/* SPDX-FileCopyrightText: 2011-2022 Blender Foundation
 *
 * SPDX-License-Identifier: Apache-2.0 */

#include "node_color.h"
#include "stdcycles.h"

point texco_remap_square(point co)
{
  return (co - point(0.5, 0.5, 0.5)) * 2.0;
}

point map_to_tube(vector dir)
{
  float u, v;
  v = (dir[2] + 1.0) * 0.5;
  float len = sqrt(dir[0] * dir[0] + dir[1] * dir[1]);
  if (len > 0.0) {
    u = (1.0 - (atan2(dir[0] / len, dir[1] / len) / M_PI)) * 0.5;
  }
  else {
    v = u = 0.0; /* To avoid un-initialized variables. */
  }
  return point(u, v, 0.0);
}

point map_to_sphere(vector dir)
{
  float len = length(dir);
  float v, u;
  if (len > 0.0) {
    if (dir[0] == 0.0 && dir[1] == 0.0) {
      u = 0.0; /* Otherwise domain error. */
    }
    else {
      u = (1.0 - atan2(dir[0], dir[1]) / M_PI) / 2.0;
    }
    v = 1.0 - acos(dir[2] / len) / M_PI;
  }
  else {
    v = u = 0.0; /* To avoid un-initialized variables. */
  }
  return point(u, v, 0.0);
}

color image_texture_lookup(string filename,
                           float u,
                           float v,
                           output float Alpha,
                           int compress_as_srgb,
                           int ignore_alpha,
                           int unassociate_alpha,
                           int is_float,
                           int is_tiled,
                           string interpolation,
                           string extension)
{
  /* Flip the y coordinate, but preserve UDIM tiles. */
  float flip_v;
  if (is_tiled) {
    float v_i = (int)v;
    flip_v = v_i + (1.0 - (v - v_i));
  }
  else {
    flip_v = 1.0 - v;
  }
  color rgb = (color)texture(
      filename, u, flip_v, "wrap", extension, "interp", interpolation, "alpha", Alpha);

  if (ignore_alpha) {
    Alpha = 1.0;
  }
  else if (unassociate_alpha) {
    rgb = color_unpremultiply(rgb, Alpha);

    if (!is_float)
      rgb = min(rgb, 1.0);
  }

  if (compress_as_srgb) {
    rgb = color_srgb_to_scene_linear(rgb);
  }

  return rgb;
}

shader node_image_texture(int use_mapping = 0,
                          matrix mapping = matrix(0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0),
                          point Vector = P,
                          string filename = "",
                          string projection = "flat",
                          string interpolation = "smartcubic",
                          string extension = "periodic",
                          float projection_blend = 0.0,
                          int compress_as_srgb = 0,
                          int ignore_alpha = 0,
                          int unassociate_alpha = 0,
                          int is_tiled = 0,
                          int is_float = 1,
                          output color Color = 0.0,
                          output float Alpha = 1.0)
{
  point p = Vector;

  if (use_mapping)
    p = transform(mapping, p);

  if (projection == "flat") {
    Color = image_texture_lookup(filename,
                                 p[0],
                                 p[1],
                                 Alpha,
                                 compress_as_srgb,
                                 ignore_alpha,
                                 unassociate_alpha,
                                 is_float,
                                 is_tiled,
                                 interpolation,
                                 extension);
  }
  else if (projection == "box") {
    /* object space normal */
    vector Nob = transform("world", "object", N);

    /* project from direction vector to barycentric coordinates in triangles */
    vector signed_Nob = Nob;
    Nob = vector(fabs(Nob[0]), fabs(Nob[1]), fabs(Nob[2]));
    Nob /= (Nob[0] + Nob[1] + Nob[2]);

    /* basic idea is to think of this as a triangle, each corner representing
     * one of the 3 faces of the cube. in the corners we have single textures,
     * in between we blend between two textures, and in the middle we a blend
     * between three textures.
     *
     * the `Nxyz` values are the barycentric coordinates in an equilateral
     * triangle, which in case of blending, in the middle has a smaller
     * equilateral triangle where 3 textures blend. this divides things into
     * 7 zones, with an if () test for each zone. */

    vector weight = vector(0.0, 0.0, 0.0);
    float blend = projection_blend;
    float limit = 0.5 * (1.0 + blend);

    /* first test for corners with single texture */
    if (Nob[0] > limit * (Nob[0] + Nob[1]) && Nob[0] > limit * (Nob[0] + Nob[2])) {
      weight[0] = 1.0;
    }
    else if (Nob[1] > limit * (Nob[0] + Nob[1]) && Nob[1] > limit * (Nob[1] + Nob[2])) {
      weight[1] = 1.0;
    }
    else if (Nob[2] > limit * (Nob[0] + Nob[2]) && Nob[2] > limit * (Nob[1] + Nob[2])) {
      weight[2] = 1.0;
    }
    else if (blend > 0.0) {
      /* in case of blending, test for mixes between two textures */
      if (Nob[2] < (1.0 - limit) * (Nob[1] + Nob[0])) {
        weight[0] = Nob[0] / (Nob[0] + Nob[1]);
        weight[0] = clamp((weight[0] - 0.5 * (1.0 - blend)) / blend, 0.0, 1.0);
        weight[1] = 1.0 - weight[0];
      }
      else if (Nob[0] < (1.0 - limit) * (Nob[1] + Nob[2])) {
        weight[1] = Nob[1] / (Nob[1] + Nob[2]);
        weight[1] = clamp((weight[1] - 0.5 * (1.0 - blend)) / blend, 0.0, 1.0);
        weight[2] = 1.0 - weight[1];
      }
      else if (Nob[1] < (1.0 - limit) * (Nob[0] + Nob[2])) {
        weight[0] = Nob[0] / (Nob[0] + Nob[2]);
        weight[0] = clamp((weight[0] - 0.5 * (1.0 - blend)) / blend, 0.0, 1.0);
        weight[2] = 1.0 - weight[0];
      }
      else {
        /* last case, we have a mix between three */
        weight[0] = ((2.0 - limit) * Nob[0] + (limit - 1.0)) / (2.0 * limit - 1.0);
        weight[1] = ((2.0 - limit) * Nob[1] + (limit - 1.0)) / (2.0 * limit - 1.0);
        weight[2] = ((2.0 - limit) * Nob[2] + (limit - 1.0)) / (2.0 * limit - 1.0);
      }
    }
    else {
      /* Desperate mode, no valid choice anyway, fallback to one side.*/
      weight[0] = 1.0;
    }

    Color = color(0.0, 0.0, 0.0);
    Alpha = 0.0;

    float tmp_alpha;

    if (weight[0] > 0.0) {
      point UV = point((signed_Nob[0] < 0.0) ? 1.0 - p[1] : p[1], p[2], 0.0);
      Color += weight[0] * image_texture_lookup(filename,
                                                UV[0],
                                                UV[1],
                                                tmp_alpha,
                                                compress_as_srgb,
                                                ignore_alpha,
                                                unassociate_alpha,
                                                is_float,
                                                0,
                                                interpolation,
                                                extension);
      Alpha += weight[0] * tmp_alpha;
    }
    if (weight[1] > 0.0) {
      point UV = point((signed_Nob[1] > 0.0) ? 1.0 - p[0] : p[0], p[2], 0.0);
      Color += weight[1] * image_texture_lookup(filename,
                                                UV[0],
                                                UV[1],
                                                tmp_alpha,
                                                compress_as_srgb,
                                                ignore_alpha,
                                                unassociate_alpha,
                                                is_float,
                                                0,
                                                interpolation,
                                                extension);
      Alpha += weight[1] * tmp_alpha;
    }
    if (weight[2] > 0.0) {
      point UV = point((signed_Nob[2] > 0.0) ? 1.0 - p[1] : p[1], p[0], 0.0);
      Color += weight[2] * image_texture_lookup(filename,
                                                UV[0],
                                                UV[1],
                                                tmp_alpha,
                                                compress_as_srgb,
                                                ignore_alpha,
                                                unassociate_alpha,
                                                is_float,
                                                0,
                                                interpolation,
                                                extension);
      Alpha += weight[2] * tmp_alpha;
    }
  }
  else if (projection == "sphere") {
    point projected = map_to_sphere(texco_remap_square(p));
    Color = image_texture_lookup(filename,
                                 projected[0],
                                 projected[1],
                                 Alpha,
                                 compress_as_srgb,
                                 ignore_alpha,
                                 unassociate_alpha,
                                 is_float,
                                 0,
                                 interpolation,
                                 extension);
  }
  else if (projection == "tube") {
    point projected = map_to_tube(texco_remap_square(p));
    Color = image_texture_lookup(filename,
                                 projected[0],
                                 projected[1],
                                 Alpha,
                                 compress_as_srgb,
                                 ignore_alpha,
                                 unassociate_alpha,
                                 is_float,
                                 0,
                                 interpolation,
                                 extension);
  }
}
