#include "raylib.h"
#include "raymath.h"
#include "rlgl.h"
#include <cmath>
#include <optional>

#include "boid-playground.hpp"
#include "raycast.cpp"

static float vector2_atan2(Vector2 a) {
	return std::atan2(a.y, a.x);
}

static Vector2 vector2_mul_value(Vector2 v, float value) {
	return { v.x * value, v.y * value };
}

static Vector2 vector2_div_value(Vector2 v, float value) {
	return { v.x / value, v.y / value };
}

static Vector2 vector2_from_angle(float angle) {
	return { std::cos(angle), std::sin(angle) };
}

static void boid_rand_init(World *world, Boid *boid, float border) {
	float world_width = world->size.x;
	float world_height = world->size.y;
	boid->pos.x = GetRandomValue(border, world_width-border);
	boid->pos.y = GetRandomValue(border, world_height-border);

	float facing = GetRandomValue(0, 2*PI);
	boid->dir = Vector2Rotate({ 1, 0 }, facing);
	boid->speed = GetRandomValue(world->min_speed, world->max_speed);
}

static Vector2 get_center_point(std::vector<Vector2> &points) {
	Vector2 center = { 0, 0 };
	for (int i = 0; i < points.size(); i++) {
		center.x += points[i].x;
		center.y += points[i].y;
	}
	center.x /= points.size();
	center.y /= points.size();
	return center;
}

static void draw_obstacle(Obstacle *obstacle, Color color) {
	std::vector<Vector2> *points = &obstacle->points;
	int point_count = points->size();

	rlBegin(RL_TRIANGLES);
	{
		rlColor4ub(color.r, color.g, color.b, color.a);
		for (int j = 0; j < point_count-1; j++) {
			Vector2 *point1 = &(*points)[j];
			Vector2 *point2 = &(*points)[j+1];
			rlVertex2f(point1->x, point1->y);
			rlVertex2f(obstacle->center.x, obstacle->center.y);
			rlVertex2f(point2->x, point2->y);
		}

		rlVertex2f((*points)[point_count-1].x, (*points)[point_count-1].y);
		rlVertex2f(obstacle->center.x, obstacle->center.y);
		rlVertex2f((*points)[0].x, (*points)[0].y);
	}
	rlEnd();
}

static void draw_debug_boid_obstacle_avoidance(Visuals *visuals, World *world, Boid *boid) {
	Vector2 pos = boid->pos;

	int ray_count = world->collision_avoidance_ray_count * 2 + 1;
	float ray_angles[ray_count];
	fill_avoidance_ray_angles(ray_angles, ray_count, world->collision_avoidance_ray_angle);

	float facing = std::atan2(boid->dir.y, boid->dir.x);
	for (int i = 0; i < ray_count; i++) {
		Vector2 ray_dir = {
			std::cos(facing + ray_angles[i]),
			std::sin(facing + ray_angles[i])
		};

		RayHitResult hit_result;
		get_intersect_with_world(&hit_result, pos, ray_dir, world);
		bool hit_obstacle = (hit_result.hit != -1 && hit_result.hit <= world->collision_avoidance_distance);

		Color ray_color = GREEN;
		float ray_length = world->collision_avoidance_distance;
		if (hit_obstacle) {
			ray_length = hit_result.hit;
			ray_color = BLUE;
		}

		Vector2 hit_pos = Vector2Add(pos, Vector2Multiply(ray_dir, { ray_length, ray_length }));
		DrawLine(pos.x, pos.y, hit_pos.x, hit_pos.y, ray_color);
		if (hit_obstacle) {
			DrawCircle(hit_pos.x, hit_pos.y, visuals->boid_edge_size * 0.05, ray_color);
		}
	}
}

static Vector2 get_collision_avoidance_dir(World *world, Boid *boid) {
	int ray_count = world->collision_avoidance_ray_count * 2 + 1;
	float ray_angles[ray_count];
	fill_avoidance_ray_angles(ray_angles, ray_count, world->collision_avoidance_ray_angle);

	int best_avoidance = -1;
	Vector2 avoidance_dir = { 0, 0 };
	float facing = std::atan2(boid->dir.y, boid->dir.x);
	bool got_hit = false;
	RayHitResult hit_results[ray_count];

	for (int i = 0; i < ray_count; i++) {
		Vector2 ray_dir = vector2_from_angle(facing + ray_angles[i]);
		get_intersect_with_world(&hit_results[i], boid->pos, ray_dir, world);
		if (hit_results[i].hit != -1 && hit_results[i].hit <= world->collision_avoidance_distance) {
			got_hit = true;
		}

		if (hit_results[i].hit > hit_results[best_avoidance].hit || best_avoidance == -1) {
			avoidance_dir = ray_dir;
			best_avoidance = i;
		}
	}

	if (got_hit) {
		return avoidance_dir;
	} else {
		return { 0, 0 };
	}
}

static int count_out_of_bounds_boids(World *world) {
	int count = 0;
	for (int i = 0; i < world->boids.size(); i++) {
		Vector2 *pos = &world->boids[i].pos;

		bool x_out_of_bounds = (pos->x <= 0 || pos->x >= world->size.x);
		bool y_out_of_bounds = (pos->y <= 0 || pos->y >= world->size.y);
		if (x_out_of_bounds || y_out_of_bounds)  {
			count++;
		}
	}
	return count;
}

static void draw_circle_sector(Vector2 center, float radius, float start_angle, float end_angle, int segments, Color color) {
	rlBegin(RL_TRIANGLES);
	float angle_step = (end_angle - start_angle) / segments;
	for (int i = 0; i < segments; i++)
	{
		rlColor4ub(color.r, color.g, color.b, color.a);
		float angle = start_angle + i * angle_step;
		float nextAngle = start_angle + (i+1) * angle_step;

		rlVertex2f(center.x, center.y);
		rlVertex2f(center.x + cosf(nextAngle)*radius, center.y + sinf(nextAngle)*radius);
		rlVertex2f(center.x + cosf(angle)    *radius, center.y + sinf(angle)    *radius);
	}
	rlEnd();
}

static int get_boids_in_view_cone(Boid **boids_in_view, Boid *boid, float view_radius, float view_angle, Boid *boids, int boid_count) {
	int count = 0;
	float dot_threshold = Vector2DotProduct(boid->dir, Vector2Rotate(boid->dir, view_angle/2));

	for (int i = 0; i < boid_count; i++) {
		if (&boids[i] == boid) continue;

		Vector2 dir_to_boid = Vector2Normalize(Vector2Subtract(boids[i].pos, boid->pos));
		float dot = Vector2DotProduct(boid->dir, dir_to_boid);
		if (dot >= dot_threshold && Vector2DistanceSqr(boids[i].pos, boid->pos) <= view_radius * view_radius) {
			boids_in_view[count] = &boids[i];
			count++;
		}
	}

	return count;
}

static void world_update(World *world) {
	float dt = GetFrameTime();

	for (int i = 0; i < world->boids.size(); i++) {
		Boid *boid = &world->boids[i];
		Vector2 acc = { 1, 0 };

		Boid *local_boids[world->boids.size()];
		int local_boids_count = get_boids_in_view_cone(local_boids, boid, world->view_radius, world->view_angle, world->boids.data(), world->boids.size());

		if (local_boids_count > 0) {
			Vector2 separation_force = { 0, 0 };
			Vector2 flock_center  = { 0, 0 };
			Vector2 flock_heading = { 0, 0 };
			for (int j = 0; j < local_boids_count; j++) {
				flock_heading = Vector2Add(flock_heading, local_boids[j]->dir);
				flock_center  = Vector2Add(flock_center , local_boids[j]->pos);

				Vector2 pos_diff = Vector2Subtract(boid->pos, local_boids[j]->pos);
				float dist_sqr = Vector2LengthSqr(pos_diff);
				if (dist_sqr <= world->separation_radius * world->separation_radius) {
					separation_force = Vector2Add(separation_force, vector2_div_value(pos_diff, dist_sqr));
				}
			}
			flock_center = vector2_div_value(flock_center, local_boids_count);

			Vector2 alignment_force = Vector2Normalize(flock_heading);
			alignment_force = vector2_mul_value(alignment_force, world->max_speed);
			alignment_force = vector2_mul_value(alignment_force, world->alignment_strength);
			acc = Vector2Add(acc, alignment_force);

			Vector2 cohesion_force = Vector2Normalize(Vector2Subtract(flock_center, boid->pos));
			cohesion_force = vector2_mul_value(cohesion_force, world->max_speed);
			cohesion_force = vector2_mul_value(cohesion_force, world->cohesion_strength);
			acc = Vector2Add(acc, cohesion_force);

			separation_force = Vector2Normalize(separation_force);
			separation_force = vector2_mul_value(separation_force, world->max_speed);
			separation_force = vector2_mul_value(separation_force, world->separation_strength);
			acc = Vector2Add(acc, separation_force);
		}

		// Apply obstacle avoidance to accelaration
		Vector2 collision_avoidance = get_collision_avoidance_dir(world, boid);
		collision_avoidance = vector2_mul_value(collision_avoidance, world->max_speed);
		collision_avoidance = vector2_mul_value(collision_avoidance, world->collision_avoidance_strength);
		acc = Vector2Add(acc, collision_avoidance);

		// Clamp accelaration
		Vector2 clamped_acc = acc;
		float acc_size = Vector2Length(acc);
		if (acc_size > world->max_steer_speed) {
			clamped_acc = vector2_mul_value(Vector2Normalize(acc), world->max_steer_speed);
		}

		// Apply accelaration
		Vector2 velocity = Vector2Multiply(boid->dir, { boid->speed, boid->speed });
		velocity = Vector2Add(velocity, vector2_mul_value(clamped_acc, dt));

		boid->dir = Vector2Normalize(velocity);
		boid->speed = Vector2Length(velocity);

		boid->speed = Clamp(boid->speed, world->min_speed, world->max_speed);
		Vector2 step = vector2_mul_value(boid->dir, boid->speed * dt);
		Vector2 target_pos = Vector2Add(boid->pos, step);

		// Check collisions
		RayHitResult hit_result;
		get_intersect_with_world(&hit_result, target_pos, step, world);
		if (hit_result.hit == -1 || hit_result.hit > 2) {
			boid->pos = target_pos;
		}

		if (world->looping_walls) {
			if (boid->pos.x > world->size.x) {
				boid->pos.x -= world->size.x;
			} else if (boid->pos.x < 0) {
				boid->pos.x += world->size.x;
			}
			if (boid->pos.y > world->size.y) {
				boid->pos.y -= world->size.y;
			} else if (boid->pos.y < 0) {
				boid->pos.y += world->size.y;
			}
		}
	}
}

static void world_draw(World *world, Visuals *visuals) {
	for (int i = 0; i < world->obstacles.size(); i++) {
		draw_obstacle(&world->obstacles[i], GRAY);
	}

	if (visuals->draw_view_cone) {
		Color view_cone_color = Fade(GRAY, 0.4);
		for (int i = 0; i < world->boids.size(); i++) {
			Boid *boid = &world->boids[i];
			Vector2 pos = boid->pos;
			float facing = std::atan2(boid->dir.y, boid->dir.x);

			float view_angle = world->view_angle;
			float segments = 16;

			draw_circle_sector(pos, world->view_radius, facing - view_angle/2, facing + view_angle/2, segments, view_cone_color);
		}
	}

	float boid_length = visuals->boid_edge_size * std::sqrt(3)/2;
	float boid_width = visuals->boid_edge_size * 0.6;
	for (int i = 0; i < world->boids.size(); i++) {
		Boid *boid = &world->boids[i];

		if (visuals->draw_collision_avoidance_rays) {
			draw_debug_boid_obstacle_avoidance(visuals, world, boid);
		}

		Vector2 triangle[] = {
			{  boid_length*2/3.0f, 0 },
			{ -boid_length*1/3.0f, -boid_width/2 },
			{ -boid_length*1/3.0f, boid_width/2 },
		};

		float facing = std::atan2(boid->dir.y, boid->dir.x);
		for (int i = 0; i < 3; i++) {
			triangle[i] = Vector2Add(boid->pos, Vector2Rotate(triangle[i], facing));
		}

		DrawTriangle(triangle[0], triangle[1], triangle[2], BLACK);

		if (visuals->draw_boid_direction) {
			DrawCircle(boid->pos.x, boid->pos.y, visuals->boid_edge_size * 0.05, RED);
			Vector2 look_pos = Vector2Add(boid->pos, Vector2Multiply(boid->dir, { 30, 30 }));
			DrawLine(boid->pos.x, boid->pos.y, look_pos.x, look_pos.y, RED);
		}
	}
}

int main() {
	SetTraceLogLevel(LOG_TRACE);

    int screen_width = 1280;
    int screen_height = 720;

    raylib::Color text_color(LIGHTGRAY);
    raylib::Window window(screen_width, screen_height, "Boid Playground");

    SetTargetFPS(60);

	World world;
	world.size = { (float)screen_width, (float)screen_height };
	Visuals visuals;

	float border = visuals.boid_edge_size;
	for (int i = 0; i < 100; i++) {
		Boid boid;
		boid_rand_init(&world, &boid, border);
		world.boids.push_back(boid);
	}

	// world.boids.push_back({
	// 	.pos = { 100, 100 },
	// 	.dir = { 1, 0 },
	// 	.speed = world.boid_min_speed
	// });
	// world.boids.push_back({
	// 	.pos = { 100, 120 },
	// 	.dir = { 1, 0 },
	// 	.speed = world.boid_min_speed
	// });

    // Main game loop
    while (!window.ShouldClose()) {
		// TODO: Show this on screen
		// LogTrace("%d", count_out_of_bounds_boids(&world));

		world_update(&world);

        // Draw
        BeginDrawing();
        ClearBackground(RAYWHITE);

		world_draw(&world, &visuals);

        EndDrawing();
    }

    return 0;
}