// deck.gl
// SPDX-License-Identifier: MIT
// Copyright (c) vis.gl contributors

import type {ShaderModule} from '@luma.gl/shadertools';
import project from '../project/project';

const source = /* wgsl */ `\
// Define a structure to hold both the clip-space position and the common position.
struct ProjectResult {
  clipPosition: vec4<f32>,
  commonPosition: vec4<f32>,
};

// This function mimics the GLSL version with the 'out' parameter by returning both values.
fn project_position_to_clipspace_and_commonspace(
    position: vec3<f32>,
    position64Low: vec3<f32>,
    offset: vec3<f32>
) -> ProjectResult {
  // Compute the projected position.
  let projectedPosition: vec3<f32> = project_position_vec3_f64(position, position64Low);

  // Start with the provided offset.
  var finalOffset: vec3<f32> = offset;

  // Get whether a rotation is needed and the rotation matrix.
  let rotationResult = project_needs_rotation(projectedPosition);

  // If rotation is needed, update the offset.
  if (rotationResult.needsRotation) {
    finalOffset = rotationResult.transform * offset;
  }

  // Compute the common position.
  let commonPosition: vec4<f32> = vec4<f32>(projectedPosition + finalOffset, 1.0);

  // Convert to clip-space.
  let clipPosition: vec4<f32> = project_common_position_to_clipspace(commonPosition);

  return ProjectResult(clipPosition, commonPosition);
}

// A convenience overload that returns only the clip-space position.
fn project_position_to_clipspace(
    position: vec3<f32>,
    position64Low: vec3<f32>,
    offset: vec3<f32>
) -> vec4<f32> {
  return project_position_to_clipspace_and_commonspace(position, position64Low, offset).clipPosition;
}
`;

const vs = /* glsl */ `\
vec4 project_position_to_clipspace(
  vec3 position, vec3 position64Low, vec3 offset, out vec4 commonPosition
) {
  vec3 projectedPosition = project_position(position, position64Low);
  mat3 rotation;
  if (project_needs_rotation(projectedPosition, rotation)) {
    // offset is specified as ENU
    // when in globe projection, rotate offset so that the ground alighs with the surface of the globe
    offset = rotation * offset;
  }
  commonPosition = vec4(projectedPosition + offset, 1.0);
  return project_common_position_to_clipspace(commonPosition);
}

vec4 project_position_to_clipspace(
  vec3 position, vec3 position64Low, vec3 offset
) {
  vec4 commonPosition;
  return project_position_to_clipspace(position, position64Low, offset, commonPosition);
}
`;

export default {
  name: 'project32',
  dependencies: [project],
  source,
  vs
} as ShaderModule;