/*
  Copyright 2012-2019 David Robillard <http://drobilla.net>

  Permission to use, copy, modify, and/or distribute this software for any
  purpose with or without fee is hereby granted, provided that the above
  copyright notice and this permission notice appear in all copies.

  THIS SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
  WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
  ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
  OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/

/**
   @file pugl_gl3_test.c A simple test of OpenGL 3 with Pugl.

   This is an example of using OpenGL for pixel-perfect 2D drawing.  It uses
   pixel coordinates for positions and sizes so that things work roughly like a
   typical 2D graphics API.

   The program draws a bunch of rectangles with borders, using instancing.
   Each rectangle has origin, size, and fill color attributes, which are shared
   for all four vertices.  On each frame, a single buffer with all the
   rectangle data is sent to the GPU, and everything is drawn with a single
   draw call.

   This is not particularly realistic or optimal, but serves as a decent rough
   benchmark for how much simple geometry you can draw.  The number of
   rectangles can be given on the command line.  For reference, it begins to
   struggle to maintain 60 FPS on my machine (1950x + Vega64) with more than
   about 100000 rectangles.
*/

#define GL_SILENCE_DEPRECATION 1

#include "shader_utils.h"
#include "test_utils.h"

#include "glad/glad.h"

#include "pugl/gl.h"
#include "pugl/pugl.h"
#include "pugl/pugl_gl.h"

#include <math.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

static const int defaultWidth  = 512;
static const int defaultHeight = 512;

typedef struct
{
	float pos[2];
	float size[2];
	float fillColor[4];
} Rect;

// clang-format off
static const GLfloat rectVertices[] = {
	0.0f, 0.0f, // TL
	1.0f, 0.0f, // TR
	0.0f, 1.0f, // BL
	1.0f, 1.0f, // BR
};
// clang-format on

static const GLuint rectIndices[4] = {0, 1, 2, 3};

typedef struct
{
	PuglTestOptions opts;
	PuglWorld*      world;
	PuglView*       view;
	size_t          numRects;
	Rect*           rects;
	Program         drawRect;
	GLuint          vao;
	GLuint          vbo;
	GLuint          instanceVbo;
	GLuint          ibo;
	GLint           u_projection;
	unsigned        framesDrawn;
	int             quit;
} PuglTestApp;

static void
onConfigure(PuglView* view, double width, double height)
{
	(void)view;

	glEnable(GL_BLEND);
	glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
	glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
	glViewport(0, 0, (int)width, (int)height);
}

static void
onExpose(PuglView* view)
{
	PuglTestApp*   app   = (PuglTestApp*)puglGetHandle(view);
	const PuglRect frame = puglGetFrame(view);
	const double   time  = puglGetTime(puglGetWorld(view));

	// Construct projection matrix for 2D window surface (in pixels)
	mat4 proj;
	mat4Ortho(proj,
	          0.0f,
	          (float)frame.width,
	          0.0f,
	          (float)frame.height,
	          -1.0f,
	          1.0f);

	// Clear and bind everything that is the same for every rect
	glClear(GL_COLOR_BUFFER_BIT);
	glUseProgram(app->drawRect.program);
	glBindVertexArray(app->vao);

	// Set projection matrix uniform
	glUniformMatrix4fv(app->u_projection, 1, GL_FALSE, (const GLfloat*)&proj);

	for (size_t i = 0; i < app->numRects; ++i) {
		Rect*       rect      = &app->rects[i];
		const float normal    = i / (float)app->numRects;
		const float offset[2] = {normal * 128.0f, normal * 128.0f};

		// Move rect around in an arbitrary way that looks cool
		rect->pos[0] =
		        (float)(frame.width - rect->size[0] + offset[0]) *
		        (sinf((float)time * rect->size[0] / 64.0f + normal) + 1.0f) /
		        2.0f;
		rect->pos[1] =
		        (float)(frame.height - rect->size[1] + offset[1]) *
		        (cosf((float)time * rect->size[1] / 64.0f + normal) + 1.0f) /
		        2.0f;
	}

	glBufferSubData(GL_ARRAY_BUFFER,
	                0,
	                (GLsizeiptr)(app->numRects * sizeof(Rect)),
	                app->rects);

	glDrawElementsInstanced(GL_TRIANGLE_STRIP,
	                        4,
	                        GL_UNSIGNED_INT,
	                        NULL,
	                        (GLsizei)(app->numRects * 4));

	++app->framesDrawn;
}

static PuglStatus
onEvent(PuglView* view, const PuglEvent* event)
{
	PuglTestApp* app = (PuglTestApp*)puglGetHandle(view);

	printEvent(event, "Event: ", app->opts.verbose);

	switch (event->type) {
	case PUGL_CONFIGURE:
		onConfigure(view, event->configure.width, event->configure.height);
		break;
	case PUGL_EXPOSE: onExpose(view); break;
	case PUGL_CLOSE: app->quit = 1; break;
	case PUGL_KEY_PRESS:
		if (event->key.key == 'q' || event->key.key == PUGL_KEY_ESCAPE) {
			app->quit = 1;
		}
		break;
	default: break;
	}

	return PUGL_SUCCESS;
}

static Rect*
makeRects(const size_t numRects)
{
	const float minSize  = (float)defaultWidth / 64.0f;
	const float maxSize  = (float)defaultWidth / 6.0f;
	const float boxAlpha = 0.2f;

	Rect* rects = (Rect*)calloc(numRects, sizeof(Rect));
	for (size_t i = 0; i < numRects; ++i) {
		const float s = (sinf((float)i) / 2.0f + 0.5f);
		const float c = (cosf((float)i) / 2.0f + 0.5f);

		rects[i].size[0]      = minSize + s * maxSize;
		rects[i].size[1]      = minSize + c * maxSize;
		rects[i].fillColor[1] = s / 2.0f + 0.25f;
		rects[i].fillColor[2] = c / 2.0f + 0.25f;
		rects[i].fillColor[3] = boxAlpha;
	}

	return rects;
}

static char*
loadShader(const char* const path)
{
	FILE* const file = fopen(path, "r");
	if (!file) {
		logError("Failed to open '%s'\n", path);
		return NULL;
	}

	fseek(file, 0, SEEK_END);
	const size_t fileSize = (size_t)ftell(file);

	fseek(file, 0, SEEK_SET);
	char* source = (char*)calloc(1, fileSize + 1u);

	fread(source, 1, fileSize, file);
	fclose(file);

	return source;
}

int
main(int argc, char** argv)
{
	PuglTestApp app;
	memset(&app, 0, sizeof(app));

	const PuglRect frame = {0, 0, defaultWidth, defaultHeight};

	// Parse command line options
	app.numRects = 1024;
	app.opts     = puglParseTestOptions(&argc, &argv);
	if (app.opts.help) {
		puglPrintTestUsage("pugl_gl3_test", "[NUM_RECTS]");
		return 1;
	}

	// Parse number of rectangles argument, if given
	if (argc == 1) {
		char* endptr = NULL;
		app.numRects = (size_t)strtol(argv[0], &endptr, 10);
		if (endptr != argv[0] + strlen(argv[0])) {
			puglPrintTestUsage("pugl_gl3_test", "[NUM_RECTS]");
			return 1;
		}
	}

	// Create world, view, and rect data
	app.world = puglNewWorld();
	app.view  = puglNewView(app.world);
	app.rects = makeRects(app.numRects);

	// Set up world and view
	puglSetClassName(app.world, "PuglGL3Test");
	puglSetFrame(app.view, frame);
	puglSetMinSize(app.view, defaultWidth / 4, defaultHeight / 4);
	puglSetAspectRatio(app.view, 1, 1, 16, 9);
	puglSetBackend(app.view, puglGlBackend());
	puglSetViewHint(app.view, PUGL_USE_COMPAT_PROFILE, PUGL_FALSE);
	puglSetViewHint(app.view, PUGL_USE_DEBUG_CONTEXT, app.opts.errorChecking);
	puglSetViewHint(app.view, PUGL_CONTEXT_VERSION_MAJOR, 3);
	puglSetViewHint(app.view, PUGL_CONTEXT_VERSION_MINOR, 3);
	puglSetViewHint(app.view, PUGL_RESIZABLE, app.opts.resizable);
	puglSetViewHint(app.view, PUGL_SAMPLES, app.opts.samples);
	puglSetViewHint(app.view, PUGL_DOUBLE_BUFFER, app.opts.doubleBuffer);
	puglSetViewHint(app.view, PUGL_SWAP_INTERVAL, app.opts.doubleBuffer);
	puglSetViewHint(app.view, PUGL_IGNORE_KEY_REPEAT, PUGL_TRUE);
	puglSetHandle(app.view, &app);
	puglSetEventFunc(app.view, onEvent);

	const PuglStatus st = puglCreateWindow(app.view, "Pugl OpenGL 3");
	if (st) {
		return logError("Failed to create window (%s)\n", puglStrerror(st));
	}

	// Enter context to set up GL stuff
	puglEnterContext(app.view, false);

	// Load GL functions via GLAD
	if (!gladLoadGLLoader((GLADloadproc)&puglGetProcAddress)) {
		logError("Failed to load GL\n");
		puglFreeView(app.view);
		puglFreeWorld(app.world);
		return 1;
	}

	// Load shader sources
	char* const vertexSource   = loadShader("shaders/rect.vert");
	char* const fragmentSource = loadShader("shaders/rect.frag");
	if (!vertexSource || !fragmentSource) {
		logError("Failed to load shader sources\n");
		puglFreeView(app.view);
		puglFreeWorld(app.world);
		return 1;
	}

	// Compile rectangle shaders and program
	app.drawRect = compileProgram(vertexSource, fragmentSource);
	free(fragmentSource);
	free(vertexSource);
	if (!app.drawRect.program) {
		puglFreeView(app.view);
		puglFreeWorld(app.world);
		return 1;
	}

	// Get location of rectangle shader uniforms
	app.u_projection =
	        glGetUniformLocation(app.drawRect.program, "u_projection");

	// Generate/bind a VAO to track state
	glGenVertexArrays(1, &app.vao);
	glBindVertexArray(app.vao);

	// Generate/bind a VBO to store vertex position data
	glGenBuffers(1, &app.vbo);
	glBindBuffer(GL_ARRAY_BUFFER, app.vbo);
	glBufferData(GL_ARRAY_BUFFER,
	             sizeof(rectVertices),
	             rectVertices,
	             GL_STATIC_DRAW);

	// Attribute 0 is position, 2 floats from the VBO
	glEnableVertexAttribArray(0);
	glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 2 * sizeof(GLfloat), NULL);

	// Generate/bind a VBO to store instance attribute data
	glGenBuffers(1, &app.instanceVbo);
	glBindBuffer(GL_ARRAY_BUFFER, app.instanceVbo);
	glBufferData(GL_ARRAY_BUFFER,
	             (GLsizeiptr)(app.numRects * sizeof(Rect)),
	             app.rects,
	             GL_STREAM_DRAW);

	// Attribute 1 is Rect::position
	glEnableVertexAttribArray(1);
	glVertexAttribDivisor(1, 4);
	glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, sizeof(Rect), NULL);

	// Attribute 2 is Rect::size
	glEnableVertexAttribArray(2);
	glVertexAttribDivisor(2, 4);
	glVertexAttribPointer(2,
	                      2,
	                      GL_FLOAT,
	                      GL_FALSE,
	                      sizeof(Rect),
	                      (const void*)offsetof(Rect, size));

	// Attribute 3 is Rect::fillColor
	glEnableVertexAttribArray(3);
	glVertexAttribDivisor(3, 4);
	glVertexAttribPointer(3,
	                      4,
	                      GL_FLOAT,
	                      GL_FALSE,
	                      sizeof(Rect),
	                      (const void*)offsetof(Rect, fillColor));

	// Set up the IBO to index into the VBO
	glGenBuffers(1, &app.ibo);
	glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, app.ibo);
	glBufferData(GL_ELEMENT_ARRAY_BUFFER,
	             sizeof(rectIndices),
	             rectIndices,
	             GL_STATIC_DRAW);

	// Finally ready to go, leave GL context and show the window
	puglLeaveContext(app.view, false);
	puglShowWindow(app.view);

	// Grind away, drawing continuously
	PuglFpsPrinter fpsPrinter = {puglGetTime(app.world)};
	while (!app.quit) {
		puglPostRedisplay(app.view);
		puglDispatchEvents(app.world);
		puglPrintFps(app.world, &fpsPrinter, &app.framesDrawn);
	}

	// Delete GL stuff
	puglEnterContext(app.view, false);
	glDeleteBuffers(1, &app.ibo);
	glDeleteBuffers(1, &app.vbo);
	glDeleteBuffers(1, &app.instanceVbo);
	glDeleteVertexArrays(1, &app.vao);
	deleteProgram(app.drawRect);
	puglLeaveContext(app.view, false);

	// Tear down view and world
	puglFreeView(app.view);
	puglFreeWorld(app.world);
	return 0;
}