#!/usr/bin/env python

# Pylint: Disable name warnings
# pylint: disable-msg=C0103

"""Load and process SRTM data. Originally written by OpenStreetMap
Edited by CanberraUAV"""

from HTMLParser import HTMLParser
import httplib
import re
import pickle
import os.path
import os
import zipfile
import array
import math
import multiprocessing
from MAVProxy.modules.lib import mp_util
import tempfile

childTileDownload = {}
childFileListDownload = {}
filelistDownloadActive = 0

class NoSuchTileError(Exception):
    """Raised when there is no tile for a region."""
    def __init__(self, lat, lon):
        Exception.__init__(self)
        self.lat = lat
        self.lon = lon

    def __str__(self):
        return "No SRTM tile for %d, %d available!" % (self.lat, self.lon)


class WrongTileError(Exception):
    """Raised when the value of a pixel outside the tile area is requested."""
    def __init__(self, tile_lat, tile_lon, req_lat, req_lon):
        Exception.__init__(self)
        self.tile_lat = tile_lat
        self.tile_lon = tile_lon
        self.req_lat = req_lat
        self.req_lon = req_lon

    def __str__(self):
        return "SRTM tile for %d, %d does not contain data for %d, %d!" % (
            self.tile_lat, self.tile_lon, self.req_lat, self.req_lon)

class InvalidTileError(Exception):
    """Raised when the SRTM tile file contains invalid data."""
    def __init__(self, lat, lon):
        Exception.__init__(self)
        self.lat = lat
        self.lon = lon

    def __str__(self):
        return "SRTM tile for %d, %d is invalid!" % (self.lat, self.lon)

class SRTMDownloader():
    """Automatically download SRTM tiles."""
    def __init__(self, server="firmware.ardupilot.org",
                 directory="/SRTM/",
                 cachedir=None,
                 offline=0,
                 debug=False):

        if cachedir is None:
            try:
                cachedir = os.path.join(os.environ['HOME'], '.tilecache/SRTM')
            except Exception:
                cachedir = os.path.join(tempfile.gettempdir(), 'MAVProxySRTM')

        self.debug = debug
        self.offline = offline
        self.offlinemessageshown = 0
        if self.offline == 1 and self.debug:
            print("Map Module in Offline mode")
        self.first_failure = False
        self.server = server
        self.directory = directory
        self.cachedir = cachedir
        if self.debug:
            print("SRTMDownloader - server=%s, directory=%s." % (self.server, self.directory))
        if not os.path.exists(cachedir):
            mp_util.mkdir_p(cachedir)
        self.filelist = {}
        self.filename_regex = re.compile(
                r"([NS])(\d{2})([EW])(\d{3})\.hgt\.zip")
        self.filelist_file = os.path.join(self.cachedir, "filelist_python")
        self.min_filelist_len = 14500

    def loadFileList(self):
        """Load a previously created file list or create a new one if none is
            available."""
        try:
            data = open(self.filelist_file, 'rb')
        except IOError:
            '''print("No SRTM cached file list. Creating new one!")'''
            if self.offline == 0:
                self.createFileList()
            return
        try:
            self.filelist = pickle.load(data)
            data.close()
            if len(self.filelist) < self.min_filelist_len:
                self.filelist = {}
                if self.offline == 0:
                    self.createFileList()
        except:
            '''print("Unknown error loading cached SRTM file list. Creating new one!")'''
            if self.offline == 0:
                self.createFileList()

    def createFileList(self):
        """SRTM data is split into different directories, get a list of all of
            them and create a dictionary for easy lookup."""
        global childFileListDownload
        global filelistDownloadActive
        mypid = os.getpid()
        if mypid not in childFileListDownload or not childFileListDownload[mypid].is_alive():
            childFileListDownload[mypid] = multiprocessing.Process(target=self.createFileListHTTP)
            filelistDownloadActive = 1
            childFileListDownload[mypid].start()
            filelistDownloadActive = 0

    def getURIWithRedirect(self, url):
        '''fetch a URL with redirect handling'''
        tries = 0
        while tries < 5:
                conn = httplib.HTTPConnection(self.server)
                conn.request("GET", url)
                r1 = conn.getresponse()
                if r1.status in [301, 302, 303, 307]:
                    location = r1.getheader('Location')
                    if self.debug:
                        print("redirect from %s to %s" % (url, location))
                    url = location
                    conn.close()
                    tries += 1
                    continue
                data = r1.read()
                conn.close()
                return data
        return None

    def createFileListHTTP(self):
        """Create a list of the available SRTM files on the server using
        HTTP file transfer protocol (rather than ftp).
        30may2010  GJ ORIGINAL VERSION
        """
        mp_util.child_close_fds()
        if self.debug:
            print("Connecting to %s" % self.server, self.directory)
        try:
            data = self.getURIWithRedirect(self.directory)
        except Exception:
            return
        parser = parseHTMLDirectoryListing()
        parser.feed(data)
        continents = parser.getDirListing()
        if self.debug:
            print('continents: ', continents)

        for continent in continents:
            if not continent[0].isalpha() or continent.startswith('README'):
                continue
            if self.debug:
                print("Downloading file list for: ", continent)
            url = "%s%s" % (self.directory,continent)
            if self.debug:
                print("fetching %s" % url)
            try:
                data = self.getURIWithRedirect(url)
            except Exception as ex:
                print("Failed to download %s : %s" % (url, ex))
                continue
            parser = parseHTMLDirectoryListing()
            parser.feed(data)
            files = parser.getDirListing()

            for filename in files:
                self.filelist[self.parseFilename(filename)] = (
                            continent, filename)

            '''print(self.filelist)'''
        # Add meta info
        self.filelist["server"] = self.server
        self.filelist["directory"] = self.directory
        tmpname = self.filelist_file + ".tmp"
        with open(tmpname , 'wb') as output:
            pickle.dump(self.filelist, output)
            output.close()
            try:
                os.unlink(self.filelist_file)
            except Exception:
                pass
            try:
                os.rename(tmpname, self.filelist_file)
            except Exception:
                pass
        if self.debug:
            print("created file list with %u entries" % len(self.filelist))

    def parseFilename(self, filename):
        """Get lat/lon values from filename."""
        match = self.filename_regex.match(filename)
        if match is None:
            # TODO?: Raise exception?
            '''print("Filename", filename, "unrecognized!")'''
            return None
        lat = int(match.group(2))
        lon = int(match.group(4))
        if match.group(1) == "S":
            lat = -lat
        if match.group(3) == "W":
            lon = -lon
        return lat, lon

    def getTile(self, lat, lon):
        """Get a SRTM tile object. This function can return either an SRTM1 or
            SRTM3 object depending on what is available, however currently it
            only returns SRTM3 objects."""
        global childFileListDownload
        global filelistDownloadActive
        mypid = os.getpid()
        if mypid in childFileListDownload and childFileListDownload[mypid].is_alive():
            if self.debug:
                print("still getting file list")
            return 0
        elif not os.path.isfile(self.filelist_file) and filelistDownloadActive == 0:
            self.createFileList()
            return 0
        elif not self.filelist:
            if self.debug:
                print("Filelist download complete, loading data ", self.filelist_file)
            data = open(self.filelist_file, 'rb')
            self.filelist = pickle.load(data)
            data.close()

        try:
            continent, filename = self.filelist[(int(lat), int(lon))]
        except KeyError:
            if len(self.filelist) > self.min_filelist_len:
                # we appear to have a full filelist - this must be ocean
                return SRTMOceanTile(int(lat), int(lon))
            return 0

        global childTileDownload
        mypid = os.getpid()
        if not os.path.exists(os.path.join(self.cachedir, filename)):
            if not mypid in childTileDownload or not childTileDownload[mypid].is_alive():
                try:
                    childTileDownload[mypid] = multiprocessing.Process(target=self.downloadTile, args=(str(continent), str(filename)))
                    childTileDownload[mypid].start()
                except Exception as ex:
                    if mypid in childTileDownload:
                        childTileDownload.pop(mypid)
                    return 0
                '''print("Getting Tile")'''
            return 0
        elif mypid in childTileDownload and childTileDownload[mypid].is_alive():
            '''print("Still Getting Tile")'''
            return 0
        # TODO: Currently we create a new tile object each time.
        # Caching is required for improved performance.
        try:
            return SRTMTile(os.path.join(self.cachedir, filename), int(lat), int(lon))
        except InvalidTileError:
            return 0

    def downloadTile(self, continent, filename):
        #Use HTTP
        mp_util.child_close_fds()
        if self.offline == 1:
            return
        filepath = "%s%s%s" % \
                     (self.directory,continent,filename)
        try:
            data = self.getURIWithRedirect(filepath)
            if data:
                self.ftpfile = open(os.path.join(self.cachedir, filename), 'wb')
                self.ftpfile.write(data)
                self.ftpfile.close()
                self.ftpfile = None
        except Exception as e:
            if not self.first_failure:
                print("SRTM Download failed %s on server %s" % (filepath, self.server))
                self.first_failure = True
            pass


class SRTMTile:
    """Base class for all SRTM tiles.
        Each SRTM tile is size x size pixels big and contains
        data for the area from (lat, lon) to (lat+1, lon+1) inclusive.
        This means there is a 1 pixel overlap between tiles. This makes it
        easier for as to interpolate the value, because for every point we
        only have to look at a single tile.
        """
    def __init__(self, f, lat, lon):
        try:
            zipf = zipfile.ZipFile(f, 'r')
        except Exception:
            raise InvalidTileError(lat, lon)
        names = zipf.namelist()
        if len(names) != 1:
            raise InvalidTileError(lat, lon)
        data = zipf.read(names[0])
        self.size = int(math.sqrt(len(data)/2)) # 2 bytes per sample
        # Currently only SRTM1/3 is supported
        if self.size not in (1201, 3601):
            raise InvalidTileError(lat, lon)
        self.data = array.array('h', data)
        self.data.byteswap()
        if len(self.data) != self.size * self.size:
            raise InvalidTileError(lat, lon)
        self.lat = lat
        self.lon = lon

    @staticmethod
    def _avg(value1, value2, weight):
        """Returns the weighted average of two values and handles the case where
            one value is None. If both values are None, None is returned.
        """
        if value1 is None:
            return value2
        if value2 is None:
            return value1
        return value2 * weight + value1 * (1 - weight)

    def calcOffset(self, x, y):
        """Calculate offset into data array. Only uses to test correctness
            of the formula."""
        # Datalayout
        # X = longitude
        # Y = latitude
        # Sample for size 1201x1201
        #  (   0/1200)     (   1/1200)  ...    (1199/1200)    (1200/1200)
        #  (   0/1199)     (   1/1199)  ...    (1199/1199)    (1200/1199)
        #       ...            ...                 ...             ...
        #  (   0/   1)     (   1/   1)  ...    (1199/   1)    (1200/   1)
        #  (   0/   0)     (   1/   0)  ...    (1199/   0)    (1200/   0)
        #  Some offsets:
        #  (0/1200)     0
        #  (1200/1200)  1200
        #  (0/1199)     1201
        #  (1200/1199)  2401
        #  (0/0)        1201*1200
        #  (1200/0)     1201*1201-1
        return x + self.size * (self.size - y - 1)

    def getPixelValue(self, x, y):
        """Get the value of a pixel from the data, handling voids in the
            SRTM data."""
        assert x < self.size, "x: %d<%d" % (x, self.size)
        assert y < self.size, "y: %d<%d" % (y, self.size)
        # Same as calcOffset, inlined for performance reasons
        offset = x + self.size * (self.size - y - 1)
        #print(offset)
        value = self.data[offset]
        if value == -32768:
            return -1 # -32768 is a special value for areas with no data
        return value


    def getAltitudeFromLatLon(self, lat, lon):
        """Get the altitude of a lat lon pair, using the four neighbouring
            pixels for interpolation.
        """
        # print("-----\nFromLatLon", lon, lat)
        lat -= self.lat
        lon -= self.lon
        # print("lon, lat", lon, lat)
        if lat < 0.0 or lat >= 1.0 or lon < 0.0 or lon >= 1.0:
            raise WrongTileError(self.lat, self.lon, self.lat+lat, self.lon+lon)
        x = lon * (self.size - 1)
        y = lat * (self.size - 1)
        # print("x,y", x, y)
        x_int = int(x)
        x_frac = x - int(x)
        y_int = int(y)
        y_frac = y - int(y)
        # print("frac", x_int, x_frac, y_int, y_frac)
        value00 = self.getPixelValue(x_int, y_int)
        value10 = self.getPixelValue(x_int+1, y_int)
        value01 = self.getPixelValue(x_int, y_int+1)
        value11 = self.getPixelValue(x_int+1, y_int+1)
        value1 = self._avg(value00, value10, x_frac)
        value2 = self._avg(value01, value11, x_frac)
        value  = self._avg(value1,  value2, y_frac)
        # print("%4d %4d | %4d\n%4d %4d | %4d\n-------------\n%4d" % (
        #        value00, value10, value1, value01, value11, value2, value))
        return value

class SRTMOceanTile(SRTMTile):
    '''a tile for areas of zero altitude'''
    def __init__(self, lat, lon):
        self.lat = lat
        self.lon = lon

    def getAltitudeFromLatLon(self, lat, lon):
        return 0


class parseHTMLDirectoryListing(HTMLParser):

    def __init__(self):
        #print("parseHTMLDirectoryListing.__init__")
        HTMLParser.__init__(self)
        self.title="Undefined"
        self.isDirListing = False
        self.dirList=[]
        self.inTitle = False
        self.inHyperLink = False
        self.currAttrs=""
        self.currHref=""

    def handle_starttag(self, tag, attrs):
        #print("Encountered the beginning of a %s tag" % tag)
        if tag=="title":
            self.inTitle = True
        if tag == "a":
            self.inHyperLink = True
            self.currAttrs=attrs
            for attr in attrs:
                if attr[0]=='href':
                    self.currHref = attr[1]


    def handle_endtag(self, tag):
        #print("Encountered the end of a %s tag" % tag)
        if tag=="title":
            self.inTitle = False
        if tag == "a":
            # This is to avoid us adding the parent directory to the list.
            if self.currHref!="":
                self.dirList.append(self.currHref)
            self.currAttrs=""
            self.currHref=""
            self.inHyperLink = False

    def handle_data(self,data):
        if self.inTitle:
            self.title = data
            '''print("title=%s" % data)'''
            if "Index of" in self.title:
                #print("it is an index!!!!")
                self.isDirListing = True
        if self.inHyperLink:
            # We do not include parent directory in listing.
            if  "Parent Directory" in data:
                self.currHref=""

    def getDirListing(self):
        return self.dirList

#DEBUG ONLY
if __name__ == '__main__':
    downloader = SRTMDownloader()
    downloader.loadFileList()
    import time
    start = time.time()
    while time.time() - start < 30:
        tile = downloader.getTile(-36, 149)
        if tile:
            print(tile.getAltitudeFromLatLon(-35.282, 149.1287))
            break
        time.sleep(0.2)
