Allow custom sorting when displaying several articles

A new form variable is accepted, "sort", to allow custom sorting when
several articles are rendered (default view, atom feed or list view).

The sort variable uses a very simple sort specification format:

[+-]?<field>?

Where "-" means reverse order, while "+" is regular, ascending, order.
Field specifies what article field will be used when sorting; title,
author, created, updated and uuid are accepted.

Both values are optional, and when one is omitted, a default will be used
according to the type of view being rendered.

Note: since "+" is used to encode " " in URLs, " " is accepted as an alias
for "+" to make easier to write URLs with sort specification manually.

diff --git a/blitiri.cgi b/blitiri.cgi
index 781659958e0539d84d361998cfbf0e464df373f0..d709f305658e43d375171040fcbae698df3e4821 100755 (executable)
--- a/blitiri.cgi
+++ b/blitiri.cgi
@@ -869,20 +869,6 @@ class Article (object):
                        self.load()
                return self._comments
 
-       def __cmp__(self, other):
-               if self.path == other.path:
-                       return 0
-               if not self.created:
-                       return 1
-               if not other.created:
-                       return -1
-               if self.created < other.created:
-                       return -1
-               return 1
-
-       def title_cmp(self, other):
-               return cmp(self.title, other.title)
-
 
        def add_comment(self, author, raw_content, link = ''):
                c = Comment(self, len(self.comments))
@@ -1154,6 +1140,37 @@ def render_style():
        print 'Content-type: text/css\r\n\r\n',
        print default_css
 
+# Get a dictionary with sort() arguments (key and reverse) by parsing the sort
+# specification format:
+# [+-]?<key>?
+# Where "-" is used to specify reverse order, while "+" is regular, ascending,
+# order (reverse = False). The key value is an Article's attribute name (title,
+# author, created, updated and uuid are accepted), and will be used as key for
+# sorting. If a value is omitted, that value is taken from the default, which
+# should be provided using the same format specification, with the difference
+# that all values must be provided for the default.
+def get_sort_args(sort_str, default):
+       def parse(s):
+               d = dict()
+               if not s:
+                       return d
+               key = None
+               if len(s) > 0:
+                       # accept ' ' as an alias of '+' since '+' is translated
+                       # to ' ' in URLs
+                       if s[0] in ('+', ' ', '-'):
+                               key = s[1:]
+                               d['reverse'] = (s[0] == '-')
+                       else:
+                               key = s
+               if key in ('title', 'author', 'created', 'updated', 'uuid'):
+                       d['key'] = lambda a: getattr(a, key)
+               return d
+       args = parse(default)
+       assert args['key'] is not None and args['reverse'] is not None
+       args.update(parse(sort_str))
+       return args
+
 def handle_cgi():
        import cgitb; cgitb.enable()
 
@@ -1162,6 +1179,7 @@ def handle_cgi():
        month = int(form.getfirst("month", 0))
        day = int(form.getfirst("day", 0))
        tags = set(form.getlist("tag"))
+       sort_str = form.getfirst("sort", None)
        uuid = None
        atom = False
        style = False
@@ -1220,7 +1238,7 @@ def handle_cgi():
        db = ArticleDB(os.path.join(data_path, 'db'))
        if atom:
                articles = db.get_articles(tags = tags)
-               articles.sort(reverse = True)
+               articles.sort(**get_sort_args(sort_str, '-created'))
                render_atom(articles[:index_articles])
        elif style:
                render_style()
@@ -1232,7 +1250,7 @@ def handle_cgi():
                render_html( [article], db, year, enable_comments )
        elif artlist:
                articles = db.get_articles()
-               articles.sort(cmp = Article.title_cmp)
+               articles.sort(**get_sort_args(sort_str, '+title'))
                render_artlist(articles, db)
        elif comment and enable_comments:
                form_data = CommentFormData(author.strip().replace('\n', ' '),
@@ -1282,7 +1300,7 @@ def handle_cgi():
                                form_data )
        else:
                articles = db.get_articles(year, month, day, tags)
-               articles.sort(reverse = True)
+               articles.sort(**get_sort_args(sort_str, '-created'))
                if not year and not month and not day and not tags:
                        articles = articles[:index_articles]
                render_html(articles, db, year)