OsmApi.py

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

###########################################################################
##                                                                       ##
## Copyrights Etienne Chové <chove@crans.org> 2009-2010                  ##
##                                                                       ##
## This program is free software: you can redistribute it and/or modify  ##
## it under the terms of the GNU General Public License as published by  ##
## the Free Software Foundation, either version 3 of the License, or     ##
## (at your option) any later version.                                   ##
##                                                                       ##
## This program is distributed in the hope that it will be useful,       ##
## but WITHOUT ANY WARRANTY; without even the implied warranty of        ##
## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         ##
## GNU General Public License for more details.                          ##
##                                                                       ##
## You should have received a copy of the GNU General Public License     ##
## along with this program.  If not, see <http://www.gnu.org/licenses/>. ##
##                                                                       ##
###########################################################################

## HomePage : http://wiki.openstreetmap.org/wiki/PythonOsmApi

###########################################################################
## History                                                               ##
###########################################################################
## 0.2.19  2010-05-24 Add debug message on ApiError                      ##
## 0.2.18  2010-04-20 Fix ChangesetClose and _http_request               ##
## 0.2.17  2010-01-02 Capabilities implementation                        ##
## 0.2.16  2010-01-02 ChangesetsGet by Alexander Rampp                   ##
## 0.2.15  2009-12-16 xml encoding error for < and >                     ##
## 0.2.14  2009-11-20 changesetautomulti parameter                       ##
## 0.2.13  2009-11-16 modify instead update for osc                      ##
## 0.2.12  2009-11-14 raise ApiError on 4xx errors -- Xoff               ##
## 0.2.11  2009-10-14 unicode error on ChangesetUpload                   ##
## 0.2.10  2009-10-14 RelationFullRecur definition                       ##
## 0.2.9   2009-10-13 automatic changeset management                     ##
##                    ChangesetUpload implementation                     ##
## 0.2.8   2009-10-13 *(Create|Update|Delete) use not unique _do method  ##
## 0.2.7   2009-10-09 implement all missing fonctions except             ##
##                    ChangesetsGet and GetCapabilities                  ##
## 0.2.6   2009-10-09 encoding clean-up                                  ##
## 0.2.5   2009-10-09 implements NodesGet, WaysGet, RelationsGet         ##
##                               ParseOsm, ParseOsc                      ##
## 0.2.4   2009-10-06 clean-up                                           ##
## 0.2.3   2009-09-09 keep http connection alive for multiple request    ##
##                    (Node|Way|Relation)Get return None when object     ##
##                    have been deleted (raising error before)           ##
## 0.2.2   2009-07-13 can identify applications built on top of the lib  ##
## 0.2.1   2009-05-05 some changes in constructor -- chove@crans.org     ##
## 0.2     2009-05-01 initial import                                     ##
###########################################################################

__version__ = '0.2.19'

import httplib, base64, xml.dom.minidom, time, sys, urllib

class ApiError(Exception):
    	
    def __init__(self, status, reason, payload):
        self.status  = status
        self.reason  = reason
        self.payload = payload
    
    def __str__(self):
        return "Request failed: " + str(self.status) + " - " + self.reason + " - " + self.payload

###########################################################################
## Main class                                                            ##

class OsmApi:
        
    def __init__(self,
        username = None,
        password = None,
        passwordfile = None,
        appid = "",
        created_by = "PythonOsmApi/"+__version__,
        api = "www.openstreetmap.org",
        changesetauto = False,
        changesetautotags = {},
        changesetautosize = 500,
        changesetautomulti = 1,
        debug = False,
        proxy_host = None,
        proxy_port = None
        ):
    
        # debug
        self._debug = debug
        
        # Get username
        if username:
            self._username = username
        elif passwordfile:
            self._username =  open(passwordfile).readline().split(":")[0].strip()            
    
        # Get password
        if password:
            self._password   = password
        elif passwordfile:
            for l in open(passwordfile).readlines():
                l = l.strip().split(":")
                if l[0] == self._username:
                    self._password = l[1]

        # Changest informations
        self._changesetauto      = changesetauto      # auto create and close changesets
        self._changesetautotags  = changesetautotags  # tags for automatic created changesets
        self._changesetautosize  = changesetautosize  # change count for auto changeset
        self._changesetautosize  = changesetautosize  # change count for auto changeset
        self._changesetautomulti = changesetautomulti # close a changeset every # upload
        self._changesetautocpt   = 0
        self._changesetautodata  = []                 # data to upload for auto group
        self._proxy_host = proxy_host                 # optional proxy host
        self._proxy_port = proxy_port                 # optional proxy port. Must be a numerical value
        
        # Get API
        self._api = api

        # Get created_by
        if not appid:
            self._created_by = created_by
        else:
            self._created_by = appid + " (" + created_by + ")"

        # Initialisation     
        self._CurrentChangesetId = 0
        
        # Http connection
        if self._proxy_host:
            self._conn = httplib.HTTPConnection(self._proxy_host, self._proxy_port)
        else:
            self._conn = httplib.HTTPConnection(self._api, 80)

    def __del__(self):
        if self._changesetauto:
            self._changesetautoflush(True)
        return None

    #######################################################################
    # Capabilities                                                        #
    #######################################################################
    
    def Capabilities(self):
        """ Returns ApiCapabilities. """
        uri = "/api/capabilities"
        data = self._get(uri)
        data = xml.dom.minidom.parseString(data)
        print data.getElementsByTagName("osm")
        data = data.getElementsByTagName("osm")[0].getElementsByTagName("api")[0]
        result = {}
        for elem in data.childNodes:
            if elem.nodeType <> elem.ELEMENT_NODE:
                continue
            result[elem.nodeName] = {}
            print elem.nodeName
            for k, v in elem.attributes.items():
                try:
                    result[elem.nodeName][k] = float(v)
                except:
                    result[elem.nodeName][k] = v
        return result

    #######################################################################
    # Node                                                                #
    #######################################################################

    def NodeGet(self, NodeId, NodeVersion = -1):
        """ Returns NodeData for node #NodeId. """
        uri = "/api/0.6/node/"+str(NodeId)
        if NodeVersion <> -1: uri += "/"+str(NodeVersion)
        data = self._get(uri)
        if not data: return data
        data = xml.dom.minidom.parseString(data)
        data = data.getElementsByTagName("osm")[0].getElementsByTagName("node")[0]
        return self._DomParseNode(data)

    def NodeCreate(self, NodeData):
        """ Creates a node. Returns updated NodeData (without timestamp). """
        return self._do("create", "node", NodeData)
            
    def NodeUpdate(self, NodeData):
        """ Updates node with NodeData. Returns updated NodeData (without timestamp). """
        return self._do("modify", "node", NodeData)

    def NodeDelete(self, NodeData):
        """ Delete node with NodeData. Returns updated NodeData (without timestamp). """
        return self._do("delete", "node", NodeData)

    def NodeHistory(self, NodeId):
        """ Returns dict(NodeVerrsion: NodeData). """
        uri = "/api/0.6/node/"+str(NodeId)+"/history"
        data = self._get(uri)
        data = xml.dom.minidom.parseString(data)
        result = {}
        for data in data.getElementsByTagName("osm")[0].getElementsByTagName("node"):
            data = self._DomParseNode(data)
            result[data[u"version"]] = data
        return result

    def NodeWays(self, NodeId):
        """ Returns [WayData, ... ] containing node #NodeId. """
        uri = "/api/0.6/node/%d/ways"%NodeId
        data = self._get(uri)
        data = xml.dom.minidom.parseString(data)
        result = []
        for data in data.getElementsByTagName("osm")[0].getElementsByTagName("way"):
            data = self._DomParseRelation(data)
            result.append(data)
        return result
    
    def NodeRelations(self, NodeId):
        """ Returns [RelationData, ... ] containing node #NodeId. """
        uri = "/api/0.6/node/%d/relations"%NodeId
        data = self._get(uri)
        data = xml.dom.minidom.parseString(data)
        result = []
        for data in data.getElementsByTagName("osm")[0].getElementsByTagName("relation"):
            data = self._DomParseRelation(data)
            result.append(data)
        return result

    def NodesGet(self, NodeIdList):
        """ Returns dict(NodeId: NodeData) for each node in NodeIdList """
        uri  = "/api/0.6/nodes?nodes=" + ",".join([str(x) for x in NodeIdList])
        data = self._get(uri)
        data = xml.dom.minidom.parseString(data)
        result = {}
        for data in data.getElementsByTagName("osm")[0].getElementsByTagName("node"):
            data = self._DomParseNode(data)
            result[data[u"id"]] = data
        return result

    #######################################################################
    # Way                                                                 #
    #######################################################################

    def WayGet(self, WayId, WayVersion = -1):
        """ Returns WayData for way #WayId. """
        uri = "/api/0.6/way/"+str(WayId)
        if WayVersion <> -1: uri += "/"+str(WayVersion)
        data = self._get(uri)
        if not data: return data
        data = xml.dom.minidom.parseString(data)
        data = data.getElementsByTagName("osm")[0].getElementsByTagName("way")[0]
        return self._DomParseWay(data)
    
    def WayCreate(self, WayData):
        """ Creates a way. Returns updated WayData (without timestamp). """
        return self._do("create", "way", WayData)

    def WayUpdate(self, WayData):
        """ Updates way with WayData. Returns updated WayData (without timestamp). """
        return self._do("modify", "way", WayData)

    def WayDelete(self, WayData):
        """ Delete way with WayData. Returns updated WayData (without timestamp). """
        return self._do("delete", "way", WayData)

    def WayHistory(self, WayId):
        """ Returns dict(WayVerrsion: WayData). """
        uri = "/api/0.6/way/"+str(WayId)+"/history"
        data = self._get(uri)
        data = xml.dom.minidom.parseString(data)
        result = {}
        for data in data.getElementsByTagName("osm")[0].getElementsByTagName("way"):
            data = self._DomParseWay(data)
            result[data[u"version"]] = data
        return result
    
    def WayRelations(self, WayId):
        """ Returns [RelationData, ...] containing way #WayId. """
        uri = "/api/0.6/way/%d/relations"%WayId
        data = self._get(uri)
        data = xml.dom.minidom.parseString(data)
        result = []
        for data in data.getElementsByTagName("osm")[0].getElementsByTagName("relation"):
            data = self._DomParseRelation(data)
            result.append(data)
        return result

    def WayFull(self, WayId):
        """ Return full data for way WayId as list of {type: node|way|relation, data: {}}. """
        uri = "/api/0.6/way/"+str(WayId)+"/full"
        data = self._get(uri)
        return self.ParseOsm(data)

    def WaysGet(self, WayIdList):
        """ Returns dict(WayId: WayData) for each way in WayIdList """
        uri = "/api/0.6/ways?ways=" + ",".join([str(x) for x in WayIdList])
        data = self._get(uri)
        data = xml.dom.minidom.parseString(data)
        result = {}
        for data in data.getElementsByTagName("osm")[0].getElementsByTagName("way"):
            data = self._DomParseWay(data)
            result[data[u"id"]] = data
        return result

    #######################################################################
    # Relation                                                            #
    #######################################################################

    def RelationGet(self, RelationId, RelationVersion = -1):
        """ Returns RelationData for relation #RelationId. """
        uri = "/api/0.6/relation/"+str(RelationId)
        if RelationVersion <> -1: uri += "/"+str(RelationVersion)
        data = self._get(uri)
        if not data: return data
        data = xml.dom.minidom.parseString(data)
        data = data.getElementsByTagName("osm")[0].getElementsByTagName("relation")[0]
        return self._DomParseRelation(data)

    def RelationCreate(self, RelationData):
        """ Creates a relation. Returns updated RelationData (without timestamp). """
        return self._do("create", "relation", RelationData)
    
    def RelationUpdate(self, RelationData):
        """ Updates relation with RelationData. Returns updated RelationData (without timestamp). """
        return self._do("modify", "relation", RelationData)

    def RelationDelete(self, RelationData):
        """ Delete relation with RelationData. Returns updated RelationData (without timestamp). """
        return self._do("delete", "relation", RelationData)

    def RelationHistory(self, RelationId):
        """ Returns dict(RelationVerrsion: RelationData). """
        uri = "/api/0.6/relation/"+str(RelationId)+"/history"
        data = self._get(uri)
        data = xml.dom.minidom.parseString(data)
        result = {}
        for data in data.getElementsByTagName("osm")[0].getElementsByTagName("relation"):
            data = self._DomParseRelation(data)
            result[data[u"version"]] = data
        return result
    
    def RelationRelations(self, RelationId):
        """ Returns list of RelationData containing relation #RelationId. """
        uri = "/api/0.6/relation/%d/relations"%RelationId
        data = self._get(uri)
        data = xml.dom.minidom.parseString(data)
        result = []
        for data in data.getElementsByTagName("osm")[0].getElementsByTagName("relation"):
            data = self._DomParseRelation(data)
            result.append(data)
        return result

    def RelationFullRecur(self, RelationId):
        """ Return full data for relation RelationId. Recurisve version relation of relations. """
        data = []
        todo = [RelationId]
        done = []
        while todo:
            rid = todo.pop(0)
            done.append(rid)
            temp = self.RelationFull(rid)
            for item in temp:
                if item["type"] <> "relation":
                    continue
                if item["data"]["id"] in done:
                    continue
                todo.append(item["data"]["id"])            
            data += temp
        return data
    
    def RelationFull(self, RelationId):
        """ Return full data for relation RelationId as list of {type: node|way|relation, data: {}}. """
        uri = "/api/0.6/relation/"+str(RelationId)+"/full"
        data = self._get(uri)
        return self.ParseOsm(data)

    def RelationsGet(self, RelationIdList):
        """ Returns dict(RelationId: RelationData) for each relation in RelationIdList """
        uri = "/api/0.6/relations?relations=" + ",".join([str(x) for x in RelationIdList])
        data = self._get(uri)
        data = xml.dom.minidom.parseString(data)
        result = {}
        for data in data.getElementsByTagName("osm")[0].getElementsByTagName("relation"):
            data = self._DomParseRelation(data)
            result[data[u"id"]] = data            
        return result

    #######################################################################
    # Changeset                                                           #
    #######################################################################

    def ChangesetGet(self, ChangesetId):
        """ Returns ChangesetData for changeset #ChangesetId. """
        data = self._get("/api/0.6/changeset/"+str(ChangesetId))
        data = xml.dom.minidom.parseString(data)
        data = data.getElementsByTagName("osm")[0].getElementsByTagName("changeset")[0]
        return self._DomParseChangeset(data)
    
    def ChangesetUpdate(self, ChangesetTags = {}):
        """ Updates current changeset with ChangesetTags. """
        if self._CurrentChangesetId == -1:
            raise Exception, "No changeset currently opened"
        if u"created_by" not in ChangesetTags:
            ChangesetTags[u"created_by"] = self._created_by
        result = self._put("/api/0.6/changeset/"+str(self._CurrentChangesetId), self._XmlBuild("changeset", {u"tag": ChangesetTags}))
        return self._CurrentChangesetId

    def ChangesetCreate(self, ChangesetTags = {}):
        """ Opens a changeset. Returns #ChangesetId. """
        if self._CurrentChangesetId:
            raise Exception, "Changeset alreadey opened"
        if u"created_by" not in ChangesetTags:
            ChangesetTags[u"created_by"] = self._created_by
        result = self._put("/api/0.6/changeset/create", self._XmlBuild("changeset", {u"tag": ChangesetTags}))
        self._CurrentChangesetId = int(result)
        return self._CurrentChangesetId
    
    def ChangesetClose(self):
        """ Closes current changeset. Returns #ChangesetId. """
        if not self._CurrentChangesetId:
            raise Exception, "No changeset currently opened"
        result = self._put("/api/0.6/changeset/"+str(self._CurrentChangesetId)+"/close", u"")
        CurrentChangesetId = self._CurrentChangesetId
        self._CurrentChangesetId = 0
        return CurrentChangesetId

    def ChangesetUpload(self, ChangesData):
        """ Upload data. ChangesData is a list of dict {type: node|way|relation, action: create|delete|modify, data: {}}. Returns list with updated ids. """
        data = ""
        data += u"<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n"
        data += u"<osmChange version=\"0.6\" generator=\"" + self._created_by + "\">\n"
        for change in ChangesData:
            data += u"<"+change["action"]+">\n"
            change["data"]["changeset"] = self._CurrentChangesetId
            data += self._XmlBuild(change["type"], change["data"], False).decode("utf-8")
            data += u"</"+change["action"]+">\n"
        data += u"</osmChange>"
        data = self._http("POST", "/api/0.6/changeset/"+str(self._CurrentChangesetId)+"/upload", True, data.encode("utf-8"))
        data = xml.dom.minidom.parseString(data)
        data = data.getElementsByTagName("diffResult")[0]
        data = [x for x in data.childNodes if x.nodeType == x.ELEMENT_NODE]
        for i in range(len(ChangesData)):
            if ChangesData[i]["action"] == "delete":
                ChangesData[i]["data"].pop("version")
            else:
                ChangesData[i]["data"]["version"] = int(data[i].getAttribute("new_id"))
        return ChangesData
        
    def ChangesetDownload(self, ChangesetId):
        """ Download data from a changeset. Returns list of dict {type: node|way|relation, action: create|delete|modify, data: {}}. """
        uri = "/api/0.6/changeset/"+str(ChangesetId)+"/download"
        data = self._get(uri)
        return self.ParseOsc(data)
    
    def ChangesetsGet(self, min_lon=None, min_lat=None, max_lon=None, max_lat=None,
                      userid=None, username=None,
                      closed_after=None, created_before=None,
                      only_open=False, only_closed=False):
        """ Returns dict(ChangsetId: ChangesetData) matching all criteria. """
        
        uri = "/api/0.6/changesets"
        params = {}
        if min_lon or min_lat or max_lon or max_lat:
            params["bbox"] = ",".join([str(min_lon),str(min_lat),str(max_lon),str(max_lat)])
        if userid:
            params["user"] = userid
        if username:
            params["display_name"] = username
        if closed_after and not created_before:
            params["time"] = closed_after
        if created_before:
            if not closed_after:
                closed_after = "1970-01-01T00:00:00Z"
            params["time"] = closed_after + "," + created_before
        if only_open:
            params["open"] = 1
        if only_closed:
            params["closed"] = 1
            
        if params:
            uri += "?" + urllib.urlencode(params)
                
        data = self._get(uri)
        data = xml.dom.minidom.parseString(data)
        data = data.getElementsByTagName("osm")[0].getElementsByTagName("changeset")
        result = {}
        for curChangeset in data:
            tmpCS = self._DomParseChangeset(curChangeset)
            result[tmpCS["id"]] = tmpCS
        return result
    
    #######################################################################
    # Other                                                               #
    #######################################################################

    def Map(self, min_lon, min_lat, max_lon, max_lat):
        """ Download data in bounding box. Returns list of dict {type: node|way|relation, data: {}}. """
        uri = "/api/0.6/map?bbox=%f,%f,%f,%f"%(min_lon, min_lat, max_lon, max_lat)
        data = self._get(uri)
        return self.ParseOsm(data)

    #######################################################################
    # Data parser                                                         #
    #######################################################################
    
    def ParseOsm(self, data):
        """ Parse osm data. Returns list of dict {type: node|way|relation, data: {}}. """
        data = xml.dom.minidom.parseString(data)
        data = data.getElementsByTagName("osm")[0]
        result = []
        for elem in data.childNodes:
            if elem.nodeName == u"node":
                result.append({u"type": elem.nodeName, u"data": self._DomParseNode(elem)})
            elif elem.nodeName == u"way":
                result.append({u"type": elem.nodeName, u"data": self._DomParseWay(elem)})                        
            elif elem.nodeName == u"relation":
                result.append({u"type": elem.nodeName, u"data": self._DomParseRelation(elem)})
        return result    

    def ParseOsc(self, data):
        """ Parse osc data. Returns list of dict {type: node|way|relation, action: create|delete|modify, data: {}}. """
        data = xml.dom.minidom.parseString(data)
        data = data.getElementsByTagName("osmChange")[0]
        result = []
        for action in data.childNodes:
            if action.nodeName == u"#text": continue
            for elem in action.childNodes:
                if elem.nodeName == u"node":
                    result.append({u"action":action.nodeName, u"type": elem.nodeName, u"data": self._DomParseNode(elem)})
                elif elem.nodeName == u"way":
                    result.append({u"action":action.nodeName, u"type": elem.nodeName, u"data": self._DomParseWay(elem)})                        
                elif elem.nodeName == u"relation":
                    result.append({u"action":action.nodeName, u"type": elem.nodeName, u"data": self._DomParseRelation(elem)})
        return result

    #######################################################################
    # Internal http function                                              #
    #######################################################################

    def _do(self, action, OsmType, OsmData):
        if self._changesetauto:
            self._changesetautodata.append({"action":action, "type":OsmType, "data":OsmData})
            self._changesetautoflush()
            return None
        else:
            return self._do_manu(action, OsmType, OsmData)
            
    def _do_manu(self, action, OsmType, OsmData):        
        if not self._CurrentChangesetId:
            raise Exception, "You need to open a changeset before uploading data"
        if u"timestamp" in OsmData:
            OsmData.pop(u"timestamp")
        OsmData[u"changeset"] = self._CurrentChangesetId
        if action == "create":
            if OsmData.get(u"id", -1) > 0:
                raise Exception, "This "+OsmType+" already exists"
            result = self._put("/api/0.6/"+OsmType+"/create", self._XmlBuild(OsmType, OsmData))
            OsmData[u"id"] = int(result.strip())
            OsmData[u"version"] = 1
            return OsmData
        elif action == "modify":
            result = self._put("/api/0.6/"+OsmType+"/"+str(OsmData[u"id"]), self._XmlBuild(OsmType, OsmData))
            OsmData[u"version"] = int(result.strip())
            return OsmData
        elif action =="delete":
            result = self._delete("/api/0.6/"+OsmType+"/"+str(OsmData[u"id"]), self._XmlBuild(OsmType, OsmData))
            OsmData[u"version"] = int(result.strip())
            OsmData[u"visible"] = False
            return OsmData
    
    def flush(self):
        return self._changesetautoflush(True)
        
    def _changesetautoflush(self, force = False):
        while (len(self._changesetautodata) >= self._changesetautosize) or (force and self._changesetautodata):
            if self._changesetautocpt == 0:
                self.ChangesetCreate(self._changesetautotags)
            self.ChangesetUpload(self._changesetautodata[:self._changesetautosize])
            self._changesetautodata = self._changesetautodata[self._changesetautosize:]
            self._changesetautocpt += 1
            if self._changesetautocpt == self._changesetautomulti:
                self.ChangesetClose()
                self._changesetautocpt = 0
        if self._changesetautocpt and force:
            self.ChangesetClose()
            self._changesetautocpt = 0
        return None
        
    def _http_request(self, cmd, path, auth, send):
        if self._debug:
            path2 = path
            if len(path2) > 50:
                path2 = path2[:50]+"[...]"
            print >>sys.stderr, "%s %s %s"%(time.strftime("%Y-%m-%d %H:%M:%S"),cmd,path2)
        self._conn.putrequest(cmd, path)
        self._conn.putheader('User-Agent', self._created_by)
        if auth:
            self._conn.putheader('Authorization', 'Basic ' + base64.encodestring(self._username + ':' + self._password).strip())
        if send <> None:
            self._conn.putheader('Content-Length', len(send))
        self._conn.endheaders()
        if send:
            self._conn.send(send)
        response = self._conn.getresponse()
        if response.status <> 200:
            payload = response.read().strip()
            if response.status == 410:
                return None
            raise ApiError(response.status, response.reason, payload)
        if self._debug:
            print >>sys.stderr, "%s %s %s done"%(time.strftime("%Y-%m-%d %H:%M:%S"),cmd,path2)
        return response.read()
    
    def _http(self, cmd, path, auth, send):

        if self._proxy_host:
            path = self._api + path

        i = 0
        while True:
            i += 1
            try:
                return self._http_request(cmd, path, auth, send)
            except ApiError, e:
                if e.status >= 500:
                    if i == 5: raise
                    if i <> 1: time.sleep(5)
                    self._conn = httplib.HTTPConnection(self._api, 80)
                else: raise
            except Exception:
                if i == 5: raise
                if i <> 1: time.sleep(5)
                self._conn = httplib.HTTPConnection(self._api, 80)
    
    def _get(self, path):
        return self._http('GET', path, False, None)

    def _put(self, path, data):
        return self._http('PUT', path, True, data)
    
    def _delete(self, path, data):
        return self._http('DELETE', path, True, data)
    
    #######################################################################
    # Internal dom function                                               #
    #######################################################################
    
    def _DomGetAttributes(self, DomElement):
        """ Returns a formated dictionnary of attributes of a DomElement. """
        result = {}
        for k, v in DomElement.attributes.items():
            if k == u"uid"         : v = int(v)
            elif k == u"changeset" : v = int(v)
            elif k == u"version"   : v = int(v)
            elif k == u"id"        : v = int(v)
            elif k == u"lat"       : v = float(v)
            elif k == u"lon"       : v = float(v)
            elif k == u"open"      : v = v=="true"
            elif k == u"visible"   : v = v=="true"
            elif k == u"ref"       : v = int(v)
            result[k] = v
        return result            
        
    def _DomGetTag(self, DomElement):
        """ Returns the dictionnary of tags of a DomElement. """
        result = {}
        for t in DomElement.getElementsByTagName("tag"):
            k = t.attributes["k"].value
            v = t.attributes["v"].value
            result[k] = v
        return result

    def _DomGetNd(self, DomElement):
        """ Returns the list of nodes of a DomElement. """
        result = []
        for t in DomElement.getElementsByTagName("nd"):
            result.append(int(int(t.attributes["ref"].value)))
        return result            

    def _DomGetMember(self, DomElement):
        """ Returns a list of relation members. """
        result = []
        for m in DomElement.getElementsByTagName("member"):
            result.append(self._DomGetAttributes(m))
        return result

    def _DomParseNode(self, DomElement):
        """ Returns NodeData for the node. """
        result = self._DomGetAttributes(DomElement)
        result[u"tag"] = self._DomGetTag(DomElement)
        return result

    def _DomParseWay(self, DomElement):
        """ Returns WayData for the way. """
        result = self._DomGetAttributes(DomElement)
        result[u"tag"] = self._DomGetTag(DomElement)
        result[u"nd"]  = self._DomGetNd(DomElement)        
        return result
    
    def _DomParseRelation(self, DomElement):
        """ Returns RelationData for the relation. """
        result = self._DomGetAttributes(DomElement)
        result[u"tag"]    = self._DomGetTag(DomElement)
        result[u"member"] = self._DomGetMember(DomElement)
        return result

    def _DomParseChangeset(self, DomElement):
        """ Returns ChangesetData for the changeset. """
        result = self._DomGetAttributes(DomElement)
        result[u"tag"] = self._DomGetTag(DomElement)
        return result

    #######################################################################
    # Internal xml builder                                                #
    #######################################################################

    def _XmlBuild(self, ElementType, ElementData, WithHeaders = True):

        xml  = u""
        if WithHeaders:
            xml += u"<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n"
            xml += u"<osm version=\"0.6\" generator=\"" + self._created_by + "\">\n"

        # <element attr="val">
        xml += u"  <" + ElementType
        if u"id" in ElementData:
            xml += u" id=\"" + str(ElementData[u"id"]) + u"\""        
        if u"lat" in ElementData:
            xml += u" lat=\"" + str(ElementData[u"lat"]) + u"\""        
        if u"lon" in ElementData:
            xml += u" lon=\"" + str(ElementData[u"lon"]) + u"\""
        if u"version" in ElementData:
            xml += u" version=\"" + str(ElementData[u"version"]) + u"\""
        xml += u" visible=\"" + str(ElementData.get(u"visible", True)).lower() + u"\""
        if ElementType in [u"node", u"way", u"relation"]:
            xml += u" changeset=\"" + str(self._CurrentChangesetId) + u"\""
        xml += u">\n"

        # <tag... />
        for k, v in ElementData.get(u"tag", {}).items():
            xml += u"    <tag k=\""+self._XmlEncode(k)+u"\" v=\""+self._XmlEncode(v)+u"\"/>\n"

        # <member... />
        for member in ElementData.get(u"member", []):
            xml += u"    <member type=\""+member[u"type"]+"\" ref=\""+str(member[u"ref"])+u"\" role=\""+self._XmlEncode(member[u"role"])+"\"/>\n"

        # <nd... />
        for ref in ElementData.get(u"nd", []):
            xml += u"    <nd ref=\""+str(ref)+u"\"/>\n"

        # </element>
        xml += u"  </" + ElementType + u">\n"
        
        if WithHeaders:
            xml += u"</osm>\n"

        return xml.encode("utf8")

    def _XmlEncode(self, text):
        return text.replace("&", "&amp;").replace("\"", "&quot;").replace("<","&lt;").replace(">","&gt;")

## End of main class                                                     ##
###########################################################################