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

"""
***************************************************************************
    general.py
    ---------------------
    Date                 : April 2013
    Copyright            : (C) 2013 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__ = 'April 2013'
__copyright__ = '(C) 2013, Victor Olaya'

from qgis.core import (QgsApplication,
                       QgsProcessingAlgorithm,
                       QgsProcessingParameterEnum,
                       QgsProcessingParameterFeatureSink,
                       QgsProcessingParameterVectorDestination,
                       QgsProcessingParameterRasterDestination,
                       QgsProcessingOutputLayerDefinition,
                       QgsProject)
from processing.core.Processing import Processing
from processing.gui.Postprocessing import handleAlgorithmResults
from processing.gui.AlgorithmDialog import AlgorithmDialog
from qgis.utils import iface


def algorithmHelp(id):
    """
    Prints algorithm parameters with their types. Also
    provides information about parameters and outputs,
    and their acceptable values.

    :param id: An algorithm's ID
    :type id: str
    """
    alg = QgsApplication.processingRegistry().algorithmById(id)
    if alg is not None:
        print('{} ({})\n'.format(alg.displayName(), alg.id()))
        if alg.shortDescription():
            print(alg.shortDescription() + '\n')
        if alg.shortHelpString():
            print(alg.shortHelpString() + '\n')
        print('\n----------------')
        print('Input parameters')
        print('----------------')
        for p in alg.parameterDefinitions():
            print('\n{}: {}'.format(p.name(), p.description()))

            print('\n\tParameter type:\t{}'.format(p.__class__.__name__))

            if isinstance(p, QgsProcessingParameterEnum):
                opts = []
                for i, o in enumerate(p.options()):
                    opts.append('\t\t- {}: {}'.format(i, o))
                print('\n\tAvailable values:\n{}'.format('\n'.join(opts)))

            parameter_type = QgsApplication.processingRegistry().parameterType(p.type())
            accepted_types = parameter_type.acceptedPythonTypes() if parameter_type is not None else []
            if accepted_types:
                opts = []
                for t in accepted_types:
                    opts.append('\t\t- {}'.format(t))
                print('\n\tAccepted data types:')
                print('\n'.join(opts))

        print('\n----------------')
        print('Outputs')
        print('----------------')

        for o in alg.outputDefinitions():
            print('\n{}:  <{}>'.format(o.name(), o.__class__.__name__))
            if o.description():
                print('\t' + o.description())

    else:
        print('Algorithm "{}" not found.'.format(id))


def run(algOrName, parameters, onFinish=None, feedback=None, context=None, is_child_algorithm=False):
    """
    Executes given algorithm and returns its outputs as dictionary object.

    :param algOrName: Either an instance of an algorithm, or an algorithm's ID
    :param parameters: Algorithm parameters dictionary
    :param onFinish: optional function to run after the algorithm has completed
    :param feedback: Processing feedback object
    :param context: Processing context object
    :param is_child_algorithm: Set to True if this algorithm is being run as part of a larger algorithm,
    i.e. it is a sub-part of an algorithm which calls other Processing algorithms.

    :returns algorithm results as a dictionary, or None if execution failed
    :rtype: Union[dict, None]
    """
    if onFinish or not is_child_algorithm:
        return Processing.runAlgorithm(algOrName, parameters, onFinish, feedback, context)
    else:
        # for child algorithms, we disable to default post-processing step where layer ownership
        # is transferred from the context to the caller. In this case, we NEED the ownership to remain
        # with the context, so that further steps in the algorithm have guaranteed access to the layer.
        def post_process(_alg, _context, _feedback):
            return

        return Processing.runAlgorithm(algOrName, parameters, onFinish=post_process, feedback=feedback, context=context)


def runAndLoadResults(algOrName, parameters, feedback=None, context=None):
    """
    Executes given algorithm and load its results into the current QGIS project
    when possible.

    :param algOrName: Either an instance of an algorithm, or an algorithm's ID
    :param parameters: Algorithm parameters dictionary
    :param feedback: Processing feedback object
    :param context: Processing context object

    :returns algorithm results as a dictionary, or None if execution failed
    :rtype: Union[dict, None]
    """
    if isinstance(algOrName, QgsProcessingAlgorithm):
        alg = algOrName
    else:
        alg = QgsApplication.processingRegistry().createAlgorithmById(algOrName)

    # output destination parameters to point to current project
    for param in alg.parameterDefinitions():
        if not param.name() in parameters:
            continue

        if isinstance(param, (QgsProcessingParameterFeatureSink, QgsProcessingParameterVectorDestination,
                              QgsProcessingParameterRasterDestination)):
            p = parameters[param.name()]
            if not isinstance(p, QgsProcessingOutputLayerDefinition):
                parameters[param.name()] = QgsProcessingOutputLayerDefinition(p, QgsProject.instance())
            else:
                p.destinationProject = QgsProject.instance()
                parameters[param.name()] = p

    return Processing.runAlgorithm(alg, parameters=parameters, onFinish=handleAlgorithmResults, feedback=feedback,
                                   context=context)


def createAlgorithmDialog(algOrName, parameters={}):
    """
    Creates and returns an algorithm dialog for the specified algorithm, prepopulated
    with a given set of parameters. It is the caller's responsibility to execute
    and delete this dialog.

    :param algOrName: Either an instance of an algorithm, or an algorithm's ID
    :param parameters: Initial algorithm parameters dictionary

    :returns algorithm results as a dictionary, or None if execution failed
    :rtype: Union[dict, None]
    """
    if isinstance(algOrName, QgsProcessingAlgorithm):
        alg = algOrName.create()
    else:
        alg = QgsApplication.processingRegistry().createAlgorithmById(algOrName)

    if alg is None:
        return False

    dlg = alg.createCustomParametersWidget(iface.mainWindow())

    if not dlg:
        dlg = AlgorithmDialog(alg, parent=iface.mainWindow())

    dlg.setParameters(parameters)

    return dlg


def execAlgorithmDialog(algOrName, parameters={}):
    """
    Executes an algorithm dialog for the specified algorithm, prepopulated
    with a given set of parameters.

    :param algOrName: Either an instance of an algorithm, or an algorithm's ID
    :param parameters: Initial algorithm parameters dictionary

    :returns algorithm results as a dictionary, or None if execution failed
    :rtype: Union[dict, None]
    """
    dlg = createAlgorithmDialog(algOrName, parameters)
    if dlg is None:
        return {}

    canvas = iface.mapCanvas()
    prevMapTool = canvas.mapTool()
    dlg.show()
    dlg.exec_()
    if canvas.mapTool() != prevMapTool:
        try:
            canvas.mapTool().reset()
        except:
            pass
        canvas.setMapTool(prevMapTool)

    results = dlg.results()
    # make sure the dialog is destroyed and not only hidden on pressing Esc
    dlg.close()
    return results
