QGIS/python/plugins/processing/algs/qgis/SelectByAttribute.py

"""
***************************************************************************
    SelectByAttribute.py
    ---------------------
    Date                 : May 2010
    Copyright            : (C) 2010 by Michael Minn
    Email                : pyqgis at michaelminn dot com
***************************************************************************
*                                                                         *
*   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 Minn"
__date__ = "May 2010"
__copyright__ = "(C) 2010, Michael Minn"

from qgis.PyQt.QtCore import QMetaType
from qgis.core import (
    QgsExpression,
    QgsVectorLayer,
    QgsProcessing,
    QgsProcessingException,
    QgsProcessingAlgorithm,
    QgsProcessingParameterVectorLayer,
    QgsProcessingParameterField,
    QgsProcessingParameterEnum,
    QgsProcessingParameterString,
    QgsProcessingOutputVectorLayer,
)
from processing.algs.qgis.QgisAlgorithm import QgisAlgorithm


class SelectByAttribute(QgisAlgorithm):
    INPUT = "INPUT"
    FIELD = "FIELD"
    OPERATOR = "OPERATOR"
    VALUE = "VALUE"
    METHOD = "METHOD"
    OUTPUT = "OUTPUT"

    OPERATORS = [
        "=",
        "<>",
        ">",
        ">=",
        "<",
        "<=",
        "begins with",
        "contains",
        "is null",
        "is not null",
        "does not contain",
    ]
    STRING_OPERATORS = ["begins with", "contains", "does not contain"]

    def tags(self):
        return self.tr("select,attribute,value,contains,null,field").split(",")

    def group(self):
        return self.tr("Vector selection")

    def groupId(self):
        return "vectorselection"

    def __init__(self):
        super().__init__()

    def flags(self):
        return (
            super().flags()
            | QgsProcessingAlgorithm.Flag.FlagNoThreading
            | QgsProcessingAlgorithm.Flag.FlagNotAvailableInStandaloneTool
        )

    def initAlgorithm(self, config=None):
        self.operators = [
            "=",
            "≠",
            ">",
            "≥",
            "<",
            "≤",
            self.tr("begins with"),
            self.tr("contains"),
            self.tr("is null"),
            self.tr("is not null"),
            self.tr("does not contain"),
        ]

        self.methods = [
            self.tr("creating new selection"),
            self.tr("adding to current selection"),
            self.tr("removing from current selection"),
            self.tr("selecting within current selection"),
        ]

        self.addParameter(
            QgsProcessingParameterVectorLayer(
                self.INPUT,
                self.tr("Input layer"),
                types=[QgsProcessing.SourceType.TypeVector],
            )
        )
        self.addParameter(
            QgsProcessingParameterField(
                self.FIELD,
                self.tr("Selection attribute"),
                parentLayerParameterName=self.INPUT,
            )
        )
        self.addParameter(
            QgsProcessingParameterEnum(
                self.OPERATOR, self.tr("Operator"), self.operators, defaultValue=0
            )
        )
        self.addParameter(
            QgsProcessingParameterString(self.VALUE, self.tr("Value"), optional=True)
        )
        self.addParameter(
            QgsProcessingParameterEnum(
                self.METHOD,
                self.tr("Modify current selection by"),
                self.methods,
                defaultValue=0,
            )
        )

        self.addOutput(
            QgsProcessingOutputVectorLayer(self.OUTPUT, self.tr("Selected (attribute)"))
        )

    def name(self):
        return "selectbyattribute"

    def displayName(self):
        return self.tr("Select by attribute")

    def shortDescription(self):
        return self.tr(
            "Selects features from a vector layer based on an attribute from the layer."
        )

    def processAlgorithm(self, parameters, context, feedback):
        layer = self.parameterAsVectorLayer(parameters, self.INPUT, context)

        fieldName = self.parameterAsString(parameters, self.FIELD, context)
        operator = self.OPERATORS[
            self.parameterAsEnum(parameters, self.OPERATOR, context)
        ]
        value = self.parameterAsString(parameters, self.VALUE, context)

        fields = layer.fields()

        idx = fields.lookupField(fieldName)
        if idx < 0:
            raise QgsProcessingException(
                self.tr("Field '{}' was not found in layer").format(fieldName)
            )

        fieldType = fields[idx].type()

        if fieldType != QMetaType.Type.QString and operator in self.STRING_OPERATORS:
            op = "".join('"%s", ' % o for o in self.STRING_OPERATORS)
            raise QgsProcessingException(
                self.tr("Operators {0} can be used only with string fields.").format(op)
            )

        field_ref = QgsExpression.quotedColumnRef(fieldName)
        quoted_val = QgsExpression.quotedValue(value)
        if operator == "is null":
            expression_string = f"{field_ref} IS NULL"
        elif operator == "is not null":
            expression_string = f"{field_ref} IS NOT NULL"
        elif operator == "begins with":
            expression_string = f"{field_ref} LIKE '{value}%'"
        elif operator == "contains":
            expression_string = f"{field_ref} LIKE '%{value}%'"
        elif operator == "does not contain":
            expression_string = f"{field_ref} NOT LIKE '%{value}%'"
        else:
            expression_string = f"{field_ref} {operator} {quoted_val}"

        method = self.parameterAsEnum(parameters, self.METHOD, context)
        if method == 0:
            behavior = QgsVectorLayer.SelectBehavior.SetSelection
        elif method == 1:
            behavior = QgsVectorLayer.SelectBehavior.AddToSelection
        elif method == 2:
            behavior = QgsVectorLayer.SelectBehavior.RemoveFromSelection
        elif method == 3:
            behavior = QgsVectorLayer.SelectBehavior.IntersectSelection

        expression = QgsExpression(expression_string)
        if expression.hasParserError():
            raise QgsProcessingException(expression.parserErrorString())

        layer.selectByExpression(expression_string, behavior)

        return {self.OUTPUT: parameters[self.INPUT]}