"""
    Flowblade Movie Editor is a nonlinear video editor.
    Copyright 2012 Janne Liljeblad.

    This file is part of Flowblade Movie Editor <http://code.google.com/p/flowblade>.

    Flowblade Movie Editor 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 3 of the License, or
    (at your option) any later version.

    Flowblade Movie Editor is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with Flowblade Movie Editor.  If not, see <http://www.gnu.org/licenses/>.
"""

"""
Module manages undo and redo stacks and executes edit actions from them
on user requests.
"""
import editorstate

set_post_undo_redo_edit_mode = None # This is set at startup to avoid circular imports

# Max stack size
MAX_UNDOS = 35

# EditActions are placed in this stack after their do_edit()
# method has been called
undo_stack = []

# Index is the stack pointer that tracks done undos and redos.
# The value of index is index of next undo + 1
# The value of index is index of next redo or == stack size if
# no redos.
index = 0

# Some menu items are set active/deactive based on undo stack state
save_item = None
undo_item = None 
redo_item = None

def set_post_undo_redo_callback(undo_redo_callback):
    global set_post_undo_redo_edit_mode
    set_post_undo_redo_edit_mode = undo_redo_callback

def set_menu_items(uimanager):
    global save_item, undo_item, redo_item
    save_item = uimanager.get_widget("/MenuBar/FileMenu/Save")
    undo_item = uimanager.get_widget("/MenuBar/EditMenu/Undo")
    redo_item = uimanager.get_widget("/MenuBar/EditMenu/Redo")

def register_edit(undo_edit):
    """
    Adds a performed EditAction into undo stack
    """
    global index
    
    # New edit action clears all redos(== undos after index)
    if index != len(undo_stack) and (len(undo_stack) != 0):
        del undo_stack[index:]
 
    # Keep stack in size, if too big remove undo at 0
    if len(undo_stack) > MAX_UNDOS:
        del undo_stack[0]
        index = index - 1
        
    # Add to stack and grow index
    undo_stack.append(undo_edit);
    index = index + 1
    
    save_item.set_sensitive(True) # Disabled at load and save, first edit enables
    undo_item.set_sensitive(True)
    redo_item.set_sensitive(False)

def do_undo():
    global index
    
    if index == 0:
        return
    
    # Empty stack, no undos
    if len(undo_stack) == 0:
        undo_item.set_sensitive(False)
        redo_item.set_sensitive(False)
        return

    # After undo we may change edit mode
    _set_post_edit_mode()
    
    # Move stack pointer down and do undo
    index = index - 1
    undo_edit = undo_stack[index]
    undo_edit.undo()
    
    if index == 0:
        undo_item.set_sensitive(False)
    
    redo_item.set_sensitive(True)
    
def do_redo():
    global index
        
    # If we are at the top of the stack, can't do redo
    if index == len(undo_stack):
        redo_item.set_sensitive(False)
        return
        
    # Empty stack, no redos
    if len(undo_stack) == 0:
        redo_item.set_sensitive(False)
        return

    # After redo we may change edit mode
    _set_post_edit_mode()

    # Do redo and move stack pointer up
    redo_edit = undo_stack[index]
    redo_edit.redo()
    index = index + 1

    if index == len(undo_stack):
        redo_item.set_sensitive(False)

    undo_item.set_sensitive(True)

def _set_post_edit_mode():
    if editorstate.edit_mode != editorstate.INSERT_MOVE:
        set_post_undo_redo_edit_mode()
        
