1 files changed, 90 insertions, 0 deletions

diff --git a/src/blackjack.rs b/src/blackjack.rs
new file mode 100644
index 0000000..ac0060a
--- /dev/null
+++ b/src/blackjack.rs
@@ -0,0 +1,90 @@
+//! Shared blackjack rules and wire state.
+
+use serde::{Deserialize, Serialize};
+
+pub const DECKS: usize = 6;
+pub const SUITS: [char; 4] = ['C', 'D', 'H', 'S'];
+pub const RANKS: [&str; 13] = [
+    "2", "3", "4", "5", "6", "7", "8", "9", "10", "J", "Q", "K", "A",
+];
+
+/// A fresh, unshuffled six-deck shoe.
+pub fn fresh_shoe() -> Vec<String> {
+    let mut shoe = Vec::with_capacity(DECKS * 52);
+    for _ in 0..DECKS {
+        for suit in SUITS {
+            for rank in RANKS {
+                shoe.push(format!("{rank}{suit}"));
+            }
+        }
+    }
+    shoe
+}
+
+pub fn card_value(card: &str) -> u8 {
+    let rank = &card[..card.len().saturating_sub(1)];
+    match rank {
+        "A" => 11,
+        "10" | "J" | "Q" | "K" => 10,
+        _ => rank.parse().unwrap_or(0),
+    }
+}
+
+/// Best total: aces count as 11 until that would bust the hand.
+pub fn hand_total(cards: &[String]) -> u8 {
+    let mut total = 0u16;
+    let mut aces = 0u16;
+    for card in cards {
+        if card_value(card) == 11 {
+            aces += 1;
+            total += 1;
+        } else {
+            total += card_value(card) as u16;
+        }
+    }
+    for _ in 0..aces {
+        if total + 10 <= 21 {
+            total += 10;
+        }
+    }
+    total.min(255) as u8
+}
+
+pub fn is_blackjack(cards: &[String]) -> bool {
+    cards.len() == 2 && hand_total(cards) == 21
+}
+
+pub fn is_red_suit(card: &str) -> bool {
+    matches!(card.chars().last(), Some('D') | Some('H'))
+}
+
+pub fn card_label(card: &str) -> String {
+    let Some(suit) = card.chars().last() else {
+        return card.to_string();
+    };
+    let rank = &card[..card.len() - 1];
+    let suit = match suit {
+        'C' => '♣',
+        'D' => '♦',
+        'H' => '♥',
+        'S' => '♠',
+        other => other,
+    };
+    format!("{rank}{suit}")
+}
+
+#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
+pub struct BlackjackState {
+    pub session_id: String,
+    pub phase: String,
+    pub player: Vec<String>,
+    pub dealer: Vec<String>,
+    pub player_total: u8,
+    pub dealer_total: u8,
+    pub bet: u64,
+    pub base_bet: u64,
+    pub balance: i64,
+    pub actions: Vec<String>,
+    pub result: String,
+    pub winnings: u64,
+}