#!/usr/bin/python
# -*- coding: utf-8; tab-width: 4; indent-tabs-mode: nil; -*-

import re
import imp
import os

class WSGIRouter(object):
    """ parse http uri and call the proper handler (controller in MVC terms)
    """
    def __init__( self, handlers=(), fallback=None ):
        """ handlers = list of tuples in the form ( regex, handler )
            groups in regex are passed to handlers within environ['router.args']

            fallback = if defined, is the default handler to be called if no
            regex in 'handlers' matches
        """
        self.handlers = handlers
        self.fallback = fallback

    def __call__( self, environ, start_response ):
        #
        # search form matching handler
        #
        for regex, handler in self.handlers:
            match = re.match( '^' + regex + '$', environ['SCRIPT_URL'])
            if match:
                environ['router.args'] = match.groups()
                return handler( environ, start_response )

        #
        # use fallback ( if defined )
        #
        if self.fallback:
            environ['router.args'] = [
                token for token in environ['SCRIPT_URL'].split('/') if token ]
            return self.fallback( environ, start_response )

        #
        # last resort
        #
        start_response( '202 Accepted', [('Content-Type', 'text/plain')] )
        return [ "WSGIRouter: I have no route for '%s'" % environ['SCRIPT_URL'] ]

class WSGISmartRouter(object):
    """ like WSGIRouter, but before calling fallback handler,
        searches in 'cont_dir' folder for a file matching the url.

        uri = http://<server[:port]>/lorem/ipsum/dolor/sit

        handler:                             environ['router.args']:

        any handler matching in handlers     - capture groups -
        <cont_dir>/lorem/ipsum/dolor/sit     ()
        <cont_dir>/lorem/ipsum/dolor         ('sit')
        <cont_dir>/lorem/ipsum               ('dolor','sit')
        <cont_dir>/lorem                     ('ipsum','dolor','sit')
        fallback                             ('lorem','ipsum','dolor','sit')
    """
    def __init__( self, handlers=(), fallback=None, cont_dir='.' ):
        self.handlers = handlers
        self.fallback = fallback
        self.cont_dir = os.path.normpath( os.path.join( os.path.split(__file__)[0], cont_dir ) ) + '/'

    def __call__( self, environ, start_response ):
        #
        # search form matching handler
        #
        for regex, handler in self.handlers:
            match = re.match( '^' + regex + '$', environ['SCRIPT_URL'])
            if match:
                environ['router.args'] = match.groups()
                return handler( environ, start_response )

        #
        # search in filesystem for matching file
        #
        tokens = [ token for token in environ['SCRIPT_URL'].split('/') if token ]

        #for idx in range( 1, len( tokens ) + 1 ): # from shortest path to longest one
        # from longest path to shortest one
        for idx in range( len( tokens ) , 0, -1 ):
            module = os.path.normpath( self.cont_dir + '/'.join( tokens[:idx] ) + '.py' )
            args = tokens[idx:]

            try:
                handler = imp.load_source( 'application', module )
                environ['router.args'] = args

                if environ['REQUEST_METHOD'] == 'GET' and hasattr( handler, 'get' ):
                    # FIXME: forse è meglio eseguire QUI la start_response
                    # e compilare il template (solo per GET e POST)
                    return handler.get( environ, start_response )

                elif environ['REQUEST_METHOD'] == 'POST' and hasattr( handler, 'post' ):
                    return handler.post( environ, start_response )

                elif hasattr( handler, 'application' ):
                    return handler.application( environ, start_response )

            except IOError:
                # not found! Better luck next time...
                pass

        #
        # use fallback ( if defined )
        #
        if self.fallback:
            environ['router.args'] = tokens
            return self.fallback( environ, start_response )

        #
        # last resort
        #
        start_response( '202 Accepted', [('Content-Type', 'text/plain')] )
        return [ "WSGISmartRouter: I have no route for '%s'" % environ['SCRIPT_URL'] ]