class Schema :

    def __init__(self, schema) :

        self._schema = schema

    def get_attrs(self, entity) :

        return self._schema[entity][0]

    def get_relations(self, entity) :

        return self._schema[entity][1]

    def get_attr_index(self, entity, attr) :

        return list(self._schema[entity][0]).index(attr)

SCHEMA = Schema({'societe': ( ('nom','ville'),

                              [('concerne_par','affaire'),

                               ] ),

                 'affaire': ( ('ref',),

                              [('concerne','societe'),

                               ('concerne_par', 'document')

                               ] ),

                 'document':( ('fichier', 'annee','mois','jour','type'),

                              [('concerne','affaire'),

                               ] ),

                 })

DATA = { 'societe': [ ('CETIAD', 'Dijon'),

                      ('EDF_R&D', 'Clamart'),

                      ('Logilab', 'Paris'),

                      ],

         'affaire': [ ('CTIA01', 'CETIAD'),

                      ('EDFR01', 'EDF_R&D'),

                      ('EDFR02', 'EDF_R&D'),

                      ],

         'document':[ ('CTIA01-040906-PRE-1-01.pdf','2004','09','06','PRE','CTIA01'),

                      ('EDFR01-050201-CLI-1-01.pdf','2005','02','01','CLI','EDFR01'),

                      ('EDFR01-050322-OFR-1-01.pdf','2005','03','22','OFR','EDFR01'),

                      ],

         }

def get_data(entity, where=[]) :

    for value in DATA[entity] :

        for index, val in where :

            if value[index] != val :

                break

        else :

            yield value

class PathParser :

    def __init__(self, schema, path) :

        self.schema = schema

        self.path = path

        self._components = iter([comp for comp in self.path.split('/') if comp])

        self._entity = None

        self._attr = None

        self._rel = None

        self._restrictions = []

    def parse(self) :

        self._entity = self._components.next()

        try:

            self.process_entity()

        except StopIteration :

            pass

    def process_entity(self) :

        _next = self._components.next()

        if _next in self.schema.get_attrs(self._entity) :

            self._attr = _next

            _next = self._components.next()

            self._restrictions.append( (self._entity, self._attr, _next) )

            self._attr = None

            self._rel = None

            self.process_entity()

    def get_list(self) :

        if self._rel :

            return

        elif self._attr :

            where = []

            for e,a,v in self._restrictions :

                i = self.schema.get_attr_index(e, a)

                where.append( (i,v) )

            i = self.schema.get_attr_index(self._entity, self._attr)

            for values in get_data(self._entity,where) :

                yield values[i]+'/'

        else :

            attr_restrict = [a for e,a,v in self._restrictions]

            for attr in self.schema.get_attrs(self._entity) :

                if attr not in attr_restrict :

                    yield attr+'/'

            for data in DATA[self._entity]:

                yield data[0]

            for nom, entity in self.schema.get_relations(self._entity) :

                yield nom+'/'

                yield entity+'/'

def ls(path) :

    p = PathParser(SCHEMA,path)

    p.parse()

    return list(p.get_list())

class SytPathParser :

    def __init__(self, schema, path) :

        self.schema = schema

        self.path = path

        self._components = iter([comp for comp in self.path.split('/') if comp])

        self._e_type = None

        self._restrictions = []

        self._alphabet = list('ABCDEFGHIJKLMNOPQRSTUVWXYZ')

    def parse(self):

        self._var = self._alphabet.pop(0)

        self._e_type = self._components.next()

        e_type = self._e_type.capitalize()

        self._restrictions.append('%s is %s' % (self._var, e_type))

        try:

            self.process_entity()

        except StopIteration :

            pass

        return 'Any %s WHERE %s' % (self._var, ', '.join(self._restrictions))

    def process_entity(self) :

        _next = self._components.next()

        if _next in self.schema.get_attrs(self._e_type) :

            attr = _next

            try:

                _next = self._components.next()

                self._restrictions.append('%s %s %s' % (self._var, attr, _next))

            except StopIteration:

                a_var = self._alphabet.pop(0)

                self._restrictions.append('%s %s %s' % (self._var, attr, a_var) )

                self._var = a_var

                raise

        elif _next in [r for r,e in self.schema.get_relations(self._e_type)]:

            rel = _next

            r_var = self._alphabet.pop(0)

            self._restrictions.append('%s %s %s' % (self._var, rel, r_var))

            self._var = r_var

            try:

                _next = self._components.next()

                self._restrictions.append('%s is %s' % (r_var, _next.capitalize()))

            except StopIteration:

                raise

        self.process_entity()

def to_rql(path) :

    p = SytPathParser(SCHEMA,path)

    return p.parse()