rustrails-record 0.1.2

use std::{
    cell::RefCell,
    sync::atomic::{AtomicU32, AtomicU64, Ordering},
};

use rustrails_support::{database, runtime};
use sea_orm::{ConnectionTrait, DatabaseConnection};

use crate::base::{Record, RecordError};

type TransactionCallback = Box<dyn FnOnce() + Send>;

#[derive(Default)]
struct TransactionLevel {
    savepoint_name: Option<String>,
    after_commit: Vec<TransactionCallback>,
    after_rollback: Vec<TransactionCallback>,
}

impl TransactionLevel {
    fn outermost() -> Self {
        Self::default()
    }

    fn nested(savepoint_name: String) -> Self {
        Self {
            savepoint_name: Some(savepoint_name),
            ..Self::default()
        }
    }

    fn absorb(&mut self, nested: Self) {
        self.after_commit.extend(nested.after_commit);
        self.after_rollback.extend(nested.after_rollback);
    }
}

enum FinalizeAction {
    Commit,
    Rollback,
}

enum TransactionBoundary {
    Outermost,
    Nested(String),
}

thread_local! {
    static OPEN_TRANSACTION_COUNT: AtomicU32 = const { AtomicU32::new(0) };
    static SAVEPOINT_SEQUENCE: AtomicU32 = const { AtomicU32::new(0) };
    static CURRENT_TRANSACTION_ID: RefCell<Option<String>> = const { RefCell::new(None) };
    static TRANSACTION_LEVELS: RefCell<Vec<TransactionLevel>> = const { RefCell::new(Vec::new()) };
}

static NEXT_TRANSACTION_ID: AtomicU64 = AtomicU64::new(1);

/// Returns the number of currently open transaction scopes on this thread.
#[must_use]
pub fn open_transactions() -> u32 {
    OPEN_TRANSACTION_COUNT.with(|count| count.load(Ordering::SeqCst))
}

/// Returns `true` when any transaction scope is currently open on this thread.
#[must_use]
pub fn transaction_open() -> bool {
    open_transactions() > 0
}

/// Returns the current outermost transaction identifier, if one is active.
#[must_use]
pub fn current_transaction_id() -> Option<String> {
    CURRENT_TRANSACTION_ID.with(|current| current.borrow().clone())
}

/// Registers a callback to run after the outermost transaction commits.
///
/// When no transaction is open, the callback runs immediately.
pub fn after_commit<F>(callback: F)
where
    F: FnOnce() + Send + 'static,
{
    let mut callback = Some(Box::new(callback) as TransactionCallback);
    let registered = TRANSACTION_LEVELS.with(|levels| {
        let mut levels = levels.borrow_mut();
        if let Some(level) = levels.last_mut() {
            level
                .after_commit
                .push(callback.take().expect("after_commit callback should exist"));
            true
        } else {
            false
        }
    });

    if !registered {
        callback.expect("after_commit callback should exist outside transactions")();
    }
}

/// Registers a callback to run when the current transaction scope rolls back.
pub fn after_rollback<F>(callback: F)
where
    F: FnOnce() + Send + 'static,
{
    let mut callback = Some(Box::new(callback) as TransactionCallback);
    TRANSACTION_LEVELS.with(|levels| {
        let mut levels = levels.borrow_mut();
        if let Some(level) = levels.last_mut() {
            level.after_rollback.push(
                callback
                    .take()
                    .expect("after_rollback callback should exist"),
            );
        }
    });
}

/// Executes a closure inside a database transaction.
///
/// The helper uses explicit `BEGIN` / `COMMIT` / `ROLLBACK` statements against the
/// provided connection so the closure can keep working with a [`DatabaseConnection`].
/// Nested calls use savepoints so inner failures can roll back without aborting the
/// outermost transaction.
pub async fn transaction<F, Fut, T>(db: &DatabaseConnection, f: F) -> Result<T, RecordError>
where
    F: FnOnce(&DatabaseConnection) -> Fut + Send,
    Fut: std::future::Future<Output = Result<T, RecordError>> + Send,
    T: Send,
{
    begin_transaction_scope(db).await?;

    match f(db).await {
        Ok(value) => {
            commit_transaction_scope(db).await?;
            Ok(value)
        }
        Err(error) => {
            rollback_transaction_scope(db).await?;
            Err(error)
        }
    }
}

/// Synchronous wrapper for [`transaction`].
pub fn transaction_sync<F, Fut, T>(f: F) -> Result<T, RecordError>
where
    F: FnOnce(&DatabaseConnection) -> Fut + Send,
    Fut: std::future::Future<Output = Result<T, RecordError>> + Send,
    T: Send,
{
    database::with_db(|db| runtime::block_on(transaction(db, f)))
}

async fn begin_transaction_scope(db: &DatabaseConnection) -> Result<(), RecordError> {
    if transaction_open() {
        let savepoint_name = next_savepoint_name();
        execute_transaction_control(db, &format!("SAVEPOINT {savepoint_name}")).await?;
        OPEN_TRANSACTION_COUNT.with(|count| {
            count.fetch_add(1, Ordering::SeqCst);
        });
        TRANSACTION_LEVELS.with(|levels| {
            levels
                .borrow_mut()
                .push(TransactionLevel::nested(savepoint_name));
        });
    } else {
        let transaction_id = next_transaction_id();
        execute_transaction_control(db, "BEGIN").await?;
        OPEN_TRANSACTION_COUNT.with(|count| count.store(1, Ordering::SeqCst));
        SAVEPOINT_SEQUENCE.with(|sequence| sequence.store(0, Ordering::SeqCst));
        CURRENT_TRANSACTION_ID.with(|current| {
            current.replace(Some(transaction_id));
        });
        TRANSACTION_LEVELS.with(|levels| {
            levels.borrow_mut().push(TransactionLevel::outermost());
        });
    }

    Ok(())
}

async fn commit_transaction_scope(db: &DatabaseConnection) -> Result<(), RecordError> {
    match current_transaction_boundary() {
        Some(TransactionBoundary::Outermost) => {
            execute_or_reset_state(db, "COMMIT").await?;
            let callbacks = finish_outermost_transaction(FinalizeAction::Commit);
            run_callbacks(callbacks);
            Ok(())
        }
        Some(TransactionBoundary::Nested(savepoint_name)) => {
            execute_or_reset_state(db, &format!("RELEASE SAVEPOINT {savepoint_name}")).await?;
            merge_nested_transaction_into_parent();
            Ok(())
        }
        None => Ok(()),
    }
}

async fn rollback_transaction_scope(db: &DatabaseConnection) -> Result<(), RecordError> {
    match current_transaction_boundary() {
        Some(TransactionBoundary::Outermost) => {
            execute_or_reset_state(db, "ROLLBACK").await?;
            let callbacks = finish_outermost_transaction(FinalizeAction::Rollback);
            run_callbacks(callbacks);
            Ok(())
        }
        Some(TransactionBoundary::Nested(savepoint_name)) => {
            execute_or_reset_state(db, &format!("ROLLBACK TO SAVEPOINT {savepoint_name}")).await?;
            let callbacks = rollback_nested_transaction();
            run_callbacks(callbacks);
            Ok(())
        }
        None => Ok(()),
    }
}

async fn execute_or_reset_state(db: &DatabaseConnection, sql: &str) -> Result<(), RecordError> {
    if let Err(error) = execute_transaction_control(db, sql).await {
        reset_transaction_state();
        Err(error)
    } else {
        Ok(())
    }
}

async fn execute_transaction_control(
    db: &DatabaseConnection,
    sql: &str,
) -> Result<(), RecordError> {
    db.execute_unprepared(sql).await?;
    Ok(())
}

fn current_transaction_boundary() -> Option<TransactionBoundary> {
    TRANSACTION_LEVELS.with(|levels| {
        let levels = levels.borrow();
        levels.last().map(|level| match &level.savepoint_name {
            Some(savepoint_name) => TransactionBoundary::Nested(savepoint_name.clone()),
            None => TransactionBoundary::Outermost,
        })
    })
}

fn merge_nested_transaction_into_parent() {
    TRANSACTION_LEVELS.with(|levels| {
        let mut levels = levels.borrow_mut();
        let nested = levels
            .pop()
            .expect("nested transaction state should exist during commit");
        let parent = levels
            .last_mut()
            .expect("parent transaction state should exist during nested commit");
        parent.absorb(nested);
    });
    OPEN_TRANSACTION_COUNT.with(|count| {
        count.fetch_sub(1, Ordering::SeqCst);
    });
}

fn rollback_nested_transaction() -> Vec<TransactionCallback> {
    let callbacks = TRANSACTION_LEVELS.with(|levels| {
        let mut levels = levels.borrow_mut();
        levels
            .pop()
            .expect("nested transaction state should exist during rollback")
            .after_rollback
    });
    OPEN_TRANSACTION_COUNT.with(|count| {
        count.fetch_sub(1, Ordering::SeqCst);
    });
    callbacks
}

fn finish_outermost_transaction(action: FinalizeAction) -> Vec<TransactionCallback> {
    OPEN_TRANSACTION_COUNT.with(|count| count.store(0, Ordering::SeqCst));
    SAVEPOINT_SEQUENCE.with(|sequence| sequence.store(0, Ordering::SeqCst));
    CURRENT_TRANSACTION_ID.with(|current| {
        current.replace(None);
    });

    TRANSACTION_LEVELS.with(|levels| {
        let mut levels = levels.borrow_mut();
        let outermost = levels
            .pop()
            .expect("outermost transaction state should exist during finalization");
        levels.clear();
        match action {
            FinalizeAction::Commit => outermost.after_commit,
            FinalizeAction::Rollback => outermost.after_rollback,
        }
    })
}

fn next_transaction_id() -> String {
    format!("tx-{}", NEXT_TRANSACTION_ID.fetch_add(1, Ordering::Relaxed))
}

fn next_savepoint_name() -> String {
    SAVEPOINT_SEQUENCE.with(|sequence| {
        let next = sequence.fetch_add(1, Ordering::SeqCst) + 1;
        format!("sp_{next}")
    })
}

fn reset_transaction_state() {
    OPEN_TRANSACTION_COUNT.with(|count| count.store(0, Ordering::SeqCst));
    SAVEPOINT_SEQUENCE.with(|sequence| sequence.store(0, Ordering::SeqCst));
    CURRENT_TRANSACTION_ID.with(|current| {
        current.replace(None);
    });
    TRANSACTION_LEVELS.with(|levels| levels.borrow_mut().clear());
}

fn run_callbacks(callbacks: Vec<TransactionCallback>) {
    for callback in callbacks {
        callback();
    }
}

/// Trait for records that support transactional operations.
pub trait Transactional: Record {
    /// Executes a closure inside a database transaction.
    async fn transaction<F, Fut, T>(db: &DatabaseConnection, f: F) -> Result<T, RecordError>
    where
        F: FnOnce(&DatabaseConnection) -> Fut + Send,
        Fut: std::future::Future<Output = Result<T, RecordError>> + Send,
        T: Send,
    {
        crate::transactions::transaction(db, f).await
    }
}

#[cfg(test)]
mod tests {
    use std::{
        collections::HashMap,
        sync::{
            Arc, Mutex,
            atomic::{AtomicUsize, Ordering as AtomicOrdering},
        },
    };

    use sea_orm::{ConnectionTrait, Schema};
    use serde_json::{Value, json};

    use super::{
        Transactional, after_commit, after_rollback, current_transaction_id, open_transactions,
        transaction, transaction_open, transaction_sync,
    };
    use crate::{
        Record, RecordError,
        base::test_support::{TestUser, setup_db, test_user},
        persistence::AsyncPersistence,
        querying::AsyncQuerying,
    };
    use rustrails_support::{database, runtime};

    fn run_sync_transaction_test(test: impl FnOnce() + Send + 'static) {
        std::thread::spawn(move || {
            let _rt = runtime::init_runtime();
            database::establish("sqlite::memory:")
                .expect("sqlite in-memory connection should succeed");
            runtime::block_on(async {
                let db = database::db();
                let schema = Schema::new(db.get_database_backend());
                db.execute(&schema.create_table_from_entity(test_user::Entity))
                    .await
                    .expect("test_users table should be created");
            });
            test();
        })
        .join()
        .unwrap();
    }

    fn user_attrs(name: &str, email: &str) -> HashMap<String, Value> {
        HashMap::from([
            ("name".to_owned(), json!(name)),
            ("email".to_owned(), json!(email)),
        ])
    }

    impl Transactional for TestUser {}

    #[tokio::test]
    async fn transaction_commits_on_success() {
        let db = setup_db().await;

        transaction(&db, |txn| {
            let txn = txn.clone();
            async move {
                TestUser::create(
                    HashMap::from([
                        ("name".to_owned(), json!("Alice")),
                        ("email".to_owned(), json!("alice@example.com")),
                    ]),
                    &txn,
                )
                .await?;
                Ok(())
            }
        })
        .await
        .expect("transaction should commit");

        assert_eq!(TestUser::count(&db).await.expect("count should succeed"), 1);
    }

    #[tokio::test]
    async fn transaction_rolls_back_on_error() {
        let db = setup_db().await;

        let error = transaction(&db, |txn| {
            let txn = txn.clone();
            async move {
                TestUser::create(
                    HashMap::from([
                        ("name".to_owned(), json!("Alice")),
                        ("email".to_owned(), json!("alice@example.com")),
                    ]),
                    &txn,
                )
                .await?;
                Err::<(), RecordError>(RecordError::Invalid("force rollback".to_owned()))
            }
        })
        .await
        .expect_err("transaction should fail");

        assert!(matches!(error, RecordError::Invalid(message) if message == "force rollback"));
        assert_eq!(TestUser::count(&db).await.expect("count should succeed"), 0);
    }

    #[tokio::test]
    async fn transaction_returns_closure_value() {
        let db = setup_db().await;

        let id = transaction(&db, |txn| {
            let txn = txn.clone();
            async move {
                let user = TestUser::create(
                    HashMap::from([
                        ("name".to_owned(), json!("Alice")),
                        ("email".to_owned(), json!("alice@example.com")),
                    ]),
                    &txn,
                )
                .await?;
                user.id().ok_or(RecordError::NotSaved)
            }
        })
        .await
        .expect("transaction should return a value");

        assert_eq!(id, 1);
    }

    #[tokio::test]
    async fn transactional_trait_delegates_to_helper() {
        let db = setup_db().await;

        TestUser::transaction(&db, |txn| {
            let txn = txn.clone();
            async move {
                TestUser::create(
                    HashMap::from([
                        ("name".to_owned(), json!("Bob")),
                        ("email".to_owned(), json!("bob@example.com")),
                    ]),
                    &txn,
                )
                .await?;
                Ok(())
            }
        })
        .await
        .expect("trait helper should commit");

        let user = TestUser::find(1, &db).await.expect("user should exist");
        assert_eq!(user.name, "Bob");
    }

    #[tokio::test]
    async fn rollback_preserves_rows_outside_failed_transaction() {
        let db = setup_db().await;

        TestUser::create(
            HashMap::from([
                ("name".to_owned(), json!("Alice")),
                ("email".to_owned(), json!("alice@example.com")),
            ]),
            &db,
        )
        .await
        .expect("seed insert should succeed");

        let _: Result<(), RecordError> = transaction(&db, |txn| {
            let txn = txn.clone();
            async move {
                TestUser::create(
                    HashMap::from([
                        ("name".to_owned(), json!("Bob")),
                        ("email".to_owned(), json!("bob@example.com")),
                    ]),
                    &txn,
                )
                .await?;
                Err(RecordError::Invalid("rollback".to_owned()))
            }
        })
        .await;

        assert_eq!(TestUser::count(&db).await.expect("count should succeed"), 1);
    }

    #[tokio::test]
    async fn transaction_commits_multiple_writes() {
        let db = setup_db().await;

        transaction(&db, |txn| {
            let txn = txn.clone();
            async move {
                for (name, email) in [("Alice", "alice@example.com"), ("Bob", "bob@example.com")] {
                    TestUser::create(
                        HashMap::from([
                            ("name".to_owned(), json!(name)),
                            ("email".to_owned(), json!(email)),
                        ]),
                        &txn,
                    )
                    .await?;
                }
                Ok(())
            }
        })
        .await
        .expect("multi-write transaction should commit");

        assert_eq!(TestUser::count(&db).await.expect("count should succeed"), 2);
    }

    #[tokio::test]
    async fn transaction_rolls_back_multiple_writes() {
        let db = setup_db().await;

        let error = transaction(&db, |txn| {
            let txn = txn.clone();
            async move {
                for (name, email) in [("Alice", "alice@example.com"), ("Bob", "bob@example.com")] {
                    TestUser::create(
                        HashMap::from([
                            ("name".to_owned(), json!(name)),
                            ("email".to_owned(), json!(email)),
                        ]),
                        &txn,
                    )
                    .await?;
                }
                Err::<(), RecordError>(RecordError::Invalid("rollback all writes".to_owned()))
            }
        })
        .await
        .expect_err("multi-write transaction should fail");

        assert!(matches!(error, RecordError::Invalid(message) if message == "rollback all writes"));
        assert_eq!(TestUser::count(&db).await.expect("count should succeed"), 0);
    }

    #[tokio::test]
    async fn transaction_exposes_uncommitted_writes_inside_closure() {
        let db = setup_db().await;

        let visible_count = transaction(&db, |txn| {
            let txn = txn.clone();
            async move {
                TestUser::create(
                    HashMap::from([
                        ("name".to_owned(), json!("Alice")),
                        ("email".to_owned(), json!("alice@example.com")),
                    ]),
                    &txn,
                )
                .await?;
                TestUser::count(&txn).await
            }
        })
        .await
        .expect("transaction should return the in-transaction count");

        assert_eq!(visible_count, 1);
        assert_eq!(TestUser::count(&db).await.expect("count should succeed"), 1);
    }

    #[tokio::test]
    async fn transaction_rolls_back_writes_visible_inside_failed_closure() {
        let db = setup_db().await;

        let visible_count = transaction(&db, |txn| {
            let txn = txn.clone();
            async move {
                TestUser::create(
                    HashMap::from([
                        ("name".to_owned(), json!("Alice")),
                        ("email".to_owned(), json!("alice@example.com")),
                    ]),
                    &txn,
                )
                .await?;
                let count = TestUser::count(&txn).await?;
                Err::<u64, RecordError>(RecordError::Invalid(format!(
                    "count before rollback: {count}"
                )))
            }
        })
        .await
        .expect_err("transaction should fail");

        assert!(
            matches!(visible_count, RecordError::Invalid(message) if message == "count before rollback: 1")
        );
        assert_eq!(TestUser::count(&db).await.expect("count should succeed"), 0);
    }

    #[tokio::test]
    async fn transaction_can_read_seeded_rows_and_insert_more() {
        let db = setup_db().await;

        TestUser::create(
            HashMap::from([
                ("name".to_owned(), json!("Alice")),
                ("email".to_owned(), json!("alice@example.com")),
            ]),
            &db,
        )
        .await
        .expect("seed insert should succeed");

        let counts = transaction(&db, |txn| {
            let txn = txn.clone();
            async move {
                let before = TestUser::count(&txn).await?;
                TestUser::create(
                    HashMap::from([
                        ("name".to_owned(), json!("Bob")),
                        ("email".to_owned(), json!("bob@example.com")),
                    ]),
                    &txn,
                )
                .await?;
                let after = TestUser::count(&txn).await?;
                Ok((before, after))
            }
        })
        .await
        .expect("transaction should commit");

        assert_eq!(counts, (1, 2));
        assert_eq!(TestUser::count(&db).await.expect("count should succeed"), 2);
    }

    #[tokio::test]
    #[ignore = "Nested savepoint-backed transactions are supported on the same connection"]
    async fn nested_transaction_on_same_connection_returns_database_error() {
        let db = setup_db().await;

        let error = transaction(&db, |txn| {
            let txn = txn.clone();
            async move {
                TestUser::create(
                    HashMap::from([
                        ("name".to_owned(), json!("Outer")),
                        ("email".to_owned(), json!("outer@example.com")),
                    ]),
                    &txn,
                )
                .await?;

                let nested = transaction(&txn, |inner_txn| {
                    let inner_txn = inner_txn.clone();
                    async move {
                        TestUser::create(
                            HashMap::from([
                                ("name".to_owned(), json!("Inner")),
                                ("email".to_owned(), json!("inner@example.com")),
                            ]),
                            &inner_txn,
                        )
                        .await?;
                        Ok(())
                    }
                })
                .await;

                assert!(nested.is_err());
                nested
            }
        })
        .await
        .expect_err("nested transaction should fail on the same connection");

        assert!(matches!(error, RecordError::Database(_)));
        assert_eq!(TestUser::count(&db).await.expect("count should succeed"), 0);
    }

    #[tokio::test]
    async fn transaction_rollback_preserves_seeded_rows_on_multiwrite_failure() {
        let db = setup_db().await;

        TestUser::create(
            HashMap::from([
                ("name".to_owned(), json!("Alice")),
                ("email".to_owned(), json!("alice@example.com")),
            ]),
            &db,
        )
        .await
        .expect("seed insert should succeed");

        let _ = transaction(&db, |txn| {
            let txn = txn.clone();
            async move {
                for (name, email) in [("Bob", "bob@example.com"), ("Carol", "carol@example.com")] {
                    TestUser::create(
                        HashMap::from([
                            ("name".to_owned(), json!(name)),
                            ("email".to_owned(), json!(email)),
                        ]),
                        &txn,
                    )
                    .await?;
                }
                Err::<(), RecordError>(RecordError::NotSaved)
            }
        })
        .await;

        assert_eq!(TestUser::count(&db).await.expect("count should succeed"), 1);
        assert_eq!(
            TestUser::find(1, &db)
                .await
                .expect("seed row should still exist")
                .name,
            "Alice"
        );
    }

    #[tokio::test]
    async fn manual_rollback_via_not_saved_error_rolls_back() {
        let db = setup_db().await;

        let error = transaction(&db, |txn| {
            let txn = txn.clone();
            async move {
                TestUser::create(
                    HashMap::from([
                        ("name".to_owned(), json!("Alice")),
                        ("email".to_owned(), json!("alice@example.com")),
                    ]),
                    &txn,
                )
                .await?;
                Err::<(), RecordError>(RecordError::NotSaved)
            }
        })
        .await
        .expect_err("manual rollback should bubble the original error");

        assert!(matches!(error, RecordError::NotSaved));
        assert_eq!(TestUser::count(&db).await.expect("count should succeed"), 0);
    }

    #[tokio::test]
    async fn transactional_trait_can_return_tuple_values() {
        let db = setup_db().await;

        let result = TestUser::transaction(&db, |txn| {
            let txn = txn.clone();
            async move {
                let user = TestUser::create(
                    HashMap::from([
                        ("name".to_owned(), json!("Alice")),
                        ("email".to_owned(), json!("alice@example.com")),
                    ]),
                    &txn,
                )
                .await?;
                Ok((
                    user.id().expect("id should be assigned"),
                    TestUser::count(&txn).await?,
                ))
            }
        })
        .await
        .expect("trait helper should return tuple values");

        assert_eq!(result, (1, 1));
    }

    #[tokio::test]
    async fn transaction_without_writes_can_return_existing_count() {
        let db = setup_db().await;

        TestUser::create(
            HashMap::from([
                ("name".to_owned(), json!("Alice")),
                ("email".to_owned(), json!("alice@example.com")),
            ]),
            &db,
        )
        .await
        .expect("seed insert should succeed");

        let count = transaction(&db, |txn| {
            let txn = txn.clone();
            async move { TestUser::count(&txn).await }
        })
        .await
        .expect("read-only transaction should commit");

        assert_eq!(count, 1);
    }

    #[tokio::test]
    async fn transaction_commits_updates_to_existing_rows() {
        let db = setup_db().await;
        let user = TestUser::create(
            HashMap::from([
                ("name".to_owned(), json!("Alice")),
                ("email".to_owned(), json!("alice@example.com")),
            ]),
            &db,
        )
        .await
        .expect("seed insert should succeed");
        let id = user.id().expect("seed row should have an id");

        transaction(&db, |txn| {
            let txn = txn.clone();
            async move {
                let mut user = TestUser::find(id, &txn).await?;
                user.update_attributes(
                    HashMap::from([("name".to_owned(), json!("Updated Alice"))]),
                    &txn,
                )
                .await?;
                Ok(())
            }
        })
        .await
        .expect("update transaction should commit");

        let reloaded = TestUser::find(id, &db)
            .await
            .expect("updated row should load after commit");
        assert_eq!(reloaded.name, "Updated Alice");
        assert_eq!(reloaded.email, "alice@example.com");
    }

    #[tokio::test]
    async fn transaction_rolls_back_updates_to_existing_rows() {
        let db = setup_db().await;
        let user = TestUser::create(
            HashMap::from([
                ("name".to_owned(), json!("Alice")),
                ("email".to_owned(), json!("alice@example.com")),
            ]),
            &db,
        )
        .await
        .expect("seed insert should succeed");
        let id = user.id().expect("seed row should have an id");

        let error = transaction(&db, |txn| {
            let txn = txn.clone();
            async move {
                let mut user = TestUser::find(id, &txn).await?;
                user.update_attributes(
                    HashMap::from([("name".to_owned(), json!("Updated Alice"))]),
                    &txn,
                )
                .await?;
                Err::<(), RecordError>(RecordError::Invalid("rollback update".to_owned()))
            }
        })
        .await
        .expect_err("update transaction should fail");

        assert!(matches!(error, RecordError::Invalid(message) if message == "rollback update"));

        let reloaded = TestUser::find(id, &db)
            .await
            .expect("seed row should still load after rollback");
        assert_eq!(reloaded.name, "Alice");
        assert_eq!(reloaded.email, "alice@example.com");
    }

    #[tokio::test]
    async fn nested_transaction_commits_with_savepoint_release() {
        let db = setup_db().await;

        let (outer_id, inner_id) = transaction(&db, |txn| {
            let txn = txn.clone();
            async move {
                TestUser::create(user_attrs("Outer", "outer@example.com"), &txn).await?;
                let outer_id = current_transaction_id().expect("outer transaction id should exist");

                let inner_id = transaction(&txn, |inner_txn| {
                    let inner_txn = inner_txn.clone();
                    async move {
                        assert_eq!(open_transactions(), 2);
                        TestUser::create(user_attrs("Inner", "inner@example.com"), &inner_txn)
                            .await?;
                        Ok::<String, RecordError>(
                            current_transaction_id()
                                .expect("nested transaction should reuse the outer id"),
                        )
                    }
                })
                .await?;

                assert_eq!(TestUser::count(&txn).await?, 2);
                Ok((outer_id, inner_id))
            }
        })
        .await
        .expect("nested transaction should commit");

        assert_eq!(outer_id, inner_id);
        assert_eq!(TestUser::count(&db).await.expect("count should succeed"), 2);
    }

    #[test]
    fn transaction_sync_commits_on_success() {
        run_sync_transaction_test(|| {
            transaction_sync(|txn| {
                let txn = txn.clone();
                async move {
                    TestUser::create(
                        HashMap::from([
                            ("name".to_owned(), json!("Alice")),
                            ("email".to_owned(), json!("alice@example.com")),
                        ]),
                        &txn,
                    )
                    .await?;
                    Ok(())
                }
            })
            .expect("transaction should commit");

            let count = runtime::block_on(async {
                let db = database::db();
                TestUser::count(&db).await.expect("count should succeed")
            });
            assert_eq!(count, 1);
        });
    }

    #[tokio::test]
    async fn nested_transaction_rollback_to_savepoint_preserves_outer_changes() {
        let db = setup_db().await;

        transaction(&db, |txn| {
            let txn = txn.clone();
            async move {
                TestUser::create(user_attrs("Outer", "outer@example.com"), &txn).await?;

                let error = transaction(&txn, |inner_txn| {
                    let inner_txn = inner_txn.clone();
                    async move {
                        TestUser::create(user_attrs("Inner", "inner@example.com"), &inner_txn)
                            .await?;
                        Err::<(), RecordError>(RecordError::Invalid("rollback inner".to_owned()))
                    }
                })
                .await
                .expect_err("inner transaction should roll back to its savepoint");

                assert!(
                    matches!(error, RecordError::Invalid(message) if message == "rollback inner")
                );
                assert_eq!(open_transactions(), 1);
                assert_eq!(TestUser::count(&txn).await?, 1);

                TestUser::create(user_attrs("AfterInner", "after@example.com"), &txn).await?;
                Ok(())
            }
        })
        .await
        .expect("outer transaction should still commit");

        assert_eq!(TestUser::count(&db).await.expect("count should succeed"), 2);
        assert_eq!(
            TestUser::find(1, &db)
                .await
                .expect("outer row should persist")
                .name,
            "Outer"
        );
        assert_eq!(
            TestUser::find(2, &db)
                .await
                .expect("post-rollback outer row should persist")
                .name,
            "AfterInner"
        );
    }

    #[tokio::test]
    async fn after_commit_fires_after_outermost_commit_only() {
        let db = setup_db().await;
        let calls = Arc::new(AtomicUsize::new(0));
        let transaction_calls = Arc::clone(&calls);

        transaction(&db, move |txn| {
            let txn = txn.clone();
            let calls = Arc::clone(&transaction_calls);
            let outer_calls = Arc::clone(&calls);
            async move {
                after_commit(move || {
                    outer_calls.fetch_add(1, AtomicOrdering::SeqCst);
                });

                let nested_calls = Arc::clone(&calls);
                transaction(&txn, move |inner_txn| {
                    let inner_txn = inner_txn.clone();
                    let calls = Arc::clone(&nested_calls);
                    let inner_calls = Arc::clone(&calls);
                    async move {
                        TestUser::create(user_attrs("Inner", "inner@example.com"), &inner_txn)
                            .await?;
                        after_commit(move || {
                            inner_calls.fetch_add(1, AtomicOrdering::SeqCst);
                        });
                        assert_eq!(calls.load(AtomicOrdering::SeqCst), 0);
                        Ok(())
                    }
                })
                .await?;

                assert_eq!(calls.load(AtomicOrdering::SeqCst), 0);
                Ok(())
            }
        })
        .await
        .expect("outer transaction should commit");

        assert_eq!(calls.load(AtomicOrdering::SeqCst), 2);
    }

    #[tokio::test]
    async fn after_commit_callbacks_fire_in_registration_order_across_nested_transactions() {
        let db = setup_db().await;
        let events = Arc::new(Mutex::new(Vec::new()));
        let transaction_events = Arc::clone(&events);

        transaction(&db, move |txn| {
            let txn = txn.clone();
            let events = Arc::clone(&transaction_events);
            let outer_events = Arc::clone(&events);
            async move {
                after_commit(move || outer_events.lock().unwrap().push("outer-1".to_owned()));

                let nested_events = Arc::clone(&events);
                transaction(&txn, move |inner_txn| {
                    let inner_txn = inner_txn.clone();
                    let inner_events = Arc::clone(&nested_events);
                    async move {
                        after_commit(move || {
                            inner_events.lock().unwrap().push("inner-1".to_owned());
                        });
                        TestUser::create(user_attrs("Inner", "inner@example.com"), &inner_txn)
                            .await?;
                        Ok(())
                    }
                })
                .await?;

                let trailing_events = Arc::clone(&events);
                after_commit(move || {
                    trailing_events.lock().unwrap().push("outer-2".to_owned());
                });
                Ok(())
            }
        })
        .await
        .expect("callback ordering transaction should commit");

        assert_eq!(
            *events.lock().unwrap(),
            vec![
                "outer-1".to_owned(),
                "inner-1".to_owned(),
                "outer-2".to_owned()
            ]
        );
    }

    #[tokio::test]
    async fn after_commit_callbacks_do_not_fire_when_outer_transaction_rolls_back() {
        let db = setup_db().await;
        let calls = Arc::new(AtomicUsize::new(0));
        let transaction_calls = Arc::clone(&calls);

        let error = transaction(&db, move |txn| {
            let txn = txn.clone();
            let calls = Arc::clone(&transaction_calls);
            let outer_calls = Arc::clone(&calls);
            async move {
                after_commit(move || {
                    outer_calls.fetch_add(1, AtomicOrdering::SeqCst);
                });

                let nested_calls = Arc::clone(&calls);
                transaction(&txn, move |inner_txn| {
                    let inner_txn = inner_txn.clone();
                    let calls = Arc::clone(&nested_calls);
                    let inner_calls = Arc::clone(&calls);
                    async move {
                        after_commit(move || {
                            inner_calls.fetch_add(1, AtomicOrdering::SeqCst);
                        });
                        TestUser::create(user_attrs("Inner", "inner@example.com"), &inner_txn)
                            .await?;
                        Ok(())
                    }
                })
                .await?;

                Err::<(), RecordError>(RecordError::Invalid("rollback outer".to_owned()))
            }
        })
        .await
        .expect_err("outer transaction should roll back");

        assert!(matches!(error, RecordError::Invalid(message) if message == "rollback outer"));
        assert_eq!(calls.load(AtomicOrdering::SeqCst), 0);
    }

    #[tokio::test]
    async fn after_commit_callbacks_are_cleared_after_commit() {
        let db = setup_db().await;
        let calls = Arc::new(AtomicUsize::new(0));

        transaction(&db, |_| {
            let calls = Arc::clone(&calls);
            async move {
                after_commit(move || {
                    calls.fetch_add(1, AtomicOrdering::SeqCst);
                });
                Ok(())
            }
        })
        .await
        .expect("first transaction should commit");

        transaction(&db, |_| async move { Ok(()) })
            .await
            .expect("second transaction should commit");

        assert_eq!(calls.load(AtomicOrdering::SeqCst), 1);
    }

    #[tokio::test]
    async fn after_rollback_fires_on_outermost_rollback() {
        let db = setup_db().await;
        let calls = Arc::new(AtomicUsize::new(0));
        let callback_calls = Arc::clone(&calls);

        let error = transaction(&db, move |_txn| {
            let outer_calls = Arc::clone(&callback_calls);
            async move {
                after_rollback(move || {
                    outer_calls.fetch_add(1, AtomicOrdering::SeqCst);
                });
                Err::<(), RecordError>(RecordError::Invalid("rollback outer".to_owned()))
            }
        })
        .await
        .expect_err("transaction should roll back");

        assert!(matches!(error, RecordError::Invalid(message) if message == "rollback outer"));
        assert_eq!(calls.load(AtomicOrdering::SeqCst), 1);
    }

    #[tokio::test]
    async fn nested_rollback_fires_only_inner_after_rollback_callbacks() {
        let db = setup_db().await;
        let calls = Arc::new(Mutex::new(Vec::new()));
        let transaction_calls = Arc::clone(&calls);

        transaction(&db, move |txn| {
            let txn = txn.clone();
            let calls = Arc::clone(&transaction_calls);
            let outer_calls = Arc::clone(&calls);
            async move {
                after_rollback(move || outer_calls.lock().unwrap().push("outer".to_owned()));

                let nested_calls = Arc::clone(&calls);
                let error = transaction(&txn, move |inner_txn| {
                    let inner_txn = inner_txn.clone();
                    let calls = Arc::clone(&nested_calls);
                    let inner_calls = Arc::clone(&calls);
                    async move {
                        after_rollback(move || {
                            inner_calls.lock().unwrap().push("inner".to_owned())
                        });
                        TestUser::create(user_attrs("Inner", "inner@example.com"), &inner_txn)
                            .await?;
                        Err::<(), RecordError>(RecordError::Invalid("rollback inner".to_owned()))
                    }
                })
                .await
                .expect_err("inner transaction should roll back");

                assert!(
                    matches!(error, RecordError::Invalid(message) if message == "rollback inner")
                );
                assert_eq!(*calls.lock().unwrap(), vec!["inner".to_owned()]);
                Ok(())
            }
        })
        .await
        .expect("outer transaction should commit");

        assert_eq!(*calls.lock().unwrap(), vec!["inner".to_owned()]);
    }

    #[tokio::test]
    async fn nested_successful_after_rollback_callbacks_fire_if_outer_transaction_rolls_back() {
        let db = setup_db().await;
        let calls = Arc::new(Mutex::new(Vec::new()));
        let transaction_calls = Arc::clone(&calls);

        let error = transaction(&db, move |txn| {
            let txn = txn.clone();
            let calls = Arc::clone(&transaction_calls);
            let outer_calls = Arc::clone(&calls);
            async move {
                after_rollback(move || outer_calls.lock().unwrap().push("outer".to_owned()));

                let nested_calls = Arc::clone(&calls);
                transaction(&txn, move |inner_txn| {
                    let inner_txn = inner_txn.clone();
                    let calls = Arc::clone(&nested_calls);
                    let inner_calls = Arc::clone(&calls);
                    async move {
                        after_rollback(move || {
                            inner_calls.lock().unwrap().push("inner".to_owned())
                        });
                        TestUser::create(user_attrs("Inner", "inner@example.com"), &inner_txn)
                            .await?;
                        Ok(())
                    }
                })
                .await?;

                Err::<(), RecordError>(RecordError::Invalid("rollback outer".to_owned()))
            }
        })
        .await
        .expect_err("outer transaction should roll back");

        assert!(matches!(error, RecordError::Invalid(message) if message == "rollback outer"));
        assert_eq!(
            *calls.lock().unwrap(),
            vec!["outer".to_owned(), "inner".to_owned()]
        );
    }

    #[tokio::test]
    async fn after_rollback_callbacks_are_cleared_after_rollback() {
        let db = setup_db().await;
        let calls = Arc::new(AtomicUsize::new(0));
        let callback_calls = Arc::clone(&calls);

        let _ = transaction(&db, move |_txn| {
            let outer_calls = Arc::clone(&callback_calls);
            async move {
                after_rollback(move || {
                    outer_calls.fetch_add(1, AtomicOrdering::SeqCst);
                });
                Err::<(), RecordError>(RecordError::Invalid("rollback once".to_owned()))
            }
        })
        .await;

        transaction(&db, |_| async move { Ok(()) })
            .await
            .expect("later transaction should commit");

        assert_eq!(calls.load(AtomicOrdering::SeqCst), 1);
    }

    #[tokio::test]
    async fn open_transactions_starts_closed() {
        assert_eq!(open_transactions(), 0);
        assert!(!transaction_open());
    }

    #[tokio::test]
    async fn open_transactions_tracks_nested_depth() {
        let db = setup_db().await;

        assert_eq!(open_transactions(), 0);

        transaction(&db, |txn| {
            let txn = txn.clone();
            async move {
                assert_eq!(open_transactions(), 1);
                transaction(&txn, |_| async move {
                    assert_eq!(open_transactions(), 2);
                    Ok(())
                })
                .await?;
                assert_eq!(open_transactions(), 1);
                Ok(())
            }
        })
        .await
        .expect("nested transaction should commit");

        assert_eq!(open_transactions(), 0);
    }

    #[tokio::test]
    async fn transaction_open_reflects_current_state() {
        let db = setup_db().await;

        assert!(!transaction_open());

        transaction(&db, |txn| {
            let txn = txn.clone();
            async move {
                assert!(transaction_open());
                transaction(&txn, |_| async move {
                    assert!(transaction_open());
                    Ok(())
                })
                .await?;
                assert!(transaction_open());
                Ok(())
            }
        })
        .await
        .expect("transaction should commit");

        assert!(!transaction_open());
    }

    #[tokio::test]
    async fn current_transaction_id_is_none_outside_transactions() {
        assert_eq!(current_transaction_id(), None);

        let db = setup_db().await;
        transaction(&db, |_| async move { Ok(()) })
            .await
            .expect("transaction should commit");

        assert_eq!(current_transaction_id(), None);
    }

    #[tokio::test]
    async fn current_transaction_id_is_stable_across_nested_transactions() {
        let db = setup_db().await;

        let (outer_id, inner_id, after_inner_id) = transaction(&db, |txn| {
            let txn = txn.clone();
            async move {
                let outer_id = current_transaction_id().expect("outer transaction id should exist");
                let inner_id = transaction(&txn, |_| async move {
                    Ok::<String, RecordError>(
                        current_transaction_id().expect("nested transaction id should exist"),
                    )
                })
                .await?;
                let after_inner_id =
                    current_transaction_id().expect("outer transaction id should still exist");
                Ok((outer_id, inner_id, after_inner_id))
            }
        })
        .await
        .expect("transaction should commit");

        assert_eq!(outer_id, inner_id);
        assert_eq!(outer_id, after_inner_id);
    }

    #[tokio::test]
    async fn current_transaction_id_changes_between_outer_transactions() {
        let db = setup_db().await;

        let first = transaction(&db, |_| async move {
            Ok::<String, RecordError>(
                current_transaction_id().expect("transaction id should exist"),
            )
        })
        .await
        .expect("first transaction should commit");

        let second = transaction(&db, |_| async move {
            Ok::<String, RecordError>(
                current_transaction_id().expect("transaction id should exist"),
            )
        })
        .await
        .expect("second transaction should commit");

        assert_ne!(first, second);
    }

    #[tokio::test]
    async fn transaction_state_clears_after_outer_rollback() {
        let db = setup_db().await;

        let error = transaction(&db, |_| async move {
            assert_eq!(open_transactions(), 1);
            assert!(transaction_open());
            assert!(current_transaction_id().is_some());
            Err::<(), RecordError>(RecordError::Invalid("rollback outer".to_owned()))
        })
        .await
        .expect_err("transaction should roll back");

        assert!(matches!(error, RecordError::Invalid(message) if message == "rollback outer"));
        assert_eq!(open_transactions(), 0);
        assert!(!transaction_open());
        assert_eq!(current_transaction_id(), None);
    }

    #[tokio::test]
    async fn nested_rollback_restores_outer_transaction_state() {
        let db = setup_db().await;

        transaction(&db, |txn| {
            let txn = txn.clone();
            async move {
                let outer_id = current_transaction_id().expect("outer transaction id should exist");
                let _ = transaction(&txn, |_| async move {
                    assert_eq!(open_transactions(), 2);
                    Err::<(), RecordError>(RecordError::Invalid("rollback inner".to_owned()))
                })
                .await
                .expect_err("inner transaction should roll back");

                assert_eq!(open_transactions(), 1);
                assert!(transaction_open());
                assert_eq!(
                    current_transaction_id().expect("outer transaction id should remain"),
                    outer_id
                );
                Ok(())
            }
        })
        .await
        .expect("outer transaction should commit");

        assert_eq!(open_transactions(), 0);
        assert_eq!(current_transaction_id(), None);
    }
}