use std::collections::HashMap;
use std::sync::{Arc, RwLock};

use crate::cert_store::CertBundle;

/// Dynamic SNI-based certificate resolver.
/// Used by the TLS stack to select the right certificate based on client SNI.
pub struct SniResolver {
    /// Domain -> certificate bundle mapping
    certs: RwLock<HashMap<String, Arc<CertBundle>>>,
    /// Fallback certificate (used when no SNI or no match)
    fallback: RwLock<Option<Arc<CertBundle>>>,
}

impl SniResolver {
    pub fn new() -> Self {
        Self {
            certs: RwLock::new(HashMap::new()),
            fallback: RwLock::new(None),
        }
    }

    /// Register a certificate for a domain.
    pub fn add_cert(&self, domain: String, bundle: CertBundle) {
        let mut certs = self.certs.write().unwrap();
        certs.insert(domain, Arc::new(bundle));
    }

    /// Set the fallback certificate.
    pub fn set_fallback(&self, bundle: CertBundle) {
        let mut fallback = self.fallback.write().unwrap();
        *fallback = Some(Arc::new(bundle));
    }

    /// Resolve a certificate for the given SNI domain.
    pub fn resolve(&self, domain: &str) -> Option<Arc<CertBundle>> {
        let certs = self.certs.read().unwrap();

        // Try exact match
        if let Some(bundle) = certs.get(domain) {
            return Some(Arc::clone(bundle));
        }

        // Try wildcard match (e.g., *.example.com)
        if let Some(dot_pos) = domain.find('.') {
            let wildcard = format!("*.{}", &domain[dot_pos + 1..]);
            if let Some(bundle) = certs.get(&wildcard) {
                return Some(Arc::clone(bundle));
            }
        }

        // Fallback
        let fallback = self.fallback.read().unwrap();
        fallback.clone()
    }

    /// Remove a certificate for a domain.
    pub fn remove_cert(&self, domain: &str) {
        let mut certs = self.certs.write().unwrap();
        certs.remove(domain);
    }

    /// Get the number of registered certificates.
    pub fn cert_count(&self) -> usize {
        self.certs.read().unwrap().len()
    }
}

impl Default for SniResolver {
    fn default() -> Self {
        Self::new()
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::cert_store::{CertBundle, CertMetadata, CertSource};

    fn make_bundle(domain: &str) -> CertBundle {
        CertBundle {
            key_pem: format!("KEY-{}", domain),
            cert_pem: format!("CERT-{}", domain),
            ca_pem: None,
            metadata: CertMetadata {
                domain: domain.to_string(),
                source: CertSource::Static,
                issued_at: 0,
                expires_at: 0,
                renewed_at: None,
            },
        }
    }

    #[test]
    fn test_exact_domain_resolve() {
        let resolver = SniResolver::new();
        resolver.add_cert("example.com".to_string(), make_bundle("example.com"));
        let result = resolver.resolve("example.com");
        assert!(result.is_some());
        assert_eq!(result.unwrap().cert_pem, "CERT-example.com");
    }

    #[test]
    fn test_wildcard_resolve() {
        let resolver = SniResolver::new();
        resolver.add_cert("*.example.com".to_string(), make_bundle("*.example.com"));
        let result = resolver.resolve("sub.example.com");
        assert!(result.is_some());
        assert_eq!(result.unwrap().cert_pem, "CERT-*.example.com");
    }

    #[test]
    fn test_fallback() {
        let resolver = SniResolver::new();
        resolver.set_fallback(make_bundle("fallback"));
        let result = resolver.resolve("unknown.com");
        assert!(result.is_some());
        assert_eq!(result.unwrap().cert_pem, "CERT-fallback");
    }

    #[test]
    fn test_no_match_no_fallback() {
        let resolver = SniResolver::new();
        resolver.add_cert("example.com".to_string(), make_bundle("example.com"));
        let result = resolver.resolve("other.com");
        assert!(result.is_none());
    }

    #[test]
    fn test_remove_cert() {
        let resolver = SniResolver::new();
        resolver.add_cert("example.com".to_string(), make_bundle("example.com"));
        assert_eq!(resolver.cert_count(), 1);
        resolver.remove_cert("example.com");
        assert_eq!(resolver.cert_count(), 0);
        assert!(resolver.resolve("example.com").is_none());
    }
}