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

"""
***************************************************************************
    FieldPyculator.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 & NextGIS'
__date__ = 'August 2012'
__copyright__ = '(C) 2012, Victor Olaya & NextGIS'

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

__revision__ = '$Format:%H$'

import sys
from PyQt4.QtCore import *
from qgis.core import *
from processing.core.GeoAlgorithm import GeoAlgorithm
from processing.core.GeoAlgorithmExecutionException import \
        GeoAlgorithmExecutionException
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 FieldsPyculator(GeoAlgorithm):

    INPUT_LAYER = 'INPUT_LAYER'
    FIELD_NAME = 'FIELD_NAME'
    FIELD_TYPE = 'FIELD_TYPE'
    FIELD_LENGTH = 'FIELD_LENGTH'
    FIELD_PRECISION = 'FIELD_PRECISION'
    GLOBAL = 'GLOBAL'
    FORMULA = 'FORMULA'
    OUTPUT_LAYER = 'OUTPUT_LAYER'
    RESULT_VAR_NAME = 'value'

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

    def defineCharacteristics(self):
        self.name = 'Advanced Python 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'
                          , 'NewField'))
        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, 0))
        self.addParameter(ParameterString(self.GLOBAL, 'Global expression',
                          multiline=True, optional=True))
        self.addParameter(ParameterString(self.FORMULA, 'Formula', 'value = ',
                          multiline=True))
        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)
        code = self.getParameterValue(self.FORMULA)
        globalExpression = self.getParameterValue(self.GLOBAL)
        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()
        new_ns = {}

        # Run global code
        if globalExpression.strip() != '':
            try:
                bytecode = compile(globalExpression, '<string>', 'exec')
                exec bytecode in new_ns
            except:
                raise GeoAlgorithmExecutionException(
                    'FieldPyculator code execute error\n'
                    + "Global code block can't be executed!%s \n %s"
                    % (unicode(sys.exc_info()[0].__name__),
                       unicode(sys.exc_info()[1])))

        # Replace all fields tags
        fields = provider.fields()
        num = 0
        for field in fields:
            field_name = unicode(field.name())
            replval = '__attr[' + str(num) + ']'
            code = code.replace('<' + field_name + '>', replval)
            num += 1

        # Replace all special vars
        code = code.replace('$id', '__id')
        code = code.replace('$geom', '__geom')
        need_id = code.find('__id') != -1
        need_geom = code.find('__geom') != -1
        need_attrs = code.find('__attr') != -1

        # Compile
        try:
            bytecode = compile(code, '<string>', 'exec')
        except:
            raise GeoAlgorithmExecutionException(
                    'FieldPyculator code execute error\n'
                    + "Field code block can't be executed! %s \n %s",
                    unicode(sys.exc_info()[0].__name__),
                    unicode(sys.exc_info()[1]))

        # Run
        features = vector.features(layer)
        nFeatures = len(features)
        nElement = 1
        for feat in features:
            progress.setPercentage(int(100 * nElement / nFeatures))
            attrs = feat.attributes()
            feat_id = feat.id()

            # Add needed vars
            if need_id:
                new_ns['__id'] = feat_id

            if need_geom:
                geom = feat.geometry()
                new_ns['__geom'] = geom

            if need_attrs:
                pyattrs = [a for a in attrs]
                new_ns['__attr'] = pyattrs

            # Clear old result
            if self.RESULT_VAR_NAME in new_ns:
                del new_ns[self.RESULT_VAR_NAME]

            # Exec
            exec bytecode in new_ns

            # Check result
            if self.RESULT_VAR_NAME not in new_ns:
                raise GeoAlgorithmExecutionException(
                    'FieldPyculator code execute error\n'
                    + "Field code block does not return '%s1' variable! \
                    Please declare this variable in your code!"
                    % self.RESULT_VAR_NAME)

            # Write feature
            nElement += 1
            outFeat.setGeometry(feat.geometry())
            attrs.append(new_ns[self.RESULT_VAR_NAME])
            outFeat.setAttributes(attrs)
            writer.addFeature(outFeat)

        del writer

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