1 files changed, 132 insertions, 0 deletions

diff --git a/src/roulette.rs b/src/roulette.rs
new file mode 100644
index 0000000..b59f92e
--- /dev/null
+++ b/src/roulette.rs
@@ -0,0 +1,132 @@
+//! European roulette rules shared by the server and client.
+
+use serde::{Deserialize, Serialize};
+
+/// European wheel clockwise from zero.
+pub const WHEEL: [u8; 37] = [
+    0, 32, 15, 19, 4, 21, 2, 25, 17, 34, 6, 27, 13, 36, 11, 30, 8, 23, 10, 5,
+    24, 16, 33, 1, 20, 14, 31, 9, 22, 18, 29, 7, 28, 12, 35, 3, 26,
+];
+
+pub const RED_NUMBERS: [u8; 18] = [
+    1, 3, 5, 7, 9, 12, 14, 16, 18, 19, 21, 23, 25, 27, 30, 32, 34, 36,
+];
+
+/// Total return on a winning straight (35:1 plus the stake).
+pub const STRAIGHT_RETURN: u64 = 36;
+/// Total return on a winning outside bet (1:1 plus the stake).
+pub const EVEN_MONEY_RETURN: u64 = 2;
+
+pub fn is_red(number: u8) -> bool {
+    RED_NUMBERS.contains(&number)
+}
+
+pub fn is_black(number: u8) -> bool {
+    number != 0 && !is_red(number)
+}
+
+pub fn color(number: u8) -> &'static str {
+    if number == 0 {
+        "green"
+    } else if is_red(number) {
+        "red"
+    } else {
+        "black"
+    }
+}
+
+pub fn is_even(number: u8) -> bool {
+    number != 0 && number % 2 == 0
+}
+
+pub fn is_odd(number: u8) -> bool {
+    number != 0 && number % 2 == 1
+}
+
+pub fn rtp() -> f64 {
+    36.0 / 37.0
+}
+
+#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
+pub struct NumberBet {
+    pub number: u8,
+    pub amount: u64,
+}
+
+#[derive(Debug, Clone, Default, PartialEq, Eq, Serialize, Deserialize)]
+pub struct Bets {
+    #[serde(default)]
+    pub red: u64,
+    #[serde(default)]
+    pub black: u64,
+    #[serde(default)]
+    pub even: u64,
+    #[serde(default)]
+    pub odd: u64,
+    #[serde(default)]
+    pub numbers: Vec<NumberBet>,
+}
+
+impl Bets {
+    pub fn total(&self) -> u64 {
+        let mut total = self
+            .red
+            .saturating_add(self.black)
+            .saturating_add(self.even)
+            .saturating_add(self.odd);
+        for bet in &self.numbers {
+            total = total.saturating_add(bet.amount);
+        }
+        total
+    }
+
+    pub fn is_empty(&self) -> bool {
+        self.total() == 0
+    }
+
+    /// Total returned for a winning number, including returned stakes.
+    pub fn winnings(&self, number: u8) -> u64 {
+        let mut winnings = 0u64;
+
+        if number != 0 {
+            if is_red(number) {
+                winnings = winnings.saturating_add(self.red.saturating_mul(EVEN_MONEY_RETURN));
+            } else {
+                winnings =
+                    winnings.saturating_add(self.black.saturating_mul(EVEN_MONEY_RETURN));
+            }
+            if is_even(number) {
+                winnings = winnings.saturating_add(self.even.saturating_mul(EVEN_MONEY_RETURN));
+            } else {
+                winnings = winnings.saturating_add(self.odd.saturating_mul(EVEN_MONEY_RETURN));
+            }
+        }
+
+        for bet in &self.numbers {
+            if bet.number == number {
+                winnings = winnings
+                    .saturating_add(bet.amount.saturating_mul(STRAIGHT_RETURN));
+            }
+        }
+
+        winnings
+    }
+
+    pub fn validate(&self, balance: u64) -> Result<(), String> {
+        if self.is_empty() {
+            return Err("Place at least one bet".to_string());
+        }
+        if self.total() > balance {
+            return Err("Insufficient balance".to_string());
+        }
+        for bet in &self.numbers {
+            if bet.number > 36 {
+                return Err(format!("Invalid number: {}", bet.number));
+            }
+            if bet.amount == 0 {
+                return Err("A bet amount must be positive".to_string());
+            }
+        }
+        Ok(())
+    }
+}