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

"""
***************************************************************************
    ExtractByExpression.py
    ---------------------
    Date                 : October 2016
    Copyright            : (C) 2016 by Nyall Dawson
***************************************************************************
*                                                                         *
*   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__ = 'Nyall Dawson'
__date__ = 'October 2016'
__copyright__ = '(C) 2016, Nyall Dawson'

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

__revision__ = '$Format:%H$'

from qgis.core import (QgsExpression,
                       QgsFeatureRequest,
                       QgsApplication,
                       QgsProcessingUtils)

from processing.core.GeoAlgorithmExecutionException import GeoAlgorithmExecutionException
from processing.core.parameters import ParameterVector
from processing.core.outputs import OutputVector
from processing.algs.qgis.QgisAlgorithm import QgisAlgorithm
from processing.core.parameters import ParameterExpression


class ExtractByExpression(QgisAlgorithm):

    INPUT = 'INPUT'
    EXPRESSION = 'EXPRESSION'
    OUTPUT = 'OUTPUT'

    def icon(self):
        return QgsApplication.getThemeIcon("/providerQgis.svg")

    def svgIconPath(self):
        return QgsApplication.iconPath("providerQgis.svg")

    def tags(self):
        return self.tr('extract,filter,expression,field').split(',')

    def group(self):
        return self.tr('Vector selection tools')

    def __init__(self):
        super().__init__()
        self.addParameter(ParameterVector(self.INPUT,
                                          self.tr('Input Layer')))
        self.addParameter(ParameterExpression(self.EXPRESSION,
                                              self.tr("Expression"), parent_layer=self.INPUT))
        self.addOutput(OutputVector(self.OUTPUT, self.tr('Extracted (expression)')))

    def name(self):
        return 'extractbyexpression'

    def displayName(self):
        return self.tr('Extract by expression')

    def processAlgorithm(self, parameters, context, feedback):
        layer = QgsProcessingUtils.mapLayerFromString(self.getParameterValue(self.INPUT), context)
        expression_string = self.getParameterValue(self.EXPRESSION)
        writer = self.getOutputFromName(self.OUTPUT).getVectorWriter(layer.fields(), layer.wkbType(), layer.crs(),
                                                                     context)

        expression = QgsExpression(expression_string)
        if not expression.hasParserError():
            req = QgsFeatureRequest().setFilterExpression(expression_string)
        else:
            raise GeoAlgorithmExecutionException(expression.parserErrorString())

        for f in layer.getFeatures(req):
            writer.addFeature(f)

        del writer