serve.js

var express = require("express");
var bodyParser = require("body-parser");
var expressLogging = require("express-logging");
var queryString = require("querystring");
var path = require("path");
var conf = require("./config");
var jwtDecode = require("jwt-decode")

function handleErr(err, response) {
  response.statusCode = 500;
  response.write("Function invocation failed: " + err.toString());
  response.end();
  console.log("Error during invocation: ", err);
  return;
}

function createCallback(response) {
  return function callback(err, lambdaResponse) {
    if (err) {
      return handleErr(err, response);
    }

    response.statusCode = lambdaResponse.statusCode;
    for (const key in lambdaResponse.headers) {
      response.setHeader(key, lambdaResponse.headers[key]);
    }
    response.write(
      lambdaResponse.isBase64Encoded
        ? Buffer.from(lambdaResponse.body, "base64")
        : lambdaResponse.body
    );
    response.end();
  }
}

function promiseCallback(promise, callback) {
  if (!promise) return;
  if (typeof promise.then !== "function") return;
  if (typeof callback !== "function") return;

  promise.then(
    function(data) {callback(null, data)},
    function(err) {callback(err, null)}
  );
}

function buildClientContext(headers) {
  // inject a client context based on auth header https://github.com/netlify/netlify-lambda/pull/57
  if (!headers['authorization']) return;

  const parts = headers['authorization'].split(' ');
  if (parts.length !== 2 || parts[0] !== 'Bearer') return;

  try {
    return {
      identity: { url: 'NETLIFY_LAMBDA_LOCALLY_EMULATED_IDENTITY_URL', token: 'NETLIFY_LAMBDA_LOCALLY_EMULATED_IDENTITY_TOKEN' },
      user: jwtDecode(parts[1])
    };
  } catch (e) {
    return; // Ignore errors - bearer token is not a JWT, probably not intended for us
  }
}

function createHandler(dir, static) {
  return function(request, response) {
    // handle proxies without path re-writes (http-servr)
    var cleanPath = request.path.replace(/^\/.netlify\/functions/, "")

    var func = cleanPath.split("/").filter(function(e) {
      return e;
    })[0];
    var module = path.join(process.cwd(), dir, func);
    if(static) {
      delete require.cache[require.resolve(module)]
    }
    var handler;
    try {
      handler = require(module);
    } catch (err) {
      handleErr(err, response);
      return;
    }

    var isBase64 =
      request.body &&
      !(request.headers["content-type"] || "").match(/text|application|multipart\/form-data/);
    var lambdaRequest = {
      path: request.path,
      httpMethod: request.method,
      queryStringParameters: queryString.parse(request.url.split(/\?(.+)/)[1]),
      headers: request.headers,
      body: isBase64 ? Buffer.from(request.body.toString(), "utf8").toString("base64") : request.body,
      isBase64Encoded: isBase64
    };

    var callback = createCallback(response);

    var promise = handler.handler(lambdaRequest, { clientContext: buildClientContext(request.headers) || {} }, callback);
    promiseCallback(promise, callback);
  };
}

exports.listen = function(port, static) {
  var config = conf.load();
  var app = express();
  var dir = config.build.functions || config.build.Functions;
  app.use(bodyParser.raw({limit: "6mb"}));
  app.use(bodyParser.text({limit: "6mb", type: "*/*"}));
  app.use(expressLogging(console, {
    blacklist: ["/favicon.ico"],
  }));

  app.get("/favicon.ico", function(req, res) {
    res.status(204).end();
  });
  app.all("*", createHandler(dir, static));

  app.listen(port, function(err) {
    if (err) {
      console.error("Unable to start lambda server: ", err);
      process.exit(1);
    }

    console.log(`Lambda server is listening on ${port}`);
  });

  return {
    clearCache: function(chunk) {
      var module = path.join(process.cwd(), dir, chunk);
      delete require.cache[require.resolve(module)];
    }
  };
};