/* ScummVM - Graphic Adventure Engine
 *
 * ScummVM is the legal property of its developers, whose names
 * are too numerous to list here. Please refer to the COPYRIGHT
 * file distributed with this source distribution.
 *
 * 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 3 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, see <http://www.gnu.org/licenses/>.
 *
 */

#ifndef BACKENDS_GRAPHICS_OPENGL_PIPELINES_PIPELINE_H
#define BACKENDS_GRAPHICS_OPENGL_PIPELINES_PIPELINE_H

#include "graphics/opengl/system_headers.h"

#include "backends/graphics/opengl/texture.h"

#include "math/matrix4.h"

namespace OpenGL {

class Framebuffer;

/**
 * Interface for OpenGL pipeline functionality.
 *
 * This encapsulates differences in various rendering pipelines used for
 * OpenGL, OpenGL ES 1, and OpenGL ES 2.
 */
class Pipeline {
public:
	Pipeline();
	virtual ~Pipeline() {}

	/**
	 * Activate the pipeline.
	 *
	 * This sets the OpenGL state to make use of drawing with the given
	 * OpenGL pipeline.
	 */
	void activate();

	/**
	 * Deactivate the pipeline.
	 */
	void deactivate();

	/**
	 * Set framebuffer to render to.
	 *
	 * Client is responsible for any memory management related to framebuffer.
	 *
	 * @param framebuffer Framebuffer to activate.
	 * @return Formerly active framebuffer.
	 */
	Framebuffer *setFramebuffer(Framebuffer *framebuffer);

	/**
	 * Set modulation color.
	 *
	 * @param r Red component in [0,1].
	 * @param g Green component in [0,1].
	 * @param b Blue component in [0,1].
	 * @param a Alpha component in [0,1].
	 */
	virtual void setColor(GLfloat r, GLfloat g, GLfloat b, GLfloat a) = 0;

	/**
	 * Draw a texture rectangle to the currently active framebuffer.
	 *
	 * @param texture     Texture to use for drawing.
	 * @param coordinates x1, y1, x2, y2 coordinates where to draw the texture.
	 */
	virtual void drawTexture(const GLTexture &texture, const GLfloat *coordinates, const GLfloat *texcoords) = 0;

	void drawTexture(const GLTexture &texture, const GLfloat *coordinates) {
		drawTexture(texture, coordinates, texture.getTexCoords());
	}

	void drawTexture(const GLTexture &texture, GLfloat x, GLfloat y, GLfloat w, GLfloat h) {
		const GLfloat coordinates[4*2] = {
			x,     y,
			x + w, y,
			x,     y + h,
			x + w, y + h
		};
		drawTexture(texture, coordinates, texture.getTexCoords());
	}

	void drawTexture(const GLTexture &texture, GLfloat x, GLfloat y, GLfloat w, GLfloat h, const Common::Rect &clip) {
		const GLfloat coordinates[4*2] = {
			x,     y,
			x + w, y,
			x,     y + h,
			x + w, y + h
		};

		const uint tw = texture.getWidth(),
			  th = texture.getHeight();

		if (tw == 0 || th == 0) {
			// Nothing to display
			return;
		}

		const GLfloat texcoords[4*2] = {
			(float)clip.left  / tw, (float)clip.top    / th,
			(float)clip.right / tw, (float)clip.top    / th,
			(float)clip.left  / tw, (float)clip.bottom / th,
			(float)clip.right / tw, (float)clip.bottom / th
		};

		drawTexture(texture, coordinates, texcoords);
	}

	/**
	 * Set the projection matrix.
	 *
	 * This is intended to be only ever be used by Framebuffer subclasses.
	 */
	virtual void setProjectionMatrix(const Math::Matrix4 &projectionMatrix) = 0;

protected:
	/**
	 * Activate the pipeline.
	 *
	 * This sets the OpenGL state to make use of drawing with the given
	 * OpenGL pipeline.
	 */
	virtual void activateInternal() = 0;

	/**
	 * Deactivate the pipeline.
	 */
	virtual void deactivateInternal() {}

	bool isActive() const { return _isActive; }

	Framebuffer *_activeFramebuffer;

private:
	bool _isActive;

	/** Currently active rendering pipeline. */
	static Pipeline *activePipeline;

public:
	/**
	 * Set new pipeline.
	 *
	 * Client is responsible for any memory management related to pipelines.
	 *
	 * @param pipeline Pipeline to activate.
	 * @return Formerly active pipeline.
	 */
	static Pipeline *setPipeline(Pipeline *pipeline);

	/**
	 * Query the currently active rendering pipeline.
	 */
	static Pipeline *getActivePipeline() { return activePipeline; }
};

} // End of namespace OpenGL

#endif