# -*- coding: utf-8 -*-
# Copyright (C) 2013, the codeeditor development team
#
# Pyzo is distributed under the terms of the (new) BSD License.
# The full license can be found in 'license.txt'.

"""
Code editor extensions that change its behaviour (i.e. how it reacts to keys)
"""


from ..qt import QtGui,QtCore
Qt = QtCore.Qt

from ..misc import ustr, ce_option
from ..parsers.tokens import (CommentToken,UnterminatedStringToken)
from ..parsers import BlockState

class HomeKey(object):
    
    def keyPressEvent(self,event):
        # Home or shift + home
        if event.key() == Qt.Key_Home and \
                event.modifiers() in (Qt.NoModifier, Qt.ShiftModifier):
            # Prepare
            cursor = self.textCursor()
            shiftDown = event.modifiers() == Qt.ShiftModifier
            moveMode = [cursor.MoveAnchor, cursor.KeepAnchor][shiftDown]
            # Get leading whitespace
            text = ustr(cursor.block().text())
            leadingWhitespace = text[:len(text)-len(text.lstrip())]
            # Get current position and move to start of whitespace
            i = cursor.positionInBlock()
            cursor.movePosition(cursor.StartOfBlock, moveMode)
            cursor.movePosition(cursor.Right, moveMode, len(leadingWhitespace))
            # If we were alread there, move to start of block
            if cursor.positionInBlock() == i:
                cursor.movePosition(cursor.StartOfBlock, moveMode)
            # Done
            self.setTextCursor(cursor)
        else:
            super(HomeKey, self).keyPressEvent(event)

class EndKey(object):
    
    def keyPressEvent(self,event):
        if event.key() == Qt.Key_End and \
                event.modifiers() in (Qt.NoModifier, Qt.ShiftModifier):
            # Prepare
            cursor = self.textCursor()
            shiftDown = event.modifiers() == Qt.ShiftModifier
            moveMode = [cursor.MoveAnchor, cursor.KeepAnchor][shiftDown]
            # Get current position and move to end of line
            i = cursor.positionInBlock()
            cursor.movePosition(cursor.EndOfLine, moveMode)
            # If alread at end of line, move to end of block
            if cursor.positionInBlock() == i:
                cursor.movePosition(cursor.EndOfBlock, moveMode)
            # Done
            self.setTextCursor(cursor)
        else:
            super(EndKey, self).keyPressEvent(event)

class NumpadPeriodKey(object):
    """
    If the numpad decimal separator key is pressed, always insert
    a period (.) even if due to localization that key is mapped to a
    comma (,). When editing code, period is the decimal separator
    independent of localization
    """
    def keyPressEvent(self,event):
        # Check for numpad comma
        if event.key() == QtCore.Qt.Key_Comma and \
                event.modifiers() & QtCore.Qt.KeypadModifier:
                    
            # Create a new QKeyEvent to substitute the original one
            event = QtGui.QKeyEvent(event.type(), QtCore.Qt.Key_Period,
                event.modifiers(), '.', event.isAutoRepeat(), event.count())
            
        super(NumpadPeriodKey, self).keyPressEvent(event)


class Indentation(object):
    
    def __cursorIsInLeadingWhitespace(self,cursor = None):
        """
        Checks wether the given cursor is in the leading whitespace of a block, i.e.
        before the first non-whitespace character. The cursor is not modified.
        If the cursor is not given or is None, the current textCursor is used
        """
        if cursor is None:
            cursor = self.textCursor()
        
        # Get the text of the current block up to the cursor
        textBeforeCursor = ustr(cursor.block().text())[:cursor.positionInBlock()]
        return textBeforeCursor.lstrip() == '' #If we trim it and it is empty, it's all whitespace
    
    def keyPressEvent(self,event):
        key = event.key()
        modifiers = event.modifiers()
        #Tab key
        if key == Qt.Key_Tab:
            if modifiers == Qt.NoModifier:
                if self.textCursor().hasSelection(): #Tab pressed while some area was selected
                    self.indentSelection()
                    return
                elif self.__cursorIsInLeadingWhitespace():
                    #If the cursor is in the leading whitespace, indent and move cursor to end of whitespace
                    cursor = self.textCursor()
                    self.indentBlock(cursor)
                    self.setTextCursor(cursor)
                    return
                    
                elif self.indentUsingSpaces():
                    #Insert space-tabs
                    cursor=self.textCursor()
                    w = self.indentWidth()
                    cursor.insertText(' '*(w-((cursor.positionInBlock() + w ) % w)))
                    return
                #else: default behaviour, insert tab character
            else: #Some other modifiers + Tab: ignore
                return

        # If backspace is pressed in the leading whitespace, (except for at the first 
        # position of the line), and there is no selection
        # dedent that line and move cursor to end of whitespace
        if key == Qt.Key_Backspace and modifiers == Qt.NoModifier and \
                self.__cursorIsInLeadingWhitespace() and not self.textCursor().atBlockStart() \
                and not self.textCursor().hasSelection():
            # Create a cursor, dedent the block and move screen cursor to the end of the whitespace
            cursor = self.textCursor()
            self.dedentBlock(cursor)
            self.setTextCursor(cursor)
            return
        
        # todo: Same for delete, I think not (what to do with the cursor?)
        
        # Auto-unindent
        if event.key() == Qt.Key_Delete:
            cursor = self.textCursor()
            if not cursor.hasSelection():
                cursor.movePosition(cursor.EndOfBlock, cursor.KeepAnchor)
                if not cursor.hasSelection() and cursor.block().next().isValid():
                    cursor.beginEditBlock()
                    cursor.movePosition(cursor.NextBlock)
                    self.indentBlock(cursor, -99)  # dedent as much as we can
                    cursor.deletePreviousChar()
                    cursor.endEditBlock()
                    return
        
        super(Indentation, self).keyPressEvent(event)
        
class AutoIndent(object):
    """
    Auto indentation. This extension only adds the autoIndent property, for the
    actual indentation, the editor should derive from some AutoIndenter object
    """
    
    def autoIndent(self):
        """ autoIndent()
        
        Get whether auto indentation is enabled.
        
        """
        return self.__autoIndent
    
    @ce_option(True)
    def setAutoIndent(self,value):
        """ setAutoIndent(value)
        
        Set whether to enable auto indentation.  
        
        """
        self.__autoIndent = bool(value)
        
        
class PythonAutoIndent(object):
    
    def keyPressEvent(self,event):
        super(PythonAutoIndent, self).keyPressEvent(event)
        if not self.autoIndent():
            return
        
        #This extension code is run *after* key is processed by QPlainTextEdit
        
        if event.key() in (Qt.Key_Enter,Qt.Key_Return):
            cursor=self.textCursor()
            previousBlock=cursor.block().previous()
            if previousBlock.isValid():
                line = ustr(previousBlock.text())
                indent=line[:len(line)-len(line.lstrip())]
                if line.endswith(':'): 
                    # We only need to add indent if the : is not in a (multiline)
                    # string or comment. Therefore, find out what the syntax
                    # highlighter thinks of the previous line.
                    ppreviousBlock = previousBlock.previous() # the block before previous
                    ppreviousState = ppreviousBlock.userState() if previousBlock.isValid() else 0
                    lastElementToken = list(self.parser().parseLine(previousBlock.text(),ppreviousState))[-1]
                        # Because there's at least a : on that line, the list is never empty
                    
                    if (not isinstance(lastElementToken, (CommentToken, UnterminatedStringToken, BlockState))):
                        #TODO: check correct identation (no mixed space/tabs)
                        if self.indentUsingSpaces():
                            indent+=' '*self.indentWidth()
                        else:
                            indent+='\t'
                cursor.insertText(indent)
                #This prevents jump to start of line when up key is pressed
                self.setTextCursor(cursor)

class SmartCopyAndPaste(object):
    """
    Smart copy and paste allows copying and pasting blocks
    
    """
    
    
    @staticmethod
    def __setCursorPositionAndAnchor(cursor, position, anchor):
        cursor.setPosition(anchor)
        cursor.setPosition(position, cursor.KeepAnchor)
        
    @classmethod    
    def __ensureCursorBeforeAnchor(cls, cursor):
        """
        Given a cursor, modify it such that the cursor.position() is before or
        at cursor.anchor() and not the other way around.
        
        Returns: anchorBeforeCursor, i.e. whether originally the anchor was
        before the cursor
        """
        start = cursor.selectionStart()
        end = cursor.selectionEnd()
        # Remember whether the cursor is before or after the anchor
        anchorBeforeCursor = cursor.anchor() < cursor.position()
        
        cls.__setCursorPositionAndAnchor(cursor, start, end)

        # Return wheter originally the cursor was before the anchor
        return anchorBeforeCursor
        
    def copy(self):
        """
        Smart copy: if selection is multi-line and in front of the start of the
        selection there is only whitespace, extend the selection to include only
        whitespace
        """
        cursor = self.textCursor()
        start = cursor.selectionStart()
        end = cursor.selectionEnd()
        
        # For our convenience, ensure that position is at start and
        # anchor is at the end, but remember whether originally the
        # anchor was before the cursor or the other way around
        anchorBeforeCursor = self.__ensureCursorBeforeAnchor(cursor)
        
        # Check if we have multi-line selection.
        block = cursor.block()
        # Use > not >= to ensure we don't count it as multi-line if the cursor
        # is just at the beginning of the next block (consistent with 'CodeEditor.doForSelectedLines')
        if end > (block.position() + block.length()):

            # Now check if there is only whitespace before the start of selection
            # If so, include this whitespace in the selection and update the 
            # selection of the editor
            textBeforeSelection = block.text()[:cursor.positionInBlock()]
            if len(textBeforeSelection.strip()) == 0:
                start = block.position() # Move start to include leading whitespace
                
                # Update the textcursor of our editor. If originally the
                # anchor was before the cursor, restore that situation
                if anchorBeforeCursor:
                    self.__setCursorPositionAndAnchor(cursor, end, start)
                else:
                    self.__setCursorPositionAndAnchor(cursor, start, end)
                    
                self.setTextCursor(cursor)

        
        # Call our supers copy slot to do the actual copying
        super().copy()
        
    def cut(self):
        """
        Cutting with smart-copy: the part that is copies is the same as self.copy(),
        but the part that is removed is only the original selection
        
        see: Qt qtextcontrol.cpp, cut()
        """
        if (self.textInteractionFlags() & QtCore.Qt.TextEditable) and \
                self.textCursor().hasSelection():
            
            cursor = self.textCursor()
            self.copy()
            # Restore original cursor
            self.setTextCursor(cursor)
            cursor.removeSelectedText()

    
    def paste(self):
        """
        Smart paste
        If you paste on a position that has only whitespace in front of it,
        remove the whitespace before pasting. Combined with smart copy,
        this ensure indentation of the 
        """
        self._paste(keepSelection = False)
    def pasteAndSelect(self):
        """
        Smart paste
        Like paste(), but keep the part that was pasted selected. This allows
        you to change the indentation after pasting using tab / shift-tab
        """
        self._paste(keepSelection = True)
        
    def _paste(self, keepSelection):
        # Create a cursor of the current selection
        cursor = self.textCursor()
        
        # Ensure that position is at start and anchor is at the end.
        # This is required to ensure that with keepPositiobOnInsert
        # set, the cursor will equal the pasted text after the pasting
        self.__ensureCursorBeforeAnchor(cursor)
        
        # Change this cursor to let the position() stay at its place upon
        # inserting the new code; the anchor will move to the end of the insertion
        cursor.setKeepPositionOnInsert(True)
        super().paste()
        
        block = cursor.block()
        
        # Check if the thing to be pasted is multi-line. Use > not >=
        # to ensure we don't count it as multi-line if the cursor
        # is just at the beginning of the next block (consistent with
        # 'CodeEditor.doForSelectedLines')
        if cursor.selectionEnd() > block.position() + block.length():
        
            # Now, check if in front of the current selection there is only whitespace
            if len(block.text()[:cursor.positionInBlock()].strip())==0:
                # Note that this 'smart pasting' will be a separate item on the
                # undo stack. This is intentional: the user can undo the 'smart paste'
                # without undoing the paste
                cursor2 = QtGui.QTextCursor(cursor)
                cursor2.setPosition(cursor2.position()) # put the anchor where the cursor is
                
                # Move cursor2 to beginning of the line (selecting the whitespace)
                # and remove the selection
                cursor2.movePosition(cursor2.StartOfBlock, cursor2.KeepAnchor)
                cursor2.removeSelectedText()
        
        # Set the textcursor of this editor to the just-pasted selection
        if keepSelection:
            cursor.setKeepPositionOnInsert(False)
            self.setTextCursor(cursor)

