fix: make qbittorrent login compatible

internal/service/qbittorrent_login.go

@@ -0,0 +1,80 @@
+package service
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"io"
+	"net/http"
+	"net/url"
+	"strings"
+)
+
+type qbitLoginVariant struct {
+	name    string
+	referer bool
+	origin  bool
+}
+
+func qbitLogin(ctx context.Context, client *http.Client, baseURL, username, password string) error {
+	baseURL = strings.TrimRight(strings.TrimSpace(baseURL), "/")
+	if baseURL == "" {
+		return errors.New("qbittorrent host not configured")
+	}
+	var lastErr error
+	for _, variant := range []qbitLoginVariant{
+		{name: "minimal"},
+		{name: "referer", referer: true},
+		{name: "referer-origin", referer: true, origin: true},
+	} {
+		err := qbitLoginOnce(ctx, client, baseURL, username, password, variant)
+		if err == nil {
+			return nil
+		}
+		lastErr = err
+		if errors.Is(err, errQbitBadCredentials) {
+			return err
+		}
+	}
+	return lastErr
+}
+
+var errQbitBadCredentials = errors.New("qbittorrent: 用户名/密码错误")
+
+func qbitLoginOnce(ctx context.Context, client *http.Client, baseURL, username, password string, variant qbitLoginVariant) error {
+	form := url.Values{}
+	form.Set("username", username)
+	form.Set("password", password)
+	req, err := http.NewRequestWithContext(ctx, http.MethodPost,
+		baseURL+"/api/v2/auth/login", strings.NewReader(form.Encode()))
+	if err != nil {
+		return err
+	}
+	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
+	if variant.referer {
+		req.Header.Set("Referer", baseURL)
+	}
+	if variant.origin {
+		req.Header.Set("Origin", baseURL)
+	}
+
+	resp, err := client.Do(req)
+	if err != nil {
+		return err
+	}
+	defer resp.Body.Close()
+	raw, _ := io.ReadAll(io.LimitReader(resp.Body, 1024))
+	text := strings.TrimSpace(string(raw))
+	switch {
+	case resp.StatusCode == http.StatusOK && text == "Ok.":
+		return nil
+	case resp.StatusCode == http.StatusOK && text == "Fails.":
+		return errQbitBadCredentials
+	case resp.StatusCode == http.StatusForbidden:
+		return fmt.Errorf("qbittorrent: 403 forbidden during %s login, body=%q; check qBittorrent WebUI bypass/auth settings for the container IP and host %s", variant.name, text, baseURL)
+	case resp.StatusCode >= 400:
+		return fmt.Errorf("qbittorrent login failed during %s login: status=%d body=%q", variant.name, resp.StatusCode, text)
+	default:
+		return fmt.Errorf("qbittorrent login unexpected response during %s login: status=%d body=%q", variant.name, resp.StatusCode, text)
+	}
+}