ringkernel-core 0.4.2

//! Error types for RingKernel operations.

use thiserror::Error;

/// Result type alias for RingKernel operations.
pub type Result<T> = std::result::Result<T, RingKernelError>;

/// Comprehensive error type for RingKernel operations.
#[derive(Error, Debug)]
pub enum RingKernelError {
    // ===== Kernel Lifecycle Errors =====
    /// Kernel not found with the given ID.
    #[error("kernel not found: {0}")]
    KernelNotFound(String),

    /// Kernel is already active.
    #[error("kernel already active: {0}")]
    KernelAlreadyActive(String),

    /// Kernel is not active.
    #[error("kernel not active: {0}")]
    KernelNotActive(String),

    /// Kernel has already terminated.
    #[error("kernel already terminated: {0}")]
    KernelTerminated(String),

    /// Invalid kernel state transition.
    #[error("invalid state transition from {from:?} to {to:?}")]
    InvalidStateTransition {
        /// Current state
        from: String,
        /// Attempted target state
        to: String,
    },

    /// Invalid kernel state.
    #[error("invalid state: expected {expected}, got {actual}")]
    InvalidState {
        /// Expected state
        expected: String,
        /// Actual state
        actual: String,
    },

    /// Kernel launch failed.
    #[error("kernel launch failed: {0}")]
    LaunchFailed(String),

    /// Kernel compilation failed (NVRTC, shader compilation, etc.).
    #[error("kernel compilation failed: {0}")]
    CompilationError(String),

    // ===== Message Errors =====
    /// Queue is full, message cannot be enqueued.
    #[error("queue full: capacity {capacity}, attempted to enqueue message")]
    QueueFull {
        /// Queue capacity
        capacity: usize,
    },

    /// Queue is empty, no message to dequeue.
    #[error("queue empty")]
    QueueEmpty,

    /// Message serialization failed.
    #[error("serialization error: {0}")]
    SerializationError(String),

    /// Message deserialization failed.
    #[error("deserialization error: {0}")]
    DeserializationError(String),

    /// Message validation failed.
    #[error("message validation failed: {0}")]
    ValidationError(String),

    /// Message too large.
    #[error("message too large: {size} bytes (max: {max} bytes)")]
    MessageTooLarge {
        /// Actual message size
        size: usize,
        /// Maximum allowed size
        max: usize,
    },

    /// Message timeout.
    #[error("message timeout after {0:?}")]
    Timeout(std::time::Duration),

    // ===== Memory Errors =====
    /// GPU memory allocation failed.
    #[error("GPU memory allocation failed: {size} bytes - {reason}")]
    AllocationFailed {
        /// Requested size
        size: usize,
        /// Failure reason
        reason: String,
    },

    /// Host memory allocation failed.
    #[error("host memory allocation failed: {size} bytes")]
    HostAllocationFailed {
        /// Requested size
        size: usize,
    },

    /// Memory transfer failed.
    #[error("memory transfer failed: {0}")]
    TransferFailed(String),

    /// Invalid memory alignment.
    #[error("invalid alignment: expected {expected}, got {actual}")]
    InvalidAlignment {
        /// Expected alignment
        expected: usize,
        /// Actual alignment
        actual: usize,
    },

    /// Out of GPU memory.
    #[error("out of GPU memory: requested {requested} bytes, available {available} bytes")]
    OutOfMemory {
        /// Requested size
        requested: usize,
        /// Available memory
        available: usize,
    },

    /// Memory pool exhausted.
    #[error("memory pool exhausted")]
    PoolExhausted,

    /// Invalid index (out of bounds).
    #[error("invalid index: {0}")]
    InvalidIndex(usize),

    /// Generic memory error.
    #[error("memory error: {0}")]
    MemoryError(String),

    // ===== Backend Errors =====
    /// Backend not available.
    #[error("backend not available: {0}")]
    BackendUnavailable(String),

    /// Backend initialization failed.
    #[error("backend initialization failed: {0}")]
    BackendInitFailed(String),

    /// No suitable GPU device found.
    #[error("no GPU device found")]
    NoDeviceFound,

    /// Device selection failed.
    #[error("device selection failed: {0}")]
    DeviceSelectionFailed(String),

    /// Backend operation failed.
    #[error("backend error: {0}")]
    BackendError(String),

    // ===== Synchronization Errors =====
    /// Deadlock detected.
    #[error("deadlock detected")]
    DeadlockDetected,

    /// Lock poisoned.
    #[error("lock poisoned")]
    LockPoisoned,

    /// Channel closed.
    #[error("channel closed")]
    ChannelClosed,

    // ===== HLC Errors =====
    /// Clock skew too large.
    #[error("clock skew too large: {skew_ms}ms (max: {max_ms}ms)")]
    ClockSkew {
        /// Detected skew in milliseconds
        skew_ms: u64,
        /// Maximum allowed skew
        max_ms: u64,
    },

    /// Invalid timestamp.
    #[error("invalid timestamp")]
    InvalidTimestamp,

    // ===== K2K Messaging Errors =====
    /// K2K messaging error.
    #[error("K2K error: {0}")]
    K2KError(String),

    /// K2K destination not found.
    #[error("K2K destination not found: {0}")]
    K2KDestinationNotFound(String),

    /// K2K delivery failed.
    #[error("K2K delivery failed: {0}")]
    K2KDeliveryFailed(String),

    // ===== Pub/Sub Errors =====
    /// Pub/sub error.
    #[error("pub/sub error: {0}")]
    PubSubError(String),

    /// Topic not found.
    #[error("topic not found: {0}")]
    TopicNotFound(String),

    /// Subscription error.
    #[error("subscription error: {0}")]
    SubscriptionError(String),

    // ===== Multi-GPU Errors =====
    /// Multi-GPU coordination error.
    #[error("multi-GPU error: {0}")]
    MultiGpuError(String),

    /// Device not available.
    #[error("device not available: {0}")]
    DeviceNotAvailable(String),

    /// Cross-device transfer failed.
    #[error("cross-device transfer failed: {0}")]
    CrossDeviceTransferFailed(String),

    // ===== Telemetry Errors =====
    /// Telemetry error.
    #[error("telemetry error: {0}")]
    TelemetryError(String),

    /// Metrics collection failed.
    #[error("metrics collection failed: {0}")]
    MetricsCollectionFailed(String),

    // ===== Configuration Errors =====
    /// Invalid configuration.
    #[error("invalid configuration: {0}")]
    InvalidConfig(String),

    /// Missing required configuration.
    #[error("missing configuration: {0}")]
    MissingConfig(String),

    // ===== I/O Errors =====
    /// I/O error wrapper.
    #[error("I/O error: {0}")]
    StdIoError(#[from] std::io::Error),

    /// I/O error with string message.
    #[error("I/O error: {0}")]
    IoError(String),

    // ===== Checkpoint Errors =====
    /// Invalid checkpoint format or data.
    #[error("invalid checkpoint: {0}")]
    InvalidCheckpoint(String),

    /// Checkpoint save failed.
    #[error("checkpoint save failed: {0}")]
    CheckpointSaveFailed(String),

    /// Checkpoint restore failed.
    #[error("checkpoint restore failed: {0}")]
    CheckpointRestoreFailed(String),

    /// Checkpoint not found.
    #[error("checkpoint not found: {0}")]
    CheckpointNotFound(String),

    // ===== Health & Resilience Errors =====
    /// Health check failed.
    #[error("health check failed: {name} - {reason}")]
    HealthCheckFailed {
        /// Health check name
        name: String,
        /// Failure reason
        reason: String,
    },

    /// Circuit breaker is open.
    #[error("circuit breaker open: {name}")]
    CircuitBreakerOpen {
        /// Circuit breaker name
        name: String,
    },

    /// Retry attempts exhausted.
    #[error("retry exhausted after {attempts} attempts: {reason}")]
    RetryExhausted {
        /// Number of attempts made
        attempts: u32,
        /// Last failure reason
        reason: String,
    },

    /// Kernel watchdog timeout.
    #[error("kernel watchdog timeout: {kernel_id}")]
    WatchdogTimeout {
        /// Kernel ID that timed out
        kernel_id: String,
    },

    /// Load shedding rejected request.
    #[error("load shedding: request rejected at level {level}")]
    LoadSheddingRejected {
        /// Current degradation level
        level: String,
    },

    // ===== Migration Errors =====
    /// Kernel migration failed.
    #[error("kernel migration failed: {0}")]
    MigrationFailed(String),

    /// Migration source not ready.
    #[error("migration source not ready: {kernel_id}")]
    MigrationSourceNotReady {
        /// Source kernel ID
        kernel_id: String,
    },

    /// Migration destination unavailable.
    #[error("migration destination unavailable: device {device_id}")]
    MigrationDestinationUnavailable {
        /// Destination device ID
        device_id: usize,
    },

    // ===== Observability Errors =====
    /// Tracing error.
    #[error("tracing error: {0}")]
    TracingError(String),

    /// Span not found.
    #[error("span not found: {0}")]
    SpanNotFound(String),

    /// Metrics export failed.
    #[error("metrics export failed: {0}")]
    MetricsExportFailed(String),

    // ===== Generic Errors =====
    /// Internal error.
    #[error("internal error: {0}")]
    Internal(String),

    /// Feature not supported.
    #[error("feature not supported: {0}")]
    NotSupported(String),

    /// Operation cancelled.
    #[error("operation cancelled")]
    Cancelled,
}

impl RingKernelError {
    /// Returns true if this error is recoverable.
    pub fn is_recoverable(&self) -> bool {
        matches!(
            self,
            RingKernelError::QueueFull { .. }
                | RingKernelError::QueueEmpty
                | RingKernelError::Timeout(_)
                | RingKernelError::PoolExhausted
                | RingKernelError::CircuitBreakerOpen { .. }
                | RingKernelError::LoadSheddingRejected { .. }
        )
    }

    /// Returns true if this error indicates a resource issue.
    pub fn is_resource_error(&self) -> bool {
        matches!(
            self,
            RingKernelError::AllocationFailed { .. }
                | RingKernelError::HostAllocationFailed { .. }
                | RingKernelError::OutOfMemory { .. }
                | RingKernelError::PoolExhausted
                | RingKernelError::MigrationDestinationUnavailable { .. }
        )
    }

    /// Returns true if this is a fatal error requiring restart.
    pub fn is_fatal(&self) -> bool {
        matches!(
            self,
            RingKernelError::BackendInitFailed(_)
                | RingKernelError::NoDeviceFound
                | RingKernelError::LockPoisoned
                | RingKernelError::Internal(_)
        )
    }

    /// Returns true if this is a health/resilience related error.
    pub fn is_health_error(&self) -> bool {
        matches!(
            self,
            RingKernelError::HealthCheckFailed { .. }
                | RingKernelError::CircuitBreakerOpen { .. }
                | RingKernelError::RetryExhausted { .. }
                | RingKernelError::WatchdogTimeout { .. }
                | RingKernelError::LoadSheddingRejected { .. }
        )
    }

    /// Returns true if this is a migration-related error.
    pub fn is_migration_error(&self) -> bool {
        matches!(
            self,
            RingKernelError::MigrationFailed(_)
                | RingKernelError::MigrationSourceNotReady { .. }
                | RingKernelError::MigrationDestinationUnavailable { .. }
        )
    }

    /// Returns true if this is an observability-related error.
    pub fn is_observability_error(&self) -> bool {
        matches!(
            self,
            RingKernelError::TracingError(_)
                | RingKernelError::SpanNotFound(_)
                | RingKernelError::MetricsExportFailed(_)
                | RingKernelError::TelemetryError(_)
                | RingKernelError::MetricsCollectionFailed(_)
        )
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_error_display() {
        let err = RingKernelError::KernelNotFound("test_kernel".to_string());
        assert_eq!(format!("{}", err), "kernel not found: test_kernel");

        let err = RingKernelError::QueueFull { capacity: 1024 };
        assert!(format!("{}", err).contains("1024"));
    }

    #[test]
    fn test_error_classification() {
        assert!(RingKernelError::QueueFull { capacity: 1024 }.is_recoverable());
        assert!(RingKernelError::OutOfMemory {
            requested: 1000,
            available: 100
        }
        .is_resource_error());
        assert!(RingKernelError::LockPoisoned.is_fatal());
    }

    #[test]
    fn test_health_error_display() {
        let err = RingKernelError::HealthCheckFailed {
            name: "liveness".to_string(),
            reason: "timeout".to_string(),
        };
        assert_eq!(
            format!("{}", err),
            "health check failed: liveness - timeout"
        );

        let err = RingKernelError::CircuitBreakerOpen {
            name: "gpu_ops".to_string(),
        };
        assert_eq!(format!("{}", err), "circuit breaker open: gpu_ops");

        let err = RingKernelError::RetryExhausted {
            attempts: 5,
            reason: "connection refused".to_string(),
        };
        assert!(format!("{}", err).contains("5 attempts"));

        let err = RingKernelError::WatchdogTimeout {
            kernel_id: "kernel_42".to_string(),
        };
        assert!(format!("{}", err).contains("kernel_42"));
    }

    #[test]
    fn test_health_error_classification() {
        assert!(RingKernelError::CircuitBreakerOpen {
            name: "test".to_string()
        }
        .is_recoverable());
        assert!(RingKernelError::LoadSheddingRejected {
            level: "critical".to_string()
        }
        .is_recoverable());
        assert!(RingKernelError::HealthCheckFailed {
            name: "test".to_string(),
            reason: "failed".to_string()
        }
        .is_health_error());
        assert!(RingKernelError::WatchdogTimeout {
            kernel_id: "k1".to_string()
        }
        .is_health_error());
    }

    #[test]
    fn test_migration_error_display() {
        let err = RingKernelError::MigrationFailed("checkpoint transfer error".to_string());
        assert!(format!("{}", err).contains("checkpoint transfer error"));

        let err = RingKernelError::MigrationSourceNotReady {
            kernel_id: "kernel_1".to_string(),
        };
        assert!(format!("{}", err).contains("kernel_1"));

        let err = RingKernelError::MigrationDestinationUnavailable { device_id: 2 };
        assert!(format!("{}", err).contains("device 2"));
    }

    #[test]
    fn test_migration_error_classification() {
        assert!(RingKernelError::MigrationFailed("test".to_string()).is_migration_error());
        assert!(RingKernelError::MigrationSourceNotReady {
            kernel_id: "k1".to_string()
        }
        .is_migration_error());
        assert!(
            RingKernelError::MigrationDestinationUnavailable { device_id: 0 }.is_migration_error()
        );
        assert!(
            RingKernelError::MigrationDestinationUnavailable { device_id: 0 }.is_resource_error()
        );
    }

    #[test]
    fn test_observability_error_display() {
        let err = RingKernelError::TracingError("span creation failed".to_string());
        assert!(format!("{}", err).contains("span creation failed"));

        let err = RingKernelError::SpanNotFound("span_abc123".to_string());
        assert!(format!("{}", err).contains("span_abc123"));

        let err = RingKernelError::MetricsExportFailed("prometheus timeout".to_string());
        assert!(format!("{}", err).contains("prometheus timeout"));
    }

    #[test]
    fn test_observability_error_classification() {
        assert!(RingKernelError::TracingError("test".to_string()).is_observability_error());
        assert!(RingKernelError::SpanNotFound("test".to_string()).is_observability_error());
        assert!(RingKernelError::MetricsExportFailed("test".to_string()).is_observability_error());
        assert!(RingKernelError::TelemetryError("test".to_string()).is_observability_error());
        assert!(
            RingKernelError::MetricsCollectionFailed("test".to_string()).is_observability_error()
        );
    }
}