/*
 * TODO:
 * - organize orbit functions into interface/internal functions
 * - add an 'orbits' namespace
 *   - drop orbit from interface functions,
 *   	eg) 'orbitGetTimeOfFlight()' becomes 'getTimeOfFlight()'
 * - make an 'overlay' graphic for things like apoapsis, perisapsis, f1, f2,
 *   	flight path
 * - impulsive orbital maneuvers
 * - Hohmman transfer orbits
 * - patched conic method for transferring between 2 grav bodies
 */

#include <cassert>
#include <cmath>

#include <SDL2/SDL.h>
#include <glm/glm.hpp>
#include <glm/gtc/matrix_transform.hpp>

#include "input.h"
#include "tangerine.h"

#include "game.h"
#include "gooey.h"
#include "orbits.h"


const double SCALING = 0.001;
const vec4 g_light_direction = vec4(-2, 1, 3, 1);
const vec4 g_light_color = vec4(0.5, 0.5, 0.5, 1);
const uvec4 g_light_intensities = uvec4(1, 0, 0, 0);


void
initCamera(RenderState* rs, vec3 cam_pos, vec3 cam_focus, vec3 cam_up)
{
	float aspect_ratio = (float) rs->window_dims.x / (float) rs->window_dims.y;
	cameraInitPerspective(rs->camera, cam_pos, cam_focus, cam_up, aspect_ratio);
	GLBuffer* xform_ubo = getUBOByName(rs->gl_ctx, "matrices");
	assert(xform_ubo != nullptr);
	updateGLBuffer(xform_ubo, &rs->camera->xforms);
}
void
initLights(RenderState* rs)
{
	LightsBuffer* lb = rs->lights_buf;
	u32 idx = 0;

	// NOTE: add a directional light
	idx = (*lb->active_d_lights)++;
	lb->dl_directions[idx] = g_light_direction;
	lb->dl_colors[idx] = g_light_color;
	lb->dl_intensities[idx] = g_light_intensities;

	GLBuffer* lights_ubo = getUBOByName(rs->gl_ctx, "lights");
	assert(lights_ubo != nullptr);
	updateGLBuffer(lights_ubo, lb->buffer);
}

// FIXME: could pass EllipseParameters and Ellipse3D instead of TwoBodySystem
Entity*
initEllipseEntity(RenderState* rs,
	TwoBodySystem* system,
	u32 num_vertices)
{
	system->e3d = ellipseInit3D(system->ep, num_vertices);
	Mesh* m = meshInit(rs->rg_arena, num_vertices, num_vertices, false, true);
	vec3 vertex_color = vec3(255, 0, 255);

	for (uint i = 0; i < system->e3d.vert_count; i++) {
		m->vertices[i] = system->e3d.vertices[i];
		m->colors[i] = vertex_color;
		m->indices[i] = i;
	}

	Model* mdl = modelInitManual(rs->rg_arena, 1, m);
	RenderGroup* rg = getRenderGroupByName(rs, "manual mesh group");
	Entity* e = getFreeEntity(rg);
	initEntity(e, rs->gl_ctx,
				rs->rg_arena,
				mdl,
				rg->shader->num_vertex_attribs,
				rg->shader->attrib_mappings,
				"ellipse 01",
				GL_LINE_LOOP);

	return e;
}

Entity*
initPlanetEntity(RenderState* rs, double r)
{
	ShaderProgram* shader_lit = getShaderByName("full_lighting", rs->gl_ctx);
	RenderGroup* rg_full = getFreeRenderGroup(rs);
	initRenderGroup(rg_full, rs->rg_arena, shader_lit, 256, "lit group");
	Model* icosphere = getModelByPath(&rs->assets, "../data/icosphere.gltf");
	Entity* e = getFreeEntity(rg_full);
	assert(icosphere && e);
	initEntity(e,
				rs->gl_ctx,
				rs->rg_arena,
				icosphere,
				shader_lit->num_vertex_attribs,
				shader_lit->attrib_mappings,
				"grav body 01");
	scaleEntity(e, r);

	return e;
}

Entity*
initSatelliteEntity(RenderState* rs)
{
	u32 num_vertices = 3;
	vec3 vertex_color = vec3(255, 0, 0);
	Mesh* m = meshInit(rs->rg_arena, num_vertices, num_vertices, false, true);
	m->vertices[0] = vec3(0, 1, 0);
	m->colors[0] = vertex_color;
	m->indices[0] = 0;
	m->vertices[1] = vec3(-1, -1, 0);
	m->colors[1] = vertex_color;
	m->indices[1] = 1;
	m->vertices[2] = vec3(1, -1, 0);
	m->colors[2] = vertex_color;
	m->indices[2] = 2;

	Model* mdl = modelInitManual(rs->rg_arena, 1, m);
	RenderGroup* rg = getRenderGroupByName(rs, "manual mesh group");
	Entity* e = getFreeEntity(rg);
	initEntity(e, rs->gl_ctx,
				rs->rg_arena,
				mdl,
				rg->shader->num_vertex_attribs,
				rg->shader->attrib_mappings,
				"ship 01",
				GL_TRIANGLES);

	return e;
}

void
loadScene(GameState* gs, RenderState* rs)
{
	initCamera(rs, vec3(0, -75 / SCALING, 0), vec3(0, 0, 0), vec3(0,0,1));
	initLights(rs);
	gs->running = true;

	double a = 26564.5;		// semi-major axis in km
	double e = 0.7411;		// eccentricity
	double mu = 398601.68;	// gravitational parameter
	double r = 6378;		// body radius in km

	GameOrbit* orbit_1 = getFreeOrbit(gs);
	systemInit(orbit_1->system, gravBodyInit(mu, r), orbitInit(a, e));

	// TODO: streamline the boilerplate in init_X_Entity functions
	ShaderProgram* shader = getShaderByName("colored_vertices", rs->gl_ctx);
	initRenderGroup(
		getFreeRenderGroup(rs), rs->rg_arena, shader, 256, "manual mesh group");

	orbit_1->ellipse_entity = initEllipseEntity(rs, &orbit_1->system, 256);
	setEntityPosition(orbit_1->ellipse_entity, vec3(0, 0, 0));
	rotateEntity(orbit_1->ellipse_entity, vec3(1, 0, 0), (float) M_PI / 2);

	initPlanetEntity(rs, r);

	orbit_1->satellite_entity = initSatelliteEntity(rs);
	scaleEntity(orbit_1->satellite_entity, 1 / SCALING);
	rotateEntity(orbit_1->satellite_entity, vec3(1, 0, 0), (float) M_PI / 2);
	setEntityPosition(orbit_1->satellite_entity,
			orbit_1->system.e3d.vertices[0]);

	// NOTE: testing multiple orbits
	double a_2 = r + 10000; // km
	double e_2 = 0;
	GameOrbit* orbit_2 = getFreeOrbit(gs);
	systemInit(orbit_2->system, gravBodyInit(mu, r), orbitInit(a_2, e_2));
	orbit_2->ellipse_entity = initEllipseEntity(rs, &orbit_2->system, 256);
	setEntityPosition(orbit_2->ellipse_entity, vec3(0, 0, 0));
	rotateEntity(orbit_2->ellipse_entity, vec3(1, 0, 0), (float) M_PI / 2);
}

void
updateSatelliteModel(TwoBodySystem& sys, double time_step)
{
	Satellite& sat = sys.sat;
	sat.theta = orbitGetPropagatedTrueAnomaly(sys, sat.theta, time_step);
	sat.gamma = orbitGetFlightPathAngle(sys.ep.e, sat.theta);
	sat.r = orbitGetRadialDistance(sys.ep.e, sys.ep.p, sat.theta);
	sat.v = orbitGetVelocity(sys.epsilon, sys.body.mu, sat.r);
	sat.position = glm::vec3(polarToRect(sat.theta, sat.r), 0);
}

void
updateSatelliteEntity(Entity* e, const Satellite& sat)
{
	const static mat4 xform =
		glm::rotate(mat4(1.0), (float) M_PI_2, vec3(1, 0, 0));
	const vec3& v = sat.position;
	setEntityPosition(e, xform * vec4(v.x, v.y, v.z, 1));
}

// NOTE: use ellipseValidate(ep) before calling to avoid failing assertions
void
updateOrbit(TwoBodySystem sys, Entity& ellipse_entity)
{
#if 0
	ellipse3DUpdate(sys.ep, sys.e3d);

	for (uint i = 0; i < sys.e3d.vert_count; i++)
		ellipse_entity.mesh->vertices[i] = sys.e3d.vertices[i];

	entUpdateSimpleMesh(ellipse_entity, ellipse_entity.mesh, GL_LINE_LOOP);
#endif
}

void
preFrameCallback(RenderState* rs, void* user_data = nullptr)
{
	static InputState is = {};
	SDL_Event e;
	bool gooey_wants = false;

	while (SDL_PollEvent(&e)) {
		// FIXME: we should check for escape key here first
		gooey_wants = gooProcessEvent(e);
		if (!gooey_wants) inputProcessEvent(&is, e);
	}

	if (is.window_closed || is.escape)
		rs->running = false;

	// TODO: sim time stuff should have dedicated functions, and maybe a test
	// 	since it's pretty important that the simulation is accurate-ish
	// TODO: verify time to apoapsis/periapsis are correct
	assert(user_data != nullptr);
	GameState* gs = (GameState*) user_data;
	u64 last_sdl_tick = gs->game_time_ms;
	gs->game_time_ms = SDL_GetTicks64();
	u64 current_tick = gs->game_time_ms - last_sdl_tick;

	// NOTE: update sim time base on time since last frame * sim_speed
	if (gs->running) {
		u64 last_game_tick = gs->sim_time_ms;
		gs->sim_time_ms = gs->sim_time_ms + current_tick * gs->sim_speed;
		u32 diff_ms = gs->sim_time_ms - last_game_tick;
		double time_step = double(diff_ms) / 1000;

		for (u32 i = 0; i < gs->num_orbits; i++) {
			GameOrbit& orbit = gs->orbits[i];

			if (orbit.in_use && orbit.satellite_entity) {
				updateSatelliteModel(orbit.system, time_step);
				updateSatelliteEntity(orbit.satellite_entity, orbit.system.sat);
				// TODO: update EllipseEntity per frame
				//updateOrbit(gs->system, ellipse_entity);
			}
		}
	}
}

void
postFrameCallback(RenderState* rs, void* user_data = nullptr)
{
	assert(user_data != nullptr);
	GameState* gs = (GameState*) user_data;
	GameOrbit& orbit = gs->orbits[0];
	assert(orbit.in_use);
	gooDraw(rs->handles.window,
			orbit.system,
			gs->running,
			gs->sim_time_ms,
			gs->sim_speed);
}

#define DEFAULT_SIM_SPEED 2000
#define GAME_ARENA_SIZE 16 * 1024 * 1024	// 16MB
#define DEFAULT_MAX_ORBITS 10000
int
main()
{
	RenderState* rs = initRenderState("orbital shipping",
		uvec2(1600, 900),
		SDL_INIT_VIDEO | SDL_INIT_TIMER);

	if (rs == nullptr) {
		LOG(Error) << "Error Initialzing renderer\n";
		return 1;
	}

	if (!gooInit(rs->handles.window, rs->handles.sdl_gl_ctx)) {
		LOG(Error) << "Error Initialzing gooey\n";
		return 1;
	}

	GameState gs = {0};
	gs.arena =  arenaInit(GAME_ARENA_SIZE);
	gs.sim_speed = DEFAULT_SIM_SPEED;
	gs.max_orbits = DEFAULT_MAX_ORBITS;
	gs.orbits = ARENA_ALLOC(gs.arena, GameOrbit, DEFAULT_MAX_ORBITS);

	loadScene(&gs, rs);
	doRenderLoop(rs, 60, preFrameCallback, postFrameCallback, &gs);
	gooFree();
	freeRenderState(rs);

	return 0;
}