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Add protocol for migration service

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This commit is contained in:
Oleksii Zghurskyi
2025-08-07 23:50:00 +03:00
parent 6642523c2b
commit 860f73b731
10 changed files with 448 additions and 208 deletions
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127
Sources/DataRaft/Protocols/DatabaseServiceKeyProvider.swift
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@@ -3,51 +3,122 @@ import DataLiteCore
/// A protocol for supplying encryption keys to `DatabaseService` instances.
///
/// `DatabaseServiceKeyProvider` allows database services to delegate the responsibility of
/// retrieving, managing, and applying encryption keys. This enables separation of concerns
/// and allows for advanced strategies such as per-user key derivation, secure hardware-backed
/// storage, or biometric access control.
/// `DatabaseServiceKeyProvider` encapsulates all responsibilities for managing encryption keys
/// for one or more `DatabaseService` instances. It allows a database service to delegate key
/// retrieval, secure storage, rotation, and access control, enabling advanced security strategies
/// such as per-user key derivation, hardware-backed keys, biometric authentication, or ephemeral
/// in-memory secrets.
///
/// When assigned to a `DatabaseService`, the provider is queried automatically whenever a
/// connection is created or re-established (e.g., during service initialization or reconnect).
/// The provider is queried automatically by the database service whenever a new connection
/// is created or re-established (for example, during service initialization, after a reconnect,
/// or when the service requests a key rotation).
///
/// You can also implement error handling or diagnostics via the optional
/// ``databaseService(_:didReceive:)`` method.
/// Error handling and diagnostics related specifically to encryption or key operations
/// (such as when a key is unavailable, authentication is denied, or decryption fails)
/// are reported to the provider via the optional ``databaseService(_:didReceive:)`` callback.
/// The provider is **not** notified of generic database or connection errors unrelated to
/// encryption.
///
/// - Tip: You may throw from ``databaseServiceKey(_:)`` to indicate that the key is temporarily
/// unavailable or access is denied.
/// - Important: This protocol is **exclusively** for cryptographic key management.
/// It must not be used for generic database error handling or for concerns unrelated to
/// encryption, authorization, or key lifecycle.
///
/// ## Key Availability
///
/// There are two distinct scenarios for returning a key:
///
/// - **No Encryption Needed:**
/// Return `nil` if the target database does not require encryption (i.e., should be opened
/// in plaintext mode). This is not an error; the database service will attempt to open the
/// database without a key. If the database is in fact encrypted, this will result in a
/// decryption error at the SQLite level (e.g., `SQLITE_NOTADB`), which is handled by the
/// database service as a normal failure.
///
/// - **Key Temporarily Unavailable:**
/// Also return `nil` if the key is *temporarily* unavailable for any reason (for example,
/// the user has not yet authenticated, the device is locked, a remote key is still loading,
/// or UI authorization has not been granted).
/// Returning `nil` in this case means the database service will not attempt to open
/// the database with a key. This will not trigger an error callback.
/// When the key later becomes available (for example, after user authentication or
/// successful network retrieval), **the provider is responsible for calling**
/// ``DatabaseService/reconnect()`` on the service to re-attempt the operation with the key.
///
/// - **Error Situations:**
/// Only throw an error if a *permanent* or *unexpected* failure occurs (for example,
/// a hardware security error, a fatal storage problem, or a cryptographic failure
/// that cannot be resolved by waiting or user action).
/// Thrown errors will be reported to the provider via the error callback, and may be
/// surfaced to the UI or logs.
///
/// - Tip: Never throw for temporary unavailability (such as "user has not unlocked" or
/// "still waiting for user action")—just return `nil` in these cases.
/// Use thrown errors only for non-recoverable or unexpected failures.
///
/// ## Error Callback
///
/// The method ``databaseService(_:didReceive:)`` will be called only for errors thrown by
/// ``databaseServiceKey(_:)`` or by the key application process (such as if the key fails
/// to decrypt the database).
/// It will *not* be called for generic database or connection errors.
///
/// Implement this method if you wish to log, recover from, or respond to permanent key-related
/// failures (such as prompting the user, resetting state, or displaying errors).
public protocol DatabaseServiceKeyProvider: AnyObject {
/// Returns the encryption key to be applied to the given database service.
///
/// This method is invoked by the `DatabaseService` during initialization or reconnection
/// to retrieve the encryption key that should be applied to the new connection.
///
/// Implementations may return a static key, derive it from metadata, or load it from
/// secure storage. If the key is unavailable (e.g., user not authenticated, system locked),
/// this method may throw to indicate failure.
/// This method is invoked by the `DatabaseService` during connection initialization,
/// reconnection, or explicit key rotation. Implementations may return a static key,
/// derive it from external data, fetch it from secure hardware, or perform required
/// user authentication.
///
/// - Parameter service: The requesting database service.
/// - Returns: A `Connection.Key` representing the encryption key.
/// - Throws: Any error indicating that the key cannot be retrieved.
func databaseServiceKey(_ service: DatabaseService) throws -> Connection.Key
/// Notifies the provider that the database service encountered an error while applying a key.
/// - Returns: A `Connection.Key` representing the encryption key, or `nil` if encryption is
/// not required for this database or the key is temporarily unavailable. Returning `nil`
/// will cause the database service to attempt opening the database in plaintext mode.
/// If the database is actually encrypted, access will fail with a decryption error.
/// - Throws: Only throw for unrecoverable or unexpected errors (such as hardware failure,
/// fatal storage issues, or irrecoverable cryptographic errors). Do **not** throw for
/// temporary unavailability; instead, return `nil` and call ``DatabaseService/reconnect()``
/// later when the key becomes available.
///
/// This method is called when the service fails to retrieve or apply the encryption key.
/// You can use it to report diagnostics, attempt recovery, or update internal state.
/// - Note: This method may be called multiple times during the lifecycle of a service,
/// including after a failed decryption attempt or key rotation event.
func databaseServiceKey(_ service: DatabaseService) throws -> Connection.Key?
/// Notifies the provider that the database service encountered an error
/// related to key retrieval or application.
///
/// The default implementation is a no-op.
/// This method is called **only** when the service fails to retrieve or apply an
/// encryption key (e.g., if ``databaseServiceKey(_:)`` throws, or if the key fails
/// to decrypt the database due to a password/key mismatch).
///
/// Use this callback to report diagnostics, trigger recovery logic, prompt the user
/// for authentication, or update internal state.
/// By default, this method does nothing; implement it only if you need to respond
/// to key-related failures.
///
/// - Parameters:
/// - service: The database service reporting the error.
/// - error: The error encountered during key retrieval or application.
func databaseService(_ service: DatabaseService, didReceive error: Error)
/// Informs the service whether it should attempt to reconnect automatically.
///
/// Return `true` if the service should retry connecting (for example, if the key may
/// become available shortly). By default, returns `false`.
///
/// - Parameter service: The database service.
/// - Returns: `true` to retry, `false` to abort.
func databaseServiceShouldReconnect(_ service: DatabaseService) -> Bool
}
public extension DatabaseServiceKeyProvider {
/// Default no-op implementation of error handling callback.
///
/// This allows conforming types to ignore the error reporting mechanism
/// if they do not need to respond to key failures.
/// Default no-op implementation for key-related error reporting.
func databaseService(_ service: DatabaseService, didReceive error: Error) {}
/// Default implementation disables automatic reconnect attempts.
func databaseServiceShouldReconnect(_ service: DatabaseService) -> Bool {
false
}
}

73
Sources/DataRaft/Protocols/DatabaseServiceProtocol.swift
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@@ -3,51 +3,84 @@ import DataLiteCore
/// A protocol that defines a common interface for working with a database connection.
///
/// Conforming types provide methods for executing closures with a live `Connection`, optionally
/// wrapped in transactions. These closures are guaranteed to execute in a thread-safe and
/// serialized manner. Implementations may also support reconnecting and managing encryption keys.
/// `DatabaseServiceProtocol` abstracts the core operations required to safely interact with a
/// SQLite-compatible database. Conforming types provide thread-safe execution of closures with a live
/// `Connection`, optional transaction support, reconnection logic, and pluggable encryption key
/// management via a ``DatabaseServiceKeyProvider``.
///
/// This protocol forms the foundation for safe, modular service layers on top of a database.
///
/// ## Topics
///
/// ### Key Management
///
/// - ``DatabaseServiceKeyProvider``
/// - ``keyProvider``
///
/// ### Connection Management
///
/// - ``reconnect()``
///
/// ### Database Operations
///
/// - ``Perform``
/// - ``perform(_:)``
/// - ``perform(in:closure:)``
public protocol DatabaseServiceProtocol: AnyObject {
/// A closure that performs a database operation using an active connection.
///
/// The `Perform<T>` alias defines the signature for a database operation block
/// that receives a live `Connection` and either returns a result or throws an error.
/// It is commonly used to express atomic units of work in ``perform(_:)`` or
/// ``perform(in:closure:)`` calls.
/// The `Perform<T>` type alias defines a closure signature for a database operation that
/// receives a live `Connection` and returns a value or throws an error. This enables
/// callers to express discrete, atomic database operations for execution via
/// ``perform(_:)`` or ``perform(in:closure:)``.
///
/// - Parameter T: The result type returned by the closure.
/// - Returns: A value of type `T` produced by the closure.
/// - Throws: Any error that occurs during execution of the database operation.
/// - Parameter connection: The active database connection.
/// - Returns: The result of the operation.
/// - Throws: Any error thrown during execution of the operation.
typealias Perform<T> = (Connection) throws -> T
/// The object responsible for providing encryption keys for the database connection.
///
/// When assigned, the key provider will be queried for a new key and applied to the current
/// connection, if available.
/// When assigned, the key provider will be queried for a key and applied to the current
/// connection, if available. If key retrieval or application fails, the error is reported
/// via `databaseService(_:didReceive:)` and not thrown from the setter.
///
/// - Important: Setting this property does not guarantee that the connection becomes available;
/// error handling is asynchronous via callback.
var keyProvider: DatabaseServiceKeyProvider? { get set }
/// Re-establishes the database connection using the stored provider.
///
/// If a `keyProvider` is set, the returned connection will attempt to apply a new key.
/// If a `keyProvider` is set, the method attempts to retrieve and apply a key
/// to the new connection. All errors encountered during connection creation or
/// key application are thrown. If an error occurs that is related to encryption key
/// retrieval or application, it is also reported to the `DatabaseServiceKeyProvider`
/// via its `databaseService(_:didReceive:)` callback.
///
/// - Throws: Any error that occurs during connection creation or key application.
func reconnect() throws
/// Executes the given closure with a live connection.
/// Executes the given closure with a live connection in a thread-safe manner.
///
/// - Parameter closure: The operation to execute.
/// All invocations are serialized to prevent concurrent database access.
///
/// - Parameter closure: The database operation to perform.
/// - Returns: The result produced by the closure.
/// - Throws: Any error thrown during execution.
/// - Throws: Any error thrown by the closure.
func perform<T>(_ closure: Perform<T>) rethrows -> T
/// Executes the given closure within a transaction.
///
/// If no transaction is active, a new one is started and committed or rolled back as needed.
/// If no transaction is active, a new transaction of the specified type is started. The closure
/// is executed atomically: if it succeeds, the transaction is committed; if it throws, the
/// transaction is rolled back. If a transaction is already active, the closure is executed
/// without starting a new one.
///
/// - Parameters:
/// - transaction: The transaction type to begin.
/// - closure: The operation to execute within the transaction.
/// - transaction: The type of transaction to begin (e.g., `deferred`, `immediate`, `exclusive`).
/// - closure: The database operation to perform within the transaction.
/// - Returns: The result produced by the closure.
/// - Throws: Any error thrown by the closure or transaction.
/// - Throws: Any error thrown by the closure or transaction control statements.
func perform<T>(
in transaction: TransactionType,
closure: Perform<T>

43
Sources/DataRaft/Protocols/MigrationServiceProtocol.swift Normal file
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@@ -0,0 +1,43 @@
import Foundation
/// Protocol for managing and running database schema migrations.
public protocol MigrationServiceProtocol: AnyObject {
/// Type representing the schema version for migrations.
associatedtype Version: VersionRepresentable
/// Provider of encryption keys for the database service.
var keyProvider: DatabaseServiceKeyProvider? { get set }
/// Adds a migration to be executed by the service.
///
/// - Parameter migration: The migration to register.
/// - Throws: ``MigrationError/duplicateMigration(_:)`` if a migration with
/// the same version or script URL is already registered.
func add(_ migration: Migration<Version>) throws(MigrationError<Version>)
/// Runs all pending migrations in ascending version order.
///
/// - Throws: ``MigrationError/emptyMigrationScript(_:)`` if a migration
/// script is empty.
/// - Throws: ``MigrationError/migrationFailed(_:_:)`` if a script execution
/// or version update fails.
func migrate() throws(MigrationError<Version>)
}
@available(iOS 13.0, *)
@available(macOS 10.15, *)
public extension MigrationServiceProtocol where Self: Sendable {
/// Asynchronously runs all pending migrations in ascending order.
///
/// Performs the same logic as ``migrate()``, but runs asynchronously.
///
/// - Throws: ``MigrationError/emptyMigrationScript(_:)`` if a migration
/// script is empty.
/// - Throws: ``MigrationError/migrationFailed(_:_:)`` if a script execution
/// or version update fails.
func migrate() async throws {
try await Task(priority: .utility) {
try self.migrate()
}.value
}
}