//bundleLambdas.ts

import { build } from "esbuild";

import * as glob from "glob";

import * as path from "path";

import { promises as fs } from "fs"; // Use the promises API of fs

const handlersDir = "{PATH_TO_LAMBDA_FOLDER}";

export async function bundleLambdas() {

  const start = performance.now();

  await clearDist();

  const entryFiles = (

    await Promise.all(

      glob.sync(`${handlersDir}/**/*.ts`, { dot: true }).map(async (file) => {

        return (await hasHandlerFunction(file)) ? file : null;

      }),

    )

  ).filter(Boolean); // This will filter out null values, leaving only files with exports.handler

  const buildTasks = entryFiles.map((file: any) => {

    const relativePath = path.relative(handlersDir, file);

    const directoryName = path.dirname(relativePath);

    const fileNameWithoutExtension = path.basename(file, ".ts");

    return build({

      entryPoints: [file],

      bundle: true,

      outdir: `./dist/${directoryName}/${fileNameWithoutExtension}`,

      platform: "node",

      external: ["@aws-sdk/*"],

    });

  });

  // Run all builds in parallel

  await Promise.all(buildTasks)

    .then(() => {

      const end = performance.now();

      const duration = (end - start) / 1000;

      console.error(`\n✨ Lambda Bundle time: ${duration.toFixed(2)}s\n`);

    })

    .catch((err) => {

      console.error("Build error:", err);

      process.exit(1);

    });

}

async function clearDist() {

  try {

    await fs.rm("./dist", { recursive: true });

  } catch (err) {

    console.error("Error clearing dist folder:");

  }

  try {

    await fs.mkdir("./dist", { recursive: true });

  } catch {

    console.error("Error creating dist folder:");

  }

}

async function hasHandlerFunction(file: any) {

  const content = await fs.readFile(file, "utf-8");

  return content.includes("exports.handler");

}

bundleLambdas();

// cdk.json

// bundle lambdas before running cdk root file

{

"app": "npx ts-node bin/bundleLambdas.ts && npx ts-node --prefer-ts-exts bin/cdk-main.ts",

//...

}

// use fromAsset to grab prebuilt lambda

const lambdaFunction = new lambda.Function(this, ${id}`, {

      code: lambda.Code.fromAsset(`dist/${id}`),

      handler: `${id.split("/").pop()}.handler`,

      runtime: lambda.Runtime.NODEJS_18_X

}