v2.3.1: settle orphaned reservations on server restart

2 files changed, 201 insertions, 16 deletions

diff --git a/src/server/core.rs b/src/server/core.rs
index d4c95f6..e0f0ff2 100644
--- a/src/server/core.rs
+++ b/src/server/core.rs
@@ -17,6 +17,17 @@ pub struct ConnectionState {
     user: Option<String>,
 }
 
+/// Settle reservations left behind by a previous process.
+///
+/// Call this **once at server startup, before accepting connections**. A
+/// per-connection sweep would be wrong: it would settle another player's live
+/// hand. Only one process may own the database.
+pub fn recover_orphaned_reservations(db_path: &str) -> rusqlite::Result<usize> {
+    let mut conn = Connection::open(db_path)?;
+    database::init_db(&conn);
+    database::abandon_pending(&mut conn)
+}
+
 impl ConnectionState {
     pub fn user(&self) -> Option<&str> {
         self.user.as_deref()
@@ -269,13 +280,23 @@ impl ServerCore {
         if balance < bet {
             return "ERROR Insufficient balance".to_string();
         }
-        let balance = match database::debit(&mut self.conn, user, bet) {
-            Ok(balance) => balance,
-            Err(_) => return "ERROR Insufficient balance".to_string(),
-        };
 
         let hand = self.blackjack.deal(bet as u64);
         let session_id = self.create_blackjack_session(user, &hand);
+        let balance = match database::reserve_play(
+            &mut self.conn,
+            &session_id,
+            user,
+            "blackjack",
+            bet,
+            &hand.to_json(),
+        ) {
+            Ok(balance) => balance,
+            Err(_) => {
+                let _ = self.sessions.remove_session(&session_id);
+                return "ERROR Insufficient balance".to_string();
+            }
+        };
         self.blackjack_response(user, &session_id, hand, balance)
     }
 
@@ -330,11 +351,21 @@ impl ServerCore {
                 if hand.player.len() != 2 {
                     return "ERROR Double is only allowed on the first two cards".to_string();
                 }
-                if database::debit(&mut self.conn, user, hand.base_bet as i64).is_err() {
+                if database::extend_reservation(
+                    &mut self.conn,
+                    session_id,
+                    hand.base_bet as i64,
+                )
+                .is_err()
+                {
                     return "ERROR Insufficient balance".to_string();
                 }
                 if let Err(error) = hand.double() {
-                    let _ = database::credit(&mut self.conn, user, hand.base_bet as i64);
+                    let _ = database::refund_reservation(
+                        &mut self.conn,
+                        session_id,
+                        hand.base_bet as i64,
+                    );
                     return format!("ERROR {error}");
                 }
             }
@@ -456,7 +487,14 @@ impl ServerCore {
             .sessions
             .create_session(user, "crash".to_string(), game_state);
 
-        let balance = match database::debit(&mut self.conn, user, bet) {
+        let balance = match database::reserve_play(
+            &mut self.conn,
+            &session_id,
+            user,
+            "crash",
+            bet,
+            &round.to_json(),
+        ) {
             Ok(balance) => balance,
             Err(_) => {
                 let _ = self.sessions.remove_session(&session_id);
diff --git a/src/server/database.rs b/src/server/database.rs
index 99e0dde..3cd86e4 100644
--- a/src/server/database.rs
+++ b/src/server/database.rs
@@ -31,6 +31,20 @@ pub fn init_db(conn: &Connection) {
         [],
     )
     .unwrap();
+    // A multi-step game's reserved bet is written here in the same transaction
+    // as the debit, so a crash between reserve and settle is recoverable.
+    conn.execute(
+        "CREATE TABLE IF NOT EXISTS pending_plays (
+            session_id TEXT PRIMARY KEY,
+            username TEXT NOT NULL,
+            game_type TEXT NOT NULL,
+            bet_amount INTEGER NOT NULL,
+            details TEXT NOT NULL DEFAULT '{}',
+            created_at DATETIME DEFAULT CURRENT_TIMESTAMP
+        )",
+        [],
+    )
+    .unwrap();
 }
 
 pub fn add_user(
@@ -179,16 +193,33 @@ pub fn count_plays(conn: &Connection, username: &str) -> i64 {
 }
 
 /// Reserve a bet before a multi-step hand starts.
-pub fn debit(conn: &mut Connection, username: &str, amount: i64) -> rusqlite::Result<i64> {
+///
+/// The debit and the `pending_plays` row are one transaction. If the server
+/// dies before the hand settles, the row is what lets the next startup record
+/// the lost bet instead of leaving an orphaned deduction.
+#[allow(clippy::too_many_arguments)]
+pub fn reserve_play(
+    conn: &mut Connection,
+    session_id: &str,
+    username: &str,
+    game_type: &str,
+    bet_amount: i64,
+    details: &str,
+) -> rusqlite::Result<i64> {
     let tx = conn.transaction()?;
     let updated = tx.execute(
         "UPDATE users SET balance = balance - ?1
          WHERE username = ?2 AND balance >= ?1",
-        params![amount, username],
+        params![bet_amount, username],
     )?;
     if updated != 1 {
         return Err(rusqlite::Error::QueryReturnedNoRows);
     }
+    tx.execute(
+        "INSERT INTO pending_plays (session_id, username, game_type, bet_amount, details)
+         VALUES (?1, ?2, ?3, ?4, ?5)",
+        params![session_id, username, game_type, bet_amount, details],
+    )?;
     let balance = tx.query_row(
         "SELECT balance FROM users WHERE username = ?1",
         [username],
@@ -198,16 +229,57 @@ pub fn debit(conn: &mut Connection, username: &str, amount: i64) -> rusqlite::Re
     Ok(balance)
 }
 
-/// Put a reserved bet back (disconnect or cancel).
-pub fn credit(conn: &mut Connection, username: &str, amount: i64) -> rusqlite::Result<i64> {
+/// Add to an existing reservation (blackjack double), keeping the pending row
+/// and the debit in step.
+pub fn extend_reservation(
+    conn: &mut Connection,
+    session_id: &str,
+    amount: i64,
+) -> rusqlite::Result<i64> {
+    let tx = conn.transaction()?;
+    let updated = tx.execute(
+        "UPDATE users SET balance = balance - ?1
+         WHERE balance >= ?1
+           AND username = (SELECT username FROM pending_plays WHERE session_id = ?2)",
+        params![amount, session_id],
+    )?;
+    if updated != 1 {
+        return Err(rusqlite::Error::QueryReturnedNoRows);
+    }
+    tx.execute(
+        "UPDATE pending_plays SET bet_amount = bet_amount + ?1 WHERE session_id = ?2",
+        params![amount, session_id],
+    )?;
+    let balance = tx.query_row(
+        "SELECT balance FROM users
+         WHERE username = (SELECT username FROM pending_plays WHERE session_id = ?1)",
+        [session_id],
+        |row| row.get(0),
+    )?;
+    tx.commit()?;
+    Ok(balance)
+}
+
+/// Undo part of a reservation when the action that needed it fails.
+pub fn refund_reservation(
+    conn: &mut Connection,
+    session_id: &str,
+    amount: i64,
+) -> rusqlite::Result<i64> {
     let tx = conn.transaction()?;
     tx.execute(
-        "UPDATE users SET balance = balance + ?1 WHERE username = ?2",
-        params![amount, username],
+        "UPDATE users SET balance = balance + ?1
+         WHERE username = (SELECT username FROM pending_plays WHERE session_id = ?2)",
+        params![amount, session_id],
+    )?;
+    tx.execute(
+        "UPDATE pending_plays SET bet_amount = MAX(bet_amount - ?1, 0) WHERE session_id = ?2",
+        params![amount, session_id],
     )?;
     let balance = tx.query_row(
-        "SELECT balance FROM users WHERE username = ?1",
-        [username],
+        "SELECT balance FROM users
+         WHERE username = (SELECT username FROM pending_plays WHERE session_id = ?1)",
+        [session_id],
         |row| row.get(0),
     )?;
     tx.commit()?;
@@ -215,7 +287,7 @@ pub fn credit(conn: &mut Connection, username: &str, amount: i64) -> rusqlite::R
 }
 
 /// Settle a hand whose bet was already reserved: credit winnings, write the
-/// audit row, and return the new balance.
+/// audit row, clear the reservation, and return the new balance.
 #[allow(clippy::too_many_arguments)]
 pub fn settle_play(
     conn: &mut Connection,
@@ -255,6 +327,81 @@ pub fn settle_play(
         ],
     )?;
 
+    tx.execute(
+        "DELETE FROM pending_plays WHERE session_id = ?1",
+        [session_id],
+    )?;
+
     tx.commit()?;
     Ok(balance_after)
 }
+
+/// Settle reservations left behind by a server restart.
+///
+/// A round cannot outlive the process that held its in-memory state, so the
+/// reserved bet is forfeited and recorded, never refunded. Call this once at
+/// startup, before serving players: sweeping while rounds are live would settle
+/// someone else's hand. Returns how many orphaned plays were settled.
+pub fn abandon_pending(conn: &mut Connection) -> rusqlite::Result<usize> {
+    let tx = conn.transaction()?;
+    let pending: Vec<(String, String, String, i64, String)> = {
+        let mut statement = tx.prepare(
+            "SELECT session_id, username, game_type, bet_amount, details
+             FROM pending_plays",
+        )?;
+        let rows = statement.query_map([], |row| {
+            Ok((
+                row.get(0)?,
+                row.get(1)?,
+                row.get(2)?,
+                row.get(3)?,
+                row.get(4)?,
+            ))
+        })?;
+        rows.collect::<rusqlite::Result<_>>()?
+    };
+
+    for (session_id, username, game_type, bet_amount, details) in &pending {
+        let balance_after: i64 = tx
+            .query_row(
+                "SELECT balance FROM users WHERE username = ?1",
+                [username],
+                |row| row.get(0),
+            )
+            .unwrap_or(0);
+        let details = abandoned_details(details);
+        tx.execute(
+            "INSERT OR IGNORE INTO plays
+                (session_id, username, game_type, bet_amount, winnings,
+                 balance_after, details)
+             VALUES (?1, ?2, ?3, ?4, 0, ?5, ?6)",
+            params![
+                session_id,
+                username,
+                game_type,
+                bet_amount,
+                balance_after,
+                details
+            ],
+        )?;
+        tx.execute(
+            "DELETE FROM pending_plays WHERE session_id = ?1",
+            [session_id],
+        )?;
+    }
+
+    tx.commit()?;
+    Ok(pending.len())
+}
+
+/// Mark a game's own detail blob as abandoned without dropping its payload.
+fn abandoned_details(raw: &str) -> String {
+    let mut value: serde_json::Value = serde_json::from_str(raw)
+        .unwrap_or_else(|_| serde_json::Value::Object(serde_json::Map::new()));
+    if let Some(object) = value.as_object_mut() {
+        object.insert("result".to_string(), serde_json::json!("abandoned"));
+        object.insert("phase".to_string(), serde_json::json!("abandoned"));
+        object.insert("reason".to_string(), serde_json::json!("server_restart"));
+    }
+    value.to_string()
+}