GLSL includes inliner.mjs

import fs from "fs";

function findIncludedFile(filePath, includes) {
  let matches = [];
  for (let ii = 0; ii < includes.length; ++ii) {
    let incl = includes[ii];
    let stats = fs.lstatSync(incl);
    if (!stats.isDirectory()) {
      throw new SyntaxError(`Include path '${incl}' is not a directory`);
    }
    let includeFilePath = path.join(incl, filePath);
    if (fs.existsSync(includeFilePath) && fs.lstatSync(includeFilePath).isFile()) {
      try {
        matches.push(fs.readFileSync(includeFilePath, "utf-8"));
      } catch (e) {
        throw new ReferenceError(`Cannot read included file from '${includeFilePath}'`);
      }
    } else {
      throw new ReferenceError(`Failed to resolve file include path for '${filePath}': '${includeFilePath}' is not a valid file path`);
    }
  };
  if (matches.length <= 0) {
    throw new ReferenceError(`Cannot inline included file '${filePath}'`);
  }
  if (matches.length > 1) {
    throw new ReferenceError(`Ambigious include directive for '${filePath}'. More than one match was found`);
  }
  return matches[0];
};

function flattenShaderIncludes(source, includeDirectories) {
  let rx = /#include ((<[^>]+>)|("[^"]+"))/g;
  let match = null;
  while (match = rx.exec(source)) {
    let filePath = match[1].slice(1, -1);
    let start = match.index;
    let length = match[0].length;
    let includedFile = flattenShaderIncludes(
      findIncludedFile(filePath, includeDirectories),
      includeDirectories
    );
    source = source.substr(0, start) + includedFile + source.substr(start + length);
  };
  return source;
};

export function loadShaderFile(srcPath) {
  let src = fs.readFileSync(srcPath, "utf-8");
  let flattened = flattenShaderIncludes(src, [path.dirname(srcPath)]);
  return flattened;
};