"""!
@package core.ws

@brief Fetching and preparation of web service data for rendering.

Note: Currently only WMS is implemented.

Classes:
 - ws::RenderWMSMgr
 - ws::GDALRasterMerger

(C) 2012 by the GRASS Development Team

This program is free software under the GNU General Public License
(>=v2). Read the file COPYING that comes with GRASS for details.

@author Stepan Turek <stepan.turek seznam.cz> (mentor: Martin Landa)
"""
import os
import sys

import wx
from wx.lib.newevent import NewEvent

from grass.script import core as grass

from core          import utils
from core.debug    import Debug

from core.gconsole import CmdThread, GStderr, EVT_CMD_DONE, EVT_CMD_OUTPUT

try:
    haveGdal = True
    from osgeo import gdal
    from osgeo import gdalconst 
except ImportError:
    haveGdal = False

from grass.pydispatch.signal import Signal


class RenderWMSMgr(wx.EvtHandler):
    """!Fetch and prepare WMS data for rendering.
    """
    def __init__(self, layer, mapfile, maskfile):
        if not haveGdal:
            sys.stderr.write(_("Unable to load GDAL Python bindings.\n"\
                               "WMS layers can not be displayed without the bindings.\n"))

        self.layer = layer

        wx.EvtHandler.__init__(self)

        # thread for d.wms commands
        self.thread = CmdThread(self)
        self.Bind(EVT_CMD_DONE, self.OnDataFetched)

        self.downloading = False
        self.renderedRegion = None
        self.updateMap = True
        self.fetched_data_cmd = None

        self.cmdStdErr = GStderr(self)

        self.mapfile = mapfile
        self.maskfile = maskfile
        self.tempMap = grass.tempfile()
        self.dstSize = {}
 
        self.Bind(EVT_CMD_OUTPUT, self.OnCmdOutput)
        
        self.dataFetched = Signal('RenderWMSMgr.dataFetched')
        self.updateProgress = Signal('RenderWMSMgr.updateProgress')

    def __del__(self):
        grass.try_remove(self.tempMap)

    def Render(self, cmd):
        """!If it is needed, download missing WMS data.

        @todo lmgr deletes mapfile and maskfile when order of layers
        was changed (drag and drop) - if deleted, fetch data again
        """
        if not haveGdal:
            return

        self.dstSize['cols'] = int(os.environ["GRASS_WIDTH"])
        self.dstSize['rows'] = int(os.environ["GRASS_HEIGHT"])

        region = self._getRegionDict()
        self._fitAspect(region, self.dstSize)

        self.updateMap = True
        fetchData = False
        zoomChanged = False

        if self.renderedRegion is None or \
           cmd != self.fetched_data_cmd:
            fetchData = True
        else:
            for c in ['north', 'south', 'east', 'west']:
                if self.renderedRegion and \
                   region[c] != self.renderedRegion[c]:
                    fetchData = True
                    break

            for c in ['e-w resol', 'n-s resol']:
                if self.renderedRegion and \
                    region[c] != self.renderedRegion[c]:
                    zoomChanged = True
                    break

        if fetchData:
            self.fetched_data_cmd = None
            self.renderedRegion = region

            grass.try_remove(self.mapfile)
            grass.try_remove(self.tempMap)

            self.currentPid = self.thread.GetId()
            self.thread.abort()
            self.downloading = True

            self.fetching_cmd = cmd
            cmdList = utils.CmdTupleToList(cmd)

            if Debug.GetLevel() < 3:
                cmdList.append('--quiet')
            
            tempPngfile = None
            if "GRASS_PNGFILE" in os.environ:  
                tempPngfile = os.environ["GRASS_PNGFILE"]
            os.environ["GRASS_PNGFILE"] = self.tempMap

            tempRegion = os.environ["GRASS_REGION"]
            os.environ["GRASS_REGION"] = self._createRegionStr(region)

            self.thread.RunCmd(cmdList, env = os.environ.copy(), stderr = self.cmdStdErr)

            os.environ.pop("GRASS_PNGFILE")
            if tempPngfile:
                os.environ["GRASS_PNGFILE"] = tempPngfile

            os.environ["GRASS_REGION"] = tempRegion

    def OnCmdOutput(self, event):
        """!Print cmd output according to debug level.
        """
        if Debug.GetLevel() == 0:
            if event.type == 'error':
                sys.stderr.write(event.text)
                sys.stderr.flush()
        else:
            Debug.msg(1, event.text)

    def OnDataFetched(self, event):
        """!Fetch data
        """
        if event.pid != self.currentPid:
            return
        self.downloading = False
        if not self.updateMap:
            self.updateProgress.emit(layer=self.layer)
            self.renderedRegion = None
            self.fetched_data_cmd = None
            return

        self.mapMerger = GDALRasterMerger(targetFile = self.mapfile, region = self.renderedRegion,
                                          bandsNum = 3, gdalDriver = 'PNM', fillValue = 0)
        self.mapMerger.AddRasterBands(self.tempMap, {1 : 1, 2 : 2, 3 : 3})
        del self.mapMerger

        self.maskMerger = GDALRasterMerger(targetFile = self.maskfile, region = self.renderedRegion,
                                           bandsNum = 1, gdalDriver = 'PNM', fillValue = 0)
        #{4 : 1} alpha channel (4) to first and only channel (1) in mask
        self.maskMerger.AddRasterBands(self.tempMap, {4 : 1}) 
        del self.maskMerger

        self.fetched_data_cmd = self.fetching_cmd

        self.dataFetched.emit()

    def _getRegionDict(self):
        """!Parse string from GRASS_REGION env variable into dict.
        """
        region = {}
        parsedRegion = os.environ["GRASS_REGION"].split(';')
        for r in parsedRegion:
            r = r.split(':')
            r[0] = r[0].strip()
            if len(r) < 2:
                continue
            try:
                if r[0] in ['cols', 'rows']:
                    region[r[0]] = int(r[1])
                else:
                    region[r[0]] = float(r[1])
            except ValueError:
                region[r[0]] = r[1]

        return region

    def _createRegionStr(self, region):
        """!Create string for GRASS_REGION env variable from  dict created by _getRegionDict.
        """
        regionStr = ''
        for k, v in region.iteritems():
            item = k + ': ' + str(v)
            if regionStr:
                regionStr += '; '
            regionStr += item

        return regionStr

    def IsDownloading(self):
        """!Is it downloading any data from WMS server? 
        """
        return self.downloading

    def _fitAspect(self, region, size):
        """!Compute region parameters to have direction independent resolution.
        """
        if region['n-s resol'] > region['e-w resol']:
            delta = region['n-s resol'] * size['cols'] / 2

            center = (region['east'] - region['west'])/2

            region['east'] = center + delta + region['west']
            region['west'] = center - delta + region['west']
            region['e-w resol'] = region['n-s resol']

        else:
            delta = region['e-w resol'] * size['rows'] / 2

            center = (region['north'] - region['south'])/2 

            region['north'] = center + delta + region['south']
            region['south'] = center - delta + region['south']
            region['n-s resol'] = region['e-w resol']

    def Abort(self):
        """!Abort process"""
        self.updateMap = False
        self.thread.abort(abortall = True)        


class GDALRasterMerger:
    """!Merge rasters.

        Based on gdal_merge.py utility.
    """
    def __init__(self, targetFile, region, bandsNum, gdalDriver, fillValue = None):
        """!Create raster for merging.
        """
        self.gdalDrvType = gdalDriver

        nsRes = (region['south'] - region['north']) / region['rows']
        ewRes = (region['east'] - region['west']) / region['cols']

        self.tGeotransform = [region['west'], ewRes, 0, region['north'], 0, nsRes]

        self.tUlx, self.tUly, self.tLrx, self.tLry = self._getCorners(self.tGeotransform, region)

        driver = gdal.GetDriverByName(self.gdalDrvType)
        self.tDataset = driver.Create(targetFile, region['cols'], region['rows'], bandsNum,  gdal.GDT_Byte)

        if fillValue is not None:
            # fill raster bands with a constant value
            for iBand in range(1, self.tDataset.RasterCount + 1):
                self.tDataset.GetRasterBand(iBand).Fill(fillValue)

    def AddRasterBands(self, sourceFile, sTBands):
        """!Add raster bands from sourceFile into the merging raster.
        """
        sDataset = gdal.Open(sourceFile, gdal.GA_ReadOnly) 
        if sDataset is None:
            return

        sGeotransform = sDataset.GetGeoTransform()

        sSize = {
                    'rows' :  sDataset.RasterYSize,
                    'cols' :  sDataset.RasterXSize
                 }

        sUlx, sUly, sLrx, sLry = self._getCorners(sGeotransform, sSize)

        # figure out intersection region
        tIntsctUlx = max(self.tUlx,sUlx)
        tIntsctLrx = min(self.tLrx,sLrx)
        if self.tGeotransform[5] < 0:
            tIntsctUly = min(self.tUly,sUly)
            tIntsctLry = max(self.tLry,sLry)
        else:
            tIntsctUly = max(self.tUly,sUly)
            tIntsctLry = min(self.tLry,sLry)
        
        # do they even intersect?
        if tIntsctUlx >= tIntsctLrx:
            return
        if self.tGeotransform[5] < 0 and tIntsctUly <= tIntsctLry:
            return
        if self.tGeotransform[5] > 0 and tIntsctUly >= tIntsctLry:
            return


        # compute target window in pixel coordinates.
        tXoff = int((tIntsctUlx - self.tGeotransform[0]) / self.tGeotransform[1] + 0.1)
        tYoff = int((tIntsctUly - self.tGeotransform[3]) / self.tGeotransform[5] + 0.1)
        tXsize = int((tIntsctLrx - self.tGeotransform[0])/self.tGeotransform[1] + 0.5) - tXoff
        tYsize = int((tIntsctLry - self.tGeotransform[3])/self.tGeotransform[5] + 0.5) - tYoff

        if tXsize < 1 or tYsize < 1:
            return

        # Compute source window in pixel coordinates.
        sXoff = int((tIntsctUlx - sGeotransform[0]) / sGeotransform[1])
        sYoff = int((tIntsctUly - sGeotransform[3]) / sGeotransform[5])
        sXsize = int((tIntsctLrx - sGeotransform[0]) / sGeotransform[1] + 0.5) - sXoff
        sYsize = int((tIntsctLry - sGeotransform[3]) / sGeotransform[5] + 0.5) - sYoff

        if sXsize < 1 or sYsize < 1:
            return

        for sBandNnum, tBandNum in sTBands.iteritems():
            bandData = sDataset.GetRasterBand(sBandNnum).ReadRaster(sXoff, sYoff, sXsize,
                                                                    sYsize, tXsize, tYsize, gdal.GDT_Byte)
            self.tDataset.GetRasterBand(tBandNum).WriteRaster(tXoff, tYoff, tXsize, tYsize, bandData, 
                                                              tXsize, tYsize, gdal.GDT_Byte)

    def _getCorners(self, geoTrans, size):

        ulx = geoTrans[0]
        uly = geoTrans[3]
        lrx = geoTrans[0] + size['cols'] * geoTrans[1]
        lry = geoTrans[3] + size['rows'] * geoTrans[5]

        return ulx, uly, lrx, lry 

    def SetGeorefAndProj(self):
        """!Set georeference and projection to target file
        """
        projection = grass.read_command('g.proj', 
                                        flags = 'wf')
        self.tDataset.SetProjection(projection)

        self.tDataset.SetGeoTransform(self.tGeotransform)

    def __del__(self):
        self.tDataset = None