Index: action.py
==================================================================
--- action.py
+++ action.py
@@ -19,15 +19,15 @@
 #
 # As fallback the playlist URL is retrieved and its MIME type
 # checked, then its content regexped to guess the list format.
 # Lastly a playlist format suitable for audio players recreated.
 # Which is somewhat of a security feature; playlists get cleaned
-# up this way. The conversion is not strictly necessary for all
-# players, as basic PLS/M3U is supported by most.
+# up this way. The conversion is not strictly necessary, because
+# baseline PLS/M3U is understood by most players.
 #
-# And finally this module is also used by exporting and (perhaps
-# in the future) playlist importing features (e.g. in DND hooks).
+# And finally this module is also used by exporting and playlist
+# importing features (e.g. by the drag'n'drop module).
 #
 # Still needs some rewrites to transition off the [url] lists,
 # and work with full [rows] primarily. (And perhaps it should be
 # renamed to "playlist" module now).
 
@@ -302,15 +302,15 @@
     content = "\n".join(str.decode(errors='replace') for str in r.iter_lines())
     return (mime, content)
 
 
 
-# Extract URLs from playlist formats:
+# Extract URLs and meta infos (titles) from playlist formats.
 #
-# It's entirely regex-based at the moment, because that's more
-# resilient against mailformed XSPF or JSON.
-# Needs proper extractors later for real playlist *imports*.
+# It's mostly regex-based at the moment, because that's more
+# resilient against mailformed XSPF or JSON. But specialized
+# import helpers can be added as needed.
 #
 class extract_playlist(object):
 
     # Content of playlist file
     src = ""
@@ -383,10 +383,11 @@
                         rows.append({"url":None})
                     rows[i][name] = val;
             log.DATA("pair-rx", rows)
 
         return self.uniq(rows)
+
 
     # Single field
     def field(self, name, rules, src_part):
         if name in rules:
             vals = re.findall(rules[name], src_part, re.X)
@@ -510,10 +511,11 @@
             "format": self.mime_guess(url),
             "genre": "copy",
         }
         comb.update(row)
         return comb
+
 
     # Probe url "extensions" for common media types
     # (only care about the common audio formats, don't need an exact match or pre-probing in practice)
     def mime_guess(self, url):
         audio = re.findall("(ogg|opus|spx|aacp|aac|mpeg|mp3|m4a|mp2|flac|midi|mod|kar|aiff|wma|ram|wav)", url)
@@ -524,26 +526,37 @@
             return "video/{}".format(*audio)
         return "x-audio-video/unknown"
 
 
 
-# Save rows in one of the export formats.
+# Save rows[] in one of the export formats.
+#
+#  → The export() version uses urls[] and a template row{} as input,
+# converts it into a list of complete rows{} beforehand. It's mostly
+# utilized to expand a source playlist, merge in alternative streaming
+# server addresses.
 #
-# The export() version uses urls[]+row/title= as input, converts it into
-# a list of rows{} beforehand.
+#  → With store() a full set of rows[] is required to begin with, as
+# it performs a complete serialization.  Can save directly to a file.
+# Which is often used directly by export functions, when no internal
+# .pls/.m3u urls should be expanded or converted.
 #
-# While store() requires rows{} to begin with, to perform a full
-# conversion. Can save directly to a file name.
+# Note that this can chain to convert_playlist() itself. So there's
+# some danger for neverending loops in here. Never happened, but some
+# careful source= and dest= parameter use is advised. Use source="asis"
+# or "srv" to leave addresses alone, or "href" for input probing.
 #
 class save_playlist(object):
 
     # if converting
     source = "pls"
+ 
     # expand multiple server URLs into duplicate entries in target playlist
     multiply = True
+ 
     # constructor
-    def __init__(self, source, multiply):
+    def __init__(self, source="asis", multiply=False):
         self.source = source
         self.multiply = multiply
     
 
     # Used by playlist_convert(), to transform a list of extracted URLs
@@ -554,10 +567,11 @@
         rows = []
         for url in urls:
             row.update(url=url)
             rows.append(row)
         return self.store(rows, dest)
+
 
     # Export a playlist from rows{}
     def store(self, rows=None, dest="pls"):
     
         # can be just a single entry
@@ -582,10 +596,11 @@
         log.DATA("conversion to:", dest, "  with rows=", rows)
 
         # call conversion schemes
         converter = getattr(self, dest) or self.pls
         return converter(rows)
+
 
     # save directly
     def file(self, rows, dest, fn):
         with open(fn, "w") as f:
             f.write(self.store(rows, dest))