/*
 * Copyright (C) 2001 Brett Viren
 * Copyright (C) 2001-2015 Paul Davis <paul@linuxaudiosystems.com>
 * Copyright (C) 2006 Hans Fugal <hans@fugal.net>
 * Copyright (C) 2007-2009 David Robillard <d@drobilla.net>
 * Copyright (C) 2012-2017 Tim Mayberry <mojofunk@gmail.com>
 * Copyright (C) 2015 Nick Mainsbridge <mainsbridge@gmail.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.
 *
 * This program 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 this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */

#include <sstream>
#include <string>
#include <time.h>

#include "pbd/undo.h"
#include "pbd/xml++.h"

using namespace std;
using namespace sigc;
using namespace PBD;

UndoTransaction::UndoTransaction ()
	: _clearing (false)
{
	gettimeofday (&_timestamp, 0);
}

UndoTransaction::UndoTransaction (const UndoTransaction& rhs)
	: Command (rhs._name)
	, _clearing (false)
{
	_timestamp = rhs._timestamp;
	clear ();
	actions.insert (actions.end (), rhs.actions.begin (), rhs.actions.end ());
}

UndoTransaction::~UndoTransaction ()
{
	drop_references ();
	clear ();
}

static void
command_death (UndoTransaction* ut, Command* c)
{
	if (ut->clearing ()) {
		return;
	}

	ut->remove_command (c);

	if (ut->empty ()) {
		delete ut;
	}
}

UndoTransaction&
UndoTransaction::operator= (const UndoTransaction& rhs)
{
	if (this == &rhs) {
		return *this;
	}
	_name = rhs._name;
	clear ();
	actions.insert (actions.end (), rhs.actions.begin (), rhs.actions.end ());
	return *this;
}

void
UndoTransaction::add_command (Command* const cmd)
{
	/* catch death of command (e.g. caused by death of object to
	 * which it refers. command_death() is a normal static function
	 * so there is no need to manage this connection.
	 */

	cmd->DropReferences.connect_same_thread (*this, std::bind (&command_death, this, cmd));
	actions.push_back (cmd);
}

void
UndoTransaction::remove_command (Command* const action)
{
	list<Command*>::iterator i =std::find (actions.begin (), actions.end (), action);
	if (i == actions.end ()) {
		return;
	}
	actions.erase (i);
	delete action;
}

bool
UndoTransaction::empty () const
{
	return actions.empty ();
}

void
UndoTransaction::clear ()
{
	_clearing = true;
	for (list<Command*>::iterator i = actions.begin (); i != actions.end (); ++i) {
		delete *i;
	}
	actions.clear ();
	_clearing = false;
}

void
UndoTransaction::operator() ()
{
	for (list<Command*>::iterator i = actions.begin (); i != actions.end (); ++i) {
		(*(*i)) ();
	}
}

void
UndoTransaction::undo ()
{
	for (list<Command*>::reverse_iterator i = actions.rbegin (); i != actions.rend (); ++i) {
		(*i)->undo ();
	}
}

void
UndoTransaction::redo ()
{
	(*this) ();
}

XMLNode&
UndoTransaction::get_state () const
{
	XMLNode* node = new XMLNode ("UndoTransaction");
	node->set_property ("tv-sec", (int64_t)_timestamp.tv_sec);
	node->set_property ("tv-usec", (int64_t)_timestamp.tv_usec);
	node->set_property ("name", _name);

	list<Command*>::const_iterator it;
	for (it = actions.begin (); it != actions.end (); it++) {
		node->add_child_nocopy ((*it)->get_state ());
	}

	return *node;
}

class UndoRedoSignaller
{
public:
	UndoRedoSignaller (UndoHistory& uh)
		: _history (uh)
	{
		_history.BeginUndoRedo ();
	}

	~UndoRedoSignaller ()
	{
		_history.EndUndoRedo ();
	}

private:
	UndoHistory& _history;
};

UndoHistory::UndoHistory ()
{
	_clearing = false;
	_depth    = 0;
}

void
UndoHistory::set_depth (uint32_t d)
{
	uint32_t current_depth = UndoList.size ();

	_depth = d;

	if (d > current_depth) {
		/* not even transactions to meet request */
		return;
	}

	if (_depth > 0) {
		uint32_t cnt = current_depth - d;

		while (cnt--) {
			UndoTransaction* ut = UndoList.front ();
			UndoList.pop_front ();
			delete ut;
		}
	}
}

void
UndoHistory::add (UndoTransaction* const ut)
{
	uint32_t current_depth = UndoList.size ();

	ut->DropReferences.connect_same_thread (*this, std::bind (&UndoHistory::remove, this, ut));

	/* if the current undo history is larger than or equal to the currently
		 requested depth, then pop off at least 1 element to make space
		 at the back for new one.
		 */

	if ((_depth > 0) && current_depth && (current_depth >= _depth)) {
		uint32_t cnt = 1 + (current_depth - _depth);

		while (cnt--) {
			UndoTransaction* ut;
			ut = UndoList.front ();
			UndoList.pop_front ();
			delete ut;
		}
	}

	UndoList.push_back (ut);
	/* Adding a transacrion makes the redo list meaningless. */
	_clearing = true;
	for (std::list<UndoTransaction*>::iterator i = RedoList.begin (); i != RedoList.end (); ++i) {
		delete *i;
	}
	RedoList.clear ();
	_clearing = false;

	/* we are now owners of the transaction and must delete it when finished with it */

	Changed (); /* EMIT SIGNAL */
}

void
UndoHistory::remove (UndoTransaction* const ut)
{
	if (_clearing) {
		return;
	}

	UndoList.remove (ut);
	RedoList.remove (ut);

	Changed (); /* EMIT SIGNAL */
}

/** Undo some transactions.
 * @param n Number of transactions to undo.
 */
void
UndoHistory::undo (unsigned int n)
{
	if (n == 0) {
		return;
	}

	{
		UndoRedoSignaller exception_safe_signaller (*this);

		while (n--) {
			if (UndoList.size () == 0) {
				return;
			}
			UndoTransaction* ut = UndoList.back ();
			UndoList.pop_back ();
			ut->undo ();
			RedoList.push_back (ut);
		}
	}

	Changed (); /* EMIT SIGNAL */
}

void
UndoHistory::redo (unsigned int n)
{
	if (n == 0) {
		return;
	}

	{
		UndoRedoSignaller exception_safe_signaller (*this);

		while (n--) {
			if (RedoList.size () == 0) {
				return;
			}
			UndoTransaction* ut = RedoList.back ();
			RedoList.pop_back ();
			ut->redo ();
			UndoList.push_back (ut);
		}
	}

	Changed (); /* EMIT SIGNAL */
}

void
UndoHistory::clear_redo ()
{
	_clearing = true;
	for (std::list<UndoTransaction*>::iterator i = RedoList.begin (); i != RedoList.end (); ++i) {
		delete *i;
	}
	RedoList.clear ();
	_clearing = false;

	Changed (); /* EMIT SIGNAL */
}

void
UndoHistory::clear_undo ()
{
	_clearing = true;
	for (std::list<UndoTransaction*>::iterator i = UndoList.begin (); i != UndoList.end (); ++i) {
		delete *i;
	}
	UndoList.clear ();
	_clearing = false;

	Changed (); /* EMIT SIGNAL */
}

void
UndoHistory::clear ()
{
	clear_undo ();
	clear_redo ();

	Changed (); /* EMIT SIGNAL */
}

XMLNode&
UndoHistory::get_state (int32_t depth)
{
	XMLNode* node = new XMLNode ("UndoHistory");

	if (depth == 0) {
		return (*node);

	} else if (depth < 0) {
		/* everything */

		for (list<UndoTransaction*>::iterator it = UndoList.begin (); it != UndoList.end (); ++it) {
			node->add_child_nocopy ((*it)->get_state ());
		}

	} else {
		/* just the last "depth" transactions */

		list<UndoTransaction*> in_order;

		for (list<UndoTransaction*>::reverse_iterator it = UndoList.rbegin (); it != UndoList.rend () && depth; ++it, depth--) {
			in_order.push_front (*it);
		}

		for (list<UndoTransaction*>::iterator it = in_order.begin (); it != in_order.end (); it++) {
			node->add_child_nocopy ((*it)->get_state ());
		}
	}

	return *node;
}