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

"""
***************************************************************************
    SelectByExpression.py
    ---------------------
    Date                 : July 2014
    Copyright            : (C) 2014 by Michaël Douchin
***************************************************************************
*                                                                         *
*   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 2 of the License, or     *
*   (at your option) any later version.                                   *
*                                                                         *
***************************************************************************
"""

__author__ = 'Michael Douchin'
__date__ = 'July 2014'
__copyright__ = '(C) 2014, Michael Douchin'

# This will get replaced with a git SHA1 when you do a git archive

__revision__ = '$Format:%H$'

import processing
from qgis.core import *
from processing.core.GeoAlgorithmExecutionException import GeoAlgorithmExecutionException
from processing.parameters.ParameterVector import ParameterVector
from processing.parameters.ParameterSelection import ParameterSelection
from processing.outputs.OutputVector import OutputVector
from processing.core.GeoAlgorithm import GeoAlgorithm
from processing.parameters.ParameterString import ParameterString

class SelectByExpression(GeoAlgorithm):

    LAYERNAME = 'LAYERNAME'
    EXPRESSION= 'EXPRESSION'
    RESULT = 'RESULT'
    METHOD = 'METHOD'
    METHODS = ['creating new selection', 'adding to current selection',
               'removing from current selection']

    def defineCharacteristics(self):
        self.name = 'Select by expression'
        self.group = 'Vector selection tools'

        self.addParameter(ParameterVector(self.LAYERNAME, 'Input Layer',
                          [ParameterVector.VECTOR_TYPE_ANY]))
        self.addParameter(ParameterString(self.EXPRESSION, "Expression"))
        self.addParameter(ParameterSelection(self.METHOD,
                          'Modify current selection by', self.METHODS, 0))
        self.addOutput(OutputVector(self.RESULT, 'Output', True))

    def processAlgorithm(self, progress):

        filename = self.getParameterValue(self.LAYERNAME)
        layer = processing.getObject(filename)
        oldSelection = set(layer.selectedFeaturesIds())
        method = self.getParameterValue(self.METHOD)

        # Build QGIS request with expression
        expression = self.getParameterValue(self.EXPRESSION)
        qExp = QgsExpression(expression)
        if not qExp.hasParserError():
            qReq = QgsFeatureRequest(qExp)
        else:
            raise GeoAlgorithmExecutionException(qExp.parserErrorString())
        selected = [f.id() for f in layer.getFeatures(qReq)]

        if method == 1:
            selected = list(oldSelection.union(selected))
        elif method == 2:
            selected = list(oldSelection.difference(selected))

        # Set the selection
        layer.setSelectedFeatures(selected)

        self.setOutputValue(self.RESULT, filename)