/*
   Copyright (C) 2008 - 2015 by Mark de Wever <koraq@xs4all.nl>
   Part of the Battle for Wesnoth Project http://www.wesnoth.org/

   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.

   See the COPYING file for more details.
*/

#define GETTEXT_DOMAIN "wesnoth-lib"

#include "gui/widgets/scrollbar.hpp"

#include "gui/auxiliary/log.hpp"
#include "gui/widgets/window.hpp" // Needed for invalidate_layout()
#include "utils/foreach.tpp"

#include <boost/bind.hpp>

#define LOG_SCOPE_HEADER get_control_type() + " [" + id() + "] " + __func__
#define LOG_HEADER LOG_SCOPE_HEADER + ':'

namespace gui2
{

tscrollbar_::tscrollbar_()
	: tcontrol(COUNT)
	, state_(ENABLED)
	, item_count_(0)
	, item_position_(0)
	, visible_items_(1)
	, step_size_(1)
	, pixels_per_step_(0.0)
	, mouse_(0, 0)
	, positioner_offset_(0)
	, positioner_length_(0)
{
	connect_signal<event::MOUSE_ENTER>(boost::bind(
			&tscrollbar_::signal_handler_mouse_enter, this, _2, _3, _4));
	connect_signal<event::MOUSE_MOTION>(boost::bind(
			&tscrollbar_::signal_handler_mouse_motion, this, _2, _3, _4, _5));
	connect_signal<event::MOUSE_LEAVE>(boost::bind(
			&tscrollbar_::signal_handler_mouse_leave, this, _2, _3));
	connect_signal<event::LEFT_BUTTON_DOWN>(boost::bind(
			&tscrollbar_::signal_handler_left_button_down, this, _2, _3));
	connect_signal<event::LEFT_BUTTON_UP>(boost::bind(
			&tscrollbar_::signal_handler_left_button_up, this, _2, _3));
}

void tscrollbar_::scroll(const tscroll scroll)
{
	switch(scroll) {
		case BEGIN:
			set_item_position(0);
			break;

		case ITEM_BACKWARDS:
			if(item_position_) {
				set_item_position(item_position_ - 1);
			}
			break;

		case HALF_JUMP_BACKWARDS:
			set_item_position(item_position_ > (visible_items_ / 2)
									  ? item_position_ - (visible_items_ / 2)
									  : 0);
			break;

		case JUMP_BACKWARDS:
			set_item_position(item_position_ > visible_items_
									  ? item_position_ - visible_items_
									  : 0);
			break;

		case END:
			set_item_position(item_count_ - 1);
			break;

		case ITEM_FORWARD:
			set_item_position(item_position_ + 1);
			break;

		case HALF_JUMP_FORWARD:
			set_item_position(item_position_ + (visible_items_ / 2));
			break;

		case JUMP_FORWARD:
			set_item_position(item_position_ + visible_items_);
			break;

		default:
			assert(false);
	}
}

void tscrollbar_::place(const tpoint& origin, const tpoint& size)
{
	// Inherited.
	tcontrol::place(origin, size);

	recalculate();
}

void tscrollbar_::set_active(const bool active)
{
	if(get_active() != active) {
		set_state(active ? ENABLED : DISABLED);
	}
}

bool tscrollbar_::get_active() const
{
	return state_ != DISABLED;
}

unsigned tscrollbar_::get_state() const
{
	return state_;
}

void tscrollbar_::set_item_position(const unsigned item_position)
{
	// Set the value always execute since we update a part of the state.
	item_position_ = item_position > item_count_ - visible_items_
							 ? item_count_ - visible_items_
							 : item_position;

	item_position_ = (item_position_ + step_size_ - 1) / step_size_;

	if(all_items_visible()) {
		item_position_ = 0;
	}

	// Determine the pixel offset of the item position.
	positioner_offset_
			= static_cast<unsigned>(item_position_ * pixels_per_step_);

	update_canvas();

	assert(item_position_ <= item_count_ - visible_items_);
}

void tscrollbar_::update_canvas()
{

	FOREACH(AUTO & tmp, canvas())
	{
		tmp.set_variable("positioner_offset", variant(positioner_offset_));
		tmp.set_variable("positioner_length", variant(positioner_length_));
	}
	set_is_dirty(true);
}

void tscrollbar_::set_state(const tstate state)
{
	if(state != state_) {
		state_ = state;
		set_is_dirty(true);
	}
}

void tscrollbar_::recalculate()
{
	// We can be called before the size has been set up in that case we can't do
	// the proper recalcultion so stop before we die with an assert.
	if(!get_length()) {
		return;
	}

	// Get the available size for the slider to move.
	const int available_length = get_length() - offset_before()
								 - offset_after();

	assert(available_length > 0);

	// All visible.
	if(item_count_ <= visible_items_) {
		positioner_offset_ = offset_before();
		positioner_length_ = available_length;
		recalculate_positioner();
		item_position_ = 0;
		update_canvas();
		return;
	}

	/**
	 * @todo In the MP lobby it can happen that a listbox has first zero items,
	 * then gets filled and since there are no visible items the second assert
	 * after this block will be triggered. Use this ugly hack to avoid that
	 * case. (This hack also added the gui/widgets/window.hpp include.)
	 */
	if(!visible_items_) {
		twindow* window = get_window();
		assert(window);
		window->invalidate_layout();
		ERR_GUI_G << LOG_HEADER
				  << " Can't recalculate size, force a window layout phase.\n";
		return;
	}

	assert(step_size_);
	assert(visible_items_);

	const unsigned steps = (item_count_ - visible_items_ - step_size_)
						   / step_size_;

	positioner_length_ = available_length * visible_items_ / item_count_;
	recalculate_positioner();

	// Make sure we can also show the last step, so add one more step.
	pixels_per_step_ = (available_length - positioner_length_)
					   / static_cast<float>(steps + 1);

	set_item_position(item_position_ * step_size_);
#if 0
	std::cerr << "Scrollbar recalculate overview:\n"
		<< "item_count_ " << item_count_
		<< " visible_items_ " << visible_items_
		<< " step_size_ " << step_size_
		<< " steps " << steps
		<< "\n"
		<< "minimum_positioner_length() " << minimum_positioner_length()
		<< " maximum_positioner_length() " << maximum_positioner_length()
		<< "\n"
		<< " positioner_length_ " << positioner_length_
		<< " positioner_offset_ " << positioner_offset_
		<< "\n"
		<< "available_length " << available_length
		<< " pixels_per_step_ " << pixels_per_step_
		<< ".\n\n";
#endif
}

void tscrollbar_::recalculate_positioner()
{
	const unsigned minimum = minimum_positioner_length();
	const unsigned maximum = maximum_positioner_length();

	if(minimum == maximum) {
		positioner_length_ = maximum;
	} else if(maximum != 0 && positioner_length_ > maximum) {
		positioner_length_ = maximum;
	} else if(positioner_length_ < minimum) {
		positioner_length_ = minimum;
	}
}

void tscrollbar_::move_positioner(const int distance)
{
	if(distance < 0 && -distance > static_cast<int>(positioner_offset_)) {
		positioner_offset_ = 0;
	} else {
		positioner_offset_ += distance;
	}

	const unsigned length = get_length() - offset_before() - offset_after()
							- positioner_length_;

	if(positioner_offset_ > length) {
		positioner_offset_ = length;
	}

	unsigned position
			= static_cast<unsigned>(positioner_offset_ / pixels_per_step_);

	// Note due to floating point rounding the position might be outside the
	// available positions so set it back.
	if(position > item_count_ - visible_items_) {
		position = item_count_ - visible_items_;
	}

	if(position != item_position_) {
		item_position_ = position;

		child_callback_positioner_moved();

		fire(event::NOTIFY_MODIFIED, *this, NULL);

		// positioner_moved_notifier_.notify();
	}
#if 0
	std::cerr << "Scrollbar move overview:\n"
		<< "item_count_ " << item_count_
		<< " visible_items_ " << visible_items_
		<< " step_size_ " << step_size_
		<< "\n"
		<< "minimum_positioner_length() " << minimum_positioner_length()
		<< " maximum_positioner_length() " << maximum_positioner_length()
		<< "\n"
		<< " positioner_length_ " << positioner_length_
		<< " positioner_offset_ " << positioner_offset_
		<< "\n"
		<< " pixels_per_step_ " << pixels_per_step_
		<< " item_position_ " << item_position_
		<< ".\n\n";
#endif
	update_canvas();
}

void tscrollbar_::load_config_extra()
{
	// These values won't change so set them here.
	FOREACH(AUTO & tmp, canvas())
	{
		tmp.set_variable("offset_before", variant(offset_before()));
		tmp.set_variable("offset_after", variant(offset_after()));
	}
}

void tscrollbar_::signal_handler_mouse_enter(const event::tevent event,
											 bool& handled,
											 bool& halt)
{
	DBG_GUI_E << LOG_HEADER << ' ' << event << ".\n";

	// Send the motion under our event id to make debugging easier.
	signal_handler_mouse_motion(event, handled, halt, get_mouse_position());
}

void tscrollbar_::signal_handler_mouse_motion(const event::tevent event,
											  bool& handled,
											  bool& halt,
											  const tpoint& coordinate)
{
	DBG_GUI_E << LOG_HEADER << ' ' << event << " at " << coordinate << ".\n";

	tpoint mouse = coordinate;
	mouse.x -= get_x();
	mouse.y -= get_y();

	switch(state_) {
		case ENABLED:
			if(on_positioner(mouse)) {
				set_state(FOCUSSED);
			}

			break;

		case PRESSED: {
			const int distance = get_length_difference(mouse_, mouse);
			mouse_ = mouse;
			move_positioner(distance);
		} break;

		case FOCUSSED:
			if(!on_positioner(mouse)) {
				set_state(ENABLED);
			}
			break;

		case DISABLED:
			// Shouldn't be possible, but seems to happen in the lobby
			// if a resize layout happens during dragging.
			halt = true;
			break;

		default:
			assert(false);
	}
	handled = true;
}

void tscrollbar_::signal_handler_mouse_leave(const event::tevent event,
											 bool& handled)
{
	DBG_GUI_E << LOG_HEADER << ' ' << event << ".\n";

	if(state_ == FOCUSSED) {
		set_state(ENABLED);
	}
	handled = true;
}


void tscrollbar_::signal_handler_left_button_down(const event::tevent event,
												  bool& handled)
{
	DBG_GUI_E << LOG_HEADER << ' ' << event << ".\n";

	tpoint mouse = get_mouse_position();
	mouse.x -= get_x();
	mouse.y -= get_y();

	if(on_positioner(mouse)) {
		assert(get_window());
		mouse_ = mouse;
		get_window()->mouse_capture();
		set_state(PRESSED);
	}

	const int bar = on_bar(mouse);

	if(bar == -1) {
		scroll(HALF_JUMP_BACKWARDS);
		fire(event::NOTIFY_MODIFIED, *this, NULL);
		// positioner_moved_notifier_.notify();
	} else if(bar == 1) {
		scroll(HALF_JUMP_FORWARD);
		fire(event::NOTIFY_MODIFIED, *this, NULL);
		// positioner_moved_notifier_.notify();
	} else {
		assert(bar == 0);
	}

	handled = true;
}

void tscrollbar_::signal_handler_left_button_up(const event::tevent event,
												bool& handled)
{
	DBG_GUI_E << LOG_HEADER << ' ' << event << ".\n";

	tpoint mouse = get_mouse_position();
	mouse.x -= get_x();
	mouse.y -= get_y();

	if(state_ != PRESSED) {
		return;
	}

	assert(get_window());
	get_window()->mouse_capture(false);

	if(on_positioner(mouse)) {
		set_state(FOCUSSED);
	} else {
		set_state(ENABLED);
	}

	handled = true;
}

} // namespace gui2