//! Enhanced common error types and utilities for HFT error consolidation
//!
//! This module provides consolidated error types and utilities used across
//! all Foxhunt services with proper categorization for metrics.

use serde::{Deserialize, Serialize};
use std::fmt;
use std::time::Duration;
use thiserror::Error;
use crate::error::ErrorCategory;

/// Enhanced common error type for all Foxhunt services
#[derive(Debug, Error)]
pub enum CommonError {
    /// Database operation failed - wraps database-specific errors
    #[error("Database error: {0}")]
    Database(#[from] crate::database::DatabaseError),
    
    /// Configuration is invalid or missing required parameters
    #[error("Configuration error: {0}")]
    Configuration(String),
    
    /// Network communication error occurred
    #[error("Network error: {0}")]
    Network(String),
    
    /// Service-specific error with categorization for metrics
    #[error("Service error: {category} - {message}")]
    Service {
        /// Error category for classification
        category: ErrorCategory,
        /// Descriptive error message
        message: String
    },
    
    /// Input validation failed with field context
    #[error("Validation error: {field} - {message}")]
    Validation {
        /// Field that failed validation
        field: String,
        /// Validation error message
        message: String
    },
    
    /// Operation exceeded maximum allowed execution time
    #[error("Timeout error: operation took {actual_ms}ms, max allowed {max_ms}ms")]
    Timeout {
        /// Actual execution time in milliseconds
        actual_ms: u64,
        /// Maximum allowed execution time in milliseconds
        max_ms: u64
    },
    
    /// Authentication failed
    #[error("Authentication error: {0}")]
    Authentication(String),
    
    /// Authorization/Permission denied
    #[error("Authorization error: {0}")]
    Authorization(String),
    
    /// Resource not found
    #[error("{resource} not found: {identifier}")]
    NotFound {
        /// Type of resource
        resource: String,
        /// Resource identifier
        identifier: String
    },
    
    /// Service unavailable
    #[error("Service unavailable: {service} - {reason}")]
    ServiceUnavailable {
        /// Service name
        service: String,
        /// Reason for unavailability
        reason: String
    },
    
    /// Rate limit exceeded
    #[error("Rate limit exceeded: {limit_type}")]
    RateLimited {
        /// Type of rate limit
        limit_type: String
    },
    
    /// Resource exhausted
    #[error("Resource exhausted: {resource}")]
    ResourceExhausted {
        /// Resource that was exhausted
        resource: String
    },
    
    /// Serialization/Deserialization error
    #[error("Serialization error: {0}")]
    Serialization(String),
    
    /// Internal server error
    #[error("Internal error: {0}")]
    Internal(String),
    
    /// Connection error
    #[error("Connection error: {endpoint} - {reason}")]
    Connection {
        /// Connection endpoint
        endpoint: String,
        /// Connection failure reason
        reason: String
    },
    
    /// Order/Trading specific errors
    #[error("Trading error: {0}")]
    Trading(String),
    
    /// ML/Model specific errors
    #[error("ML error: {model} - {message}")]
    ML {
        /// Model name
        model: String,
        /// Error message
        message: String
    },
    
    /// Risk management errors
    #[error("Risk error: {risk_type} - {message}")]
    Risk {
        /// Type of risk violation
        risk_type: String,
        /// Risk error message
        message: String
    },
}

// ErrorCategory is now imported from crate::error

impl fmt::Display for ErrorCategory {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            Self::MarketData => write!(f, "MARKET_DATA"),
            Self::Trading => write!(f, "TRADING"),
            Self::Network => write!(f, "NETWORK"),
            Self::System => write!(f, "SYSTEM"),
            Self::Configuration => write!(f, "CONFIGURATION"),
            Self::Validation => write!(f, "VALIDATION"),
            Self::Critical => write!(f, "CRITICAL"),
            Self::Security => write!(f, "SECURITY"),
            Self::ML => write!(f, "ML"),
            Self::Risk => write!(f, "RISK"),
            Self::Database => write!(f, "DATABASE"),
        }
    }
}

/// Enhanced retry strategies for error recovery
#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
pub enum RetryStrategy {
    /// Do not retry - error is permanent
    NoRetry,
    /// Retry immediately without delay
    Immediate,
    /// Linear backoff with fixed intervals
    Linear {
        /// Base delay in milliseconds between retries
        base_delay_ms: u64,
    },
    /// Exponential backoff with jitter
    Exponential {
        /// Base delay in milliseconds for exponential backoff
        base_delay_ms: u64,
        /// Maximum delay cap in milliseconds
        max_delay_ms: u64,
    },
    /// Wait for circuit breaker to close
    CircuitBreaker,
    /// Custom retry for HFT scenarios
    HftCustom {
        /// Initial delay in nanoseconds for HFT
        initial_delay_ns: u64,
        /// Maximum retries before giving up
        max_retries: u32,
    },
}

impl RetryStrategy {
    /// Calculate delay for retry attempt
    #[must_use]
    pub fn calculate_delay(&self, attempt: u32) -> Option<Duration> {
        match self {
            Self::NoRetry => None,
            Self::Immediate => Some(Duration::from_millis(0)),
            Self::Linear { base_delay_ms } => {
                Some(Duration::from_millis(base_delay_ms * u64::from(attempt)))
            }
            Self::Exponential {
                base_delay_ms,
                max_delay_ms,
            } => {
                let delay_ms = base_delay_ms * 2_u64.pow(attempt.min(10));
                let capped_delay = delay_ms.min(*max_delay_ms);

                // Add simple jitter (±10%)
                let jitter_ms = capped_delay / 10;
                let final_delay = capped_delay.saturating_sub(jitter_ms / 2);

                Some(Duration::from_millis(final_delay))
            }
            Self::CircuitBreaker => Some(Duration::from_secs(30)),
            Self::HftCustom { initial_delay_ns, .. } => {
                let delay_ns = initial_delay_ns * u64::from(attempt);
                Some(Duration::from_nanos(delay_ns))
            }
        }
    }

    /// Get maximum recommended retry attempts
    #[must_use]
    pub const fn max_attempts(&self) -> Option<u32> {
        match self {
            Self::NoRetry => Some(0),
            Self::Immediate => Some(3),
            Self::Linear { .. } => Some(5),
            Self::Exponential { .. } => Some(7),
            Self::CircuitBreaker => Some(1),
            Self::HftCustom { max_retries, .. } => Some(*max_retries),
        }
    }
}

/// Error severity for HFT metrics
#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
pub enum ErrorSeverity {
    /// Trace level - detailed diagnostic information
    Trace,
    /// Debug level - debugging information
    Debug,
    /// Info level - informational messages
    Info,
    /// Warn level - warning messages
    Warn,
    /// Error level - error messages
    Error,
    /// Critical level - critical errors requiring immediate attention
    Critical,
}

impl fmt::Display for ErrorSeverity {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            Self::Trace => write!(f, "TRACE"),
            Self::Debug => write!(f, "DEBUG"),
            Self::Info => write!(f, "INFO"),
            Self::Warn => write!(f, "WARN"),
            Self::Error => write!(f, "ERROR"),
            Self::Critical => write!(f, "CRITICAL"),
        }
    }
}

impl CommonError {
    /// Get error category for metrics
    pub fn category(&self) -> ErrorCategory {
        match self {
            Self::Database(_) => ErrorCategory::Database,
            Self::Configuration(_) => ErrorCategory::Configuration,
            Self::Network(_) => ErrorCategory::Network,
            Self::Service { category, .. } => *category,
            Self::Validation { .. } => ErrorCategory::Validation,
            Self::Timeout { .. } => ErrorCategory::System,
            Self::Authentication(_) => ErrorCategory::Security,
            Self::Authorization(_) => ErrorCategory::Security,
            Self::NotFound { .. } => ErrorCategory::System,
            Self::ServiceUnavailable { .. } => ErrorCategory::System,
            Self::RateLimited { .. } => ErrorCategory::System,
            Self::ResourceExhausted { .. } => ErrorCategory::System,
            Self::Serialization(_) => ErrorCategory::System,
            Self::Internal(_) => ErrorCategory::Critical,
            Self::Connection { .. } => ErrorCategory::Network,
            Self::Trading(_) => ErrorCategory::Trading,
            Self::ML { .. } => ErrorCategory::ML,
            Self::Risk { .. } => ErrorCategory::Risk,
        }
    }

    /// Get error severity for HFT monitoring
    pub fn severity(&self) -> ErrorSeverity {
        match self {
            Self::Internal(_) => ErrorSeverity::Critical,
            Self::Authentication(_) => ErrorSeverity::Critical,
            Self::Configuration(_) => ErrorSeverity::Critical,
            Self::Risk { .. } => ErrorSeverity::Critical,
            Self::Trading(_) => ErrorSeverity::Error,
            Self::ML { .. } => ErrorSeverity::Error,
            Self::Database(_) => ErrorSeverity::Error,
            Self::Authorization(_) => ErrorSeverity::Warn,
            Self::Timeout { .. } => ErrorSeverity::Warn,
            Self::Network(_) => ErrorSeverity::Warn,
            Self::Connection { .. } => ErrorSeverity::Warn,
            Self::ServiceUnavailable { .. } => ErrorSeverity::Warn,
            Self::RateLimited { .. } => ErrorSeverity::Warn,
            Self::ResourceExhausted { .. } => ErrorSeverity::Warn,
            Self::Validation { .. } => ErrorSeverity::Info,
            Self::NotFound { .. } => ErrorSeverity::Info,
            Self::Serialization(_) => ErrorSeverity::Info,
            Self::Service { .. } => ErrorSeverity::Error,
        }
    }

    /// Get retry strategy for this error
    pub fn retry_strategy(&self) -> RetryStrategy {
        match self {
            Self::Authentication(_) => RetryStrategy::NoRetry,
            Self::Authorization(_) => RetryStrategy::NoRetry,
            Self::Configuration(_) => RetryStrategy::NoRetry,
            Self::Validation { .. } => RetryStrategy::NoRetry,
            Self::NotFound { .. } => RetryStrategy::NoRetry,
            Self::Network(_) => RetryStrategy::Exponential {
                base_delay_ms: 100,
                max_delay_ms: 5000,
            },
            Self::Connection { .. } => RetryStrategy::Exponential {
                base_delay_ms: 100,
                max_delay_ms: 5000,
            },
            Self::Timeout { .. } => RetryStrategy::Linear { base_delay_ms: 1000 },
            Self::ServiceUnavailable { .. } => RetryStrategy::Exponential {
                base_delay_ms: 1000,
                max_delay_ms: 30000,
            },
            Self::RateLimited { .. } => RetryStrategy::Linear { base_delay_ms: 5000 },
            Self::ResourceExhausted { .. } => RetryStrategy::Linear { base_delay_ms: 2000 },
            Self::Database(_) => RetryStrategy::Exponential {
                base_delay_ms: 250,
                max_delay_ms: 2000,
            },
            Self::Trading(_) => RetryStrategy::HftCustom {
                initial_delay_ns: 50000, // 50µs
                max_retries: 3,
            },
            Self::ML { .. } => RetryStrategy::Linear { base_delay_ms: 500 },
            Self::Risk { .. } => RetryStrategy::NoRetry, // Risk errors should not be retried
            _ => RetryStrategy::Immediate,
        }
    }

    /// Check if error is retryable
    pub fn is_retryable(&self) -> bool {
        !matches!(self.retry_strategy(), RetryStrategy::NoRetry)
    }

    /// Get error code for monitoring
    pub fn error_code(&self) -> &'static str {
        match self {
            Self::Database(_) => "DATABASE_ERROR",
            Self::Configuration(_) => "CONFIGURATION_ERROR",
            Self::Network(_) => "NETWORK_ERROR",
            Self::Service { .. } => "SERVICE_ERROR",
            Self::Validation { .. } => "VALIDATION_ERROR",
            Self::Timeout { .. } => "TIMEOUT_ERROR",
            Self::Authentication(_) => "AUTHENTICATION_ERROR",
            Self::Authorization(_) => "AUTHORIZATION_ERROR",
            Self::NotFound { .. } => "NOT_FOUND_ERROR",
            Self::ServiceUnavailable { .. } => "SERVICE_UNAVAILABLE_ERROR",
            Self::RateLimited { .. } => "RATE_LIMITED_ERROR",
            Self::ResourceExhausted { .. } => "RESOURCE_EXHAUSTED_ERROR",
            Self::Serialization(_) => "SERIALIZATION_ERROR",
            Self::Internal(_) => "INTERNAL_ERROR",
            Self::Connection { .. } => "CONNECTION_ERROR",
            Self::Trading(_) => "TRADING_ERROR",
            Self::ML { .. } => "ML_ERROR",
            Self::Risk { .. } => "RISK_ERROR",
        }
    }
}

/// Enhanced convenience functions for creating common errors
impl CommonError {
    /// Create a configuration error
    pub fn config<S: Into<String>>(message: S) -> Self {
        Self::Configuration(message.into())
    }

    /// Create a network error
    pub fn network<S: Into<String>>(message: S) -> Self {
        Self::Network(message.into())
    }

    /// Create a service error with category
    pub fn service<S: Into<String>>(category: ErrorCategory, message: S) -> Self {
        Self::Service {
            category,
            message: message.into(),
        }
    }

    /// Create a validation error with field context
    pub fn validation<F: Into<String>, S: Into<String>>(field: F, message: S) -> Self {
        Self::Validation {
            field: field.into(),
            message: message.into(),
        }
    }

    /// Create a timeout error
    pub fn timeout(actual_ms: u64, max_ms: u64) -> Self {
        Self::Timeout { actual_ms, max_ms }
    }

    /// Create an authentication error
    pub fn authentication<S: Into<String>>(message: S) -> Self {
        Self::Authentication(message.into())
    }

    /// Create an authorization error
    pub fn authorization<S: Into<String>>(message: S) -> Self {
        Self::Authorization(message.into())
    }

    /// Create a not found error
    pub fn not_found<R: Into<String>, I: Into<String>>(resource: R, identifier: I) -> Self {
        Self::NotFound {
            resource: resource.into(),
            identifier: identifier.into(),
        }
    }

    /// Create a service unavailable error
    pub fn service_unavailable<S: Into<String>, R: Into<String>>(service: S, reason: R) -> Self {
        Self::ServiceUnavailable {
            service: service.into(),
            reason: reason.into(),
        }
    }

    /// Create a rate limited error
    pub fn rate_limited<S: Into<String>>(limit_type: S) -> Self {
        Self::RateLimited {
            limit_type: limit_type.into(),
        }
    }

    /// Create a resource exhausted error
    pub fn resource_exhausted<S: Into<String>>(resource: S) -> Self {
        Self::ResourceExhausted {
            resource: resource.into(),
        }
    }

    /// Create a serialization error
    pub fn serialization<S: Into<String>>(message: S) -> Self {
        Self::Serialization(message.into())
    }

    /// Create an internal error
    pub fn internal<S: Into<String>>(message: S) -> Self {
        Self::Internal(message.into())
    }

    /// Create a connection error
    pub fn connection<E: Into<String>, R: Into<String>>(endpoint: E, reason: R) -> Self {
        Self::Connection {
            endpoint: endpoint.into(),
            reason: reason.into(),
        }
    }

    /// Create a trading error
    pub fn trading<S: Into<String>>(message: S) -> Self {
        Self::Trading(message.into())
    }

    /// Create an ML error
    pub fn ml<M: Into<String>, S: Into<String>>(model: M, message: S) -> Self {
        Self::ML {
            model: model.into(),
            message: message.into(),
        }
    }

    /// Create a risk error
    pub fn risk<T: Into<String>, S: Into<String>>(risk_type: T, message: S) -> Self {
        Self::Risk {
            risk_type: risk_type.into(),
            message: message.into(),
        }
    }
}

/// Result type for common operations
pub type CommonResult<T> = Result<T, CommonError>;

/// Conversion from standard library errors
impl From<std::io::Error> for CommonError {
    fn from(err: std::io::Error) -> Self {
        Self::Network(format!("IO error: {}", err))
    }
}

impl From<serde_json::Error> for CommonError {
    fn from(err: serde_json::Error) -> Self {
        Self::Serialization(format!("JSON error: {}", err))
    }
}

impl From<reqwest::Error> for CommonError {
    fn from(err: reqwest::Error) -> Self {
        Self::Network(format!("HTTP error: {}", err))
    }
}

/// gRPC Status conversion for TLI service
impl From<CommonError> for tonic::Status {
    fn from(err: CommonError) -> Self {
        match err {
            CommonError::Authentication(_) => {
                tonic::Status::unauthenticated(err.to_owned())
            }
            CommonError::Authorization(_) => {
                tonic::Status::permission_denied(err.to_owned())
            }
            CommonError::Validation { .. } => {
                tonic::Status::invalid_argument(err.to_owned())
            }
            CommonError::NotFound { .. } => {
                tonic::Status::not_found(err.to_owned())
            }
            CommonError::ServiceUnavailable { .. } => {
                tonic::Status::unavailable(err.to_owned())
            }
            CommonError::RateLimited { .. } => {
                tonic::Status::resource_exhausted(err.to_owned())
            }
            CommonError::ResourceExhausted { .. } => {
                tonic::Status::resource_exhausted(err.to_owned())
            }
            CommonError::Timeout { .. } => {
                tonic::Status::deadline_exceeded(err.to_owned())
            }
            CommonError::Connection { .. } => {
                tonic::Status::unavailable(err.to_owned())
            }
            CommonError::Network(_) => {
                tonic::Status::unavailable(err.to_owned())
            }
            _ => tonic::Status::internal(err.to_owned()),
        }
    }
}

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

    #[test]
    fn test_error_categorization() {
        let error = CommonError::trading("Order validation failed");
        assert_eq!(error.category(), ErrorCategory::Trading);
        assert_eq!(error.severity(), ErrorSeverity::Error);
        assert!(error.is_retryable());
    }

    #[test]
    fn test_retry_strategy() {
        let auth_error = CommonError::authentication("Invalid token");
        assert_eq!(auth_error.retry_strategy(), RetryStrategy::NoRetry);
        assert!(!auth_error.is_retryable());

        let network_error = CommonError::network("Connection refused");
        assert!(network_error.is_retryable());
        match network_error.retry_strategy() {
            RetryStrategy::Exponential { .. } => (),
            _ => panic!("Expected exponential backoff for network errors"),
        }
    }

    #[test]
    fn test_hft_retry_strategy() {
        let trading_error = CommonError::trading("Order rejected");
        match trading_error.retry_strategy() {
            RetryStrategy::HftCustom { initial_delay_ns, max_retries } => {
                assert_eq!(initial_delay_ns, 50000); // 50µs
                assert_eq!(max_retries, 3);
            }
            _ => panic!("Expected HFT custom retry for trading errors"),
        }
    }

    #[test]
    fn test_error_severity() {
        let risk_error = CommonError::risk("position_limit", "Exceeded maximum position");
        assert_eq!(risk_error.severity(), ErrorSeverity::Critical);
        
        let validation_error = CommonError::validation("price", "Must be positive");
        assert_eq!(validation_error.severity(), ErrorSeverity::Info);
    }

    #[test]
    fn test_grpc_conversion() {
        let error = CommonError::authentication("Invalid credentials");
        let status: tonic::Status = error.into();
        assert_eq!(status.code(), tonic::Code::Unauthenticated);
    }
}