"""
***************************************************************************
    TopoColors.py
    --------------
    Date                 : February 2017
    Copyright            : (C) 2017 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__ = "February 2017"
__copyright__ = "(C) 2017, Nyall Dawson"

import os
import operator
import sys

from collections import defaultdict

from qgis.core import (
    QgsField,
    QgsFields,
    QgsProcessingUtils,
    QgsFeatureSink,
    QgsGeometry,
    QgsSpatialIndex,
    QgsPointXY,
    NULL,
    QgsProcessing,
    QgsProcessingException,
    QgsProcessingParameterFeatureSource,
    QgsProcessingParameterDistance,
    QgsProcessingParameterNumber,
    QgsProcessingParameterEnum,
    QgsProcessingParameterFeatureSink,
)

from qgis.PyQt.QtCore import QMetaType

from processing.algs.qgis.QgisAlgorithm import QgisAlgorithm

pluginPath = os.path.split(os.path.split(os.path.dirname(__file__))[0])[0]


class TopoColor(QgisAlgorithm):
    INPUT = "INPUT"
    MIN_COLORS = "MIN_COLORS"
    MIN_DISTANCE = "MIN_DISTANCE"
    BALANCE = "BALANCE"
    OUTPUT = "OUTPUT"

    def tags(self):
        return self.tr("topocolor,colors,graph,adjacent,assign").split(",")

    def group(self):
        return self.tr("Cartography")

    def groupId(self):
        return "cartography"

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

    def initAlgorithm(self, config=None):

        self.addParameter(
            QgsProcessingParameterFeatureSource(
                self.INPUT,
                self.tr("Input layer"),
                [QgsProcessing.SourceType.TypeVectorPolygon],
            )
        )
        self.addParameter(
            QgsProcessingParameterNumber(
                self.MIN_COLORS,
                self.tr("Minimum number of colors"),
                minValue=1,
                maxValue=1000,
                defaultValue=4,
            )
        )
        self.addParameter(
            QgsProcessingParameterDistance(
                self.MIN_DISTANCE,
                self.tr("Minimum distance between features"),
                parentParameterName=self.INPUT,
                minValue=0.0,
                defaultValue=0.0,
            )
        )
        balance_by = [
            self.tr("By feature count"),
            self.tr("By assigned area"),
            self.tr("By distance between colors"),
        ]
        self.addParameter(
            QgsProcessingParameterEnum(
                self.BALANCE,
                self.tr("Balance color assignment"),
                options=balance_by,
                defaultValue=0,
            )
        )

        self.addParameter(
            QgsProcessingParameterFeatureSink(
                self.OUTPUT,
                self.tr("Colored"),
                QgsProcessing.SourceType.TypeVectorPolygon,
            )
        )

    def name(self):
        return "topologicalcoloring"

    def displayName(self):
        return self.tr("Topological coloring")

    def shortDescription(self):
        return self.tr(
            "Assigns a color index to polygon features, so no adjacent polygons share the same color index."
        )

    def processAlgorithm(self, parameters, context, feedback):
        source = self.parameterAsSource(parameters, self.INPUT, context)
        if source is None:
            raise QgsProcessingException(
                self.invalidSourceError(parameters, self.INPUT)
            )

        min_colors = self.parameterAsInt(parameters, self.MIN_COLORS, context)
        balance_by = self.parameterAsEnum(parameters, self.BALANCE, context)
        min_distance = self.parameterAsDouble(parameters, self.MIN_DISTANCE, context)

        newFields = QgsFields()
        newFields.append(QgsField("color_id", QMetaType.Type.Int))
        fields = QgsProcessingUtils.combineFields(source.fields(), newFields)

        (sink, dest_id) = self.parameterAsSink(
            parameters,
            self.OUTPUT,
            context,
            fields,
            source.wkbType(),
            source.sourceCrs(),
        )
        if sink is None:
            raise QgsProcessingException(self.invalidSinkError(parameters, self.OUTPUT))

        features = {f.id(): f for f in source.getFeatures()}

        topology, id_graph = self.compute_graph(
            features, feedback, min_distance=min_distance
        )
        feature_colors = ColoringAlgorithm.balanced(
            features,
            balance=balance_by,
            graph=topology,
            feedback=feedback,
            min_colors=min_colors,
        )

        if len(feature_colors) == 0:
            return {self.OUTPUT: dest_id}

        max_colors = max(feature_colors.values())
        feedback.pushInfo(self.tr("{} colors required").format(max_colors))

        total = 20.0 / len(features)
        current = 0
        for feature_id, input_feature in features.items():
            if feedback.isCanceled():
                break

            output_feature = input_feature
            attributes = input_feature.attributes()
            if feature_id in feature_colors:
                attributes.append(feature_colors[feature_id])
            else:
                attributes.append(NULL)
            output_feature.setAttributes(attributes)

            sink.addFeature(output_feature, QgsFeatureSink.Flag.FastInsert)
            current += 1
            feedback.setProgress(80 + int(current * total))

        sink.finalize()
        return {self.OUTPUT: dest_id}

    @staticmethod
    def compute_graph(features, feedback, create_id_graph=False, min_distance=0):
        """compute topology from a layer/field"""
        s = Graph(sort_graph=False)
        id_graph = None
        if create_id_graph:
            id_graph = Graph(sort_graph=True)

        # skip features without geometry
        features_with_geometry = {
            f_id: f for (f_id, f) in features.items() if f.hasGeometry()
        }

        total = 70.0 / len(features_with_geometry) if features_with_geometry else 1
        index = QgsSpatialIndex()

        i = 0
        for feature_id, f in features_with_geometry.items():
            if feedback.isCanceled():
                break

            g = f.geometry()
            if min_distance > 0:
                g = g.buffer(min_distance, 5)

            engine = QgsGeometry.createGeometryEngine(g.constGet())
            engine.prepareGeometry()

            feature_bounds = g.boundingBox()
            # grow bounds a little so we get touching features
            feature_bounds.grow(feature_bounds.width() * 0.01)
            intersections = index.intersects(feature_bounds)
            for l2 in intersections:
                f2 = features_with_geometry[l2]
                if engine.intersects(f2.geometry().constGet()):
                    s.add_edge(f.id(), f2.id())
                    s.add_edge(f2.id(), f.id())
                    if id_graph:
                        id_graph.add_edge(f.id(), f2.id())

            index.addFeature(f)
            i += 1
            feedback.setProgress(int(i * total))

        for feature_id, f in features_with_geometry.items():
            if feedback.isCanceled():
                break

            if feature_id not in s.node_edge:
                s.add_edge(feature_id, None)

        return s, id_graph


class ColoringAlgorithm:

    @staticmethod
    def balanced(features, graph, feedback, balance=0, min_colors=4):
        feature_colors = {}
        # start with minimum number of colors in pool
        color_pool = set(range(1, min_colors + 1))

        # calculate count of neighbours
        neighbour_count = defaultdict(int)
        for feature_id, neighbours in graph.node_edge.items():
            neighbour_count[feature_id] += len(neighbours)

        # sort features by neighbour count - we want to handle those with more neighbours first
        sorted_by_count = [
            feature_id
            for feature_id in sorted(
                neighbour_count.items(), key=operator.itemgetter(1), reverse=True
            )
        ]
        # counts for each color already assigned
        color_counts = defaultdict(int)
        color_areas = defaultdict(float)
        for c in color_pool:
            color_counts[c] = 0
            color_areas[c] = 0

        total = 10.0 / len(sorted_by_count) if sorted_by_count else 1
        i = 0

        for feature_id, n in sorted_by_count:
            if feedback.isCanceled():
                break

            # first work out which already assigned colors are adjacent to this feature
            adjacent_colors = {
                feature_colors[neighbour]
                for neighbour in graph.node_edge[feature_id]
                if neighbour in feature_colors
            }

            # from the existing colors, work out which are available (ie non-adjacent)
            available_colors = color_pool.difference(adjacent_colors)

            feature_color = -1
            if len(available_colors) == 0:
                # no existing colors available for this feature, so add new color to pool and repeat
                min_colors += 1
                return ColoringAlgorithm.balanced(
                    features, graph, feedback, balance, min_colors
                )
            else:
                if balance == 0:
                    # choose least used available color
                    counts = [
                        (c, v) for c, v in color_counts.items() if c in available_colors
                    ]
                    feature_color = sorted(counts, key=operator.itemgetter(1))[0][0]
                    color_counts[feature_color] += 1
                elif balance == 1:
                    areas = [
                        (c, v) for c, v in color_areas.items() if c in available_colors
                    ]
                    feature_color = sorted(areas, key=operator.itemgetter(1))[0][0]
                    color_areas[feature_color] += features[feature_id].geometry().area()
                elif balance == 2:
                    min_distances = {c: sys.float_info.max for c in available_colors}
                    this_feature_centroid = (
                        features[feature_id].geometry().centroid().constGet()
                    )

                    # find features for all available colors
                    other_features = {
                        f_id: c
                        for (f_id, c) in feature_colors.items()
                        if c in available_colors
                    }

                    # loop through these, and calculate the minimum distance from this feature to the nearest
                    # feature with each assigned color
                    for other_feature_id, c in other_features.items():
                        if feedback.isCanceled():
                            break

                        other_geometry = features[other_feature_id].geometry()
                        other_centroid = other_geometry.centroid().constGet()

                        distance = this_feature_centroid.distanceSquared(other_centroid)
                        if distance < min_distances[c]:
                            min_distances[c] = distance

                    # choose color such that minimum distance is maximised! ie we want MAXIMAL separation between
                    # features with the same color
                    feature_color = sorted(
                        min_distances, key=min_distances.__getitem__, reverse=True
                    )[0]

            feature_colors[feature_id] = feature_color

            i += 1
            feedback.setProgress(70 + int(i * total))

        return feature_colors


class Graph:

    def __init__(self, sort_graph=True):
        self.sort_graph = sort_graph
        self.node_edge = {}

    def add_edge(self, i, j):
        ij = [i, j]
        if self.sort_graph:
            ij.sort()
        (i, j) = ij
        if i in self.node_edge:
            self.node_edge[i].add(j)
        else:
            self.node_edge[i] = {j}

    def make_full(self):
        g = Graph(sort_graph=False)
        for k in self.node_edge.keys():
            for v in self.node_edge[k]:
                g.add_edge(v, k)
                g.add_edge(k, v)
        return g
