#include <stdlib.h>
#include <math.h>
#include <stdio.h>
#include "vector_stack.h"

void vec_init(Vector* result, double x, double y, double z) {
    result->x = x;
    result->y = y;
    result->z = z;
}

void vec_null(Vector* result) {
    vec_init(result, 0.0, 0.0, 0.0);
}

void vec_mul_scalar(Vector* result, Vector v, double scalar) {
    vec_init(result, v.x * scalar,
                     v.y * scalar,
                     v.z * scalar);
}

double vec_mul_dot(Vector first, Vector second) {
    return first.x * second.x +
           first.y * second.y +
           first.z * second.z;
}

void vec_mul_cross(Vector* result, Vector first, Vector second) {
    return vec_init(result, first.y * second.z - first.z * second.y,
                            first.z * second.x - first.x * second.z,
                            first.x * second.y - first.y * second.x);
}

void vec_add(Vector* result, Vector first, Vector second) {
    return vec_init(result, first.x + second.x,
                            first.y + second.y,
                            first.z + second.z);
}

void vec_sub(Vector* result, Vector first, Vector second) {
    return vec_init(result, first.x - second.x,
                            first.y - second.y,
                            first.z - second.z);
}

int vec_equals(Vector first, Vector second) {
    return (first.x == second.x)
        && (first.y == second.y)
        && (first.z == second.z);
}

static const int MAX_LENGTH=128;

char* vec_to_str(Vector v) {
    char* result = (char*) malloc(MAX_LENGTH);

    if (!result) {
        return NULL;
    }

    snprintf(result, MAX_LENGTH, "[ %.2f  %.2f  %.2f ]", v.x, v.y, v.z);
    return result;
}

void vec_print(Vector v) {
    char* str = vec_to_str(v);
    printf("%s", str);
    free(str);
}

double vec_length(Vector v) {
    return sqrt(v.x * v.x
              + v.y * v.y
              + v.z * v.z);
}

int vec_norm(Vector* result, Vector v) {
    double length = vec_length(v);

    if (length == 0.0) {
        /* no norm for a null vector */
        return -1;
    }

    vec_init(result, v.x / length,
                     v.y / length,
                     v.z / length);

    return 0;
}

int vec_collinear(Vector first, Vector second) {
    Vector cross, nullVector;

    vec_mul_cross(&cross, first, second);
    vec_null(&nullVector);
    int result = vec_equals(nullVector, cross);

    return result;
}