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

# Copyright (c) 2009 - 2020 Detlev Offenbach <detlev@die-offenbachs.de>
#

"""
Module implementing the history filter model.
"""


from PyQt5.QtCore import Qt, QDateTime, QModelIndex, QAbstractProxyModel

from .HistoryModel import HistoryModel


class HistoryData(object):
    """
    Class storing some history data.
    """
    def __init__(self, offset, frequency=0):
        """
        Constructor
        
        @param offset tail offset (integer)
        @param frequency frequency (integer)
        """
        self.tailOffset = offset
        self.frequency = frequency
    
    def __eq__(self, other):
        """
        Special method implementing equality.
        
        @param other reference to the object to check against (HistoryData)
        @return flag indicating equality (boolean)
        """
        return (
            self.tailOffset == other.tailOffset and
            (self.frequency == -1 or other.frequency == -1 or
             self.frequency == other.frequency)
        )
    
    def __lt__(self, other):
        """
        Special method determining less relation.
        
        Note: Like the actual history entries the index mapping is sorted in
        reverse order by offset
        
        @param other reference to the history data object to compare against
            (HistoryEntry)
        @return flag indicating less (boolean)
        """
        return self.tailOffset > other.tailOffset


class HistoryFilterModel(QAbstractProxyModel):
    """
    Class implementing the history filter model.
    """
    FrequencyRole = HistoryModel.MaxRole + 1
    MaxRole = FrequencyRole
    
    def __init__(self, sourceModel, parent=None):
        """
        Constructor
        
        @param sourceModel reference to the source model (QAbstractItemModel)
        @param parent reference to the parent object (QObject)
        """
        super(HistoryFilterModel, self).__init__(parent)
        
        self.__loaded = False
        self.__filteredRows = []
        self.__historyDict = {}
        self.__scaleTime = QDateTime()
        
        self.setSourceModel(sourceModel)
    
    def historyContains(self, url):
        """
        Public method to check the history for an entry.
        
        @param url URL to check for (string)
        @return flag indicating success (boolean)
        """
        self.__load()
        return url in self.__historyDict
    
    def historyLocation(self, url):
        """
        Public method to get the row number of an entry in the source model.
        
        @param url URL to check for (tring)
        @return row number in the source model (integer)
        """
        self.__load()
        if url not in self.__historyDict:
            return 0
        
        return self.sourceModel().rowCount() - self.__historyDict[url]
    
    def data(self, index, role=Qt.DisplayRole):
        """
        Public method to get data from the model.
        
        @param index index of history entry to get data for (QModelIndex)
        @param role data role (integer)
        @return history entry data
        """
        if role == self.FrequencyRole and index.isValid():
            return self.__filteredRows[index.row()].frequency
        
        return QAbstractProxyModel.data(self, index, role)
    
    def setSourceModel(self, sourceModel):
        """
        Public method to set the source model.
        
        @param sourceModel reference to the source model (QAbstractItemModel)
        """
        if self.sourceModel() is not None:
            self.sourceModel().modelReset.disconnect(self.__sourceReset)
            self.sourceModel().dataChanged.disconnect(self.__sourceDataChanged)
            self.sourceModel().rowsInserted.disconnect(
                self.__sourceRowsInserted)
            self.sourceModel().rowsRemoved.disconnect(self.__sourceRowsRemoved)
        
        super(HistoryFilterModel, self).setSourceModel(sourceModel)
        
        if self.sourceModel() is not None:
            self.__loaded = False
            self.sourceModel().modelReset.connect(self.__sourceReset)
            self.sourceModel().dataChanged.connect(self.__sourceDataChanged)
            self.sourceModel().rowsInserted.connect(self.__sourceRowsInserted)
            self.sourceModel().rowsRemoved.connect(self.__sourceRowsRemoved)
    
    def __sourceDataChanged(self, topLeft, bottomRight):
        """
        Private slot to handle the change of data of the source model.
        
        @param topLeft index of top left data element (QModelIndex)
        @param bottomRight index of bottom right data element (QModelIndex)
        """
        self.dataChanged.emit(
            self.mapFromSource(topLeft), self.mapFromSource(bottomRight))
    
    def headerData(self, section, orientation, role=Qt.DisplayRole):
        """
        Public method to get the header data.
        
        @param section section number (integer)
        @param orientation header orientation (Qt.Orientation)
        @param role data role (integer)
        @return header data
        """
        return self.sourceModel().headerData(section, orientation, role)
    
    def recalculateFrequencies(self):
        """
        Public method to recalculate the frequencies.
        """
        self.__sourceReset()
    
    def __sourceReset(self):
        """
        Private slot to handle a reset of the source model.
        """
        self.beginResetModel()
        self.__loaded = False
        self.endResetModel()
    
    def rowCount(self, parent=None):
        """
        Public method to determine the number of rows.
        
        @param parent index of parent (QModelIndex)
        @return number of rows (integer)
        """
        if parent is None:
            parent = QModelIndex()
        
        self.__load()
        if parent.isValid():
            return 0
        return len(self.__historyDict)
    
    def columnCount(self, parent=None):
        """
        Public method to get the number of columns.
        
        @param parent index of parent (QModelIndex)
        @return number of columns (integer)
        """
        if parent is None:
            parent = QModelIndex()
        
        return self.sourceModel().columnCount(self.mapToSource(parent))
    
    def mapToSource(self, proxyIndex):
        """
        Public method to map an index to the source model index.
        
        @param proxyIndex reference to a proxy model index (QModelIndex)
        @return source model index (QModelIndex)
        """
        self.__load()
        sourceRow = self.sourceModel().rowCount() - proxyIndex.internalId()
        return self.sourceModel().index(sourceRow, proxyIndex.column())
    
    def mapFromSource(self, sourceIndex):
        """
        Public method to map an index to the proxy model index.
        
        @param sourceIndex reference to a source model index (QModelIndex)
        @return proxy model index (QModelIndex)
        """
        self.__load()
        url = sourceIndex.data(HistoryModel.UrlStringRole)
        if url not in self.__historyDict:
            return QModelIndex()
        
        sourceOffset = self.sourceModel().rowCount() - sourceIndex.row()
        
        try:
            row = self.__filteredRows.index(HistoryData(sourceOffset, -1))
        except ValueError:
            return QModelIndex()
        
        return self.createIndex(row, sourceIndex.column(), sourceOffset)
    
    def index(self, row, column, parent=None):
        """
        Public method to create an index.
        
        @param row row number for the index (integer)
        @param column column number for the index (integer)
        @param parent index of the parent item (QModelIndex)
        @return requested index (QModelIndex)
        """
        if parent is None:
            parent = QModelIndex()
        
        self.__load()
        if (
            row < 0 or
            row >= self.rowCount(parent) or
            column < 0 or
            column >= self.columnCount(parent)
        ):
            return QModelIndex()
        
        return self.createIndex(row, column,
                                self.__filteredRows[row].tailOffset)

    def parent(self, index):
        """
        Public method to get the parent index.
        
        @param index index of item to get parent (QModelIndex)
        @return index of parent (QModelIndex)
        """
        return QModelIndex()
    
    def __load(self):
        """
        Private method to load the model data.
        """
        if self.__loaded:
            return
        
        self.__filteredRows = []
        self.__historyDict = {}
        self.__scaleTime = QDateTime.currentDateTime()
        
        for sourceRow in range(self.sourceModel().rowCount()):
            idx = self.sourceModel().index(sourceRow, 0)
            url = idx.data(HistoryModel.UrlStringRole)
            if url not in self.__historyDict:
                sourceOffset = self.sourceModel().rowCount() - sourceRow
                self.__filteredRows.append(
                    HistoryData(sourceOffset, self.__frequencyScore(idx)))
                self.__historyDict[url] = sourceOffset
            else:
                # the url is known already, so just update the frequency score
                row = self.__filteredRows.index(
                    HistoryData(self.__historyDict[url], -1))
                self.__filteredRows[row].frequency += self.__frequencyScore(
                    idx)
        
        self.__loaded = True
    
    def __sourceRowsInserted(self, parent, start, end):
        """
        Private slot to handle the insertion of data in the source model.
        
        @param parent reference to the parent index (QModelIndex)
        @param start start row (integer)
        @param end end row (integer)
        """
        if start == end and start == 0:
            if not self.__loaded:
                return
            
            idx = self.sourceModel().index(start, 0, parent)
            url = idx.data(HistoryModel.UrlStringRole)
            currentFrequency = 0
            if url in self.__historyDict:
                row = self.__filteredRows.index(
                    HistoryData(self.__historyDict[url], -1))
                currentFrequency = self.__filteredRows[row].frequency
                self.beginRemoveRows(QModelIndex(), row, row)
                del self.__filteredRows[row]
                del self.__historyDict[url]
                self.endRemoveRows()
            
            self.beginInsertRows(QModelIndex(), 0, 0)
            self.__filteredRows.insert(
                0, HistoryData(
                    self.sourceModel().rowCount(),
                    self.__frequencyScore(idx) + currentFrequency))
            self.__historyDict[url] = self.sourceModel().rowCount()
            self.endInsertRows()
    
    def __sourceRowsRemoved(self, parent, start, end):
        """
        Private slot to handle the removal of data in the source model.
        
        @param parent reference to the parent index (QModelIndex)
        @param start start row (integer)
        @param end end row (integer)
        """
        self.__sourceReset()
    
    def removeRows(self, row, count, parent=None):
        """
        Public method to remove entries from the model.
        
        @param row row of the first entry to remove (integer)
        @param count number of entries to remove (integer)
        @param parent index of the parent entry (QModelIndex)
        @return flag indicating successful removal (boolean)
        """
        if parent is None:
            parent = QModelIndex()
        
        if (
            row < 0 or
            count <= 0 or
            row + count > self.rowCount(parent) or
            parent.isValid()
        ):
            return False
        
        lastRow = row + count - 1
        self.sourceModel().rowsRemoved.disconnect(self.__sourceRowsRemoved)
        self.beginRemoveRows(parent, row, lastRow)
        oldCount = self.rowCount()
        start = (
            self.sourceModel().rowCount() -
            self.__filteredRows[row].tailOffset
        )
        end = (
            self.sourceModel().rowCount() -
            self.__filteredRows[lastRow].tailOffset
        )
        self.sourceModel().removeRows(start, end - start + 1)
        self.endRemoveRows()
        self.sourceModel().rowsRemoved.connect(self.__sourceRowsRemoved)
        self.__loaded = False
        if oldCount - count != self.rowCount():
            self.beginResetModel()
            self.endResetModel()
        return True
    
    def __frequencyScore(self, sourceIndex):
        """
        Private method to calculate the frequency score.
        
        @param sourceIndex index of the source model (QModelIndex)
        @return frequency score (integer)
        """
        loadTime = self.sourceModel().data(
            sourceIndex, HistoryModel.DateTimeRole)
        days = loadTime.daysTo(self.__scaleTime)
        
        if days <= 1:
            return 100
        elif days < 8:      # within the last week
            return 90
        elif days < 15:     # within the last two weeks
            return 70
        elif days < 31:     # within the last month
            return 50
        elif days < 91:     # within the last 3 months
            return 30
        else:
            return 10
