#include <vector>
#include <cmath> // trig functions
#include <cstdlib> // calloc

// TODO: decide on extension library
//#include <GL/glew.h>
#include <GL/gl3w.h>

#if defined (_WIN32) 
	#include <SDL.h>
#else
	#include <SDL2/SDL.h>
#endif
#include <SDL_image.h>
#include <glm/glm.hpp>
#include <glm/geometric.hpp>
#include <glm/gtc/matrix_transform.hpp>

#include "aixlog.hpp"

#include "hexlib.h"
#include "hexgame.h"
#include "renderer.h"
#include "render_group.h"

#define MOVE_SPEED 5.f
#define ROTATE_SPEED 0.005f
#define CAMERA_Z_CLAMP_ANGLE 85.f
//#define PROJ_TYPE ORTHOGRAPHIC
#define PROJ_TYPE PERSPECTIVE
#define DEFAULT_VERTEX_SHADER_FILE "../data/default.vs"
#define DEFAULT_FRAGMENT_SHADER_FILE "../data/default.fs"

const char * LINE_FRAGMENT_SHADER_CODE =
	"#version 330 core\n"
	"out vec3 color;\n"
	"void main()\n"
	"{\n"
	"	color = vec3(0,0,0);\n"
	"}";

const char * DEBUG_FRAGMENT_SHADER_CODE =
	"#version 330 core\n"
	"out vec3 color;\n"
	"void main()\n"
	"{\n"
	"	color = vec3(1,0,0);\n"
	"}";

typedef struct clear_col
{
	real32 R;
	real32 G;
	real32 B;
	real32 A;
} clear_col;
clear_col g_clear_col { 75.f / 255.f, 135.f / 255.f, 135.f / 255.f, 1.f };

typedef struct gl_matrix_info
{
	glm::mat4 projection;
	glm::mat4 view;
	glm::mat4 model;
	glm::mat4 MVP;
} gl_matrix_info;

enum projection_type
{
	PERSPECTIVE,
	ORTHOGRAPHIC,
};

struct camera
{
	glm::vec3 position;
	float hAngle;
	float vAngle;
	glm::vec3 target;
	glm::vec3 forward;
	glm::vec3 up;
	glm::vec3 left;
};


gl_matrix_info g_scene_matrices;
gl_render_group* g_filled_hex_render_group;
gl_render_group* g_hex_line_render_group;
gl_render_group* g_debug_render_group;
gl_render_group* g_entity_render_group;
camera g_camera;


// TODO: testing lighting
renPointLight g_test_light;


bool
addTexture(SDL_Handles &handles, const char * path)
{
	// testing
	LOG(INFO) << "Loading image: " << path << "\n";
	SDL_Surface* image = IMG_Load(path);

	if (!image)
	{
		LOG(ERROR) << "IMG_Load: " << IMG_GetError() << "\n";
		return 1;
	}

	GLuint tex_id;
	glGenTextures(1, &tex_id);
	glBindTexture(GL_TEXTURE_2D, tex_id);
	glPixelStorei(GL_UNPACK_ROW_LENGTH, 0);
	glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, image->w, image->h, 0, GL_RGBA, GL_UNSIGNED_BYTE, image->pixels);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);

	// store opengl id in SDL_Surface.userdat
	image->userdata = (void*)(intptr_t) tex_id;
	handles.texSurfaces.push_back(image);

	return true;
}

v2f
getUnprojectedCoords(int32 x, int32 y, int32 vp_width, int32 vp_height)
{
	// NOTE: using depth buffer may not be as accurate as doing ray-cast
	GLfloat depth;
	glReadPixels(x, y, 1, 1, GL_DEPTH_COMPONENT, GL_FLOAT, &depth);
	glm::vec4 viewport = glm::vec4(0, 0, vp_width, vp_height);
	glm::vec3 wincoord = glm::vec3(x, y, depth);
	glm::vec3 vU = glm::unProject(wincoord, g_scene_matrices.view, g_scene_matrices.projection, viewport);
	v2f v(vU.x, vU.y);

	return v;
}

v3f
getCameraPosition()
{
	return v3f(g_camera.position.x, g_camera.position.y, g_camera.position.z);
}

void
initMatrices(projection_type p)
{
	// TODO: many constants used here should be passed as args

	if (p == PERSPECTIVE)
	{
		g_scene_matrices.projection = glm::infinitePerspective(
			glm::radians(60.f), // FoV
			16.f / 9.f, // ascpect ratio
			0.1f // near clip plane
		);

		g_camera.position = glm::vec3(640,0,100); 
		g_camera.target = glm::vec3(640,500,0);
		// inital rotation should match target direction
		glm::vec3 &p = g_camera.position;
		glm::vec3 &t = g_camera.target;
		g_camera.hAngle = 0;
		g_camera.vAngle = glm::atan((t.z - p.z) / (t.y - p.y));
		
		//////
		// TODO: add call to rotate camera here to remove duplicate code
		camera &c = g_camera;
		float &h = c.hAngle;
		float &v = c.vAngle;
		c.forward = glm::vec3(
			glm::cos(v) * glm::sin(h),
			glm::cos(v) * glm::cos(h),
			glm::sin(v)
		);

		glm::normalize(c.forward);
		//////

		g_camera.up = glm::vec3(0,1,0);
		g_camera.left = glm::normalize(glm::cross(g_camera.up, g_camera.forward));
		g_camera.up = glm::normalize(glm::cross(g_camera.forward, g_camera.left));

		g_scene_matrices.view = glm::lookAt(
			g_camera.position, // camera position
			g_camera.position + g_camera.forward,
			g_camera.up // "up" vector
		);
	}
	else // ORTHO
	{
		// left, right, bottom, top, zNear, zFar
		g_scene_matrices.projection = glm::ortho(0.f, 1280.0f, 0.f, 720.0f, 0.1f, 100.0f);
		g_scene_matrices.view = glm::lookAt(
			glm::vec3(0.0f, 0.0f, 1.0f),	// camera position
			glm::vec3(0.0f, 0.0f, 0.0f),	// look at position
			glm::vec3(0,1,0)				// "up" vector
		);
	}	

	g_scene_matrices.model = glm::mat4(1.0f);
	g_scene_matrices.MVP = g_scene_matrices.projection * g_scene_matrices.view * g_scene_matrices.model; 
}

void
openglDebugCallback(GLenum source, GLenum type, GLuint id, GLenum severity,
					GLsizei length, const GLchar* message, const void* userParam)
{
	LOG((type == GL_DEBUG_TYPE_ERROR) ? ERROR : DEBUG)
		<< (type == GL_DEBUG_TYPE_ERROR ? "** GL ERROR **" : "")
		<< ", type: " << type
		<< ", severity: " << severity
		<< ", message: " << message << "\n";
}

bool
initRenderer(SDL_Handles &handles, v2i vpDims)
{
	SDL_GL_SetAttribute(SDL_GL_CONTEXT_FLAGS, SDL_GL_CONTEXT_FORWARD_COMPATIBLE_FLAG);
	SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_CORE);
	SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
	SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE, 24);
	SDL_GL_SetAttribute(SDL_GL_STENCIL_SIZE, 8);
	SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 3);
	SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 3);
	SDL_GL_SetSwapInterval(1);	// vsync
	SDL_GetCurrentDisplayMode(0, &handles.currentDisplayMode);
	handles.window = 
		SDL_CreateWindow("hexgame", SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED,
							vpDims.x, vpDims.y, SDL_WINDOW_OPENGL|SDL_WINDOW_RESIZABLE);
	
	if (handles.window == NULL)	{
		LOG(ERROR) << SDL_GetError() << "\n";
		return false;
	}

	handles.glContext = SDL_GL_CreateContext(handles.window);
	gl3wInit(); // TODO: decide on extension library

	LOG(INFO) << "opengl vendor: " << glGetString(GL_VENDOR) << "\n";
	LOG(INFO)<< "opengl renderer: " << glGetString(GL_RENDERER) << "\n";
	LOG(INFO) << "opengl version: " << glGetString(GL_VERSION) << "\n";
	
	glEnable(GL_DEPTH_TEST);
	glEnable(GL_LINE_SMOOTH);

	// TODO: blending, these options break the http://www.opengl-tutorial.org tutorials atm
	// Setup render state: alpha-blending enabled, polygon fill
#if 1
	glEnable(GL_BLEND);
	glBlendEquation(GL_FUNC_ADD);
	glBlendFunc(GL_ONE, GL_SRC_ALPHA);
	glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
#endif

	// TODO: glDebugMessageCallback is only availabe  from >v4.3
	//  check and warn if context doesn't support this function here
	glEnable (GL_DEBUG_OUTPUT);
	glDebugMessageCallback((GLDEBUGPROC) openglDebugCallback, 0);
	// hide VRAM debug messages
	glDebugMessageControl(GL_DONT_CARE, 33361, GL_DONT_CARE, 0, 0, GL_FALSE);

	g_filled_hex_render_group = (gl_render_group *) std::calloc(1, sizeof(gl_render_group));
	g_hex_line_render_group = (gl_render_group *) std::calloc(1, sizeof(gl_render_group));
	g_debug_render_group = (gl_render_group *) std::calloc(1, sizeof(gl_render_group));
	g_entity_render_group = (gl_render_group *) std::calloc(1, sizeof(gl_render_group));

	if (!g_filled_hex_render_group || !g_hex_line_render_group
		|| !g_debug_render_group || !g_entity_render_group)
	{
		return false;
	}
	
	const char* vs_code = utilDumpTextFile(DEFAULT_VERTEX_SHADER_FILE);
	const char* fs_code = utilDumpTextFile(DEFAULT_FRAGMENT_SHADER_FILE);

	if (!rgInitShaderProgram(g_filled_hex_render_group, vs_code, fs_code)
		|| !rgInitShaderProgram(g_hex_line_render_group, vs_code, LINE_FRAGMENT_SHADER_CODE)
		|| !rgInitShaderProgram(g_debug_render_group, vs_code, DEBUG_FRAGMENT_SHADER_CODE)
		|| !rgInitShaderProgram(g_entity_render_group, vs_code, fs_code))
	{
		return false;
	}

	return true;
}

void
fillTriangleBufferFromHex(GLfloat buf[], int idx,  const hex_info &hex)
{
	// triangles
	for (int i = 0; i < 6; i++)
	{
		// vertex 0
		buf[idx + 0] = (GLfloat) hex.XPos;
		buf[idx + 1] = (GLfloat) hex.YPos;
		buf[idx + 2] = (GLfloat) 0.f;

		// vertex 1
		buf[idx + 3] = (GLfloat) hex.vertices[i].x;
		buf[idx + 4] = (GLfloat) hex.vertices[i].y;
		buf[idx + 5] = (GLfloat) 0.f;

		if (i == 5)	// re-use the first point for the last triangle
		{
			// vertex 2
			buf[idx + 6] = (GLfloat) hex.vertices[0].x;
			buf[idx + 7] = (GLfloat) hex.vertices[0].y;
			buf[idx + 8] = (GLfloat) 0.f;
		}
		else
		{
			// vertex 2
			buf[idx + 6] = (GLfloat) hex.vertices[i + 1].x;
			buf[idx + 7] = (GLfloat) hex.vertices[i + 1].y;
			buf[idx + 8] = (GLfloat) 0.f;
		}
		
		// we've added 9 GLfloats per loop
		idx += 9;
	}
}

void
fillHexLineBuffer(GLfloat buf[], int len, std::vector<hex_info>* hexes)
{
	Point p1, p2;
	int idx = 0;
	for (int i = 0; i < (int) hexes->size(); i++)
	{
		hex_info hxi = (*hexes)[i];
		for (int j = 0; j < 6; j ++)
		{
			if (j == 5) // wrap
			{
				p1 = hxi.vertices[j];
				p2 = hxi.vertices[0];
			}
			else
			{
				p1 = hxi.vertices[j];
				p2 = hxi.vertices[j + 1];
			}
			
			buf[idx + 0] = p1.x;
			buf[idx + 1] = p1.y;
			buf[idx + 2] = 0.f;
			buf[idx + 3] = p2.x;
			buf[idx + 4] = p2.y;
			buf[idx + 5] = 0.f;
			idx += 6;
		}
	}
}

bool
createScene(std::vector<hex_info>* hexes, Entity* entities, uint32 entity_count)
{
	initMatrices(PROJ_TYPE);

	// Vertex Data
	// TODO: index duplicate vertices
	// http://www.opengl-tutorial.org/intermediate-tutorials/tutorial-9-vbo-indexing/
	int hex_count = (int) hexes->size();
	// 6 triangles * 3 vertices per triangle * 3 floats per vertex = 54
	int vbuf_len = hex_count * 6 * 3 * 3;

	// TODO: surely there's a way to use indexed drawing for line vertices eg) line_loop
	// 	and still use one buffer for multiple shapes/paths gldrawarraysintanced?, gldrawelements?
	// 	https://gamedev.stackexchange.com/questions/104310/opengl-4-5-primitive-restart-vs-base-index
	int line_vertices_per_hex = 6 * 2; // 12 vertices since we're using line segments atm
	int line_buf_len = hexes->size() * line_vertices_per_hex * 3; // 3 floats per vertex

	// temporary buffers
	GLfloat* vbuf = (GLfloat*) std::calloc(vbuf_len, sizeof(GLfloat));
	GLfloat* cbuf = (GLfloat*) std::calloc(vbuf_len, sizeof(GLfloat));
	GLfloat* line_buf = (GLfloat*) std::calloc(vbuf_len, sizeof(GLfloat));

	for (int i = 0; i < hex_count; i++)
		fillTriangleBufferFromHex(vbuf, 54 * i, (*hexes)[i]);


	rgInitGLBufferObject(&g_filled_hex_render_group->vertex_buffer, vbuf_len,
				GL_DYNAMIC_DRAW, GL_ARRAY_BUFFER, vbuf);

	// color data for hex vertices

	rgFillColorBuffer(cbuf, vbuf_len, hexes);
	rgInitGLBufferObject(&g_filled_hex_render_group->color_buffer, vbuf_len,
				GL_DYNAMIC_DRAW, GL_ARRAY_BUFFER,  cbuf);

	// cheat at vertex normals since all hexes lay flat on z-axis
	
	GLfloat* normal_buf = (GLfloat*) std::calloc(vbuf_len, sizeof(GLfloat));
	for (int i = 0; i < vbuf_len; i += 3) {
		normal_buf[i] = 0;
		normal_buf[i + 1] = 0;
		normal_buf[i + 2] = 1;
	}
	rgInitGLBufferObject(&g_filled_hex_render_group->vertex_normals, vbuf_len,
		GL_STATIC_DRAW, GL_ARRAY_BUFFER, normal_buf);
	g_filled_hex_render_group->use_normals = true;

	// hex line vertex data

	fillHexLineBuffer(line_buf, line_buf_len, hexes);
	rgInitGLBufferObject(&g_hex_line_render_group->vertex_buffer, line_buf_len,
				GL_STATIC_DRAW, GL_ARRAY_BUFFER,  line_buf);
	// TODO: add a color buffer to hex_line and debug render groups to re-use
	// 	fragment shaders and simplify draw rgDraw()

	// free temporary buffers
	std::free(vbuf);
	std::free(cbuf);
	std::free(line_buf);
	std::free(normal_buf);
	vbuf = cbuf = line_buf = normal_buf = nullptr;

	// debug draw vertexes
	int len = 4 * 3; // 4 vertices, 3 floats per vertex
	rgInitGLBufferObject(&g_debug_render_group->vertex_buffer, len,
				GL_DYNAMIC_DRAW, GL_ARRAY_BUFFER,  0);

	// entities

	// TODO: wtf, I only accounted for 1 entity in the entity render group :(
	// 	probably need one render_group struct for each entity
	for (uint i = 0; i < entity_count; i++)
		rgInitEntity(g_entity_render_group, &entities[i]);

	// lights
	// TODO: load light properties from scene/level files

	g_test_light.light_ID = glGetUniformLocation(g_entity_render_group->program_id, "light_position");
	g_test_light.position = glm::vec3(640, 500, 400); // above center of hexgrid
	g_test_light.direction = glm::vec3(0, 0, 0) - g_test_light.position; // back towards test entity
	g_test_light.color = glm::vec3(1.f, 1.f, 1.f);
	g_test_light.intensity = 1.f;

	return true;
}

void
moveCamera(bool up, bool left, bool down, bool right, bool forward, bool backward)
{
	if (!up && !left && !down && !right && !forward && !backward)
		return;

	glm::vec3 f = g_camera.forward;
	glm::vec3 u = g_camera.up;
	glm::vec3 old = g_camera.position;
	glm::vec3 &p = g_camera.position;
	glm::vec3 v(0.f); // normalized direction
	
	// TODO: still seems like we're adding magnitude when moving in 2 directions
#if 0
	if (forward) v = glm::normalize(v + f);
	if (backward) v = glm::normalize(v - f);
	if (up) v = glm::normalize(v + u);
	if (down) v = glm::normalize(v - u);
	if (left) v -= glm::normalize(glm::cross(f, u));
	if (right) v -= glm::normalize(glm::cross(u, f));
#else
	if (forward) v +=  f;
	if (backward) v -= f;
	if (up) v += u;
	if (down) v -= u;
	if (left) v -= glm::cross(f, u);
	if (right) v -= glm::cross(u, f);
#endif

	p += (v * MOVE_SPEED);
	glm::vec3 diff = old - p;
	g_scene_matrices.view = glm::translate(g_scene_matrices.view, diff);
	g_scene_matrices.MVP = g_scene_matrices.projection * g_scene_matrices.view * g_scene_matrices.model; 
}

void
rotateCamera(int32	xrel, int32 yrel)
{
	camera &c = g_camera;
	float &h = c.hAngle;
	float &v = c.vAngle;
	h += ROTATE_SPEED * xrel;
	v -= ROTATE_SPEED * yrel;

	// clamp vAngle to prevent gimbal lock
	float a = glm::radians(CAMERA_Z_CLAMP_ANGLE);
	if (v < (-1 * a)) v = (-1 * a);
	if (v > a) v = a;
	
	c.forward = glm::vec3(
		glm::cos(v) * glm::sin(h),
		glm::cos(v) * glm::cos(h),
		glm::sin(v)
	);

	glm::normalize(c.forward);
	c.up = glm::vec3(0,0,1);
	c.left = glm::normalize(glm::cross(c.forward, c.up));
	c.up = glm::normalize(glm::cross(c.left, c.forward));

	g_scene_matrices.view = glm::lookAt(c.position, c.position + c.forward, c.up);
	g_scene_matrices.MVP = g_scene_matrices.projection * g_scene_matrices.view * g_scene_matrices.model; 
}

// NOTE: don't need this yet
void
rollCamera(bool CW, bool CCW)
{
#if 0
	if ((!CW && !CCW) || (CW && CCW))
		return;

	float a = 0.005f;
	if (CW) a *= 1;
	if (CCW) a *= -1;
	camera &c = g_camera;
	glm::mat4 m = glm::rotate(glm::mat4(1.f), a, c.forward);
	glm::vec4 v(c.up.x, c.up.y, c.up.z, 0);
	v = v * m;
	g_camera.up = glm::vec3(v.x, v.y, v.z);
	g_scene_matrices.view *= m;
	g_scene_matrices.MVP = g_scene_matrices.projection * g_scene_matrices.view * g_scene_matrices.model; 
#endif
}

void
renderFrame(std::vector<hex_info> *hexes, Entity* entities, uint32 entity_count)
{
	glClearColor(g_clear_col.R, g_clear_col.G, g_clear_col.B, g_clear_col.A);
	glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);

	glm::mat4 m_model = g_scene_matrices.model;
	glm::mat4 m_view = g_scene_matrices.view;
	glm::mat4 m_projection = g_scene_matrices.projection;

	// filled hexes

	// get new colors every frame
	gl_render_group* rg = g_filled_hex_render_group;
	rgFillColorBuffer(rg->color_buffer.buffer, rg->color_buffer.buffer_len, hexes);
	rgDraw(rg, GL_TRIANGLES, m_model, m_view, m_projection,
		g_test_light.position, g_test_light.light_ID);

	// hex lines

	rgDraw(g_hex_line_render_group, GL_LINES, m_model, m_view, m_projection,
		g_test_light.position, g_test_light.light_ID);

	// TODO: update and send array of lights (pos, dir, color, intesity to shaders
	// 	every frame through	rgDrawIndexed()
	// entities
	for (uint i = 0; i < entity_count; i++) {
		rgDrawIndexed(
			g_entity_render_group, GL_TRIANGLES,
			entities[i].mesh->model_transform, m_view, m_projection,
			g_test_light.position, g_test_light.light_ID
		);
	}
}

void
renderDebug(std::vector<Point> &vertices)
{
	// TODO: indexed line drawing
	real64 buf[4 * 3] = {
		vertices[0].x, vertices[0].y, 0,
		vertices[1].x, vertices[1].y, 0,
		vertices[2].x, vertices[2].y, 0,
		vertices[3].x, vertices[3].y, 0,
	};

	// copy vertexes to render group
	gl_render_group* rg = g_debug_render_group;
	for (int i = 0; i < 12; i++)
		rg->vertex_buffer.buffer[i] = buf[i];

	rgDraw(rg, GL_LINE_LOOP, g_scene_matrices.model, g_scene_matrices.view,
		g_scene_matrices.projection, g_test_light.position, g_test_light.light_ID, true);
}

void
freeBuffers()
{
	std::vector<gl_render_group*> groups = {
		g_filled_hex_render_group,
		g_hex_line_render_group,
		g_debug_render_group,
		g_entity_render_group
	};
	
	for (gl_render_group* group : groups)
		rgFree(group);
}