[koharu] improve format selection (#6088)

- allow specifying more than one possible format
- ignore not available formats

docs/configuration.rst

@@ -2689,14 +2689,17 @@ Description
 extractor.koharu.format
 -----------------------
 Type
-    ``string``
+    * ``string``
+    * ``list`` of ``strings``
 Default
-    ``"original"``
+    ``["0", "1600", "1280", "980", "780"]``
 Description
-    Name of the image format to download.
+    Name(s) of the image format to download.
+
+    When more than one format is given, the first available one is selected.
 
-    | Available formats are
-    | ``"780"``, ``"980"``, ``"1280"``, ``"1600"``, ``"0"``/``"original"``
+    | Possible formats are
+    | ``"780"``, ``"980"``, ``"1280"``, ``"1600"``, ``"0"`` (original)
 
 
 extractor.lolisafe.domain

gallery_dl/extractor/koharu.py

@@ -161,16 +161,29 @@ def images(self, _):
         return results
 
     def _select_format(self, formats):
-        if not self.fmt or self.fmt == "original":
-            fmtid = "0"
+        fmt = self.fmt
+
+        if not fmt or fmt == "best":
+            fmtids = ("0", "1600", "1280", "980", "780")
+        elif isinstance(fmt, str):
+            fmtids = fmt.split(",")
+        elif isinstance(fmt, list):
+            fmtids = fmt
         else:
-            fmtid = str(self.fmt)
+            fmtids = (str(self.fmt),)
 
-        try:
-            fmt = formats[fmtid]
-        except KeyError:
+        for fmtid in fmtids:
+            try:
+                fmt = formats[fmtid]
+                if fmt["id"]:
+                    break
+            except KeyError:
+                self.log.debug("%s: Format %s is not available",
+                               self.groups[0], fmtid)
+        else:
             raise exception.NotFoundError("format")
 
+        self.log.debug("%s: Selected format %s", self.groups[0], fmtid)
         fmt["w"] = fmtid
         return fmt