uri templating in python

git-svn-id: http://freebase-python.googlecode.com/svn/trunk@7 5914aa95-5b3a-0410-a3b5-7b719e7fe9b2

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diff --git a/freebase/uritemplate.py b/freebase/uritemplate.py
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+# ========================================================================
+# Copyright (c) 2007, Metaweb Technologies, Inc.
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions
+# are met:
+#     * Redistributions of source code must retain the above copyright
+#       notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+#       copyright notice, this list of conditions and the following
+#       disclaimer in the documentation and/or other materials provided
+#       with the distribution.
+# 
+# THIS SOFTWARE IS PROVIDED BY METAWEB TECHNOLOGIES AND CONTRIBUTORS
+# ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+# FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL METAWEB
+# TECHNOLOGIES OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+# BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+# LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+# CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+# ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+# POSSIBILITY OF SUCH DAMAGE.
+# ========================================================================
+
+#
+# URI Templating in Python
+#
+# see http://bitworking.org/projects/URI-Templates/
+#  and http://bitworking.org/news/URI_Templates
+#
+# this implementation can also parse URIs, as long as the
+#   template is sufficiently specific.  to allow this to work
+#   the '/' character is forbidden in keys when parsing.  
+#   later it should be possible to loosen this restriction.
+#
+# TODO:
+#   simplify the syntax calling in - currently
+#     uri = new URITemplate(ut.template).run({...})
+#   allow parsing to be aware of www. and trailing /
+#   nail down quoting issues
+#
+
+import os, sys, re
+
+class URITemplate(object):
+    VARREF = re.compile(r'\{([0-9a-zA-Z_]+)\}')
+
+    def __init__(self, s):
+        self.template = s;
+
+        self.params = []
+        tsplit = self.VARREF.split(s)
+        rxs = ['^']
+        for i in range(len(tsplit)):
+            if i % 2:
+                # track the vars used
+                self.params.append(tsplit[i])
+                # vars match any string
+                # XXX vars are assumed to lack '/' - this is imperfect...
+                rxs.append('([^/]*)')
+            else:
+                # quote special chars regexp interpretation
+                rxs.append(re.escape(tsplit[i]))
+        rxs.append('$')
+        self._parser = re.compile(''.join(rxs))
+
+    def __repr__(self):
+        return '<URITemplate %r>' % self.template
+
+    def run (self, **args):
+        def repl(m):
+            key = m.group(1)
+            return args[key]
+        
+        uri = self.VARREF.sub(repl,self.template)
+
+        # XXX for testing, compare this to args array
+        if self.parse(uri) is None:
+            print 're-parsing generated uri failed: %r, %r' % (uri, self.template)
+
+        return uri
+
+
+    def parse(self, uri):
+        m = self._parser.match(uri)
+        if m is None:
+            return None
+        return dict(zip(self.params, m.groups()))
+    
+if __name__ == '__main__':
+    ut = URITemplate('xxx{key}yyy')
+    print ut.run(key='ABC')