Preprocess cloudformation yml files

// In order to automatically deploy our ApiStage from Cloudformation, our
// Deployment resource name needs to be unique. In order to achieve this, 
// we are to create a preprocessor that will find the string "$TIMESTAMP$"
// and replace it with the system time. This will allow us to create a unique
// resource name.
const fs = require("fs")
const path = require("path")

const replacements = [
    { input: /\$TIMESTAMP\$/g, output: Date.now().toString() }
]

const getAllFiles = function (dirPath, arrayOfFiles) {
    files = fs.readdirSync(dirPath)

    arrayOfFiles = arrayOfFiles || []

    files.forEach(file => {
        if (fs.statSync(dirPath + "/" + file).isDirectory()) {
            arrayOfFiles = getAllFiles(dirPath + "/" + file, arrayOfFiles)
        } else {
            arrayOfFiles.push(path.join(dirPath, "/", file))
        }
    })

    return arrayOfFiles.filter(s => s.endsWith('/template.yml') || s.endsWith('/template.yaml'));
}

const projectPath = path.join(__dirname, '../');
const inputPath = path.join(projectPath, 'api/');
console.log(`Preprocessing Templates from: ${inputPath}`)
const outputPath = path.join(__dirname, '../dist/api/')
const templates = getAllFiles(inputPath);

templates.forEach(template => {
    fs.readFile(template, 'utf8', function (err, data) {
        if (err) throw err;

        replacements.forEach(replacement => {
            if (template.startsWith(inputPath)) {
                let outPath = path.join(outputPath, template.slice(inputPath.length));

                // Create any needed output directories
                fs.mkdirSync(path.dirname(outPath), { recursive: true });

                console.log(`PreProcessing: ./${template.slice(projectPath.length)} => ./${outPath.slice(projectPath.length)}`)
                templateOutput = data.replace(replacement.input, replacement.output);
                fs.writeFileSync(outPath, templateOutput)
            } else {
                throw `Template: ${template} is not in the directory ${inputPath}`;
            }
        });

    });
})