use std::collections::HashMap;
use std::net::IpAddr;
use std::sync::Arc;
use std::time::Instant;
use tokio::sync::RwLock;

/// Rate limiter for login attempts: max 5 failures per 60 seconds per IP.
#[derive(Clone)]
pub struct LoginRateLimiter {
    attempts: Arc<RwLock<HashMap<IpAddr, Vec<Instant>>>>,
}

const MAX_ATTEMPTS: usize = 5;
const WINDOW_SECS: u64 = 60;

impl LoginRateLimiter {
    pub fn new() -> Self {
        Self {
            attempts: Arc::new(RwLock::new(HashMap::new())),
        }
    }

    pub async fn check(&self, ip: IpAddr) -> bool {
        let mut attempts = self.attempts.write().await;
        let now = Instant::now();
        let entry = attempts.entry(ip).or_default();
        entry.retain(|t| now.duration_since(*t).as_secs() < WINDOW_SECS);
        entry.len() < MAX_ATTEMPTS
    }

    pub async fn record_failure(&self, ip: IpAddr) {
        let mut attempts = self.attempts.write().await;
        let entry = attempts.entry(ip).or_default();
        entry.push(Instant::now());
    }

    /// Periodic cleanup of expired entries for IPs that are no longer active.
    pub async fn cleanup(&self) {
        let mut attempts = self.attempts.write().await;
        let now = Instant::now();
        attempts.retain(|_, timestamps| {
            timestamps.retain(|t| now.duration_since(*t).as_secs() < WINDOW_SECS);
            !timestamps.is_empty()
        });
    }
}

/// General-purpose rate limiter for sensitive endpoints.
/// Tracks request counts per (method, IP) with configurable limits and windows.
#[derive(Clone)]
pub struct EndpointRateLimiter {
    /// Map of (method, ip) -> list of request timestamps
    requests: Arc<RwLock<HashMap<(String, IpAddr), Vec<Instant>>>>, // Instant for monotonic rate limiting
    /// Per-method configuration: (max_requests, window_secs)
    limits: Arc<HashMap<String, (usize, u64)>>,
}

impl EndpointRateLimiter {
    pub fn new() -> Self {
        let mut limits = HashMap::new();
        // Financial operations: strict limits
        limits.insert("wallet.send".to_string(), (5usize, 300u64));
        limits.insert("wallet.ecash-send".to_string(), (10, 300));
        limits.insert("lnd.sendcoins".to_string(), (5, 300));
        limits.insert("lnd.payinvoice".to_string(), (10, 300));
        limits.insert("lnd.openchannel".to_string(), (3, 300));
        limits.insert("lnd.closechannel".to_string(), (3, 300));
        limits.insert("lnd.create-psbt".to_string(), (5, 300));
        limits.insert("lnd.finalize-psbt".to_string(), (5, 300));
        // Identity/credential operations
        limits.insert("identity.create".to_string(), (10, 300));
        limits.insert("identity.issue-credential".to_string(), (20, 300));
        // Backup operations (resource-intensive)
        limits.insert("backup.create".to_string(), (10, 600));
        limits.insert("backup.restore".to_string(), (5, 600));
        // Container operations
        limits.insert("container-install".to_string(), (5, 300));
        limits.insert("package.install".to_string(), (5, 300));
        // S3 backup operations (resource-intensive)
        limits.insert("backup.upload-s3".to_string(), (3, 600));
        limits.insert("backup.download-s3".to_string(), (3, 600));
        // System operations
        limits.insert("update.apply".to_string(), (2, 600));
        limits.insert("system.reboot".to_string(), (2, 300));
        limits.insert("system.shutdown".to_string(), (2, 300));
        // Password and TOTP changes
        limits.insert("auth.changePassword".to_string(), (3, 300));
        limits.insert("auth.totp.setup".to_string(), (3, 300));
        limits.insert("auth.totp.confirm".to_string(), (5, 300));
        // Federation join: prevent invite-code brute force
        limits.insert("federation.join".to_string(), (5, 60));
        limits.insert("federation.invite".to_string(), (10, 300));
        // Inter-node federation RPCs (unauthenticated, need stricter limits)
        limits.insert("federation.peer-joined".to_string(), (10, 60));
        limits.insert("federation.peer-address-changed".to_string(), (10, 60));
        limits.insert("federation.peer-did-changed".to_string(), (5, 60));
        limits.insert("federation.get-state".to_string(), (30, 60));
        // DID rotation: sensitive identity operation
        limits.insert("node.rotate-did".to_string(), (3, 600));

        Self {
            requests: Arc::new(RwLock::new(HashMap::new())),
            limits: Arc::new(limits),
        }
    }

    /// Check if a request is allowed. Returns true if within limits.
    pub async fn check(&self, method: &str, ip: IpAddr) -> bool {
        let (max_req, window) = match self.limits.get(method) {
            Some(config) => *config,
            None => return true, // Not rate-limited
        };

        let key = (method.to_string(), ip);
        let mut requests = self.requests.write().await;
        let now = Instant::now();
        let entry = requests.entry(key).or_default();
        entry.retain(|t| now.duration_since(*t).as_secs() < window);
        entry.len() < max_req
    }

    /// Record a request for rate limiting purposes.
    pub async fn record(&self, method: &str, ip: IpAddr) {
        if !self.limits.contains_key(method) {
            return; // Not rate-limited, skip tracking
        }
        let key = (method.to_string(), ip);
        let mut requests = self.requests.write().await;
        let entry = requests.entry(key).or_default();
        entry.push(Instant::now());
    }

    /// Periodic cleanup of expired entries.
    pub async fn cleanup(&self) {
        let mut requests = self.requests.write().await;
        let now = Instant::now();
        requests.retain(|(method, _), timestamps| {
            let window = self
                .limits
                .get(method)
                .map(|(_, w)| *w)
                .unwrap_or(300);
            timestamps.retain(|t| now.duration_since(*t).as_secs() < window);
            !timestamps.is_empty()
        });
    }
}

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

    #[tokio::test]
    async fn test_rate_limiter_allows_under_limit() {
        let limiter = LoginRateLimiter::new();
        let ip: IpAddr = "127.0.0.1".parse().unwrap_or(std::net::IpAddr::V4(std::net::Ipv4Addr::LOCALHOST));

        for _ in 0..MAX_ATTEMPTS {
            assert!(limiter.check(ip).await);
            limiter.record_failure(ip).await;
        }
    }

    #[tokio::test]
    async fn test_rate_limiter_blocks_over_limit() {
        let limiter = LoginRateLimiter::new();
        let ip: IpAddr = "127.0.0.1".parse().unwrap_or(std::net::IpAddr::V4(std::net::Ipv4Addr::LOCALHOST));

        for _ in 0..MAX_ATTEMPTS {
            limiter.record_failure(ip).await;
        }

        assert!(!limiter.check(ip).await);
    }

    #[tokio::test]
    async fn test_rate_limiter_different_ips() {
        let limiter = LoginRateLimiter::new();
        let ip1: IpAddr = "127.0.0.1".parse().unwrap_or(std::net::IpAddr::V4(std::net::Ipv4Addr::LOCALHOST));
        let ip2: IpAddr = "192.168.1.1".parse().unwrap_or(std::net::IpAddr::V4(std::net::Ipv4Addr::LOCALHOST));

        for _ in 0..MAX_ATTEMPTS {
            limiter.record_failure(ip1).await;
        }

        // ip1 should be blocked
        assert!(!limiter.check(ip1).await);
        // ip2 should still be allowed
        assert!(limiter.check(ip2).await);
    }
}