add: user coins and transactions

crates/core/src/model/economy.rs

@@ -0,0 +1,36 @@
+use serde::{Serialize, Deserialize};
+use tetratto_shared::{snow::Snowflake, unix_epoch_timestamp};
+
+use super::auth::User;
+
+#[derive(Serialize, Deserialize)]
+pub struct CoinTransfer {
+    pub id: usize,
+    pub created: usize,
+    pub sender: usize,
+    pub receiver: usize,
+    pub amount: i32,
+}
+
+impl CoinTransfer {
+    /// Create a new [`CoinTransfer`].
+    pub fn new(sender: usize, receiver: usize, amount: i32) -> Self {
+        Self {
+            id: Snowflake::new().to_string().parse::<usize>().unwrap(),
+            created: unix_epoch_timestamp(),
+            sender,
+            receiver,
+            amount,
+        }
+    }
+
+    /// Apply the effects of this transaction onto the sender and receiver balances.
+    ///
+    /// # Returns
+    /// `(sender bankrupt, receiver bankrupt)`
+    pub fn apply(&self, sender: &mut User, receiver: &mut User) -> (bool, bool) {
+        sender.coins -= self.amount;
+        receiver.coins += self.amount;
+        (sender.coins < 0, receiver.coins < 0)
+    }
+}