source: mauRepo/MolesManager/trunk/src/libs/postgisutil.py @ 8423

'''
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 16 Jun 2012

@author: Maurizio Nagni
'''
import logging
import unicodedata

from logging import StreamHandler
ilogging = logging.getLogger('postgisutil')
ilogging.addHandler(StreamHandler())
ilogging.setLevel(logging.INFO)


def create_st_setSRID(west, south, east, north, srid = 4326):
    '''
        Create a string useful to build bounding box for queries
        @param west: the west longitude (in decimal degrees)  
        @param south: the south latitude (in decimal degrees)        
        @param east: the east longitude (in decimal degrees)  
        @param north: the north latitude (in decimal degrees)
        @param srid: an integer value that uniquely identifies the Spatial Referencing System (SRS) within the database       
        @return: Returns a postgis string describing a BOX3D using EPSG:4326 decimal degree
    '''
    return 'st_setSRID(\'BOX3D(%d %d, %d %d)\'::box3d, %d)' \
        % (west, south, east, north, srid)

def unifyGeometries(bboxes, epb):
    return _processGeometries(bboxes, epb, 'ST_Union')

def unifyGeometriesAsBBox(bboxes, epb):
    union = _processGeometries(bboxes, epb, 'ST_Union')
    if union is not None:
        return getBox2D(union, epb)
    return None

def intersectGeometries(bboxes, epb):
    return _processGeometries(bboxes, epb, 'ST_Intersection')

def getBox2D(geometry, epb):
    cmdString = 'SELECT ST_Box2D(st_setSRID(\'%s\', 4326));' % (geometry)
    bbox = normalizeUnicode(epb.executeNative(cmdString).first()[0])
    return bbox
        
def _processGeometries(bboxes, epb, function):
    '''
        Unifies a collection of geometries
        @param bboxes: the collection of bboxes to unify
        @param epb: a 'executeNative' enabled EPB
        @param function: one of the following: ST_Union, ST_Intersection
        @return: a string representing the union or None if invalid or a POINT   
    '''
    if len(bboxes) == 0:
        return None            
    union = None
    for bbox in bboxes:
        if union == None:
            if 'st_setSRID' in bbox:
                unionCmd = 'SELECT ST_AsText(%s);' % (bbox)
            else:
                unionCmd = 'SELECT ST_AsText(ST_GeomFromText(\'%s\',4326));' % (bbox)                    
        else:
            unionCmd = 'SELECT ST_AsText(%s(ST_GeomFromText(\'%s\', 4326), %s));' % (function, union, bbox)
        ilogging.debug(unionCmd)                
        union = normalizeUnicode(epb.executeNative(unionCmd).first()[0])
        if 'POINT(' in union:
                union = None
            
    return union

def normalizeUnicode(text):
    if isinstance(text, unicode):
        return unicodedata.normalize('NFKD', text).encode('ascii','ignore')
    return text