#include <algorithm>
#include <cmath>

#include "Decals.h"

#define NORMAL_OFFSET 0.02f

enum corner { SW, SE, NE, NW };

void bind(struct Decals *d, XYZ location, float size, XYZ normal,
          int poly, Model *model, XYZ move, float rotation,
          XYZ right, XYZ up, enum corner direction)
{
	float x, y;
	switch (direction) {
	case SW:
		x = -1.0f;
		y = -1.0f;
		break;
	case NW:
		x = 1.0f;
		y = -1.0f;
		break;
	case NE:
		x = 1.0f;
		y = 1.0f;
		break;
	case SE:
		x = -1.0f;
		y = 1.0f;
		break;
	}

	size_t i = d->len * 8 + d->numpoints[d->len];
	d->points[i] = location + right * x + up * y;
	d->texcoordsx[i] = x * 0.5f + 0.5f;
	d->texcoordsy[i] = y * 0.5f + 0.5f;

	XYZ temp;
	if ((move.x == 0 && move.y == 0 && move.z == 0 && rotation == 0)
	    || segCrossTrigon(d->points[i] + normal / 25,
	                      d->points[i] - normal / 25,
	                      model->vertex + model->Triangles[poly].vertex[0],
	                      model->vertex + model->Triangles[poly].vertex[1],
	                      model->vertex + model->Triangles[poly].vertex[2],
	                      &normal, &temp)) {
		d->numpoints[d->len]++;
		return;
	}

	const auto n = normal / 25.0f;
	const float countinc = std::max(0.01f, std::min(1.0f / size, 0.2f));
	int good = -1;
	float count = 1.0f - countinc;
	while (good == -1 && count > -1.0f) {
		d->texcoordsx[i] = x * 0.5f + 0.5f;
		d->texcoordsy[i] = y * count * 0.5f + 0.5f;
		d->points[i] = location + right * x + up * (y * count);
		count -= countinc;
		good = model->LineCheck2(d->points[i] + n,
		                         d->points[i] - n,
		                         &temp, move, rotation);
	}
	if (good > -1) {
		d->numpoints[d->len]++;
		i++;
	}

	good = -1;
	count = 1.0f - countinc;
	while (good == -1 && count > -1.0f) {
		d->texcoordsx[i] = x * count * 0.5f + 0.5f;
		d->texcoordsy[i] = y * 0.5f + 0.5f;
		d->points[i] = location + right * (x * count) + up * y;
		count -= countinc;
		good = model->LineCheck2(d->points[i] + n,
		                         d->points[i] - n,
		                         &temp, move, rotation);
	}
	if (good > -1) {
		d->numpoints[d->len]++;
		return;
	}

	float count2 = 1.0f - countinc;
	while (good == -1 && count2 > -1.0f){
		count = 1.0f - countinc;
		while (good == -1 && count > -1.0f) {
			d->texcoordsx[i] = x * count2 * 0.5f + 0.5f;
			d->texcoordsy[i] = y * count * 0.5f + 0.5f;
			d->points[i] = location + right * (x * count2) + up * (y * count);
			count -= countinc;
			good = model->LineCheck2(d->points[i] + n,
			                         d->points[i] - n,
			                         &temp, move, rotation);
		}
		count2 -= countinc;
	}
	if (good > -1)
		d->numpoints[d->len]++;
}

void addDecal(struct Decals *d, enum decal kind, XYZ location, float size,
              XYZ normal, int poly, Model *model, XYZ move, float rotation)
{
	if (d->len >= MAX_DECALS)
		return;
	d->kind[d->len] = kind;
	d->alive[d->len] = 0;

	float normalv[] = {abs(normal.x), abs(normal.y), abs(normal.z)};
	unsigned char major = 0;
	if (normalv[1] > normalv[major])
		major = 1;
	if (normalv[2] > normalv[major])
		major = 2;

	XYZ right = {0.0f};
	if (normalv[0] == 1.0f || normalv[1] == 1.0f || normalv[2] == 1.0f) {
		if ((major == 0 && normal.x > 0) || major == 1)
			right.z = -1.0f;
		else if (major == 0)
			right.z = 1.0f;
		else
			right.x = normal.z;
	} else {
		XYZ axis = {0.0f};
		((float *) &axis)[major] = 1.0f;
		right = crossProduct(axis, normal);
	}

	d->numpoints[d->len] = 0;
	XYZ up = normalize(crossProduct(normal, right)) * (size / 3);
	right = normalize(right) * (size / 3);
	bind(d, location, size, normal, poly, model,
	     move, rotation, right, up, SW);
	bind(d, location, size, normal, poly, model,
	     move, rotation, right, up, NW);
	bind(d, location, size, normal, poly, model,
	     move, rotation, right, up, NE);
	bind(d, location, size, normal, poly, model,
	     move, rotation, right, up, SE);
	for (int i = 0; i < d->numpoints[d->len]; ++i)
		d->points[d->len * 8 + i] += normal * NORMAL_OFFSET;
	d->len++;
}