1 files changed, 123 insertions, 0 deletions
diff --git a/meetingtools/mimeparse.py b/meetingtools/mimeparse.py
new file mode 100644
index 0000000..0fd91e7
--- /dev/null
+++ b/meetingtools/mimeparse.py
@@ -0,0 +1,123 @@
+"""MIME-Type Parser
+
+This module provides basic functions for handling mime-types. It can handle
+matching mime-types against a list of media-ranges. See section 14.1 of 
+the HTTP specification [RFC 2616] for a complete explanation.
+
+   http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.1
+
+Contents:
+    - parse_mime_type():   Parses a mime-type into its component parts.
+    - parse_media_range(): Media-ranges are mime-types with wild-cards and a 'q' quality parameter.
+    - quality():           Determines the quality ('q') of a mime-type when compared against a list of media-ranges.
+    - quality_parsed():    Just like quality() except the second parameter must be pre-parsed.
+    - best_match():        Choose the mime-type with the highest quality ('q') from a list of candidates. 
+"""
+
+__version__ = "0.1.2"
+__author__ = 'Joe Gregorio'
+__email__ = "joe@bitworking.org"
+__credits__ = ""
+
+def parse_mime_type(mime_type):
+    """Carves up a mime-type and returns a tuple of the
+       (type, subtype, params) where 'params' is a dictionary
+       of all the parameters for the media range.
+       For example, the media range 'application/xhtml;q=0.5' would
+       get parsed into:
+
+       ('application', 'xhtml', {'q', '0.5'})
+       """
+    parts = mime_type.split(";")
+    params = dict([tuple([s.strip() for s in param.split("=")])\
+            for param in parts[1:] ])
+    full_type = parts[0].strip()
+    # Java URLConnection class sends an Accept header that includes a single "*"
+    # Turn it into a legal wildcard.
+    if full_type == '*': full_type = '*/*'
+    (type, subtype) = full_type.split("/")
+    return (type.strip(), subtype.strip(), params)
+
+def parse_media_range(range):
+    """Carves up a media range and returns a tuple of the
+       (type, subtype, params) where 'params' is a dictionary
+       of all the parameters for the media range.
+       For example, the media range 'application/*;q=0.5' would
+       get parsed into:
+
+       ('application', '*', {'q', '0.5'})
+
+       In addition this function also guarantees that there 
+       is a value for 'q' in the params dictionary, filling it
+       in with a proper default if necessary.
+       """
+    (type, subtype, params) = parse_mime_type(range)
+    if not params.has_key('q') or not params['q'] or \
+            not float(params['q']) or float(params['q']) > 1\
+            or float(params['q']) < 0:
+        params['q'] = '1'
+    return (type, subtype, params)
+
+def fitness_and_quality_parsed(mime_type, parsed_ranges):
+    """Find the best match for a given mime-type against 
+       a list of media_ranges that have already been 
+       parsed by parse_media_range(). Returns a tuple of
+       the fitness value and the value of the 'q' quality
+       parameter of the best match, or (-1, 0) if no match
+       was found. Just as for quality_parsed(), 'parsed_ranges'
+       must be a list of parsed media ranges. """
+    best_fitness = -1 
+    best_fit_q = 0
+    (target_type, target_subtype, target_params) =\
+            parse_media_range(mime_type)
+    for (type, subtype, params) in parsed_ranges:
+        if (type == target_type or type == '*' or target_type == '*') and \
+                (subtype == target_subtype or subtype == '*' or target_subtype == '*'):
+            param_matches = reduce(lambda x, y: x+y, [1 for (key, value) in \
+                    target_params.iteritems() if key != 'q' and \
+                    params.has_key(key) and value == params[key]], 0)
+            fitness = (type == target_type) and 100 or 0
+            fitness += (subtype == target_subtype) and 10 or 0
+            fitness += param_matches
+            if fitness > best_fitness:
+                best_fitness = fitness
+                best_fit_q = params['q']
+            
+    return best_fitness, float(best_fit_q)
+
+def quality_parsed(mime_type, parsed_ranges):
+    """Find the best match for a given mime-type against
+    a list of media_ranges that have already been
+    parsed by parse_media_range(). Returns the
+    'q' quality parameter of the best match, 0 if no
+    match was found. This function bahaves the same as quality()
+    except that 'parsed_ranges' must be a list of
+    parsed media ranges. """
+    return fitness_and_quality_parsed(mime_type, parsed_ranges)[1]
+
+def quality(mime_type, ranges):
+    """Returns the quality 'q' of a mime-type when compared
+    against the media-ranges in ranges. For example:
+
+    >>> quality('text/html','text/*;q=0.3, text/html;q=0.7, text/html;level=1, text/html;level=2;q=0.4, */*;q=0.5')
+    0.7
+    
+    """ 
+    parsed_ranges = [parse_media_range(r) for r in ranges.split(",")]
+    return quality_parsed(mime_type, parsed_ranges)
+
+def best_match(supported, header):
+    """Takes a list of supported mime-types and finds the best
+    match for all the media-ranges listed in header. The value of
+    header must be a string that conforms to the format of the 
+    HTTP Accept: header. The value of 'supported' is a list of
+    mime-types.
+    
+    >>> best_match(['application/xbel+xml', 'text/xml'], 'text/*;q=0.5,*/*; q=0.1')
+    'text/xml'
+    """
+    parsed_header = [parse_media_range(r) for r in header.split(",")]
+    weighted_matches = [(fitness_and_quality_parsed(mime_type, parsed_header), mime_type)\
+            for mime_type in supported]
+    weighted_matches.sort()
+    return weighted_matches[-1][0][1] and weighted_matches[-1][1] or ''