package proxy

import (
	"context"
	"fmt"
	"io"
	"log/slog"
	"net"
	"time"

	"github.com/hexahost/gamecloud/edge-gateway/internal/config"
	"github.com/hexahost/gamecloud/edge-gateway/internal/controlplane"
	"github.com/hexahost/gamecloud/edge-gateway/internal/mc"
)

type Gateway struct {
	cfg    config.Config
	client *controlplane.Client
	log    *slog.Logger
}

func New(cfg config.Config, log *slog.Logger) *Gateway {
	return &Gateway{
		cfg:    cfg,
		client: controlplane.NewClient(cfg.APIURL, cfg.EdgeKey),
		log:    log,
	}
}

func (g *Gateway) ListenAndServe(ctx context.Context) error {
	listener, err := net.Listen("tcp", g.cfg.ListenAddr)
	if err != nil {
		return err
	}
	defer listener.Close()

	g.log.Info("edge gateway listening",
		"addr", g.cfg.ListenAddr,
		"playDomain", g.cfg.PlayDomain,
		"api", g.cfg.APIURL,
	)

	go func() {
		<-ctx.Done()
		_ = listener.Close()
	}()

	for {
		conn, err := listener.Accept()
		if err != nil {
			select {
			case <-ctx.Done():
				return nil
			default:
				g.log.Error("accept failed", "error", err)
				continue
			}
		}

		go g.handleConnection(conn)
	}
}

func (g *Gateway) handleConnection(clientConn net.Conn) {
	defer clientConn.Close()

	clientIP := clientConn.RemoteAddr().String()
	if host, _, err := net.SplitHostPort(clientIP); err == nil {
		clientIP = host
	}

	handshake, err := mc.ReadHandshake(clientConn)
	if err != nil {
		g.log.Warn("handshake failed", "error", err, "client", clientIP)
		return
	}

	slug := mc.ExtractSlug(handshake.ServerAddress, g.cfg.PlayDomain)
	if slug == "" {
		g.log.Warn("unknown hostname", "address", handshake.ServerAddress, "client", clientIP)
		return
	}

	resolve, err := g.client.Resolve(slug, clientIP)
	if err != nil {
		g.log.Warn("resolve failed", "slug", slug, "error", err)
		return
	}

	switch resolve.Action {
	case "start":
		startResp, err := g.client.Start(slug, clientIP)
		if err != nil {
			g.log.Warn("join start failed", "slug", slug, "error", err)
			return
		}
		resolve = &startResp.Resolve
	case "wait":
		resolve, err = g.waitForProxy(slug, clientIP)
		if err != nil {
			g.log.Warn("wait for server failed", "slug", slug, "error", err)
			return
		}
	case "reject":
		g.log.Info("connection rejected", "slug", slug, "message", resolve.Message)
		return
	}

	if resolve.Action != "proxy" || resolve.Backend == nil {
		g.log.Warn("no backend available", "slug", slug, "action", resolve.Action)
		return
	}

	backendAddr := fmt.Sprintf("%s:%d", resolve.Backend.Host, resolve.Backend.Port)
	backendConn, err := net.DialTimeout("tcp", backendAddr, 10*time.Second)
	if err != nil {
		g.log.Error("backend dial failed", "slug", slug, "backend", backendAddr, "error", err)
		return
	}
	defer backendConn.Close()

	if err := mc.WritePacket(backendConn, handshake.Raw); err != nil {
		g.log.Error("replay handshake failed", "slug", slug, "error", err)
		return
	}

	g.log.Info("proxying connection",
		"slug", slug,
		"client", clientIP,
		"backend", backendAddr,
		"status", resolve.Status,
	)

	pipe(clientConn, backendConn)
}

func (g *Gateway) waitForProxy(slug, clientIP string) (*controlplane.ResolveResponse, error) {
	deadline := time.Now().Add(g.cfg.StartWait)
	for time.Now().Before(deadline) {
		resolve, err := g.client.Resolve(slug, clientIP)
		if err != nil {
			return nil, err
		}
		if resolve.Action == "proxy" {
			return resolve, nil
		}
		if resolve.Action == "reject" {
			return resolve, fmt.Errorf(resolve.Message)
		}
		time.Sleep(g.cfg.PollInterval)
	}
	return nil, fmt.Errorf("timed out waiting for server to start")
}

func pipe(left, right net.Conn) {
	errCh := make(chan error, 2)
	go func() { _, err := io.Copy(right, left); errCh <- err }()
	go func() { _, err := io.Copy(left, right); errCh <- err }()
	<-errCh
}