add proxy settings

Signed-off-by: Hadi <112569860+anotherhadi@users.noreply.github.com>

back/internal/proxy/proxy.go

@@ -0,0 +1,154 @@
+package proxy
+
+import (
+	"context"
+	"fmt"
+	"math/rand/v2"
+	"net/http"
+	"net/url"
+	"os"
+	"strings"
+
+	"github.com/anotherhadi/iknowyou/config"
+)
+
+type httpClientKey struct{}
+type proxychainsConfKey struct{}
+
+// WithClient injects a proxy-aware HTTP client into the context.
+func WithClient(ctx context.Context, client *http.Client) context.Context {
+	return context.WithValue(ctx, httpClientKey{}, client)
+}
+
+// ClientFromContext returns the proxy-aware HTTP client stored in ctx,
+// or http.DefaultClient if none was set.
+func ClientFromContext(ctx context.Context) *http.Client {
+	if client, ok := ctx.Value(httpClientKey{}).(*http.Client); ok && client != nil {
+		return client
+	}
+	return http.DefaultClient
+}
+
+// WithProxychainsConf injects a proxychains config file path into the context.
+func WithProxychainsConf(ctx context.Context, confPath string) context.Context {
+	return context.WithValue(ctx, proxychainsConfKey{}, confPath)
+}
+
+// ProxychainsConfFromContext returns the proxychains config file path stored in
+// ctx, or an empty string if none was set.
+func ProxychainsConfFromContext(ctx context.Context) string {
+	if path, ok := ctx.Value(proxychainsConfKey{}).(string); ok {
+		return path
+	}
+	return ""
+}
+
+// fallbackTransport is an http.RoundTripper that tries proxies in random order
+// and falls back to the next one on network error.
+type fallbackTransport struct {
+	transports []*http.Transport
+}
+
+func (t *fallbackTransport) RoundTrip(req *http.Request) (*http.Response, error) {
+	order := rand.Perm(len(t.transports))
+	var lastErr error
+	for _, i := range order {
+		resp, err := t.transports[i].RoundTrip(req)
+		if err == nil {
+			return resp, nil
+		}
+		lastErr = err
+	}
+	return nil, lastErr
+}
+
+// NewClient builds an *http.Client that routes requests through the given
+// proxies, trying them in random order and falling back on network error.
+// Returns nil if proxies is empty.
+func NewClient(proxies []config.ProxyEntry) (*http.Client, error) {
+	if len(proxies) == 0 {
+		return nil, nil
+	}
+	transports := make([]*http.Transport, 0, len(proxies))
+	for _, p := range proxies {
+		u, err := url.Parse(p.URL)
+		if err != nil {
+			return nil, fmt.Errorf("proxy: invalid URL %q: %w", p.URL, err)
+		}
+		transports = append(transports, &http.Transport{
+			Proxy: http.ProxyURL(u),
+		})
+	}
+	return &http.Client{
+		Transport: &fallbackTransport{transports: transports},
+	}, nil
+}
+
+// WriteProxychainsConf generates a temporary proxychains4 config file from the
+// given proxy list and returns its path along with a cleanup function.
+// Returns ("", nil, nil) if proxies is empty.
+func WriteProxychainsConf(proxies []config.ProxyEntry) (string, func(), error) {
+	if len(proxies) == 0 {
+		return "", func() {}, nil
+	}
+
+	var sb strings.Builder
+	sb.WriteString("dynamic_chain\nproxy_dns\n\n[ProxyList]\n")
+
+	for _, p := range proxies {
+		u, err := url.Parse(p.URL)
+		if err != nil {
+			return "", nil, fmt.Errorf("proxy: invalid URL %q: %w", p.URL, err)
+		}
+
+		scheme := u.Scheme
+		// proxychains only knows socks4, socks5, http
+		if scheme != "socks4" && scheme != "socks5" && scheme != "http" {
+			scheme = "socks5"
+		}
+
+		host := u.Hostname()
+		port := u.Port()
+		if port == "" {
+			port = defaultPort(scheme)
+		}
+
+		line := fmt.Sprintf("%s %s %s", scheme, host, port)
+		if u.User != nil {
+			user := u.User.Username()
+			pass, _ := u.User.Password()
+			if user != "" {
+				line += " " + user
+				if pass != "" {
+					line += " " + pass
+				}
+			}
+		}
+		sb.WriteString(line + "\n")
+	}
+
+	f, err := os.CreateTemp("", "iky-proxychains-*.conf")
+	if err != nil {
+		return "", nil, fmt.Errorf("proxy: create temp conf: %w", err)
+	}
+	if _, err := f.WriteString(sb.String()); err != nil {
+		_ = f.Close()
+		_ = os.Remove(f.Name())
+		return "", nil, fmt.Errorf("proxy: write conf: %w", err)
+	}
+	_ = f.Close()
+
+	path := f.Name()
+	cleanup := func() { _ = os.Remove(path) }
+	return path, cleanup, nil
+}
+
+func defaultPort(scheme string) string {
+	switch scheme {
+	case "socks4", "socks5":
+		return "1080"
+	case "http":
+		return "8080"
+	}
+	return "1080"
+}