fix: make WebDAV upload retry reliable

settings.go

@@ -1,6 +1,8 @@
 package main
 
 import (
+	"crypto/rand"
+	"fmt"
 	"strings"
 	"time"
 
@@ -68,6 +70,9 @@ func (a *App) putSettings(c *gin.Context) {
 	} else {
 		a.storage = nil
 	}
+	// Credentials/config changes should repair already-downloaded local files
+	// immediately instead of waiting for the periodic retry interval.
+	go a.resyncPendingUploads()
 	c.JSON(200, gin.H{"ok": true})
 }
 
@@ -77,11 +82,48 @@ func (a *App) testWebDAV(c *gin.Context) {
 		c.Status(400)
 		return
 	}
+	// An empty password means "use the saved password". The password is never
+	// returned to the browser, so this also makes a fresh settings page test
+	// the credential that is actually stored by the server.
+	if v.URL == "" {
+		v.URL = a.cfg.WebDAVURL
+	}
+	if v.User == "" {
+		v.User = a.cfg.WebDAVUser
+	}
+	if v.Pass == "" {
+		v.Pass = a.cfg.WebDAVPass
+	}
+	v.Path = strings.Trim(v.Path, "/")
+	if v.Path == "" {
+		v.Path = a.cfg.WebDAVPath
+	}
+	if v.URL == "" || v.User == "" || v.Pass == "" {
+		c.JSON(400, gin.H{"ok": false, "error": "WebDAV URL、用户名或密码未配置"})
+		return
+	}
 	client := gowebdav.NewClient(v.URL, v.User, v.Pass)
 	client.SetTimeout(20 * time.Second)
 	if err := client.Connect(); err != nil {
-		c.JSON(502, gin.H{"ok": false, "error": err.Error()})
+		c.JSON(502, gin.H{"ok": false, "error": "WebDAV authentication failed: " + err.Error()})
 		return
 	}
+	if v.Path != "" {
+		if err := client.MkdirAll(v.Path, 0755); err != nil {
+			c.JSON(502, gin.H{"ok": false, "error": "WebDAV target path is not writable: " + err.Error()})
+			return
+		}
+	}
+	var token [12]byte
+	if _, err := rand.Read(token[:]); err != nil {
+		c.JSON(500, gin.H{"ok": false, "error": "failed to create test token"})
+		return
+	}
+	testPath := strings.Trim(v.Path, "/") + "/.am-downloader-test-" + fmt.Sprintf("%x", token[:])
+	if err := client.Write(testPath, []byte("ok"), 0644); err != nil {
+		c.JSON(502, gin.H{"ok": false, "error": "WebDAV write test failed: " + err.Error()})
+		return
+	}
+	_ = client.Remove(testPath)
 	c.JSON(200, gin.H{"ok": true, "path": v.Path})
 }