use std::collections::HashMap;

use rustproxy_config::{RouteConfig, RouteTarget, TlsMode};
use crate::matchers;

/// Context for route matching (subset of connection info).
pub struct MatchContext<'a> {
    pub port: u16,
    pub domain: Option<&'a str>,
    pub path: Option<&'a str>,
    pub client_ip: Option<&'a str>,
    pub tls_version: Option<&'a str>,
    pub headers: Option<&'a HashMap<String, String>>,
    pub is_tls: bool,
    /// Detected protocol: "http" or "tcp". None when unknown (e.g. pre-TLS-termination).
    pub protocol: Option<&'a str>,
}

/// Result of a route match.
pub struct RouteMatchResult<'a> {
    pub route: &'a RouteConfig,
    pub target: Option<&'a RouteTarget>,
}

/// Port-indexed route lookup with priority-based matching.
/// This is the core routing engine.
pub struct RouteManager {
    /// Routes indexed by port for O(1) port lookup.
    port_index: HashMap<u16, Vec<usize>>,
    /// All routes, sorted by priority (highest first).
    routes: Vec<RouteConfig>,
}

impl RouteManager {
    /// Create a new RouteManager from a list of routes.
    pub fn new(routes: Vec<RouteConfig>) -> Self {
        let mut manager = Self {
            port_index: HashMap::new(),
            routes: Vec::new(),
        };

        // Filter enabled routes and sort by priority
        let mut enabled_routes: Vec<RouteConfig> = routes
            .into_iter()
            .filter(|r| r.is_enabled())
            .collect();
        enabled_routes.sort_by(|a, b| b.effective_priority().cmp(&a.effective_priority()));

        // Build port index
        for (idx, route) in enabled_routes.iter().enumerate() {
            for port in route.listening_ports() {
                manager.port_index
                    .entry(port)
                    .or_default()
                    .push(idx);
            }
        }

        manager.routes = enabled_routes;
        manager
    }

    /// Find the best matching route for the given context.
    pub fn find_route<'a>(&'a self, ctx: &MatchContext<'_>) -> Option<RouteMatchResult<'a>> {
        // Get routes for this port
        let route_indices = self.port_index.get(&ctx.port)?;

        for &idx in route_indices {
            let route = &self.routes[idx];

            if self.matches_route(route, ctx) {
                // Find the best matching target within the route
                let target = self.find_target(route, ctx);
                return Some(RouteMatchResult { route, target });
            }
        }

        None
    }

    /// Check if a route matches the given context.
    fn matches_route(&self, route: &RouteConfig, ctx: &MatchContext<'_>) -> bool {
        let rm = &route.route_match;

        // Domain matching
        if let Some(ref domains) = rm.domains {
            if let Some(domain) = ctx.domain {
                let patterns = domains.to_vec();
                if !matchers::domain_matches_any(&patterns, domain) {
                    return false;
                }
            } else if ctx.is_tls {
                // TLS connection without SNI cannot match a domain-restricted route.
                // This prevents session-ticket resumption from misrouting when clients
                // omit SNI (RFC 8446 recommends but doesn't mandate SNI on resumption).
                // Wildcard-only routes (domains: ["*"]) still match since they accept all.
                let patterns = domains.to_vec();
                let is_wildcard_only = patterns.iter().all(|d| *d == "*");
                if !is_wildcard_only {
                    return false;
                }
            }
        }

        // Path matching
        if let Some(ref pattern) = rm.path {
            if let Some(path) = ctx.path {
                if !matchers::path_matches(pattern, path) {
                    return false;
                }
            } else {
                // Route requires path but none provided
                return false;
            }
        }

        // Client IP matching
        if let Some(ref client_ips) = rm.client_ip {
            if let Some(ip) = ctx.client_ip {
                if !matchers::ip_matches_any(client_ips, ip) {
                    return false;
                }
            } else {
                return false;
            }
        }

        // TLS version matching
        if let Some(ref tls_versions) = rm.tls_version {
            if let Some(version) = ctx.tls_version {
                if !tls_versions.iter().any(|v| v == version) {
                    return false;
                }
            } else {
                return false;
            }
        }

        // Header matching
        if let Some(ref patterns) = rm.headers {
            if let Some(headers) = ctx.headers {
                if !matchers::headers_match(patterns, headers) {
                    return false;
                }
            } else {
                return false;
            }
        }

        // Protocol matching
        if let Some(ref required_protocol) = rm.protocol {
            if let Some(protocol) = ctx.protocol {
                if required_protocol != protocol {
                    return false;
                }
            }
            // If protocol not yet known (None), allow match — protocol will be
            // validated after detection (post-TLS-termination peek)
        }

        true
    }

    /// Find the best matching target within a route.
    fn find_target<'a>(&self, route: &'a RouteConfig, ctx: &MatchContext<'_>) -> Option<&'a RouteTarget> {
        let targets = route.action.targets.as_ref()?;

        if targets.len() == 1 && targets[0].target_match.is_none() {
            return Some(&targets[0]);
        }

        // Sort candidates by priority (already in order from config)
        let mut best: Option<&RouteTarget> = None;
        let mut best_priority = i32::MIN;

        for target in targets {
            let priority = target.priority.unwrap_or(0);

            if let Some(ref tm) = target.target_match {
                if !self.matches_target(tm, ctx) {
                    continue;
                }
            }

            if priority > best_priority || best.is_none() {
                best = Some(target);
                best_priority = priority;
            }
        }

        // Fall back to first target without match criteria
        best.or_else(|| {
            targets.iter().find(|t| t.target_match.is_none())
        })
    }

    /// Check if a target match criteria matches the context.
    fn matches_target(
        &self,
        tm: &rustproxy_config::TargetMatch,
        ctx: &MatchContext<'_>,
    ) -> bool {
        // Port matching
        if let Some(ref ports) = tm.ports {
            if !ports.contains(&ctx.port) {
                return false;
            }
        }

        // Path matching
        if let Some(ref pattern) = tm.path {
            if let Some(path) = ctx.path {
                if !matchers::path_matches(pattern, path) {
                    return false;
                }
            } else {
                return false;
            }
        }

        // Header matching
        if let Some(ref patterns) = tm.headers {
            if let Some(headers) = ctx.headers {
                if !matchers::headers_match(patterns, headers) {
                    return false;
                }
            } else {
                return false;
            }
        }

        true
    }

    /// Get all unique listening ports.
    pub fn listening_ports(&self) -> Vec<u16> {
        let mut ports: Vec<u16> = self.port_index.keys().copied().collect();
        ports.sort();
        ports
    }

    /// Get all routes for a specific port.
    pub fn routes_for_port(&self, port: u16) -> Vec<&RouteConfig> {
        self.port_index
            .get(&port)
            .map(|indices| indices.iter().map(|&i| &self.routes[i]).collect())
            .unwrap_or_default()
    }

    /// Get the total number of enabled routes.
    pub fn route_count(&self) -> usize {
        self.routes.len()
    }

    /// Check if any route on the given port requires SNI.
    pub fn port_requires_sni(&self, port: u16) -> bool {
        let routes = self.routes_for_port(port);

        // If multiple passthrough routes on same port, SNI is needed
        let passthrough_routes: Vec<_> = routes
            .iter()
            .filter(|r| {
                r.tls_mode() == Some(&TlsMode::Passthrough)
            })
            .collect();

        if passthrough_routes.len() > 1 {
            return true;
        }

        // Single passthrough route with specific domain restriction needs SNI
        if let Some(route) = passthrough_routes.first() {
            if let Some(ref domains) = route.route_match.domains {
                let domain_list = domains.to_vec();
                // If it's not just a wildcard, SNI is needed
                if !domain_list.iter().all(|d| *d == "*") {
                    return true;
                }
            }
        }

        false
    }
}

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

    fn make_route(port: u16, domain: Option<&str>, priority: i32) -> RouteConfig {
        RouteConfig {
            id: None,
            route_match: RouteMatch {
                ports: PortRange::Single(port),
                domains: domain.map(|d| DomainSpec::Single(d.to_string())),
                path: None,
                client_ip: None,
                tls_version: None,
                headers: None,
                protocol: None,
            },
            action: RouteAction {
                action_type: RouteActionType::Forward,
                targets: Some(vec![RouteTarget {
                    target_match: None,
                    host: HostSpec::Single("localhost".to_string()),
                    port: PortSpec::Fixed(8080),
                    tls: None,
                    websocket: None,
                    load_balancing: None,
                    send_proxy_protocol: None,
                    headers: None,
                    advanced: None,
                    priority: None,
                }]),
                tls: None,
                websocket: None,
                load_balancing: None,
                advanced: None,
                options: None,
                forwarding_engine: None,
                nftables: None,
                send_proxy_protocol: None,
            },
            headers: None,
            security: None,
            name: None,
            description: None,
            priority: Some(priority),
            tags: None,
            enabled: None,
        }
    }

    #[test]
    fn test_basic_routing() {
        let routes = vec![
            make_route(80, Some("example.com"), 0),
            make_route(80, Some("other.com"), 0),
        ];
        let manager = RouteManager::new(routes);

        let ctx = MatchContext {
            port: 80,
            domain: Some("example.com"),
            path: None,
            client_ip: None,
            tls_version: None,
            headers: None,
            is_tls: false,
            protocol: None,
        };

        let result = manager.find_route(&ctx);
        assert!(result.is_some());
    }

    #[test]
    fn test_priority_ordering() {
        let routes = vec![
            make_route(80, Some("*.example.com"), 0),
            make_route(80, Some("api.example.com"), 10), // Higher priority
        ];
        let manager = RouteManager::new(routes);

        let ctx = MatchContext {
            port: 80,
            domain: Some("api.example.com"),
            path: None,
            client_ip: None,
            tls_version: None,
            headers: None,
            is_tls: false,
            protocol: None,
        };

        let result = manager.find_route(&ctx).unwrap();
        // Should match the higher-priority specific route
        assert!(result.route.route_match.domains.as_ref()
            .map(|d| d.to_vec())
            .unwrap()
            .contains(&"api.example.com"));
    }

    #[test]
    fn test_no_match() {
        let routes = vec![make_route(80, Some("example.com"), 0)];
        let manager = RouteManager::new(routes);

        let ctx = MatchContext {
            port: 443, // Different port
            domain: Some("example.com"),
            path: None,
            client_ip: None,
            tls_version: None,
            headers: None,
            is_tls: false,
            protocol: None,
        };

        assert!(manager.find_route(&ctx).is_none());
    }

    #[test]
    fn test_disabled_routes_excluded() {
        let mut route = make_route(80, Some("example.com"), 0);
        route.enabled = Some(false);
        let manager = RouteManager::new(vec![route]);
        assert_eq!(manager.route_count(), 0);
    }

    #[test]
    fn test_listening_ports() {
        let routes = vec![
            make_route(80, Some("a.com"), 0),
            make_route(443, Some("b.com"), 0),
            make_route(80, Some("c.com"), 0), // duplicate port
        ];
        let manager = RouteManager::new(routes);
        let ports = manager.listening_ports();
        assert_eq!(ports, vec![80, 443]);
    }

    #[test]
    fn test_port_requires_sni_single_passthrough() {
        let mut route = make_route(443, Some("example.com"), 0);
        route.action.tls = Some(RouteTls {
            mode: TlsMode::Passthrough,
            certificate: None,
            acme: None,
            versions: None,
            ciphers: None,
            honor_cipher_order: None,
            session_timeout: None,
        });
        let manager = RouteManager::new(vec![route]);
        // Single passthrough route with specific domain needs SNI
        assert!(manager.port_requires_sni(443));
    }

    #[test]
    fn test_port_requires_sni_wildcard_only() {
        let mut route = make_route(443, Some("*"), 0);
        route.action.tls = Some(RouteTls {
            mode: TlsMode::Passthrough,
            certificate: None,
            acme: None,
            versions: None,
            ciphers: None,
            honor_cipher_order: None,
            session_timeout: None,
        });
        let manager = RouteManager::new(vec![route]);
        // Single passthrough route with wildcard doesn't need SNI
        assert!(!manager.port_requires_sni(443));
    }

    #[test]
    fn test_routes_for_port() {
        let routes = vec![
            make_route(80, Some("a.com"), 0),
            make_route(80, Some("b.com"), 0),
            make_route(443, Some("c.com"), 0),
        ];
        let manager = RouteManager::new(routes);
        assert_eq!(manager.routes_for_port(80).len(), 2);
        assert_eq!(manager.routes_for_port(443).len(), 1);
        assert_eq!(manager.routes_for_port(8080).len(), 0);
    }

    #[test]
    fn test_wildcard_domain_matches_any() {
        let routes = vec![make_route(80, Some("*"), 0)];
        let manager = RouteManager::new(routes);

        let ctx = MatchContext {
            port: 80,
            domain: Some("anything.example.com"),
            path: None,
            client_ip: None,
            tls_version: None,
            headers: None,
            is_tls: false,
            protocol: None,
        };

        assert!(manager.find_route(&ctx).is_some());
    }

    #[test]
    fn test_tls_no_sni_rejects_domain_restricted_route() {
        let routes = vec![make_route(443, Some("example.com"), 0)];
        let manager = RouteManager::new(routes);

        // TLS connection without SNI should NOT match a domain-restricted route
        let ctx = MatchContext {
            port: 443,
            domain: None,
            path: None,
            client_ip: None,
            tls_version: None,
            headers: None,
            is_tls: true,
            protocol: None,
        };

        assert!(manager.find_route(&ctx).is_none());
    }

    #[test]
    fn test_tls_no_sni_rejects_wildcard_subdomain_route() {
        let routes = vec![make_route(443, Some("*.example.com"), 0)];
        let manager = RouteManager::new(routes);

        // TLS connection without SNI should NOT match *.example.com
        let ctx = MatchContext {
            port: 443,
            domain: None,
            path: None,
            client_ip: None,
            tls_version: None,
            headers: None,
            is_tls: true,
            protocol: None,
        };

        assert!(manager.find_route(&ctx).is_none());
    }

    #[test]
    fn test_tls_no_sni_matches_wildcard_only_route() {
        let routes = vec![make_route(443, Some("*"), 0)];
        let manager = RouteManager::new(routes);

        // TLS connection without SNI SHOULD match a wildcard-only route
        let ctx = MatchContext {
            port: 443,
            domain: None,
            path: None,
            client_ip: None,
            tls_version: None,
            headers: None,
            is_tls: true,
            protocol: None,
        };

        assert!(manager.find_route(&ctx).is_some());
    }

    #[test]
    fn test_tls_no_sni_skips_domain_restricted_matches_fallback() {
        // Two routes: first is domain-restricted, second is wildcard catch-all
        let routes = vec![
            make_route(443, Some("specific.com"), 10),
            make_route(443, Some("*"), 0),
        ];
        let manager = RouteManager::new(routes);

        // TLS without SNI should skip specific.com and fall through to wildcard
        let ctx = MatchContext {
            port: 443,
            domain: None,
            path: None,
            client_ip: None,
            tls_version: None,
            headers: None,
            is_tls: true,
            protocol: None,
        };

        let result = manager.find_route(&ctx);
        assert!(result.is_some());
        let matched_domains = result.unwrap().route.route_match.domains.as_ref()
            .map(|d| d.to_vec()).unwrap();
        assert!(matched_domains.contains(&"*"));
    }

    #[test]
    fn test_non_tls_no_domain_still_matches_domain_restricted() {
        // Non-TLS (plain HTTP) without domain should still match domain-restricted routes
        // (the HTTP proxy layer handles Host-based routing)
        let routes = vec![make_route(80, Some("example.com"), 0)];
        let manager = RouteManager::new(routes);

        let ctx = MatchContext {
            port: 80,
            domain: None,
            path: None,
            client_ip: None,
            tls_version: None,
            headers: None,
            is_tls: false,
            protocol: None,
        };

        assert!(manager.find_route(&ctx).is_some());
    }

    #[test]
    fn test_no_domain_route_matches_any_domain() {
        let routes = vec![make_route(80, None, 0)];
        let manager = RouteManager::new(routes);

        let ctx = MatchContext {
            port: 80,
            domain: Some("example.com"),
            path: None,
            client_ip: None,
            tls_version: None,
            headers: None,
            is_tls: false,
            protocol: None,
        };

        assert!(manager.find_route(&ctx).is_some());
    }

    #[test]
    fn test_target_sub_matching() {
        let mut route = make_route(80, Some("example.com"), 0);
        route.action.targets = Some(vec![
            RouteTarget {
                target_match: Some(rustproxy_config::TargetMatch {
                    ports: None,
                    path: Some("/api/*".to_string()),
                    headers: None,
                    method: None,
                }),
                host: HostSpec::Single("api-backend".to_string()),
                port: PortSpec::Fixed(3000),
                tls: None,
                websocket: None,
                load_balancing: None,
                send_proxy_protocol: None,
                headers: None,
                advanced: None,
                priority: Some(10),
            },
            RouteTarget {
                target_match: None,
                host: HostSpec::Single("default-backend".to_string()),
                port: PortSpec::Fixed(8080),
                tls: None,
                websocket: None,
                load_balancing: None,
                send_proxy_protocol: None,
                headers: None,
                advanced: None,
                priority: None,
            },
        ]);
        let manager = RouteManager::new(vec![route]);

        // Should match the API target
        let ctx = MatchContext {
            port: 80,
            domain: Some("example.com"),
            path: Some("/api/users"),
            client_ip: None,
            tls_version: None,
            headers: None,
            is_tls: false,
            protocol: None,
        };
        let result = manager.find_route(&ctx).unwrap();
        assert_eq!(result.target.unwrap().host.first(), "api-backend");

        // Should fall back to default target
        let ctx = MatchContext {
            port: 80,
            domain: Some("example.com"),
            path: Some("/home"),
            client_ip: None,
            tls_version: None,
            headers: None,
            is_tls: false,
            protocol: None,
        };
        let result = manager.find_route(&ctx).unwrap();
        assert_eq!(result.target.unwrap().host.first(), "default-backend");
    }

    fn make_route_with_protocol(port: u16, domain: Option<&str>, protocol: Option<&str>) -> RouteConfig {
        let mut route = make_route(port, domain, 0);
        route.route_match.protocol = protocol.map(|s| s.to_string());
        route
    }

    #[test]
    fn test_protocol_http_matches_http() {
        let routes = vec![make_route_with_protocol(80, None, Some("http"))];
        let manager = RouteManager::new(routes);

        let ctx = MatchContext {
            port: 80,
            domain: None,
            path: None,
            client_ip: None,
            tls_version: None,
            headers: None,
            is_tls: false,
            protocol: Some("http"),
        };
        assert!(manager.find_route(&ctx).is_some());
    }

    #[test]
    fn test_protocol_http_rejects_tcp() {
        let routes = vec![make_route_with_protocol(80, None, Some("http"))];
        let manager = RouteManager::new(routes);

        let ctx = MatchContext {
            port: 80,
            domain: None,
            path: None,
            client_ip: None,
            tls_version: None,
            headers: None,
            is_tls: false,
            protocol: Some("tcp"),
        };
        assert!(manager.find_route(&ctx).is_none());
    }

    #[test]
    fn test_protocol_none_matches_any() {
        // Route with no protocol restriction matches any protocol
        let routes = vec![make_route_with_protocol(80, None, None)];
        let manager = RouteManager::new(routes);

        let ctx_http = MatchContext {
            port: 80,
            domain: None,
            path: None,
            client_ip: None,
            tls_version: None,
            headers: None,
            is_tls: false,
            protocol: Some("http"),
        };
        assert!(manager.find_route(&ctx_http).is_some());

        let ctx_tcp = MatchContext {
            port: 80,
            domain: None,
            path: None,
            client_ip: None,
            tls_version: None,
            headers: None,
            is_tls: false,
            protocol: Some("tcp"),
        };
        assert!(manager.find_route(&ctx_tcp).is_some());
    }

    #[test]
    fn test_protocol_http_matches_when_unknown() {
        // Route with protocol: "http" should match when ctx.protocol is None
        // (pre-TLS-termination, protocol not yet known)
        let routes = vec![make_route_with_protocol(443, None, Some("http"))];
        let manager = RouteManager::new(routes);

        let ctx = MatchContext {
            port: 443,
            domain: None,
            path: None,
            client_ip: None,
            tls_version: None,
            headers: None,
            is_tls: true,
            protocol: None,
        };
        assert!(manager.find_route(&ctx).is_some());
    }
}