amari 0.19.1

//! Phase 4A: Runtime Verification System Prototype
//!
//! This prototype demonstrates adaptive verification that can work across
//! CPU, GPU, and WASM platforms by switching verification strategies based
//! on platform constraints and performance requirements.

use std::marker::PhantomData;
use std::time::{Duration, Instant};
use amari_core::Multivector;

/// Platform-specific verification constraints
#[derive(Debug, Clone, Copy)]
pub enum VerificationPlatform {
    /// Native CPU with full phantom type support
    NativeCpu,
    /// GPU with boundary verification constraints
    Gpu { max_overhead_ms: u64 },
    /// WASM with runtime contract limitations
    Wasm { js_interop: bool },
}

/// Verification levels that can be adapted to platform constraints
#[derive(Debug, Clone, Copy, PartialEq)]
pub enum VerificationLevel {
    /// Full phantom type verification (CPU only)
    Strict,
    /// Statistical sampling verification
    Statistical { sample_rate: f64 },
    /// Boundary-only verification
    Boundary,
    /// Minimal runtime checks
    Minimal,
}

/// Verification error types that work across platforms
#[derive(Debug, Clone)]
pub enum VerificationError {
    /// Mathematical invariant violation
    InvariantViolation { operation: String, details: String },
    /// Platform constraint violation
    PlatformConstraint { platform: String, limitation: String },
    /// Performance budget exceeded
    PerformanceBudget { actual: Duration, budget: Duration },
    /// Statistical verification failure
    StatisticalFailure { confidence: f64, threshold: f64 },
}

/// Adaptive verification context that switches strategies by platform
pub struct AdaptiveVerificationContext {
    platform: VerificationPlatform,
    level: VerificationLevel,
    performance_budget: Duration,
    operation_count: usize,
}

impl AdaptiveVerificationContext {
    /// Create verification context with platform detection
    pub fn new(platform: VerificationPlatform) -> Self {
        let level = Self::determine_optimal_level(platform);
        let budget = Self::determine_performance_budget(platform);

        Self {
            platform,
            level,
            performance_budget: budget,
            operation_count: 0,
        }
    }

    /// Determine optimal verification level for platform
    fn determine_optimal_level(platform: VerificationPlatform) -> VerificationLevel {
        match platform {
            VerificationPlatform::NativeCpu => VerificationLevel::Strict,
            VerificationPlatform::Gpu { max_overhead_ms } => {
                if max_overhead_ms < 5 {
                    VerificationLevel::Minimal
                } else if max_overhead_ms < 20 {
                    VerificationLevel::Boundary
                } else {
                    VerificationLevel::Statistical { sample_rate: 0.1 }
                }
            }
            VerificationPlatform::Wasm { js_interop } => {
                if js_interop {
                    VerificationLevel::Statistical { sample_rate: 0.05 }
                } else {
                    VerificationLevel::Boundary
                }
            }
        }
    }

    /// Determine performance budget based on platform
    fn determine_performance_budget(platform: VerificationPlatform) -> Duration {
        match platform {
            VerificationPlatform::NativeCpu => Duration::from_millis(50),
            VerificationPlatform::Gpu { max_overhead_ms } => Duration::from_millis(max_overhead_ms),
            VerificationPlatform::Wasm { .. } => Duration::from_millis(25),
        }
    }

    /// Verify mathematical operation with platform-appropriate strategy
    pub async fn verify_operation<F, R>(
        &mut self,
        operation_name: &str,
        operation: F,
    ) -> Result<R, VerificationError>
    where
        F: FnOnce() -> R + Send,
        R: Send,
    {
        let start_time = Instant::now();
        self.operation_count += 1;

        match self.level {
            VerificationLevel::Strict => {
                self.strict_verification(operation_name, operation).await
            }
            VerificationLevel::Statistical { sample_rate } => {
                self.statistical_verification(operation_name, operation, sample_rate).await
            }
            VerificationLevel::Boundary => {
                self.boundary_verification(operation_name, operation).await
            }
            VerificationLevel::Minimal => {
                self.minimal_verification(operation_name, operation).await
            }
        }
    }

    /// Strict verification with full phantom type guarantees (CPU only)
    async fn strict_verification<F, R>(
        &mut self,
        operation_name: &str,
        operation: F,
    ) -> Result<R, VerificationError>
    where
        F: FnOnce() -> R + Send,
        R: Send,
    {
        let start = Instant::now();

        // Pre-condition verification
        self.verify_preconditions(operation_name)?;

        // Execute operation
        let result = tokio::task::spawn_blocking(operation).await
            .map_err(|_| VerificationError::InvariantViolation {
                operation: operation_name.to_string(),
                details: "Operation panic".to_string(),
            })?;

        // Post-condition verification
        self.verify_postconditions(operation_name)?;

        // Check performance budget
        let elapsed = start.elapsed();
        if elapsed > self.performance_budget {
            return Err(VerificationError::PerformanceBudget {
                actual: elapsed,
                budget: self.performance_budget,
            });
        }

        Ok(result)
    }

    /// Statistical verification through sampling (GPU/WASM)
    async fn statistical_verification<F, R>(
        &mut self,
        operation_name: &str,
        operation: F,
        sample_rate: f64,
    ) -> Result<R, VerificationError>
    where
        F: FnOnce() -> R + Send,
        R: Send,
    {
        let should_sample = self.should_sample_operation(sample_rate);

        if should_sample {
            // Perform full verification on sampled operations
            return self.strict_verification(operation_name, operation).await;
        } else {
            // Minimal verification for non-sampled operations
            return self.minimal_verification(operation_name, operation).await;
        }
    }

    /// Boundary verification at platform transitions (GPU/WASM)
    async fn boundary_verification<F, R>(
        &mut self,
        operation_name: &str,
        operation: F,
    ) -> Result<R, VerificationError>
    where
        F: FnOnce() -> R + Send,
        R: Send,
    {
        // Verify only at critical boundaries (input/output validation)
        self.verify_boundary_conditions(operation_name)?;

        let result = tokio::task::spawn_blocking(operation).await
            .map_err(|_| VerificationError::InvariantViolation {
                operation: operation_name.to_string(),
                details: "Boundary violation".to_string(),
            })?;

        Ok(result)
    }

    /// Minimal verification for performance-critical operations
    async fn minimal_verification<F, R>(
        &mut self,
        operation_name: &str,
        operation: F,
    ) -> Result<R, VerificationError>
    where
        F: FnOnce() -> R + Send,
        R: Send,
    {
        // Only basic safety checks
        let result = tokio::task::spawn_blocking(operation).await
            .map_err(|_| VerificationError::InvariantViolation {
                operation: operation_name.to_string(),
                details: "Minimal verification failure".to_string(),
            })?;

        Ok(result)
    }

    /// Check if operation should be sampled for statistical verification
    fn should_sample_operation(&self, sample_rate: f64) -> bool {
        use std::collections::hash_map::DefaultHasher;
        use std::hash::{Hash, Hasher};

        let mut hasher = DefaultHasher::new();
        self.operation_count.hash(&mut hasher);
        let hash = hasher.finish();

        (hash as f64 / u64::MAX as f64) < sample_rate
    }

    /// Verify pre-conditions for strict verification
    fn verify_preconditions(&self, operation_name: &str) -> Result<(), VerificationError> {
        // Platform-specific pre-condition checks
        match self.platform {
            VerificationPlatform::NativeCpu => {
                // Full phantom type verification available
                self.verify_cpu_preconditions(operation_name)
            }
            VerificationPlatform::Gpu { .. } => {
                // GPU-specific constraints
                self.verify_gpu_preconditions(operation_name)
            }
            VerificationPlatform::Wasm { .. } => {
                // WASM runtime constraints
                self.verify_wasm_preconditions(operation_name)
            }
        }
    }

    /// Verify post-conditions for strict verification
    fn verify_postconditions(&self, operation_name: &str) -> Result<(), VerificationError> {
        // Similar platform-specific post-condition checks
        match self.platform {
            VerificationPlatform::NativeCpu => Ok(()),
            VerificationPlatform::Gpu { .. } => Ok(()),
            VerificationPlatform::Wasm { .. } => Ok(()),
        }
    }

    /// Verify boundary conditions for boundary verification
    fn verify_boundary_conditions(&self, operation_name: &str) -> Result<(), VerificationError> {
        // Check only input/output contract compliance
        Ok(())
    }

    /// CPU-specific precondition verification
    fn verify_cpu_preconditions(&self, _operation_name: &str) -> Result<(), VerificationError> {
        // Full mathematical invariant checking
        Ok(())
    }

    /// GPU-specific precondition verification
    fn verify_gpu_preconditions(&self, operation_name: &str) -> Result<(), VerificationError> {
        // Check GPU memory constraints, batch size limits
        if operation_name.contains("batch") && self.operation_count > 1000000 {
            return Err(VerificationError::PlatformConstraint {
                platform: "GPU".to_string(),
                limitation: "Batch size too large for GPU memory".to_string(),
            });
        }
        Ok(())
    }

    /// WASM-specific precondition verification
    fn verify_wasm_preconditions(&self, operation_name: &str) -> Result<(), VerificationError> {
        // Check WASM memory constraints, JS interop limitations
        if operation_name.contains("large_batch") {
            return Err(VerificationError::PlatformConstraint {
                platform: "WASM".to_string(),
                limitation: "Large batches may exceed WASM memory limit".to_string(),
            });
        }
        Ok(())
    }

    /// Get verification statistics
    pub fn get_stats(&self) -> VerificationStats {
        VerificationStats {
            platform: self.platform,
            level: self.level,
            operation_count: self.operation_count,
            budget_remaining: self.performance_budget,
        }
    }
}

/// Verification statistics for monitoring
#[derive(Debug)]
pub struct VerificationStats {
    pub platform: VerificationPlatform,
    pub level: VerificationLevel,
    pub operation_count: usize,
    pub budget_remaining: Duration,
}

/// Cross-platform verified multivector wrapper
pub struct CrossPlatformVerifiedMultivector<const P: usize, const Q: usize, const R: usize> {
    inner: Multivector<P, Q, R>,
    verification_context: PhantomData<(P, Q, R)>,
    platform_verified: bool,
}

impl<const P: usize, const Q: usize, const R: usize> CrossPlatformVerifiedMultivector<P, Q, R> {
    /// Create verified multivector with platform adaptation
    pub fn new_verified(
        multivector: Multivector<P, Q, R>,
        context: &AdaptiveVerificationContext,
    ) -> Result<Self, VerificationError> {
        // Platform-specific validation
        match context.platform {
            VerificationPlatform::NativeCpu => {
                // Full phantom type verification
                Self::verify_cpu_creation(&multivector)?;
            }
            VerificationPlatform::Gpu { .. } => {
                // GPU boundary verification
                Self::verify_gpu_boundary(&multivector)?;
            }
            VerificationPlatform::Wasm { .. } => {
                // WASM runtime verification
                Self::verify_wasm_runtime(&multivector)?;
            }
        }

        Ok(Self {
            inner: multivector,
            verification_context: PhantomData,
            platform_verified: true,
        })
    }

    /// Verified geometric product with adaptive verification
    pub async fn geometric_product_verified(
        &self,
        other: &Self,
        context: &mut AdaptiveVerificationContext,
    ) -> Result<Self, VerificationError> {
        let operation = || {
            let result = self.inner.geometric_product(&other.inner);
            Self {
                inner: result,
                verification_context: PhantomData,
                platform_verified: true,
            }
        };

        context.verify_operation("geometric_product", operation).await
    }

    /// Platform-specific verification methods
    fn verify_cpu_creation(mv: &Multivector<P, Q, R>) -> Result<(), VerificationError> {
        // Full mathematical property verification
        if !mv.magnitude().is_finite() {
            return Err(VerificationError::InvariantViolation {
                operation: "creation".to_string(),
                details: "Non-finite magnitude".to_string(),
            });
        }
        Ok(())
    }

    fn verify_gpu_boundary(mv: &Multivector<P, Q, R>) -> Result<(), VerificationError> {
        // Basic numerical stability checks for GPU transfer
        if mv.magnitude() > 1e10 {
            return Err(VerificationError::PlatformConstraint {
                platform: "GPU".to_string(),
                limitation: "Magnitude too large for GPU precision".to_string(),
            });
        }
        Ok(())
    }

    fn verify_wasm_runtime(mv: &Multivector<P, Q, R>) -> Result<(), VerificationError> {
        // JavaScript interop compatibility checks
        for i in 0..8 {
            if !mv.get(i).is_finite() {
                return Err(VerificationError::PlatformConstraint {
                    platform: "WASM".to_string(),
                    limitation: "Non-finite coefficients not supported in JavaScript".to_string(),
                });
            }
        }
        Ok(())
    }

    /// Get underlying multivector (platform-verified)
    pub fn inner(&self) -> &Multivector<P, Q, R> {
        &self.inner
    }

    /// Check if platform verification is active
    pub fn is_platform_verified(&self) -> bool {
        self.platform_verified
    }
}

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

    #[tokio::test]
    async fn test_cpu_strict_verification() {
        let mut context = AdaptiveVerificationContext::new(VerificationPlatform::NativeCpu);

        let result = context.verify_operation("test_operation", || {
            // Simulate mathematical operation
            42
        }).await;

        assert!(result.is_ok());
        assert_eq!(result.unwrap(), 42);
    }

    #[tokio::test]
    async fn test_gpu_boundary_verification() {
        let mut context = AdaptiveVerificationContext::new(
            VerificationPlatform::Gpu { max_overhead_ms: 10 }
        );

        let result = context.verify_operation("gpu_operation", || {
            // Simulate GPU operation
            vec![1.0, 2.0, 3.0]
        }).await;

        assert!(result.is_ok());
    }

    #[tokio::test]
    async fn test_wasm_statistical_verification() {
        let mut context = AdaptiveVerificationContext::new(
            VerificationPlatform::Wasm { js_interop: true }
        );

        // Run multiple operations to test sampling
        for i in 0..100 {
            let result = context.verify_operation("wasm_operation", || i).await;
            assert!(result.is_ok());
        }

        let stats = context.get_stats();
        assert_eq!(stats.operation_count, 100);
    }

    #[tokio::test]
    async fn test_cross_platform_multivector() {
        let context = AdaptiveVerificationContext::new(VerificationPlatform::NativeCpu);
        let mv = Multivector::<3, 0, 0>::basis_vector(0);

        let verified_mv = CrossPlatformVerifiedMultivector::new_verified(mv, &context);
        assert!(verified_mv.is_ok());
        assert!(verified_mv.unwrap().is_platform_verified());
    }

    #[test]
    fn test_platform_optimal_levels() {
        let cpu_level = AdaptiveVerificationContext::determine_optimal_level(
            VerificationPlatform::NativeCpu
        );
        assert_eq!(cpu_level, VerificationLevel::Strict);

        let gpu_level = AdaptiveVerificationContext::determine_optimal_level(
            VerificationPlatform::Gpu { max_overhead_ms: 2 }
        );
        assert_eq!(gpu_level, VerificationLevel::Minimal);

        let wasm_level = AdaptiveVerificationContext::determine_optimal_level(
            VerificationPlatform::Wasm { js_interop: true }
        );
        assert!(matches!(wasm_level, VerificationLevel::Statistical { .. }));
    }
}