package proxy

import (
	"crypto/rsa"
	"crypto/x509"
	"encoding/pem"
	"io"
	"log"
	"net/http"

	"github.com/arpinfidel/p2p-llm/config"
	"github.com/arpinfidel/p2p-llm/db"
)

type ProxyHandler struct {
	cfg                     *config.Config
	peerRepo                db.PeerRepository
	queue                   chan Request
	maxParallelRequests     int
	maxParallelPeerRequests int
}

type Request struct {
	W http.ResponseWriter
	R *http.Request
}

func NewProxyHandler(cfg *config.Config, peerRepo db.PeerRepository) *ProxyHandler {
	return &ProxyHandler{
		cfg:                     cfg,
		peerRepo:                peerRepo,
		queue:                   make(chan Request, 100), // Hardcoded queue size
		maxParallelRequests:     cfg.MaxParallelRequests,
		maxParallelPeerRequests: 5, // Hardcoded peer requests limit
	}
}

func (h *ProxyHandler) Handle(w http.ResponseWriter, r *http.Request) {
	req := Request{W: w, R: r}
	h.queue <- req
}

func (h *ProxyHandler) Run() {
	// Get peers from config
	peers := h.cfg.TrustedPeers

	// Get peers from database
	dbPeers, err := h.peerRepo.ListTrustedPeers()
	if err != nil {
		log.Printf("Error getting peers from database: %v", err)
	} else {
		for _, p := range dbPeers {
			block, _ := pem.Decode([]byte(p.PublicKey))
			if block == nil {
				continue
			}

			pubKey, err := x509.ParsePKIXPublicKey(block.Bytes)
			if err != nil {
				continue
			}

			peers = append(peers, config.Peer{
				URL:       p.URL,
				PublicKey: pubKey.(*rsa.PublicKey),
			})
		}
	}

	// Start workers for target URL
	for range h.maxParallelRequests {
		go func() {
			for req := range h.queue {
				h.Forward(req, h.cfg.TargetURL)
			}
		}()
	}

	// Start workers for each peer
	for _, peer := range peers {
		go func(p config.Peer) {
			for req := range h.queue {
				h.Forward(req, p.URL)
			}
		}(peer)
	}
}

func (h *ProxyHandler) Forward(req Request, url string) {
	// Create a new request to the target server
	targetReq, err := http.NewRequest(req.R.Method, url+req.R.URL.Path, req.R.Body)
	if err != nil {
		log.Printf("Error creating request: %v", err)
		http.Error(req.W, "Error creating request", http.StatusInternalServerError)
		return
	}

	// Copy headers from original request
	for name, values := range req.R.Header {
		for _, value := range values {
			targetReq.Header.Add(name, value)
		}
	}

	// Create HTTP client
	client := &http.Client{}

	// Send the request to the target server
	resp, err := client.Do(targetReq)
	if err != nil {
		log.Printf("Error forwarding request: %v", err)
		http.Error(req.W, "Error forwarding request", http.StatusBadGateway)
		return
	}
	defer resp.Body.Close()

	// Check if this is an SSE response
	isSSE := false
	for name, values := range resp.Header {
		for _, value := range values {
			req.W.Header().Add(name, value)
			if name == "Content-Type" && value == "text/event-stream" {
				isSSE = true
			}
		}
	}

	// Set response status code
	req.W.WriteHeader(resp.StatusCode)

	// Handle SSE responses differently
	if isSSE {
		// Set necessary headers for SSE
		req.W.Header().Set("Content-Type", "text/event-stream")
		req.W.Header().Set("Cache-Control", "no-cache")
		req.W.Header().Set("Connection", "keep-alive")
		req.W.Header().Set("Transfer-Encoding", "chunked")

		// Create a flusher if the ResponseWriter supports it
		flusher, ok := req.W.(http.Flusher)
		if !ok {
			log.Printf("ResponseWriter does not support flushing")
			http.Error(req.W, "Streaming unsupported", http.StatusInternalServerError)
			return
		}

		// Buffer for reading from response body
		buf := make([]byte, 1024)
		for {
			n, err := resp.Body.Read(buf)
			if n > 0 {
				// Write data to client
				if _, writeErr := req.W.Write(buf[:n]); writeErr != nil {
					log.Printf("Error writing to client: %v", writeErr)
					break
				}
				// Flush data immediately to client
				flusher.Flush()
			}
			if err != nil {
				if err != io.EOF {
					log.Printf("Error reading from response body: %v", err)
				}
				break
			}
		}
	} else {
		// For non-SSE responses, just copy the body
		if _, err := io.Copy(req.W, resp.Body); err != nil {
			log.Printf("Error copying response body: %v", err)
		}
	}
}