
+            train_stat(&mut c, "strength"),
+            Err(DomainError::NotEnoughGold)
+        );
     }
 
     #[test]
     fn train_stat_fails_invalid_stat() {
         let mut c = base_char();
-        assert_eq!(train_stat(&mut c, "charisma"), Err("invalid stat"));
+        assert_eq!(
+            train_stat(&mut c, "charisma"),
+            Err(DomainError::InvalidStat)
+        );
     }
 
     #[test]
@@ -283,7 +299,7 @@ mod tests {
         let mut c = base_char();
         assert_eq!(
             equip_item(&mut c, &sword(), "sword1"),
-            Err("item not in inventory")
+            Err(DomainError::ItemNotInInventory)
         );
     }
 
@@ -303,7 +319,7 @@ mod tests {
         let mut c = base_char();
         assert_eq!(
             unequip_item(&mut c, "main_hand"),
-            Err("nothing equipped in slot")
+            Err(DomainError::NothingEquippedInSlot)
         );
     }
 
@@ -407,7 +423,7 @@ mod tests {
         ];
         let mut rng = rand::rngs::StdRng::seed_from_u64(42);
         for _ in 0..100 {
-            let enemy = pick_enemy(&mut rng, &encounters, &enemies);
+            let enemy = pick_enemy(&mut rng, &encounters, &enemies).unwrap();
             assert!(enemy.id == "kobold" || enemy.id == "rat");
         }
     }