feat: add proxy transport with dns caching, subtitle handler, and stream pre-warm

pkg/net/proxytransport/transport.go

@@ -0,0 +1,86 @@
+package proxytransport
+
+import (
+	"context"
+	"fmt"
+	"net"
+	"net/http"
+	"sync"
+	"time"
+)
+
+var dnsCache sync.Map
+
+func init() {
+	go func() {
+		for {
+			time.Sleep(5 * time.Minute)
+			dnsCache.Range(func(key, _ any) bool {
+				dnsCache.Delete(key)
+				return true
+			})
+		}
+	}()
+}
+
+func newTransport(dialTimeout, tlsTimeout, headerTimeout time.Duration) *http.Transport {
+	return &http.Transport{
+		MaxIdleConns:          100,
+		MaxIdleConnsPerHost:   10,
+		IdleConnTimeout:       90 * time.Second,
+		TLSHandshakeTimeout:   tlsTimeout,
+		ResponseHeaderTimeout: headerTimeout,
+		ExpectContinueTimeout: 1 * time.Second,
+		DialContext: func(ctx context.Context, network, addr string) (net.Conn, error) {
+			host, port, err := net.SplitHostPort(addr)
+			if err != nil {
+				return nil, err
+			}
+
+			ips, ok := dnsCache.Load(host)
+			if !ok {
+				resolved, err := net.DefaultResolver.LookupIPAddr(ctx, host)
+				if err != nil {
+					return nil, fmt.Errorf("proxy dns lookup: %w", err)
+				}
+				dnsCache.Store(host, resolved)
+				ips = resolved
+			}
+
+			return dialIPs(ctx, network, host, port, ips.([]net.IPAddr), dialTimeout)
+		},
+	}
+}
+
+func dialIPs(ctx context.Context, network, host, port string, ips []net.IPAddr, timeout time.Duration) (net.Conn, error) {
+	var firstErr error
+	for _, ip := range ips {
+		select {
+		case <-ctx.Done():
+			return nil, ctx.Err()
+		default:
+		}
+		dialer := net.Dialer{Timeout: timeout}
+		conn, err := dialer.DialContext(ctx, network, net.JoinHostPort(ip.String(), port))
+		if err == nil {
+			return conn, nil
+		}
+		if firstErr == nil {
+			firstErr = err
+		}
+	}
+	return nil, fmt.Errorf("proxy dial %s: %w", host, firstErr)
+}
+
+func NewClient() *http.Client {
+	return &http.Client{
+		Transport: newTransport(10*time.Second, 10*time.Second, 30*time.Second),
+		Timeout:   60 * time.Second,
+	}
+}
+
+func NewStreamingClient() *http.Client {
+	return &http.Client{
+		Transport: newTransport(10*time.Second, 10*time.Second, 15*time.Second),
+	}
+}