#pragma once

#include <assert.h>
#include "tuples.h"
#include "matrices.h"

enum pattern_type {
  PATTERN_STRIPE,
  PATTERN_GRADIENT,
  PATTERN_RING,
  PATTERN_CHECKERS
};

struct pattern {
  enum pattern_type type;
  struct tuple a;
  struct tuple b;
  struct mat4x4 transform;
};

inline static struct pattern stripe_pattern(struct tuple a, struct tuple b)
{
  return (struct pattern) {
    PATTERN_STRIPE,
    a,
    b,
    mat4x4_identity()
  };
}

inline static struct pattern gradient_pattern(struct tuple a, struct tuple b)
{
  return (struct pattern) {
    PATTERN_GRADIENT,
    a,
    b,
    mat4x4_identity()
  };
}

inline static struct pattern ring_pattern(struct tuple a, struct tuple b)
{
  return (struct pattern) {
    PATTERN_RING,
    a,
    b,
    mat4x4_identity()
  };
}

inline static struct pattern checkers_pattern(struct tuple a, struct tuple b)
{
  return (struct pattern) {
    PATTERN_CHECKERS,
    a,
    b,
    mat4x4_identity()
  };
}

inline static struct tuple stripe_at(struct pattern pattern, struct tuple point)
{
  return ((int)floorf(point.x)) % 2 == 0 ? pattern.a : pattern.b;
}

inline static struct tuple gradient_at(struct pattern pattern, struct tuple point)
{
  struct tuple distance = tuple_sub(pattern.b, pattern.a);
  float fraction = point.x - floorf(point.x);

  return tuple_add(pattern.a, tuple_mul(distance, fraction));
}

inline static struct tuple ring_at(struct pattern pattern, struct tuple point)
{
  return ((int)floorf(sqrtf(point.x * point.x + point.z * point.z))) % 2 == 0 ? pattern.a : pattern.b;
}

inline static struct tuple checkers_at(struct pattern pattern, struct tuple point)
{
  return (int)(floorf(point.x) + floorf(point.y) + floorf(point.z)) % 2 == 0 ? pattern.a : pattern.b;
}

inline static struct tuple pattern_at_object(struct pattern pattern, struct mat4x4 object_transform, struct tuple point)
{
  struct tuple object_point = mat4x4_mul_t(mat4x4_inverse(object_transform), point);
  struct tuple pattern_point = mat4x4_mul_t(mat4x4_inverse(pattern.transform), object_point);

  switch (pattern.type) {
  case PATTERN_STRIPE:
    return stripe_at(pattern, pattern_point);
  case PATTERN_GRADIENT:
    return gradient_at(pattern, pattern_point);
  case PATTERN_RING:
    return ring_at(pattern, pattern_point);
  case PATTERN_CHECKERS:
    return checkers_at(pattern, pattern_point);
  default:
    assert(false);
    break;
  }
}