parse-glsl-argument-types.js

/**
	 * A highly readable very forgiving micro-parser for a glsl function that gets argument types
	 * @param {String} source
	 * @returns {{types: String[], names: String[]}}
	 */
function parseGLSLArgumentTypes(source) {
  const types = [];
  const names = [];
  const states = [];
  const isStartingVariableName = /^[a-zA-Z_]/;
  const isVariableChar = /[a-zA-Z_0-9]/;
  let i = 0;
  let name = null;
  let type = null;
  while (i < source.length) {
    const char = source[i];
    const nextChar = source[i + 1];
    const state = states.length > 0 ? states[states.length - 1] : null;

    // begin MULTI_LINE_COMMENT handling
    if (state === 'FUNCTION_ARGUMENTS' && char === '/' && nextChar === '*') { states.push('MULTI_LINE_COMMENT'); i += 2; continue; }
    else if (state === 'MULTI_LINE_COMMENT' && char === '*' && nextChar === '/') { states.pop(); i += 2; continue; }
    // end MULTI_LINE_COMMENT handling

    // begin COMMENT handling
    else if (state === 'FUNCTION_ARGUMENTS' && char === '/' && nextChar === '/') { states.push('COMMENT'); i += 2; continue; }
    else if (state === 'COMMENT' && char === '\n') { states.pop(); i++; continue; }
    // end COMMENT handling

    // being FUNCTION_ARGUMENTS handling
    else if (state === null && char === '(') { states.push('FUNCTION_ARGUMENTS'); i++; continue; }
    else if (state === 'FUNCTION_ARGUMENTS') {
      if (char === ')') {
        states.pop();
        break;
      }
      if (char === 'f' && nextChar === 'l' && source[i + 2] === 'o' && source[i + 3] === 'a' && source[i + 4] === 't' && source[i + 5] === ' ') {
        states.push('DECLARE_VARIABLE');
        type = 'float';
        name = '';
        i += 6;
        continue;
      } else if (char === 'i' && nextChar === 'n' && source[i + 2] === 't' && source[i + 3] === ' ') {
        states.push('DECLARE_VARIABLE');
        type = 'int';
        name = '';
        i += 4;
        continue;
      } else if (char === 'v' && nextChar === 'e' && source[i + 2] === 'c' && source[i + 3] === '2' && source[i + 4] === ' ') {
        states.push('DECLARE_VARIABLE');
        type = 'vec2';
        name = '';
        i += 5;
        continue;
      } else if (char === 'v' && nextChar === 'e' && source[i + 2] === 'c' && source[i + 3] === '3' && source[i + 4] === ' ') {
        states.push('DECLARE_VARIABLE');
        type = 'vec3';
        name = '';
        i += 5;
        continue;
      } else if (char === 'v' && nextChar === 'e' && source[i + 2] === 'c' && source[i + 3] === '4' && source[i + 4] === ' ') {
        states.push('DECLARE_VARIABLE');
        type = 'vec4';
        name = '';
        i += 5;
        continue;
      }
    }
    // end FUNCTION_ARGUMENTS handling

    // begin DECLARE_VARIABLE handling
    else if (state === 'DECLARE_VARIABLE') {
      if (name === '') {
        if (char === ' ') {
          i++;
          continue;
        }
        if (!isStartingVariableName.test(char)) {
          throw new Error('variable name is not expected string');
        }
      }
      name += char;
      if (!isVariableChar.test(nextChar)) {
        states.pop();
        names.push(name);
        types.push(type);
      }
    }
    // end DECLARE_VARIABLE handling

    // Progress to next character
    i++;
  }
  return {
    names,
    types
  };
}