//! Advanced determinism and consistency testing framework
//!
//! Provides hyper-advanced Rust patterns for:
//! - Hash-based determinism validation
//! - Async/concurrent safety testing
//! - Generic multi-format consistency
//! - Performance regression detection
//! - Automatic test consolidation

use sha2::{Digest, Sha256};
use std::fmt::Debug;
use std::sync::Arc;
use std::time::{Duration, Instant};

/// Core determinism validation trait using advanced Rust
pub trait Deterministic: Send + Sync + Debug {
    /// Generate output for determinism checking
    fn generate_output(&self) -> Vec<u8>;

    /// Get output hash for comparison
    fn output_hash(&self) -> String {
        let output = self.generate_output();
        let mut hasher = Sha256::new();
        hasher.update(&output);
        format!("{:x}", hasher.finalize())
    }

    /// Validate determinism across N runs
    fn validate_determinism(&self, iterations: usize) -> DeterminismResult {
        let hashes: Vec<_> = (0..iterations).map(|_| self.output_hash()).collect();

        let first_hash = &hashes[0];
        let all_identical = hashes.iter().all(|h| h == first_hash);

        let variance = if all_identical {
            0.0
        } else {
            let different_count = hashes.iter().filter(|h| **h != **first_hash).count();
            different_count as f32 / iterations as f32
        };

        DeterminismResult {
            all_identical,
            consistency_score: 1.0 - variance,
            iterations,
            variance,
            sample_hash: first_hash.clone(),
        }
    }
}

/// Async-safe determinism validator
#[async_trait::async_trait]
pub trait AsyncDeterministic: Send + Sync + Debug {
    async fn generate_output_async(&self) -> Vec<u8>;

    async fn validate_async_determinism(&self, iterations: usize) -> DeterminismResult {
        let futures: Vec<_> = (0..iterations)
            .map(|_| self.generate_output_async())
            .collect();

        let outputs = futures::future::join_all(futures).await;
        let hashes: Vec<_> = outputs
            .iter()
            .map(|out| {
                let mut hasher = Sha256::new();
                hasher.update(out);
                format!("{:x}", hasher.finalize())
            })
            .collect();

        let first_hash = &hashes[0];
        let all_identical = hashes.iter().all(|h| h == first_hash);
        let variance = if all_identical {
            0.0
        } else {
            hashes.iter().filter(|h| **h != **first_hash).count() as f32 / iterations as f32
        };

        DeterminismResult {
            all_identical,
            consistency_score: 1.0 - variance,
            iterations,
            variance,
            sample_hash: first_hash.clone(),
        }
    }
}

/// Generic format-agnostic validator with trait object polymorphism
pub trait FormatValidator: Send + Sync {
    fn format_name(&self) -> &'static str;
    fn validate(&self, data: &[u8]) -> Result<(), String>;
    fn transform(&self, input: &[u8]) -> Vec<u8>;
}

/// Advanced collection-based format testing
pub struct MultiFormatValidator {
    validators: Vec<Arc<dyn FormatValidator>>,
}

impl MultiFormatValidator {
    pub fn new(validators: Vec<Arc<dyn FormatValidator>>) -> Self {
        Self { validators }
    }

    /// Validate semantic equivalence across formats
    pub fn validate_equivalence(&self, base_output: &[u8]) -> EquivalenceResult {
        let results: Vec<_> = self
            .validators
            .iter()
            .map(|v| {
                let transformed = v.transform(base_output);
                EquivalenceCheck {
                    format: v.format_name(),
                    valid: v.validate(&transformed).is_ok(),
                    hash: compute_hash(&transformed),
                }
            })
            .collect();

        let all_valid = results.iter().all(|r| r.valid);

        EquivalenceResult {
            all_valid,
            results,
            consistency_score: if all_valid { 100.0 } else { 0.0 },
        }
    }
}

/// High-performance parallel test executor with timeout
pub struct ParallelTestExecutor {
    max_concurrent: usize,
    timeout: Duration,
}

impl ParallelTestExecutor {
    pub fn new(max_concurrent: usize, timeout: Duration) -> Self {
        Self {
            max_concurrent,
            timeout,
        }
    }

    /// Execute tests in parallel with safety guarantees
    pub async fn execute<F, T>(&self, tests: Vec<(&str, F)>) -> Vec<TestExecutionResult>
    where
        F: Fn() -> T + Send + 'static,
        T: Send + 'static,
    {
        let semaphore = Arc::new(tokio::sync::Semaphore::new(self.max_concurrent));

        let futures: Vec<_> = tests
            .into_iter()
            .map(|(name, test_fn)| {
                let sem = semaphore.clone();
                async move {
                    let _permit = sem.acquire().await.unwrap();
                    let start = Instant::now();

                    let result = tokio::time::timeout(self.timeout, async {
                        test_fn();
                        "passed"
                    })
                    .await;

                    let duration = start.elapsed();

                    TestExecutionResult {
                        test_name: name.to_string(),
                        passed: result.is_ok(),
                        duration,
                        error: result.err().map(|_| "timeout".to_string()),
                    }
                }
            })
            .collect();

        futures::future::join_all(futures).await
    }
}

/// Regression detection with trend analysis
pub struct RegressionDetector {
    history: Vec<BenchmarkSnapshot>,
    threshold: f32,
}

impl RegressionDetector {
    pub fn new(threshold: f32) -> Self {
        Self {
            history: Vec::new(),
            threshold,
        }
    }

    pub fn record(&mut self, snapshot: BenchmarkSnapshot) {
        self.history.push(snapshot);
    }

    pub fn detect_regressions(&self) -> Vec<RegressionAlert> {
        let mut alerts = Vec::new();

        if self.history.len() < 2 {
            return alerts;
        }

        let current = &self.history[self.history.len() - 1];
        let previous = &self.history[self.history.len() - 2];

        let consistency_delta = (previous.consistency_score - current.consistency_score).abs();
        if consistency_delta > self.threshold {
            alerts.push(RegressionAlert {
                metric: "consistency_score".to_string(),
                previous: previous.consistency_score,
                current: current.consistency_score,
                delta: consistency_delta,
            });
        }

        let performance_delta = (current.duration.as_secs_f64() - previous.duration.as_secs_f64())
            / previous.duration.as_secs_f64();

        if performance_delta > self.threshold as f64 {
            alerts.push(RegressionAlert {
                metric: "performance".to_string(),
                previous: previous.duration.as_secs_f64() as f32,
                current: current.duration.as_secs_f64() as f32,
                delta: performance_delta as f32,
            });
        }

        alerts
    }
}

// ============= Data Structures =============

#[derive(Debug, Clone)]
pub struct DeterminismResult {
    pub all_identical: bool,
    pub consistency_score: f32,
    pub iterations: usize,
    pub variance: f32,
    pub sample_hash: String,
}

#[derive(Debug, Clone)]
pub struct EquivalenceCheck {
    pub format: &'static str,
    pub valid: bool,
    pub hash: String,
}

#[derive(Debug, Clone)]
pub struct EquivalenceResult {
    pub all_valid: bool,
    pub results: Vec<EquivalenceCheck>,
    pub consistency_score: f32,
}

#[derive(Debug, Clone)]
pub struct TestExecutionResult {
    pub test_name: String,
    pub passed: bool,
    pub duration: Duration,
    pub error: Option<String>,
}

#[derive(Debug, Clone)]
pub struct BenchmarkSnapshot {
    pub timestamp: Instant,
    pub consistency_score: f32,
    pub duration: Duration,
    pub test_count: usize,
}

#[derive(Debug, Clone)]
pub struct RegressionAlert {
    pub metric: String,
    pub previous: f32,
    pub current: f32,
    pub delta: f32,
}

// ============= Helper Functions =============

pub fn compute_hash(data: &[u8]) -> String {
    let mut hasher = Sha256::new();
    hasher.update(data);
    format!("{:x}", hasher.finalize())
}

/// Macro for generating determinism tests (80/20 consolidation)
#[macro_export]
macro_rules! determinism_test {
    ($test_name:ident, $test_fn:expr) => {
        #[test]
        fn $test_name() {
            let test = $test_fn;
            let result = test.validate_determinism(5);
            assert!(
                result.all_identical,
                "Test failed determinism check. Consistency: {:.2}%",
                result.consistency_score * 100.0
            );
        }
    };
}

/// Macro for generating async determinism tests
#[macro_export]
macro_rules! async_determinism_test {
    ($test_name:ident, $test_fn:expr) => {
        #[tokio::test]
        async fn $test_name() {
            let test = $test_fn;
            let result = test.validate_async_determinism(5).await;
            assert!(
                result.all_identical,
                "Async test failed determinism check. Consistency: {:.2}%",
                result.consistency_score * 100.0
            );
        }
    };
}

/// Macro for format equivalence tests
#[macro_export]
macro_rules! format_equivalence_test {
    ($test_name:ident, $validators:expr, $output:expr) => {
        #[test]
        fn $test_name() {
            let multi_validator = MultiFormatValidator::new($validators);
            let result = multi_validator.validate_equivalence($output);
            assert!(
                result.all_valid,
                "Format equivalence test failed for {}",
                stringify!($test_name)
            );
        }
    };
}

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

    #[derive(Debug)]
    struct SimpleTest;

    impl Deterministic for SimpleTest {
        fn generate_output(&self) -> Vec<u8> {
            vec![1, 2, 3, 4, 5]
        }
    }

    #[test]
    fn test_determinism_validator_passes() {
        let test = SimpleTest;
        let result = test.validate_determinism(3);
        assert!(result.all_identical);
        assert_eq!(result.consistency_score, 1.0);
    }

    #[test]
    fn test_hash_computation() {
        let data = b"test data";
        let hash1 = compute_hash(data);
        let hash2 = compute_hash(data);
        assert_eq!(hash1, hash2);
    }
}
