wmsproxy.cgi

#!/usr/bin/env python
#-*- coding: utf-8 -*-

"""This is a proxy that we use to redirect to available WMS servers based on BBOX"""

"""
Copyright 2011 Camptocamp. All rights reserved.

Redistribution and use in source and binary forms, with or without modification, are
permitted provided that the following conditions are met:

   1. Redistributions of source code must retain the above copyright notice, this list of
      conditions and the following disclaimer.

   2. 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.

THIS SOFTWARE IS PROVIDED BY CAMPTOCAMP ``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 CAMPTOCAMP 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.

The views and conclusions contained in the software and documentation are those of the
authors and should not be interpreted as representing official policies, either expressed
or implied, of Camptocamp.
"""

config = {
    # rules are tested in the order they are defined.
    # the first match (regarding strict inclusion) is used for proxying    
    # if none matches, the default service url is used
    # Note: bbox is defined in epsg:4326 but any incoming projection is supported
    'rules': [{
        'bbox': [-5, 41, 10, 51], # France
        'service_url': 'http://www.ifremer.fr/services/wms1?',
        'layers': 'france_metropolitaine'
    },{
        'bbox': [-10, 35, 15, 55], # Europe
        'service_url': 'http://www.ifremer.fr/services/wms1?',
        'layers': 'Europe'
    }],
    'default_service_url': 'http://www.ifremer.fr/services/wms1?'
}

# DO NOT MODIFY ANYTHING BELOW THIS #
# (unless you know what you're doing)

import cgi
import sys, os

try:
    from osgeo import ogr
except:
    import ogr

try:
    from osgeo import osr
except:
    import osr


''' Gets a CGI var '''
def getVar(key, d):
    if d.has_key(key.lower()):
        return d[key.lower()][0]
    elif d.has_key(key.upper()):
        return d[key.upper()][0]
    else:
        return None


''' Checks whether coord2 is between coord1 and coord3 '''
def isBetween(coord1, coord2, coord3):
    return ((coord1 <= coord2) and (coord2 <= coord3))


'''Checks that bbox a is strictly included in bbox b'''
def checkBboxInclusion(a, b):
    return (isBetween(b[0], a[0], b[2]) and isBetween(b[1], a[1], b[3]) and isBetween(b[0], a[2], b[2]) and isBetween(b[1], a[3], b[3]))


'''Converts a bbox to string'''
def bbox2String(bbox):
    return (','.join([str(o) for o in bbox]))

def redirect(url):
    print "Status: 302 Found"
    print "Location: "+url
    print

query_string = os.environ['QUERY_STRING']
d = cgi.parse_qs(query_string)

debug = d.has_key("DEBUG") or d.has_key("debug")
if debug:
    print "Status: 200 OK"
    print "Content-Type: text/plain"
    print
    print "QUERY_STRING = "+query_string

request = getVar('request', d)
width = getVar('width', d)
height = getVar('height', d)
bbox = getVar('bbox', d)
srs = getVar('srs', d)

if ((request == None) or (request.upper() != 'GETMAP') or (width == None) or (width == 0) or (height == None) or (height == 0) or (bbox == None) or (srs == None)):
    if debug:
        print "Redirecting to default service url ..."
    redirect(config['default_service_url'] + query_string)
    sys.exit(0)

bbox = bbox.split(',')
bbox = [float(o) for o in bbox]

# reproject bbox to EPSG:4326 if required:
if (srs.upper() != 'EPSG:4326'):
    epsg4326 = osr.SpatialReference()
    epsg4326.ImportFromEPSG(4326)

    inputSRS = osr.SpatialReference()
    inputSRS.ImportFromEPSG(int(srs.split(':')[1]))

    toWGS = osr.CoordinateTransformation(inputSRS,epsg4326)

    lb = ogr.Geometry(ogr.wkbPoint)

    lb.AddPoint(bbox[0],bbox[1])
    rt = ogr.Geometry(ogr.wkbPoint)

    rt.AddPoint(bbox[2],bbox[3])

    lt = ogr.Geometry(ogr.wkbPoint)
    lt.AddPoint(bbox[0],bbox[3])
    rb = ogr.Geometry(ogr.wkbPoint)
    rb.AddPoint(bbox[2],bbox[1])

    lb.Transform(toWGS)
    rt.Transform(toWGS)
    lt.Transform(toWGS)
    rb.Transform(toWGS)

    left = min(lb.GetX(),lt.GetX())
    bottom = min(lb.GetY(),rb.GetY())
    right = max(rb.GetX(),rt.GetX())
    top = max(lt.GetY(),rt.GetY())
    bbox = [left, bottom, right, top]
    if debug:
        print "REPROJECTED BBOX = "+bbox2String(bbox)+'\n'

url = config['default_service_url'] + query_string

for rule in config['rules']:
    if debug:
        print "Checking rule: "+rule['layers']
        print "Is bbox "+bbox2String(bbox)+" included in "+bbox2String(rule['bbox'])+" ?" 

    if (checkBboxInclusion(bbox, rule['bbox'])):
        if debug:
            print "Yes"
        
        parts = query_string.split('&')
        qstr = {}
        for part in parts:
            kv = part.split('=')
            if (len(kv)==2):
                qstr[kv[0]] = kv[1]
        
        qstr['LAYERS'] = rule['layers']
        
        parts = {}
        for key,val in qstr.iteritems():
            parts[key+'='+val] = '-'
        
        url = rule['service_url'] + '&'.join(parts)

        break
    elif debug:
        print 'No => checking next rule ...\n'

redirect(url)