gistfile1.py

# -*- coding: utf-8 -*-

import cherrypy

from cherrypy._cpdispatch import Dispatcher
from sqlalchemy import sql

from amnesia import db

__all__ = ['AmnesiaDispatcher']

class AmnesiaDispatcher(Dispatcher):
    """
    This dispatcher uses a mapping procedure based on the content type of an
    entity. The ID of the entity should always come first in the path info.

    It performs the following steps:
        - check if the id can be found in the path info and is valid
        - query the database to get the corresponding content type
        - adapt (transform) the path info and call the default dispatcher to
          find the handler.

    For example, if object with id=90 is a "page":
        - /90       => /page/show/90
        - /90/show  => /page/show/90
        - /90/edit  => /page/edit/90
        - /90.json  => /page/show/90 (add "X-Accept" header with
                                      "application/json")
        - /90.xml   => /page/show/90 (adapt "X-Accept" header with
                                      "application/xml")
        - ...
     """

    accepts = {
        'json' : 'application/json',
        'xml' : 'application/xml'
    }

    q = '''SELECT ct.name FROM content c JOIN content_type ct ON
           c.content_type_id = ct.id AND c.id = :id'''

    def __call__(self, path_info):
        _path_info = [x for x in path_info.strip('/').split('/', 2) if x]

        if _path_info:
            # Do we have 123 or 123.json or ... ?
            obj_id = _path_info[0].split('.', 1)

            if len(obj_id) == 2:
                # 123.json
                (obj_id, content_type) = obj_id
            else:
                # 123
                (obj_id, content_type) = (obj_id[0], None)

            if obj_id.isdigit():
                # "show" is the default action 
                if not len(_path_info) > 1:
                    _path_info.append('show')

                _path_info.insert(2, obj_id)

                # Fetch content type for obj_id
                r = db.Session.execute(self.q, {'id' : obj_id}).fetchone()

                if r:
                    _path_info[0] = r.name.replace(' ', '_')

                    if content_type in self.accepts:
                        cherrypy.request.headers['X-Accept'] = self.accepts[content_type]

                    return super(AmnesiaDispatcher, self).__call__('/'.join(_path_info))

                raise cherrypy.NotFound()

        return super(AmnesiaDispatcher, self).__call__(path_info)