/*
 * This file is part of OpenTTD.
 * OpenTTD 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, version 2.
 * OpenTTD 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 OpenTTD. If not, see <http://www.gnu.org/licenses/>.
 */

/** @file slider.cpp Implementation of the horizontal slider widget. */

#include "../stdafx.h"
#include "../palette_func.h"
#include "../window_gui.h"
#include "../window_func.h"
#include "../strings_func.h"
#include "../zoom_func.h"
#include "slider_func.h"

#include "../safeguards.h"

static const int SLIDER_WIDTH = 3;

/**
 * Draw a slider widget with knob at given value
 * @param r Rectangle to draw the widget in
 * @param min_value Minimum value of slider
 * @param max_value Maximum value of slider
 * @param value Value to put the slider at
 * @param labels List of positions and labels to draw along the slider.
 */
void DrawSliderWidget(Rect r, int min_value, int max_value, int value, const std::map<int, StringID> &labels)
{
	/* Allow space for labels. We assume they are in the small font. */
	if (!labels.empty()) r.bottom -= GetCharacterHeight(FS_SMALL) + WidgetDimensions::scaled.hsep_normal;

	max_value -= min_value;

	/* Draw a wedge indicating low to high value. */
	const int ha = (r.bottom - r.top) / 5;
	const int sw = ScaleGUITrad(SLIDER_WIDTH);
	const int t = WidgetDimensions::scaled.bevel.top; /* Thickness of lines */
	int wx1 = r.left  + sw / 2;
	int wx2 = r.right - sw / 2;
	if (_current_text_dir == TD_RTL) std::swap(wx1, wx2);
	const uint shadow = GetColourGradient(COLOUR_GREY, 3);
	const uint fill = GetColourGradient(COLOUR_GREY, 6);
	const uint light = GetColourGradient(COLOUR_GREY, 7);
	const std::vector<Point> wedge{ Point{wx1, r.bottom - ha}, Point{wx2, r.top + ha}, Point{wx2, r.bottom - ha} };
	GfxFillPolygon(wedge, fill);
	GfxDrawLine(wedge[0].x, wedge[0].y, wedge[2].x, wedge[2].y, light, t);
	GfxDrawLine(wedge[1].x, wedge[1].y, wedge[2].x, wedge[2].y, _current_text_dir == TD_RTL ? shadow : light, t);
	GfxDrawLine(wedge[0].x, wedge[0].y, wedge[1].x, wedge[1].y, shadow, t);

	int x;
	for (auto label : labels) {
		x = label.first - min_value;
		if (_current_text_dir == TD_RTL) x = max_value - x;
		x = r.left + (x * (r.right - r.left - sw) / max_value) + sw / 2;
		GfxDrawLine(x, r.bottom - ha + 1, x, r.bottom + (label.second == STR_NULL ? 0 : WidgetDimensions::scaled.hsep_normal), shadow, t);
		if (label.second != STR_NULL) {
			Dimension d = GetStringBoundingBox(label.second, FS_SMALL);
			x = Clamp(x - d.width / 2, r.left, r.right - d.width);
			DrawString(x, x + d.width, r.bottom + 1 + WidgetDimensions::scaled.hsep_normal, label.second, TC_BLACK, SA_CENTER, false, FS_SMALL);
		}
	}

	/* Draw a slider handle indicating current value. */
	value -= min_value;
	if (_current_text_dir == TD_RTL) value = max_value - value;
	x = r.left + (value * (r.right - r.left - sw) / max_value);
	DrawFrameRect(x, r.top, x + sw, r.bottom, COLOUR_GREY, FR_NONE);
}

/**
 * Handle click on a slider widget to change the value
 * @param r      Rectangle of the widget
 * @param pt     Clicked point
 * @param value[in,out] Value to modify
 * @return       True if the value setting was modified
 */
bool ClickSliderWidget(Rect r, Point pt, int min_value, int max_value, int &value)
{
	max_value -= min_value;

	const int sw = ScaleGUITrad(SLIDER_WIDTH);
	int new_value = Clamp((pt.x - r.left - sw / 2) * max_value / (r.right - r.left - sw), 0, max_value);
	if (_current_text_dir == TD_RTL) new_value = max_value - new_value;
	new_value += min_value;

	if (new_value != value) {
		value = new_value;
		return true;
	}

	return false;
}