Prepare materials for auto heal functionality

pkg/realdebrid/util.go

@@ -2,6 +2,7 @@ package realdebrid
 
 import (
 	"math"
+	"net/http"
 	"strings"
 	"time"
 )
@@ -18,3 +19,36 @@ func RetryUntilOk[T any](fn func() (T, error)) T {
 		time.Sleep(delay)
 	}
 }
+
+func canFetchFirstByte(url string) bool {
+	// Create a new HTTP request
+	req, err := http.NewRequest("GET", url, nil)
+	if err != nil {
+		return false
+	}
+
+	// Set the Range header to request only the first byte
+	req.Header.Set("Range", "bytes=0-0")
+
+	// Execute the request
+	resp, err := http.DefaultClient.Do(req)
+	if err != nil {
+		return false
+	}
+	defer resp.Body.Close()
+
+	// If server supports partial content
+	if resp.StatusCode == http.StatusPartialContent {
+		buffer := make([]byte, 1)
+		_, err := resp.Body.Read(buffer)
+		return err == nil
+	}
+	if resp.StatusCode != http.StatusOK {
+		return false
+	}
+	// If server doesn't support partial content, try reading the first byte and immediately close
+	buffer := make([]byte, 1)
+	_, err = resp.Body.Read(buffer)
+	resp.Body.Close() // Close immediately after reading
+	return err == nil
+}