source: mauRepo/MolesManager/trunk/src/libs/epb.py @ 8445

'''
BSD Licence
Copyright (c) 2012, Science & Technology Facilities Council (STFC)
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.
    * Neither the name of the Science & Technology Facilities Council (STFC) 
        nor the names of its contributors may be used to endorse or promote 
        products derived from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS 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 THE COPYRIGHT OWNER 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.

Created on 10 Jan 2012

@author: Maurizio Nagni
'''
from sqlalchemy.orm import subqueryload
from sqlalchemy.sql.expression import text
from MolesManager.forms.date import methodsWithDecorator

class EPB(object):

    @classmethod
    def buildFilter(cls, key, keyValue):
        try:
            return '%s = \'%s\'' % (key, keyValue)
        except RuntimeError as er:
            print er

    @classmethod
    def search(cls, clazz, inst_key, session):
        """
            Searches a required instance by id
            @param clazz: the class type to search for
            @param inst_key: the instance id for which the search is done. If None return a query object
            @param session: a session to use for the query
            @return the required instance
        """
        if inst_key:
            res = session.query(clazz).get(inst_key)
        else:
            res = session.query(clazz)
            
        if res is None:
            return None
        return res            
        


    @classmethod
    def searchEager(cls, clazz, inst_id, session):
        """
            Searches a required instance by id loading eagerly ALL its field. Please use carefully because \
            it could impact the performance 
            @param clazz: the class type to search for
            @param inst_id: the instance id for which the search is done
            @param session: a session to use for the query    
            @return the required instance                    
        """
        res = session.query(clazz).options(subqueryload('*')).get(inst_id)
        if res is None:
            return None
            
        return res

    @classmethod
    def searchSelectiveLoad(cls, clazz, inst_id, attrs, session):
        """
            Searches a required instance by id loading \
            the specified fields. The parameter "attrs" is a single string or a list of attributes 
            owned by the instance of "clazz". Furthermore such list may contain 
            also the children of the main attributes. For example "attrs" may look 
            like
            ['resultAccumulation', 'identifier.authority', 'resultTime.position.dateTime8601.month', \
                      'relatedParty.party', 'result.source.function', 'permission', \
                      'geographicExtent', 'phenomenonTime', 'keywords', 'description', \
                      'inSupportOf.abstract', 'dataLineage']
            the first parameter refers to the main class so is equivalent to 
            clazz.resultAccumulation
            the second parameter is equivalent to invoke
            clazz.identifier.authority
            As single string "attrs" could be as well just 'identifier.authority'
            @param clazz: the class type to search for
            @param inst_id: the instance id for which the search is done
            @param attrs: a single string or a list of attributes to load 
            @param session: a session to use for the query
            @return the required instance              
        """          
        if session is None:
            raise Exception("Session is None!")        
        res = EPB.search(clazz, inst_id, session)
        if res is None:
            return None
        EPB._drillData(res, attrs)
        return res

    @classmethod
    def loadAttributes(cls, instance, attributes, session):
        """
            Loads the given instance with the required attributes.
            The parameter "attributes" is a single string or a list of attributes 
            owned by the instance of "clazz". Furthermore such list may contain 
            also the children of the main attributes. For example "attrs" may look 
            like
            ['resultAccumulation', 'identifier.authority', 'resultTime.position.dateTime8601.month', \
                      'relatedParty.party', 'result.source.function', 'permission', \
                      'geographicExtent', 'phenomenonTime.*', 'keywords', 'description', \
                      'inSupportOf.abstract', 'dataLineage']
            the first parameter refers to the main class so is equivalent to 
            instance.resultAccumulation
            the second parameter is equivalent to invoke
            instance.identifier.authority
            As single string "attributes" could be as well just 'identifier.authority'
            An universal marker '*' can be used to request a full loading from the attribute downward
            It does not return anything because it does not close the session
            @param instance: an instance containing the appropriate id
            @param attributes: a single string or a list of attributes to load
            @param session: the session to use for the operation                             
        """
        if instance is None:
            raise Exception("Instance is None!")
        if session is None:
            raise Exception("Session is None!")
        session.merge(instance)
        EPB._drillData(instance, attributes)                    


    @classmethod    
    def searchOrCreate(cls, clazz, session, clazz_id = None):
        if clazz_id is not None:
            return EPB.search(clazz, clazz_id, session)
        else:                        
            return clazz()
        

    @classmethod
    def getAllObjects(cls, clazz, session):     
        res = session.query(clazz)
        if res is None:
            return None
        return res

    @classmethod
    def executeNative(self, sqlNative, session):
        return session.execute(text(sqlNative))     

    @classmethod
    def _getSession(cls, dbManager, session = None):
        if session:
            return session        
        return dbManager.createDbSession()

    @classmethod
    def _drillData(cls, obj, attrs):
        """
            @param obj: its an instance already living inside an SQLAlchemy session
            @param attrs: a list of attributes owned by the obj parameter. It accepts dot separated attributes as childern of obj attributes. 
        """
        #if is a single field wrap it in a list and recalls itself
        if not isinstance(attrs, list):
            EPB._drillData(obj, [attrs])
        for item in attrs:
            attr = item.split('.')[0] 
            if attr == '*':
                EPB._drillALLData(obj)         
            elif isinstance(obj, list):
                for element in obj:
                    EPB._drillData(element, [item])
            else:
                if hasattr(obj, attr):
                    nobj = getattr(obj, attr) 
                    if len(attr) != len(item):
                        EPB._drillData(nobj, [item[len(attr) + 1:]])

    @classmethod
    def _drillALLData(cls, obj):
        if obj is None:
            return
        if isinstance(obj, list):
            for element in obj:
                EPB._drillALLData(element)
        else:
            keys = dir(obj)
            keys.extend(list(methodsWithDecorator(type(obj), "property")))
            for key in keys:
                try:
                    if '_' not in key:
                        nobj = getattr(obj, key)
                        EPB._drillALLData(nobj)
                except Exception as e:
                    pass