use anyhow::Result;
use bytes::Bytes;
use h3::server::RequestStream;
use http::{Request, Response, HeaderMap};
use std::collections::HashMap;
use std::net::SocketAddr;
use std::sync::Arc;
use tracing::{debug, info};

use crate::config::Config;
use crate::routing::{RoutingCore, RequestInfo};
use crate::file_sync::FileSyncHandler;

/// HTTP/3 specific router that handles requests with native h3 types
pub struct Http3Router {
    config: Arc<Config>,
    routing_core: Arc<RoutingCore>,
    file_sync_handlers: HashMap<String, Arc<FileSyncHandler>>,
}

impl Http3Router {
    pub fn new(
        config: Arc<Config>,
        routing_core: Arc<RoutingCore>,
        file_sync_handlers: HashMap<String, Arc<FileSyncHandler>>,
    ) -> Self {
        Self {
            config,
            routing_core,
            file_sync_handlers,
        }
    }

    /// Handle an HTTP/3 request with native h3 types
    pub async fn handle_request(
        &self,
        req: Request<()>,
        mut stream: RequestStream<h3_quinn::BidiStream<Bytes>, Bytes>,
        remote_addr: SocketAddr,
        server_name: String,
        connection_id: String,
    ) -> Result<()> {
        debug!("HTTP/3 request: {} {} (connection: {})", req.method(), req.uri(), connection_id);

        // Extract request information for routing
        let request_info = self.extract_request_info(&req, remote_addr);
        
        // Read request body
        let body_bytes = self.read_request_body(&mut stream).await?;
        
        // Route the request
        match self.route_request(&request_info, &server_name).await? {
            Some(route_result) => {
                self.handle_routed_request(
                    route_result,
                    req,
                    body_bytes,
                    &mut stream,
                    &request_info,
                    &server_name,
                ).await?;
            }
            None => {
                // No route found - return 404
                self.send_error_response(&mut stream, 404, "Not Found").await?;
            }
        }

        Ok(())
    }

    /// Extract protocol-agnostic request information
    fn extract_request_info(&self, req: &Request<()>, remote_addr: SocketAddr) -> RequestInfo {
        let method = req.method().to_string();
        let path = req.uri().path().to_string();
        
        // Convert headers to generic format
        let headers: Vec<(String, String)> = req
            .headers()
            .iter()
            .map(|(name, value)| {
                (
                    name.to_string(),
                    value.to_str().unwrap_or("").to_string(),
                )
            })
            .collect();

        RequestInfo::new(method, path, headers, remote_addr)
    }

    /// Read HTTP/3 request body with size limits
    async fn read_request_body(
        &self,
        stream: &mut RequestStream<h3_quinn::BidiStream<Bytes>, Bytes>,
    ) -> Result<Bytes> {
        let mut body_bytes = Vec::new();
        let max_body_size = 10 * 1024 * 1024; // 10MB limit
        
        while let Some(chunk) = stream.recv_data().await? {
            use bytes::Buf;
            let chunk_bytes = chunk.chunk();
            
            // Check body size limit
            if body_bytes.len() + chunk_bytes.len() > max_body_size {
                return Err(anyhow::anyhow!("Request body too large"));
            }
            
            body_bytes.extend_from_slice(chunk_bytes);
        }
        
        Ok(Bytes::from(body_bytes))
    }

    /// Route the request to the appropriate handler
    async fn route_request(
        &self,
        request_info: &RequestInfo,
        _server_name: &str,
    ) -> Result<Option<RouteResult>> {
        // Handle ACME challenges first
        if RoutingCore::is_acme_challenge(&request_info.path) {
            return Ok(Some(RouteResult::AcmeChallenge));
        }

        // TODO: Implement proper route matching based on configuration
        // For now, we'll implement basic routing logic
        
        // Check for file sync API requests
        if RoutingCore::is_file_sync_api(&request_info.path) {
            return Ok(Some(RouteResult::FileSync));
        }

        // Default to reverse proxy for now
        // In a full implementation, this would match against the configuration
        Ok(Some(RouteResult::ReverseProxy))
    }

    /// Handle a routed request
    async fn handle_routed_request(
        &self,
        route_result: RouteResult,
        req: Request<()>,
        body_bytes: Bytes,
        stream: &mut RequestStream<h3_quinn::BidiStream<Bytes>, Bytes>,
        request_info: &RequestInfo,
        server_name: &str,
    ) -> Result<()> {
        match route_result {
            RouteResult::ReverseProxy => {
                self.handle_reverse_proxy(req, body_bytes, stream, request_info, server_name).await
            }
            RouteResult::FileSync => {
                self.handle_file_sync(req, body_bytes, stream, request_info, server_name).await
            }
            RouteResult::StaticFile => {
                self.handle_static_file(req, stream, request_info).await
            }
            RouteResult::AcmeChallenge => {
                self.handle_acme_challenge(req, stream, request_info).await
            }
        }
    }

    /// Handle reverse proxy requests using HTTP/3 to HTTP/1.1 translation
    async fn handle_reverse_proxy(
        &self,
        req: Request<()>,
        _body_bytes: Bytes,
        stream: &mut RequestStream<h3_quinn::BidiStream<Bytes>, Bytes>,
        _request_info: &RequestInfo,
        _server_name: &str,
    ) -> Result<()> {
        // TODO: Implement HTTP/3 to upstream HTTP/1.1 proxy
        // This would:
        // 1. Select upstream using routing_core.select_upstream()
        // 2. Convert HTTP/3 request to HTTP/1.1 request
        // 3. Send to upstream using hyper client
        // 4. Convert HTTP/1.1 response back to HTTP/3
        // 5. Record metrics using routing_core.record_upstream_result()
        
        info!("HTTP/3 reverse proxy: {} {} -> [upstream]", req.method(), req.uri());
        
        // For now, return a placeholder response
        self.send_error_response(stream, 501, "HTTP/3 Reverse Proxy Not Yet Implemented").await
    }

    /// Handle file sync requests natively in HTTP/3
    async fn handle_file_sync(
        &self,
        req: Request<()>,
        _body_bytes: Bytes,
        stream: &mut RequestStream<h3_quinn::BidiStream<Bytes>, Bytes>,
        _request_info: &RequestInfo,
        _server_name: &str,
    ) -> Result<()> {
        // TODO: Implement native HTTP/3 file sync
        // This would convert the HTTP/3 request to work with FileSyncHandler
        
        info!("HTTP/3 file sync: {} {}", req.method(), req.uri());
        
        // For now, return a placeholder response
        self.send_error_response(stream, 501, "HTTP/3 File Sync Not Yet Implemented").await
    }

    /// Handle static file serving in HTTP/3
    async fn handle_static_file(
        &self,
        req: Request<()>,
        stream: &mut RequestStream<h3_quinn::BidiStream<Bytes>, Bytes>,
        _request_info: &RequestInfo,
    ) -> Result<()> {
        // TODO: Implement native HTTP/3 static file serving
        
        info!("HTTP/3 static file: {} {}", req.method(), req.uri());
        
        // For now, return a placeholder response
        self.send_error_response(stream, 501, "HTTP/3 Static Files Not Yet Implemented").await
    }

    /// Handle ACME challenges in HTTP/3
    async fn handle_acme_challenge(
        &self,
        req: Request<()>,
        stream: &mut RequestStream<h3_quinn::BidiStream<Bytes>, Bytes>,
        _request_info: &RequestInfo,
    ) -> Result<()> {
        // TODO: Implement HTTP/3 ACME challenge handling
        
        info!("HTTP/3 ACME challenge: {} {}", req.method(), req.uri());
        
        // For now, return a placeholder response
        self.send_error_response(stream, 501, "HTTP/3 ACME Challenge Not Yet Implemented").await
    }

    /// Send an HTTP/3 error response
    async fn send_error_response(
        &self,
        stream: &mut RequestStream<h3_quinn::BidiStream<Bytes>, Bytes>,
        status_code: u16,
        message: &str,
    ) -> Result<()> {
        let response = Response::builder()
            .status(status_code)
            .header("content-type", "text/plain")
            .body(())?;

        stream.send_response(response).await?;
        stream.send_data(Bytes::from(message.to_string())).await?;
        stream.finish().await?;
        
        Ok(())
    }

    /// Send a successful HTTP/3 response with body
    async fn send_response(
        &self,
        stream: &mut RequestStream<h3_quinn::BidiStream<Bytes>, Bytes>,
        status_code: u16,
        headers: Vec<(String, String)>,
        body: Bytes,
    ) -> Result<()> {
        let mut response_builder = Response::builder().status(status_code);
        
        // Add headers
        for (name, value) in headers {
            response_builder = response_builder.header(name, value);
        }
        
        let response = response_builder.body(())?;
        
        stream.send_response(response).await?;
        if !body.is_empty() {
            stream.send_data(body).await?;
        }
        stream.finish().await?;
        
        Ok(())
    }
}

/// Normalize HTTP/3 headers for HTTP/1.1 compatibility
pub fn normalize_h3_headers(headers: &mut http::HeaderMap) {
    // Remove HTTP/2+ pseudo-headers if present
    headers.remove(":method");
    headers.remove(":path");
    headers.remove(":scheme");
    headers.remove(":authority");
    
    // Ensure content-length is set for body requests
    if !headers.contains_key("content-length") && !headers.contains_key("transfer-encoding") {
        // Will be set later when we know the body size
    }
    
    // Remove HTTP/3 specific headers that might cause issues
    headers.remove("alt-svc");
}

/// Normalize HTTP/1.1 response headers for HTTP/3
pub fn normalize_response_headers(headers: &mut http::HeaderMap) {
    // Remove connection-specific headers
    headers.remove("connection");
    headers.remove("upgrade");
    headers.remove("proxy-connection");
    
    // HTTP/3 doesn't use transfer-encoding
    headers.remove("transfer-encoding");
    
    // Ensure proper content-length if not already set
    if !headers.contains_key("content-length") {
        // The body handling will set this if needed
    }
}

/// Result of routing a request
#[derive(Debug, Clone)]
enum RouteResult {
    ReverseProxy,
    FileSync,
    StaticFile,
    AcmeChallenge,
}

#[cfg(test)]
mod tests {
    use super::*;
    use std::net::{IpAddr, Ipv4Addr};

    fn create_test_request_info() -> RequestInfo {
        RequestInfo::new(
            "GET".to_string(),
            "/test".to_string(),
            vec![("host".to_string(), "example.com".to_string())],
            SocketAddr::new(IpAddr::V4(Ipv4Addr::new(127, 0, 0, 1)), 8080),
        )
    }

    #[tokio::test]
    async fn test_extract_request_info() {
        use http::Method;
        
        let req = Request::builder()
            .method(Method::GET)
            .uri("/test/path")
            .header("host", "example.com")
            .header("user-agent", "test-agent")
            .body(())
            .unwrap();
            
        let remote_addr = SocketAddr::new(IpAddr::V4(Ipv4Addr::new(127, 0, 0, 1)), 8080);
        
        // We can't easily test this without creating a full Http3Router
        // but we can test the logic conceptually
        assert_eq!(req.method(), "GET");
        assert_eq!(req.uri().path(), "/test/path");
    }

    #[test]
    fn test_route_patterns() {
        // Test ACME challenge detection
        let acme_info = RequestInfo::new(
            "GET".to_string(),
            "/.well-known/acme-challenge/test".to_string(),
            vec![],
            SocketAddr::new(IpAddr::V4(Ipv4Addr::new(127, 0, 0, 1)), 8080),
        );
        assert!(RoutingCore::is_acme_challenge(&acme_info.path));

        // Test file sync API detection
        let api_info = RequestInfo::new(
            "POST".to_string(),
            "/api/files/upload".to_string(),
            vec![],
            SocketAddr::new(IpAddr::V4(Ipv4Addr::new(127, 0, 0, 1)), 8080),
        );
        assert!(RoutingCore::is_file_sync_api(&api_info.path));
    }
}