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

"""
***************************************************************************
    FieldsCalculator.py
    ---------------------
    Date                 : August 2012
    Copyright            : (C) 2012 by Victor Olaya
    Email                : volayaf at gmail 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__ = 'Victor Olaya'
__date__ = 'August 2012'
__copyright__ = '(C) 2012, Victor Olaya'

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

__revision__ = '$Format:%H$'

from PyQt4.QtCore import *
from qgis.core import *
from processing.core.GeoAlgorithm import GeoAlgorithm
from processing.parameters.ParameterVector import ParameterVector
from processing.parameters.ParameterString import ParameterString
from processing.parameters.ParameterNumber import ParameterNumber
from processing.parameters.ParameterSelection import ParameterSelection
from processing.outputs.OutputVector import OutputVector
from processing.tools import dataobjects, vector


class FieldsCalculator(GeoAlgorithm):

    INPUT_LAYER = 'INPUT_LAYER'
    FIELD_NAME = 'FIELD_NAME'
    FIELD_TYPE = 'FIELD_TYPE'
    FIELD_LENGTH = 'FIELD_LENGTH'
    FIELD_PRECISION = 'FIELD_PRECISION'
    FORMULA = 'FORMULA'
    OUTPUT_LAYER = 'OUTPUT_LAYER'

    TYPE_NAMES = ['Float', 'Integer', 'String']
    TYPES = [QVariant.Double, QVariant.Int, QVariant.String]

    def defineCharacteristics(self):
        self.name = 'Field calculator'
        self.group = 'Vector table tools'
        self.addParameter(ParameterVector(self.INPUT_LAYER, 'Input layer',
                          [ParameterVector.VECTOR_TYPE_ANY], False))
        self.addParameter(ParameterString(self.FIELD_NAME, 'Result field name'
                          ))
        self.addParameter(ParameterSelection(self.FIELD_TYPE, 'Field type',
                          self.TYPE_NAMES))
        self.addParameter(ParameterNumber(self.FIELD_LENGTH, 'Field length',
                          1, 255, 10))
        self.addParameter(ParameterNumber(self.FIELD_PRECISION,
                          'Field precision', 0, 10, 5))
        self.addParameter(ParameterString(self.FORMULA, 'Formula'))
        self.addOutput(OutputVector(self.OUTPUT_LAYER, 'Output layer'))

    def processAlgorithm(self, progress):
        fieldName = self.getParameterValue(self.FIELD_NAME)
        fieldType = self.getParameterValue(self.FIELD_TYPE)
        fieldLength = self.getParameterValue(self.FIELD_LENGTH)
        fieldPrecision = self.getParameterValue(self.FIELD_PRECISION)
        formula = self.getParameterValue(self.FORMULA)
        output = self.getOutputFromName(self.OUTPUT_LAYER)

        layer = dataobjects.getObjectFromUri(
                self.getParameterValue(self.INPUT_LAYER))
        provider = layer.dataProvider()
        fields = provider.fields()
        fields.append(QgsField(fieldName, self.TYPES[fieldType], '',
                      fieldLength, fieldPrecision))
        writer = output.getVectorWriter(fields, provider.geometryType(),
                layer.crs())

        outFeat = QgsFeature()
        inGeom = QgsGeometry()
        nFeat = provider.featureCount()
        nElement = 0
        features = vector.features(layer)

        fieldnames = [field.name() for field in provider.fields()]
        fieldnames.sort(key=len, reverse=False)
        fieldidx = [fieldnames.index(field.name()) for field in
                    provider.fields()]
        print fieldidx
        for inFeat in features:
            progress.setPercentage(int(100 * nElement / nFeat))
            attrs = inFeat.attributes()
            expression = formula
            for idx in fieldidx:
                expression = expression.replace(unicode(fields[idx].name()),
                        unicode(attrs[idx]))
            try:
                result = eval(expression)
            except Exception:
                result = None
            nElement += 1
            inGeom = inFeat.geometry()
            outFeat.setGeometry(inGeom)
            attrs = inFeat.attributes()
            attrs.append(result)
            outFeat.setAttributes(attrs)
            writer.addFeature(outFeat)
        del writer

    def checkParameterValuesBeforeExecuting(self):
        # TODO check that formula is correct and fields exist
        pass