orbit-orm 0.1.0

use std::path::PathBuf;

use sqlx::error::ErrorKind;
#[cfg(feature = "mysql")]
use sqlx::mysql::MySqlDatabaseError;

/// MySQL error 1205: a lock was not released within `innodb_lock_wait_timeout`.
#[cfg(feature = "mysql")]
const ER_LOCK_WAIT_TIMEOUT: u16 = 1205;
/// MySQL error 1213: the database rolled back the transaction to break a deadlock.
#[cfg(feature = "mysql")]
const ER_LOCK_DEADLOCK: u16 = 1213;
/// PostgreSQL SQLSTATE 40P01: the database rolled back the transaction to break a deadlock.
#[cfg(feature = "postgres")]
const PG_DEADLOCK_DETECTED: &str = "40P01";
/// PostgreSQL SQLSTATE 55P03: `lock_not_available`, a `NOWAIT` or `lock_timeout` lock failed.
#[cfg(feature = "postgres")]
const PG_LOCK_NOT_AVAILABLE: &str = "55P03";

/// Any error from Orbit. Driver errors that have a variant here are classified; the rest come
/// through unchanged as `Database`.
#[derive(Debug, thiserror::Error)]
pub enum Error {
    /// The database rejected a connection, a query, or a statement, and no other variant fits.
    #[error(transparent)]
    Database(sqlx::Error),

    /// An insert or update broke a unique index or primary key. `index` is the index name when
    /// the server reports it.
    #[error("unique index `{}` was violated", .index.as_deref().unwrap_or("unknown"))]
    UniqueViolation { index: Option<String> },

    /// A row refers to a missing parent, or a parent is still referenced. `constraint` is the
    /// foreign key name when the server reports it.
    #[error("foreign key `{}` was violated", .constraint.as_deref().unwrap_or("unknown"))]
    ForeignKeyViolation { constraint: Option<String> },

    /// The database rolled back the whole transaction to break a deadlock. Run it again.
    #[error("deadlock found; the transaction was rolled back")]
    Deadlock,

    /// A lock was not released in time. Only the statement failed; the transaction is still open.
    #[error("lock wait timeout; the statement was rolled back")]
    LockWaitTimeout,

    /// A file could not be read, such as a migration's `up.sql`.
    #[error("could not read {}: {source}", path.display())]
    Read {
        path: PathBuf,
        source: std::io::Error,
    },

    /// Two migrations have the same name.
    #[error("migration `{name}` is defined more than once")]
    DuplicateMigration { name: String },

    /// A migration name does not start with a 14-digit timestamp and an underscore.
    #[error("migration `{name}` must start with a 14-digit timestamp, such as 20261108000000_name")]
    InvalidMigrationName { name: String },

    /// Two migrations share a timestamp, so their order is not defined.
    #[error("migrations `{first}` and `{second}` have the same timestamp")]
    DuplicateTimestamp { first: String, second: String },

    /// Another process is running migrations and did not finish within the lock timeout.
    #[error("another process is running migrations; gave up after {seconds} seconds")]
    MigrationsLocked { seconds: u64 },

    /// A migration's `up.sql` failed. The run stopped there; earlier migrations stay applied.
    #[error("migration `{name}` failed, so the run stopped: {source}")]
    MigrationFailed { name: String, source: sqlx::Error },

    /// A migration's `down.sql` failed. The rollback stopped there.
    #[error("migration `{name}` failed to roll back: {source}")]
    RollbackFailed { name: String, source: sqlx::Error },

    /// A migration is recorded as applied, but this migrator has no folder for it, so it cannot
    /// be rolled back. `name` is the version: the 14-digit timestamp prefix recorded in the table.
    #[error(
        "migration version `{name}` was recorded as applied, but no folder with that version \
         exists in this migrator, so it cannot be rolled back"
    )]
    UnknownMigration { name: String },

    /// A table or column name is empty or contains a quote character (a backtick or a double
    /// quote). The same rule applies to every database.
    #[error(
        "invalid identifier `{0}`: names must not be empty or contain a backtick or a double quote"
    )]
    InvalidIdentifier(String),

    /// The URL's scheme names a database whose Cargo feature is not enabled, or no database.
    /// `scheme` is the part before the first `:`, never the password.
    #[error(
        "database URL scheme `{scheme}` is not supported by this build; enable its Cargo feature"
    )]
    UnsupportedDriver { scheme: String },

    /// The database has no equivalent for this operation. `operation` names it and `driver`
    /// names the database. See `docs/laravel-differences.md` for each case.
    #[error("{operation} is not supported on {driver}")]
    Unsupported {
        operation: &'static str,
        driver: &'static str,
    },

    /// A column is not in the model's `FILLABLE` list.
    #[error("column `{column}` is not fillable on table `{table}`")]
    NotFillable { table: &'static str, column: String },

    /// A query that must find a row found none.
    #[error("no query results for table `{table}`")]
    NotFound { table: &'static str },

    /// A blocking call ran on a thread that runs async code. Run it inside `spawn_blocking`.
    #[error("blocking call on an async thread; run it inside tokio::task::spawn_blocking")]
    BlockingInRuntime,
}

impl From<sqlx::Error> for Error {
    /// Classifies the driver error by its kind, then by the driver's error code where the kind
    /// does not say enough. Anything else is kept as `Database`.
    fn from(error: sqlx::Error) -> Self {
        if let sqlx::Error::Database(db) = &error {
            match db.kind() {
                ErrorKind::UniqueViolation => {
                    return Self::UniqueViolation {
                        index: violated_name(db.as_ref(), true),
                    };
                }
                ErrorKind::ForeignKeyViolation => {
                    return Self::ForeignKeyViolation {
                        constraint: violated_name(db.as_ref(), false),
                    };
                }
                _ => {}
            }
            if let Some(kind) = lock_error(db.as_ref()) {
                return kind;
            }
        }
        Self::Database(error)
    }
}

/// The name of the violated index (`unique`) or foreign key. MySQL reports it only in the message,
/// so that is read. The other drivers return it as the constraint name; SQLite returns none.
#[cfg_attr(not(feature = "mysql"), allow(unused_variables))]
fn violated_name(db: &dyn sqlx::error::DatabaseError, unique: bool) -> Option<String> {
    #[cfg(feature = "mysql")]
    if db.try_downcast_ref::<MySqlDatabaseError>().is_some() {
        return if unique {
            duplicate_key(db.message())
        } else {
            foreign_key(db.message())
        };
    }
    db.constraint().map(str::to_owned)
}

/// The deadlock or lock-timeout error for the driver's code, if this is one.
#[cfg_attr(
    not(any(feature = "mysql", feature = "postgres")),
    allow(unused_variables)
)]
fn lock_error(db: &dyn sqlx::error::DatabaseError) -> Option<Error> {
    #[cfg(feature = "mysql")]
    if let Some(mysql) = db.try_downcast_ref::<MySqlDatabaseError>() {
        match mysql.number() {
            ER_LOCK_DEADLOCK => return Some(Error::Deadlock),
            ER_LOCK_WAIT_TIMEOUT => return Some(Error::LockWaitTimeout),
            _ => {}
        }
    }
    // The driver maps lock errors to `Other`, so they are matched by their code.
    #[cfg(feature = "postgres")]
    match db.code().as_deref() {
        Some(PG_DEADLOCK_DETECTED) => return Some(Error::Deadlock),
        Some(PG_LOCK_NOT_AVAILABLE) => return Some(Error::LockWaitTimeout),
        _ => {}
    }
    None
}

/// The index in a "Duplicate entry 'value' for key 'index'" message. MySQL 8.0.19 and later
/// prefix the table name, as in `table.index`, which is removed here.
#[cfg(feature = "mysql")]
fn duplicate_key(message: &str) -> Option<String> {
    const MARK: &str = "for key '";
    let start = message.rfind(MARK)? + MARK.len();
    let key = message[start..].strip_suffix('\'')?;
    Some(key.rsplit('.').next().unwrap_or(key).to_owned())
}

/// The constraint in a "... CONSTRAINT `name` FOREIGN KEY ..." message.
#[cfg(feature = "mysql")]
fn foreign_key(message: &str) -> Option<String> {
    const MARK: &str = "CONSTRAINT `";
    let start = message.find(MARK)? + MARK.len();
    let rest = &message[start..];
    Some(rest[..rest.find('`')?].to_owned())
}

#[cfg(all(test, feature = "mysql"))]
mod tests {
    use super::{duplicate_key, foreign_key};

    #[test]
    fn duplicate_key_reads_the_index_name() {
        assert_eq!(
            duplicate_key("Duplicate entry 'a@example.com' for key 'users_email_unique'"),
            Some("users_email_unique".to_owned())
        );
    }

    #[test]
    fn duplicate_key_drops_the_table_prefix_of_mysql_8() {
        assert_eq!(
            duplicate_key("Duplicate entry '1' for key 'users.PRIMARY'"),
            Some("PRIMARY".to_owned())
        );
    }

    #[test]
    fn duplicate_key_ignores_a_value_that_looks_like_the_marker() {
        assert_eq!(
            duplicate_key("Duplicate entry 'x' for key 'y' for key 'real_index'"),
            Some("real_index".to_owned())
        );
    }

    #[test]
    fn duplicate_key_is_none_without_a_key() {
        assert_eq!(
            duplicate_key("Can't write, because of unique constraint 'x'"),
            None
        );
    }

    #[test]
    fn foreign_key_reads_the_constraint_name() {
        assert_eq!(
            foreign_key(
                "Cannot add or update a child row: a foreign key constraint fails (`db`.`child`, \
                 CONSTRAINT `fk_child_parent` FOREIGN KEY (`parent_id`) REFERENCES `parent` (`id`))"
            ),
            Some("fk_child_parent".to_owned())
        );
        assert_eq!(foreign_key("something else"), None);
    }
}