// Request/Response validation middleware for FAANG-level safety
use std::sync::atomic::{AtomicUsize, Ordering};
use std::sync::Arc;

/// Tracks concurrent requests per client IP
#[derive(Clone)]
pub struct ConcurrencyLimiter {
    max_concurrent: usize,
    active_requests: Arc<AtomicUsize>,
}

impl ConcurrencyLimiter {
    pub fn new(max_concurrent: usize) -> Self {
        Self {
            max_concurrent,
            active_requests: Arc::new(AtomicUsize::new(0)),
        }
    }

    pub fn can_accept(&self) -> bool {
        let current = self.active_requests.load(Ordering::SeqCst);
        current < self.max_concurrent
    }

    pub fn increment(&self) {
        self.active_requests.fetch_add(1, Ordering::SeqCst);
    }

    pub fn decrement(&self) {
        self.active_requests.fetch_sub(1, Ordering::SeqCst);
    }
}

/// Request timeout guard for external API calls
pub struct TimeoutGuard {
    timeout_secs: u64,
}

impl TimeoutGuard {
    pub fn new(timeout_secs: u64) -> Self {
        Self { timeout_secs }
    }

    pub fn create_timeout(&self) -> std::time::Duration {
        std::time::Duration::from_secs(self.timeout_secs)
    }
}

/// Request size validator
pub fn validate_request_body_size(size: usize, max_bytes: usize) -> Result<(), String> {
    if size > max_bytes {
        return Err(format!(
            "Request body too large: {} bytes (max: {} bytes)",
            size, max_bytes
        ));
    }
    Ok(())
}

/// Validate response consistency for critical operations
pub fn validate_response_consistency(
    rows_affected: u64,
    expected_count: u64,
) -> Result<(), String> {
    if rows_affected != expected_count {
        return Err(format!(
            "Data consistency check failed: affected {} rows, expected {}",
            rows_affected, expected_count
        ));
    }
    Ok(())
}

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

    #[test]
    fn test_concurrency_limiter() {
        let limiter = ConcurrencyLimiter::new(2);
        assert!(limiter.can_accept());
        limiter.increment();
        assert!(limiter.can_accept());
        limiter.increment();
        assert!(!limiter.can_accept());
        limiter.decrement();
        assert!(limiter.can_accept());
    }

    #[test]
    fn test_request_size_validation() {
        assert!(validate_request_body_size(100, 1000).is_ok());
        assert!(validate_request_body_size(2000, 1000).is_err());
    }

    #[test]
    fn test_response_consistency() {
        assert!(validate_response_consistency(1, 1).is_ok());
        assert!(validate_response_consistency(1, 2).is_err());
    }
}