import fs from 'fs';
import {globSync} from 'glob';
import path from 'path';

console.log('Generating shaders');

/**
 * This script is intended to copy the glsl file to the compilation output folder,
 * change their extension to .js and export the shaders as strings in javascript.
 * It will also minify them a bit if needed and change the extension to .js
 * After that it will create a combined typescript definition file and manipulate it a bit
 * It will also create a simple package.json file to allow importing this package in webpack
 */

function glslToTs(code: string): string {
    code = code
        .trim() // strip whitespace at the start/end
        .replace(/\s*\/\/[^\n]*\n/g, '\n') // strip double-slash comments
        .replace(/\n+/g, '\n') // collapse multi line breaks
        .replace(/\n\s+/g, '\n') // strip indentation
        .replace(/\s?([+-\/*=,])\s?/g, '$1') // strip whitespace around operators
        .replace(/([;\(\),\{\}])\n(?=[^#])/g, '$1'); // strip more line breaks

    return `// This file is generated. Edit build/generate-shaders.ts, then run \`npm run codegen\`.
export default ${JSON.stringify(code).replaceAll('"', '\'')};\n`;
}

const shaderFiles = globSync('./src/shaders/glsl/*.glsl');
for (const file of shaderFiles) {
    const glslFile = fs.readFileSync(file, 'utf8');
    const tsSource = glslToTs(glslFile);
    const fileName = path.join('.', 'src', 'shaders', 'glsl', `${file.split(path.sep).splice(-1)}.g.ts`);
    fs.writeFileSync(fileName, tsSource);
}

console.log(`Finished converting ${shaderFiles.length} shaders`);