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

"""
***************************************************************************
    ProjectProvider.py
    ------------------------
    Date                 : July 2018
    Copyright            : (C) 2018 by Nyall Dawson
    Email                : nyall dot dawson 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__ = 'Nyall Dawson'
__date__ = 'July 2018'
__copyright__ = '(C) 2018, Nyall Dawson'

from qgis.core import (Qgis,
                       QgsApplication,
                       QgsProcessingProvider,
                       QgsMessageLog,
                       QgsProcessingModelAlgorithm,
                       QgsProject,
                       QgsXmlUtils)

PROJECT_PROVIDER_ID = 'project'


class ProjectProvider(QgsProcessingProvider):

    def __init__(self, project=None):
        super().__init__()
        if project is None:
            self.project = QgsProject.instance()
        else:
            self.project = project

        self.model_definitions = {} # dict of models in project
        self.is_loading = False

        # must reload models if providers list is changed - previously unavailable algorithms
        # which models depend on may now be available
        QgsApplication.processingRegistry().providerAdded.connect(self.on_provider_added)

        self.project.readProject.connect(self.read_project)
        self.project.writeProject.connect(self.write_project)
        self.project.cleared.connect(self.clear)

    def on_provider_added(self, _):
        self.refreshAlgorithms()

    def load(self):
        self.refreshAlgorithms()
        return True

    def clear(self):
        """
        Remove all algorithms from the provider
        """
        self.model_definitions = {}
        self.refreshAlgorithms()

    def add_model(self, model):
        """
        Adds a model to the provider
        :type model: QgsProcessingModelAlgorithm
        :param model: model to add
        """
        definition = model.toVariant()
        self.model_definitions[model.name()] = definition
        self.refreshAlgorithms()

    def remove_model(self, model):
        """
        Removes a model from the project
        :type model: QgsProcessingModelAlgorithm
        :param model: model to remove
        """
        if model is None:
            return

        if model.name() in self.model_definitions:
            del self.model_definitions[model.name()]

        self.refreshAlgorithms()

    def read_project(self, doc):
        """
        Reads the project model definitions from the project DOM document
        :param doc: DOM document
        """
        self.model_definitions = {}
        project_models_nodes = doc.elementsByTagName('projectModels')
        if project_models_nodes:
            project_models_node = project_models_nodes.at(0)
            model_nodes = project_models_node.childNodes()
            for n in range(model_nodes.count()):
                model_element = model_nodes.at(n).toElement()
                definition = QgsXmlUtils.readVariant(model_element)
                algorithm = QgsProcessingModelAlgorithm()
                if algorithm.loadVariant(definition):
                    self.model_definitions[algorithm.name()] = definition

        self.refreshAlgorithms()

    def write_project(self, doc):
        """
        Writes out the project model definitions into the project DOM document
        :param doc: DOM document
        """
        qgis_nodes = doc.elementsByTagName('qgis')
        if not qgis_nodes:
            return

        qgis_node = qgis_nodes.at(0)
        project_models_node = doc.createElement('projectModels')

        for a in self.algorithms():
            definition = a.toVariant()
            element = QgsXmlUtils.writeVariant(definition, doc)
            project_models_node.appendChild(element)
        qgis_node.appendChild(project_models_node)

    def name(self):
        return self.tr('Project models', 'ProjectProvider')

    def longName(self):
        return self.tr('Models embedded in the current project', 'ProjectProvider')

    def id(self):
        return PROJECT_PROVIDER_ID

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

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

    def supportsNonFileBasedOutput(self):
        return True

    def loadAlgorithms(self):
        if self.is_loading:
            return
        self.is_loading = True

        for definition in self.model_definitions.values():
            algorithm = QgsProcessingModelAlgorithm()
            if algorithm.loadVariant(definition):
                self.addAlgorithm(algorithm)
            else:
                QgsMessageLog.logMessage(
                    self.tr('Could not load model from project', 'ProjectProvider'),
                    self.tr('Processing'), Qgis.Critical)

        self.is_loading = False
