add '--items' option

this allows to specify which manga-chapters/comic-issues to download
when using gallery-dl on a manga/comic URL

gallery_dl/__init__.py

@@ -51,6 +51,13 @@ def build_cmdline_parser():
         metavar="FILE", dest="inputfile",
         help="download URLs found in local FILE",
     )
+    parser.add_argument(
+        "--items",
+        metavar="ITEM-SPEC", dest="items",
+        help=("specify which items to download through a comma seperated list "
+              "of indices or index-ranges; for example '--items -2,4,6-8,10-' "
+              "will download items 1, 2, 4, 6, 7, 8 and 10 up to the last one")
+    )
     parser.add_argument(
         "-c", "--config",
         metavar="CFG", dest="cfgfiles", action="append",
@@ -120,6 +127,8 @@ def main():
             config.set(("username",), args.username)
         if args.password:
             config.set(("password",), args.password)
+        if args.items:
+            config.set(("items",), args.items)
 
         for opt in args.option:
             parse_option(opt)

gallery_dl/job.py

@@ -1,6 +1,6 @@
 # -*- coding: utf-8 -*-
 
-# Copyright 2015, 2016 Mike Fährmann
+# Copyright 2015-2017 Mike Fährmann
 #
 # This program is free software; you can redistribute it and/or modify
 # it under the terms of the GNU General Public License version 2 as
@@ -8,7 +8,7 @@
 
 import json
 import hashlib
-from . import extractor, downloader, path, output, exception
+from . import extractor, downloader, config, util, path, output, exception
 from .extractor.message import Message
 
 
@@ -81,6 +81,9 @@ class DownloadJob(Job):
     def run(self):
         Job.run(self)
         if self.queue:
+            itemspec = config.get(("items",))
+            if itemspec:
+                self.queue = util.apply_range(self.queue, str(itemspec))
             for url in self.queue:
                 try:
                     DownloadJob(url).run()

gallery_dl/util.py

@@ -0,0 +1,47 @@
+# -*- coding: utf-8 -*-
+
+# Copyright 2017 Mike Fährmann
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License version 2 as
+# published by the Free Software Foundation.
+
+"""Utility functions"""
+
+
+def apply_range(iterable, rangespec):
+    """Return a new iterable containing only the items specified in the given
+    integer range
+    """
+    try:
+        maxval = len(iterable)
+    except TypeError:
+        maxval = 0
+    rset = parse_range(rangespec, maxval)
+    return (
+        item
+        for index, item in enumerate(iterable, 1)
+        if index in rset
+    )
+
+
+def parse_range(rangespec, maxval=0):
+    """Parse an integer range and return the resulting set
+
+    Examples
+        parse_range("-2,4,6-8,10-", 12)  -> set(1, 2, 4, 6, 7, 8, 10, 11, 12)
+        parse_range(" - 3 , 4-  4, 6-2") -> set(1, 2, 3, 4)
+    """
+    result = set()
+    for group in rangespec.split(","):
+        parts = group.split("-", maxsplit=1)
+        try:
+            if len(parts) == 1:
+                result.add(int(parts[0]))
+            else:
+                beg = int(parts[0]) if parts[0].strip() else 1
+                end = int(parts[1]) if parts[1].strip() else maxval
+                result.update(range(beg, end+1))
+        except ValueError:
+            pass
+    return result