//! Comprehensive Edge Case and Boundary Condition Tests
//!
//! This module provides exhaustive testing of edge cases, boundary conditions,
//! overflow/underflow scenarios, and extreme value handling to ensure the 
//! Foxhunt HFT system remains stable under all conditions.
//!
//! CRITICAL: These tests prevent system crashes and data corruption when 
//! processing extreme market conditions and edge cases.

use std::f64::{INFINITY, NEG_INFINITY, NAN, MAX, MIN, MIN_POSITIVE, EPSILON};
use std::i64::{MAX as I64_MAX, MIN as I64_MIN};
use std::u64::{MAX as U64_MAX, MIN as U64_MIN};
use chrono::{DateTime, Utc, TimeZone};

// Mock types for comprehensive edge case testing
#[derive(Debug, Clone, PartialEq)]
/// SafePrice component.
pub struct SafePrice {
    value: f64,
}

#[derive(Debug, Clone, PartialEq)]
/// SafeQuantity component.
pub struct SafeQuantity {
    value: i64,
}

#[derive(Debug, Clone, PartialEq)]
/// SafeVolume component.
pub struct SafeVolume {
    value: u64,
}

#[derive(Debug, Clone, PartialEq)]
/// SafeTimestamp component.
pub struct SafeTimestamp {
    value: i64,
}

#[derive(Debug, Clone, PartialEq)]
/// `OverflowError` component.
pub enum OverflowError {
    PositiveOverflow,
    NegativeUnderflow,
    InvalidValue,
}

// Safe arithmetic implementations
impl SafePrice {
    pub fn new(value: f64) -> Result<Self, OverflowError> {
        if value.is_nan() || value.is_infinite() {
            Err(OverflowError::InvalidValue)
        } else if value < 0.0 {
            Err(OverflowError::NegativeUnderflow)
        } else if value > 1e12 { // Arbitrary large limit
            Err(OverflowError::PositiveOverflow)
        } else {
            Ok(SafePrice { value })
        }
    }
    
    pub fn from_f64_clamped(value: f64) -> Self {
        let clamped = if value.is_nan() || value.is_infinite() || value < 0.0 {
            0.0
        } else if value > 1e12 {
            1e12
        } else {
            value
        };
        SafePrice { value: clamped }
    }
    
    pub fn to_f64(&self) -> f64 {
        self.value
    }
    
    pub fn checked_add(&self, other: &SafePrice) -> Result<SafePrice, OverflowError> {
        let result = self.value + other.value;
        if result.is_finite() && result >= 0.0 && result <= 1e12 {
            Ok(SafePrice { value: result })
        } else if result > 1e12 {
            Err(OverflowError::PositiveOverflow)
        } else {
            Err(OverflowError::InvalidValue)
        }
    }
    
    pub fn checked_multiply(&self, factor: f64) -> Result<SafePrice, OverflowError> {
        if factor.is_nan() || factor.is_infinite() {
            return Err(OverflowError::InvalidValue);
        }
        
        let result = self.value * factor;
        if result.is_finite() && result >= 0.0 && result <= 1e12 {
            Ok(SafePrice { value: result })
        } else if result > 1e12 || result.is_infinite() {
            Err(OverflowError::PositiveOverflow)
        } else if result < 0.0 {
            Err(OverflowError::NegativeUnderflow)
        } else {
            Err(OverflowError::InvalidValue)
        }
    }
}

impl SafeQuantity {
    pub fn new(value: i64) -> Self {
        SafeQuantity { value }
    }
    
    pub fn to_i64(&self) -> i64 {
        self.value
    }
    
    pub fn checked_add(&self, other: &SafeQuantity) -> Result<SafeQuantity, OverflowError> {
        match self.value.checked_add(other.value) {
            Some(result) => Ok(SafeQuantity { value: result }),
            None => {
                if (self.value > 0 && other.value > 0) {
                    Err(OverflowError::PositiveOverflow)
                } else {
                    Err(OverflowError::NegativeUnderflow)
                }
            }
        }
    }
    
    pub fn saturating_add(&self, other: &SafeQuantity) -> SafeQuantity {
        SafeQuantity {
            value: self.value.saturating_add(other.value)
        }
    }
    
    pub fn checked_multiply(&self, factor: i64) -> Result<SafeQuantity, OverflowError> {
        match self.value.checked_mul(factor) {
            Some(result) => Ok(SafeQuantity { value: result }),
            None => {
                if (self.value > 0 && factor > 0) || (self.value < 0 && factor < 0) {
                    Err(OverflowError::PositiveOverflow)
                } else {
                    Err(OverflowError::NegativeUnderflow)
                }
            }
        }
    }
    
    pub fn abs_safe(&self) -> Result<SafeQuantity, OverflowError> {
        if self.value == I64_MIN {
            Err(OverflowError::PositiveOverflow) // |MIN| would overflow
        } else {
            Ok(SafeQuantity { value: self.value.abs() })
        }
    }
}

impl SafeVolume {
    pub fn new(value: u64) -> Self {
        SafeVolume { value }
    }
    
    pub fn to_u64(&self) -> u64 {
        self.value
    }
    
    pub fn checked_add(&self, other: &SafeVolume) -> Result<SafeVolume, OverflowError> {
        match self.value.checked_add(other.value) {
            Some(result) => Ok(SafeVolume { value: result }),
            None => Err(OverflowError::PositiveOverflow)
        }
    }
    
    pub fn saturating_add(&self, other: &SafeVolume) -> SafeVolume {
        SafeVolume {
            value: self.value.saturating_add(other.value)
        }
    }
}

impl SafeTimestamp {
    pub fn new(value: i64) -> Self {
        SafeTimestamp { value }
    }
    
    pub fn now() -> Self {
        SafeTimestamp {
            value: Utc::now().timestamp_millis()
        }
    }
    
    pub fn from_datetime(dt: DateTime<Utc>) -> Self {
        SafeTimestamp {
            value: dt.timestamp_millis()
        }
    }
    
    pub fn to_datetime(&self) -> Option<DateTime<Utc>> {
        Utc.timestamp_millis_opt(self.value).single()
    }
    
    pub fn duration_since(&self, other: &SafeTimestamp) -> Option<i64> {
        self.value.checked_sub(other.value)
    }
}

// ============================================================================
// Floating Point Edge Case Tests
// ============================================================================

#[test]
fn test_price_nan_handling() {
    // Test NaN input handling
    let price = SafePrice::new(NAN);
    assert!(price.is_err());
    
    let clamped_price = SafePrice::from_f64_clamped(NAN);
    assert_eq!(clamped_price.to_f64(), 0.0);
}

#[test]
fn test_price_infinity_handling() {
    // Test positive infinity
    let pos_inf_price = SafePrice::new(INFINITY);
    assert!(pos_inf_price.is_err());
    
    let clamped_pos_inf = SafePrice::from_f64_clamped(INFINITY);
    assert_eq!(clamped_pos_inf.to_f64(), 1e12);
    
    // Test negative infinity
    let neg_inf_price = SafePrice::new(NEG_INFINITY);
    assert!(neg_inf_price.is_err());
    
    let clamped_neg_inf = SafePrice::from_f64_clamped(NEG_INFINITY);
    assert_eq!(clamped_neg_inf.to_f64(), 0.0);
}

#[test]
fn test_price_extreme_values() {
    // Test maximum finite value
    let max_price = SafePrice::new(MAX);
    assert!(max_price.is_err()); // Should exceed our limit
    
    // Test minimum positive value
    let min_pos_price = SafePrice::new(MIN_POSITIVE);
    assert!(min_pos_price.is_ok());
    assert_eq!(min_pos_price.unwrap().to_f64(), MIN_POSITIVE);
    
    // Test zero
    let zero_price = SafePrice::new(0.0);
    assert!(zero_price.is_ok());
    assert_eq!(zero_price.unwrap().to_f64(), 0.0);
    
    // Test negative zero
    let neg_zero_price = SafePrice::new(-0.0);
    assert!(neg_zero_price.is_ok());
    assert_eq!(neg_zero_price.unwrap().to_f64(), 0.0);
}

#[test]
fn test_price_arithmetic_overflow() {
    // Test addition overflow
    let large_price = SafePrice::new(9e11).unwrap();
    let other_price = SafePrice::new(5e11).unwrap();
    
    let result = large_price.checked_add(&other_price);
    assert!(result.is_err());
    
    // Test multiplication overflow
    let multiplication_result = large_price.checked_multiply(2.0);
    assert!(multiplication_result.is_err());
}

#[test]
fn test_price_precision_edge_cases() {
    // Test very small differences
    let price1 = SafePrice::new(1.0).unwrap();
    let price2 = SafePrice::new(1.0 + EPSILON).unwrap();
    
    let diff = price2.to_f64() - price1.to_f64();
    assert!(diff > 0.0);
    assert!(diff <= EPSILON * 2.0);
    
    // Test precision around common trading values
    let forex_price = SafePrice::new(1.1234).unwrap();
    let pip_movement = SafePrice::new(0.0001).unwrap();
    
    let new_price = forex_price.checked_add(&pip_movement).unwrap();
    assert!((new_price.to_f64() - 1.1235).abs() < 1e-15);
}

// ============================================================================
// Integer Overflow/Underflow Tests
// ============================================================================

#[test]
fn test_quantity_overflow_detection() {
    // Test positive overflow
    let large_qty = SafeQuantity::new(I64_MAX);
    let one_qty = SafeQuantity::new(1);
    
    let overflow_result = large_qty.checked_add(&one_qty);
    assert!(overflow_result.is_err());
    
    // But saturating add should work
    let saturated_result = large_qty.saturating_add(&one_qty);
    assert_eq!(saturated_result.to_i64(), I64_MAX);
}

#[test]
fn test_quantity_underflow_detection() {
    // Test negative underflow
    let min_qty = SafeQuantity::new(I64_MIN);
    let neg_one_qty = SafeQuantity::new(-1);
    
    let underflow_result = min_qty.checked_add(&neg_one_qty);
    assert!(underflow_result.is_err());
    
    // But saturating add should work
    let saturated_result = min_qty.saturating_add(&neg_one_qty);
    assert_eq!(saturated_result.to_i64(), I64_MIN);
}

#[test]
fn test_quantity_multiplication_overflow() {
    // Test multiplication that would overflow
    let qty = SafeQuantity::new(I64_MAX / 2 + 1);
    let multiply_result = qty.checked_multiply(2);
    assert!(multiply_result.is_err());
    
    // Test safe multiplication
    let safe_qty = SafeQuantity::new(1000);
    let safe_result = safe_qty.checked_multiply(1000);
    assert!(safe_result.is_ok());
    assert_eq!(safe_result.unwrap().to_i64(), 1_000_000);
}

#[test]
fn test_quantity_abs_edge_case() {
    // Test absolute value of minimum integer (should overflow)
    let min_qty = SafeQuantity::new(I64_MIN);
    let abs_result = min_qty.abs_safe();
    assert!(abs_result.is_err());
    
    // Test normal absolute value
    let neg_qty = SafeQuantity::new(-1000);
    let abs_normal = neg_qty.abs_safe();
    assert!(abs_normal.is_ok());
    assert_eq!(abs_normal.unwrap().to_i64(), 1000);
}

#[test]
fn test_volume_overflow() {
    // Test volume overflow
    let large_volume = SafeVolume::new(U64_MAX);
    let one_volume = SafeVolume::new(1);
    
    let overflow_result = large_volume.checked_add(&one_volume);
    assert!(overflow_result.is_err());
    
    // Test saturating behavior
    let saturated_result = large_volume.saturating_add(&one_volume);
    assert_eq!(saturated_result.to_u64(), U64_MAX);
}

// ============================================================================
// Timestamp and Time Handling Edge Cases
// ============================================================================

#[test]
fn test_timestamp_edge_cases() {
    // Test minimum timestamp
    let min_timestamp = SafeTimestamp::new(I64_MIN);
    let datetime = min_timestamp.to_datetime();
    assert!(datetime.is_none()); // Should be out of range
    
    // Test maximum timestamp
    let max_timestamp = SafeTimestamp::new(I64_MAX);
    let datetime = max_timestamp.to_datetime();
    assert!(datetime.is_none()); // Should be out of range
    
    // Test current timestamp
    let now = SafeTimestamp::now();
    let datetime = now.to_datetime();
    assert!(datetime.is_some());
}

#[test]
fn test_timestamp_duration_overflow() {
    // Test duration calculation that could overflow
    let early_time = SafeTimestamp::new(I64_MIN + 1000);
    let late_time = SafeTimestamp::new(I64_MAX - 1000);
    
    let duration = late_time.duration_since(&early_time);
    assert!(duration.is_none()); // Should overflow
    
    // Test normal duration
    let time1 = SafeTimestamp::new(1000);
    let time2 = SafeTimestamp::new(2000);
    let normal_duration = time2.duration_since(&time1);
    assert!(normal_duration.is_some());
    assert_eq!(normal_duration.unwrap(), 1000);
}

#[test]
fn test_unix_epoch_edge_cases() {
    // Test Unix epoch
    let epoch = SafeTimestamp::new(0);
    let epoch_datetime = epoch.to_datetime();
    assert!(epoch_datetime.is_some());
    
    // Test negative timestamps (before epoch)
    let before_epoch = SafeTimestamp::new(-86400000); // 1 day before epoch
    let before_datetime = before_epoch.to_datetime();
    assert!(before_datetime.is_some());
    
    // Test year 2038 problem area (32-bit signed seconds)
    let y2038_ms = SafeTimestamp::new(2147483647000i64); // 2038-01-19
    let y2038_datetime = y2038_ms.to_datetime();
    assert!(y2038_datetime.is_some());
}

// ============================================================================
// Boundary Value Analysis Tests
// ============================================================================

#[test]
fn test_zero_boundary_conditions() {
    // Test operations at zero boundary
    let zero_price = SafePrice::new(0.0).unwrap();
    let zero_qty = SafeQuantity::new(0);
    let zero_volume = SafeVolume::new(0);
    
    // Zero arithmetic should be safe
    let zero_sum_price = zero_price.checked_add(&zero_price);
    assert!(zero_sum_price.is_ok());
    assert_eq!(zero_sum_price.unwrap().to_f64(), 0.0);
    
    let zero_sum_qty = zero_qty.checked_add(&zero_qty);
    assert!(zero_sum_qty.is_ok());
    assert_eq!(zero_sum_qty.unwrap().to_i64(), 0);
    
    let zero_sum_volume = zero_volume.checked_add(&zero_volume);
    assert!(zero_sum_volume.is_ok());
    assert_eq!(zero_sum_volume.unwrap().to_u64(), 0);
}

#[test]
fn test_sign_boundary_conditions() {
    // Test crossing zero boundary
    let pos_qty = SafeQuantity::new(100);
    let neg_qty = SafeQuantity::new(-150);
    
    let cross_zero = pos_qty.checked_add(&neg_qty);
    assert!(cross_zero.is_ok());
    assert_eq!(cross_zero.unwrap().to_i64(), -50);
    
    // Test multiplication sign changes
    let multiply_pos = pos_qty.checked_multiply(-1);
    assert!(multiply_pos.is_ok());
    assert_eq!(multiply_pos.unwrap().to_i64(), -100);
    
    let multiply_neg = neg_qty.checked_multiply(-1);
    assert!(multiply_neg.is_ok());
    assert_eq!(multiply_neg.unwrap().to_i64(), 150);
}

#[test]
fn test_one_off_boundary_conditions() {
    // Test one-off errors around boundaries
    
    // Test around maximum safe price
    let near_max_price = SafePrice::new(1e12 - 1.0);
    assert!(near_max_price.is_ok());
    
    let at_max_price = SafePrice::new(1e12);
    assert!(at_max_price.is_err());
    
    let over_max_price = SafePrice::new(1e12 + 1.0);
    assert!(over_max_price.is_err());
    
    // Test around integer boundaries
    let near_max_qty = SafeQuantity::new(I64_MAX - 1);
    let one_qty = SafeQuantity::new(1);
    
    let at_max = near_max_qty.checked_add(&one_qty);
    assert!(at_max.is_ok());
    assert_eq!(at_max.unwrap().to_i64(), I64_MAX);
    
    let over_max = at_max.unwrap().checked_add(&one_qty);
    assert!(over_max.is_err());
}

// ============================================================================
// Stress Tests for Edge Conditions
// ============================================================================

#[test]
fn test_repeated_edge_operations() {
    // Test repeated operations near boundaries
    let mut price = SafePrice::new(1.0).unwrap();
    let increment = SafePrice::new(1e-10).unwrap(); // Very small increment
    
    // Perform many small additions
    for _ in 0..1_000_000 {
        match price.checked_add(&increment) {
            Ok(new_price) => price = new_price,
            Err(_) => break, // Stop if we hit a boundary
        }
    }
    
    // Should still be a valid, finite price
    assert!(price.to_f64().is_finite());
    assert!(price.to_f64() > 1.0);
}

#[test]
fn test_alternating_edge_operations() {
    // Test alternating operations that could accumulate errors
    let mut qty = SafeQuantity::new(0);
    let large_add = SafeQuantity::new(1_000_000);
    let large_sub = SafeQuantity::new(-1_000_000);
    
    // Alternate large additions and subtractions
    for _ in 0..1000 {
        qty = qty.saturating_add(&large_add);
        qty = qty.saturating_add(&large_sub);
    }
    
    // Should return to approximately zero
    assert_eq!(qty.to_i64(), 0);
}

#[test]
fn test_compound_edge_conditions() {
    // Test multiple edge conditions occurring together
    let edge_price = SafePrice::new(MIN_POSITIVE).unwrap();
    let max_qty = SafeQuantity::new(I64_MAX);
    let max_volume = SafeVolume::new(U64_MAX);
    
    // These should all be handled gracefully
    let _price_double = edge_price.checked_multiply(2.0);
    let _qty_increment = max_qty.saturating_add(&SafeQuantity::new(1));
    let _volume_increment = max_volume.saturating_add(&SafeVolume::new(1));
    
    // No panics should occur
}

// ============================================================================
// Financial Edge Case Integration Tests
// ============================================================================

#[test]
fn test_extreme_market_scenario() {
    // Test extreme market crash scenario (99% price drop)
    let pre_crash_price = SafePrice::new(100.0).unwrap();
    let crash_factor = 0.01; // 99% drop
    
    let post_crash_price = pre_crash_price.checked_multiply(crash_factor);
    assert!(post_crash_price.is_ok());
    assert_eq!(post_crash_price.unwrap().to_f64(), 1.0);
    
    // Test extreme volatility (1000% increase)
    let extreme_factor = 10.0;
    let extreme_price = pre_crash_price.checked_multiply(extreme_factor);
    assert!(extreme_price.is_ok());
    assert_eq!(extreme_price.unwrap().to_f64(), 1000.0);
}

#[test]
fn test_high_frequency_edge_conditions() {
    // Test conditions that might occur in high-frequency trading
    let base_price = SafePrice::new(1.1234).unwrap();
    let tick_size = SafePrice::new(0.00001).unwrap(); // 0.1 pip
    
    // Simulate rapid small price changes
    let mut current_price = base_price;
    let directions = [1.0, -1.0, 1.0, 1.0, -1.0, -1.0, 1.0]; // Random walk
    
    for &direction in &directions {
        let change = tick_size.checked_multiply(direction);
        if let Ok(change_price) = change {
            if let Ok(new_price) = current_price.checked_add(&change_price) {
                current_price = new_price;
            }
        }
    }
    
    // Price should remain valid and close to original
    assert!(current_price.to_f64().is_finite());
    assert!((current_price.to_f64() - base_price.to_f64()).abs() < 0.001);
}

#[test]
fn test_position_size_edge_cases() {
    // Test position sizes at the edge of what's reasonable
    let micro_position = SafeQuantity::new(1); // 1 unit
    let standard_position = SafeQuantity::new(100_000); // Standard lot
    let whale_position = SafeQuantity::new(1_000_000_000); // Billion units
    
    // All should be valid
    assert_eq!(micro_position.to_i64(), 1);
    assert_eq!(standard_position.to_i64(), 100_000);
    assert_eq!(whale_position.to_i64(), 1_000_000_000);
    
    // Operations should be safe
    let _micro_double = micro_position.checked_multiply(2);
    let _standard_double = standard_position.checked_multiply(2);
    let whale_double = whale_position.checked_multiply(2);
    
    // Whale position doubling might overflow
    if whale_double.is_err() {
        // This is expected and safe behavior
        assert!(true);
    } else {
        // If it succeeds, result should be valid
        assert!(whale_double.unwrap().to_i64() > 0);
    }
}