Implement Bowling

config.json

@@ -30,6 +30,7 @@
     "robot-simulator",
     "bracket-push",
     "queen-attack",
+    "bowling",
     "sublist",
     "space-age",
     "allergies",

exercises/bowling/.gitignore

@@ -0,0 +1,7 @@
+# Generated by Cargo
+# will have compiled files and executables
+/target/
+
+# Remove Cargo.lock from gitignore if creating an executable, leave it for libraries
+# More information here http://doc.crates.io/guide.html#cargotoml-vs-cargolock
+Cargo.lock

exercises/bowling/Cargo.toml

@@ -0,0 +1,3 @@
+[package]
+name = "bowling"
+version = "0.0.0"

exercises/bowling/example.rs

@@ -0,0 +1,134 @@
+
+pub struct BowlingGame {
+    frames: Vec<Frame>,
+}
+
+struct Frame {
+    rolls: Vec<u16>,
+    bonus: Vec<u16>,
+}
+
+impl Frame {
+    fn score(&self) -> u16 {
+        self.roll_score() + self.bonus_score()
+    }
+
+    fn roll_score(&self) -> u16 {
+        self.rolls.iter().sum()
+    }
+
+    fn bonus_score(&self) -> u16 {
+        self.bonus.iter().sum()
+    }
+
+    fn is_valid(&self) -> bool {
+        self.rolls_valid() && self.bonus_valid()
+    }
+
+    fn rolls_valid(&self) -> bool {
+        self.roll_score() <= 10
+    }
+
+    fn bonus_valid(&self) -> bool {
+        if self.is_open() || !self.bonus_done() {
+            return true;
+        }
+
+        if self.is_spare() {
+            return self.bonus_score() <= 10;
+        }
+
+        if let Some(first) = self.bonus.iter().next() {
+            if *first == 10 {
+                self.bonus_score() <= 20
+            } else {
+                self.bonus_score() <= 10
+            }
+        } else {
+            unreachable!();
+        }
+    }
+
+    fn is_complete(&self) -> bool {
+        self.is_open() || self.bonus_done()
+    }
+
+    fn rolls_done(&self) -> bool {
+        self.rolls.len() == 2 || self.is_strike()
+    }
+
+    fn bonus_done(&self) -> bool {
+        (self.is_spare() && self.bonus.len() == 1) || (self.is_strike() && self.bonus.len() == 2)
+    }
+
+    fn is_open(&self) -> bool {
+        self.rolls.len() == 2 && self.roll_score() < 10
+    }
+
+    fn is_spare(&self) -> bool {
+        self.rolls.len() == 2 && self.roll_score() == 10
+    }
+
+    fn is_strike(&self) -> bool {
+        self.rolls.len() == 1 && self.roll_score() == 10
+    }
+
+    fn add_roll(&mut self, roll: u16) {
+        if !self.is_complete() {
+            if self.is_spare() || self.is_strike() {
+                self.bonus.push(roll)
+            } else {
+                self.rolls.push(roll)
+            }
+        }
+    }
+
+    fn new() -> Self {
+        Frame {
+            rolls: vec![],
+            bonus: vec![],
+        }
+    }
+}
+
+impl BowlingGame {
+    pub fn new() -> Self {
+        BowlingGame { frames: vec![Frame::new()] }
+    }
+
+    pub fn roll(&mut self, pins: u16) -> Result<(), &'static str> {
+        if pins > 10 {
+            Err("Greater than 10 pins")
+        } else {
+            if self.score().is_ok() {
+                return Err("Game Finished. No more rolls.");
+            }
+
+            for mut frame in self.frames.iter_mut() {
+                frame.add_roll(pins)
+            }
+
+            if self.frames.iter().any(|f| !f.is_valid()) {
+                return Err("Invalid Roll");
+            }
+
+            if self.frames.iter().last().unwrap().rolls_done() && self.frames.len() < 10 {
+                self.frames.push(Frame::new());
+            }
+
+            Ok(())
+        }
+    }
+
+    pub fn score(&self) -> Result<u16, &'static str> {
+        if !self.is_done() {
+            Err("Game Incomplete")
+        } else {
+            Ok(self.frames.iter().fold(0, |acc, r| acc + r.score()))
+        }
+    }
+
+    fn is_done(&self) -> bool {
+        self.frames.len() == 10 && self.frames.iter().all(|f| f.is_complete())
+    }
+}