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

/** Information extracted from shader source code */
export type ShaderInfo = {
  name: string;
  language: 'glsl' | 'wgsl';
  version: number;
};

/** Extracts information from shader source code */
export function getShaderInfo(source: string, defaultName?: string): ShaderInfo {
  return {
    name: getShaderName(source, defaultName),
    language: 'glsl',
    version: getShaderVersion(source)
  };
}

/** Extracts GLSLIFY style naming of shaders: `#define SHADER_NAME ...` */
function getShaderName(shader: string, defaultName: string = 'unnamed'): string {
  const SHADER_NAME_REGEXP = /#define[^\S\r\n]*SHADER_NAME[^\S\r\n]*([A-Za-z0-9_-]+)\s*/;
  const match = SHADER_NAME_REGEXP.exec(shader);
  return match ? match[1] : defaultName;
}

/** returns GLSL shader version of given shader string */
function getShaderVersion(source: string): 100 | 300 {
  let version = 100;
  const words = source.match(/[^\s]+/g);
  if (words && words.length >= 2 && words[0] === '#version') {
    const parsedVersion = parseInt(words[1], 10);
    if (Number.isFinite(parsedVersion)) {
      version = parsedVersion;
    }
  }
  if (version !== 100 && version !== 300) {
    throw new Error(`Invalid GLSL version ${version}`);
  }
  return version;
}