Lambda Adapter w/Examples

handler.js

const { adapter } = require('./lambdaAdapter')

exports.handler = async (event, context) => await adapter(event, context, options)

handlerWithRouteOverride.js

const { adapter } = require('./lambdaAdapter')

// This post method will override the post in lambdaAdapter
const post = async function (event, context) {
  let response = {};
  
  try {
    let obj = JSON.parse(event.body);
    
    let savedObj = someCustomWayToSaveYourObjectHere(obj)
    
    response = {
      statusCode: 201,
      body: JSON.stringify(savedObj)
    };
  } catch (err) {
    console.error(err);
    response = {
      statusCode: 500,
      body: err.toString()
    };
  }
  
  return response;
};

let options = { 
  routes: {
    post
  }
}

exports.handler = async (event, context) => await adapter(event, context, options)

lambdaAdapter.js

const get = async function (event, context)  {
  let response;
  try {
    if (!event.queryStringParameters || !event.queryStringParameters.id) {
      let objs = await listYourObjectsHere();
      response = {
        statusCode: 200,
        body: JSON.stringify(objs)
      };
    } else {
      let obj = await getYourObjectHere(event.queryStringParameters.id);
      if(!obj || !obj.id) {
        response = {
          statusCode: 404
        }
      } else {
        response = {
          statusCode: 200,
          body: JSON.stringify(obj)
        };
      }
    }

  } catch (err) {
    console.error(err);
    response = {
      statusCode: 500,
      body: err.toString()
    };
  }

  return response;
};

const post = async function (event, context) {
  let response = {};

  try {
    let obj = JSON.parse(event.body);

    let savedObj = await saveYourObjectHere(obj)

    response = {
      statusCode: 201,
      body: JSON.stringify(savedObj)
    };
  } catch (err) {
    console.error(err);
    response = {
      statusCode: 500,
      body: err.toString()
    };
  }

  return response;
};

const put = async function (event, context) {
  if (!event.queryStringParameters || !event.queryStringParameters.id) {
    return {
      statusCode: 400,
      body: "'id' query parameter is required"
    };
  }
  let response;

  let obj = JSON.parse(event.body);

  try {
    let updated = await updateYourObjectHere(
      event.queryStringParameters.id,
      obj
    );

    response = {
      statusCode: 200,
      body: JSON.stringify(updated)
    };
  } catch (err) {
    console.error(err);
    response = {
      statusCode: 500,
      body: err.toString()
    };
  }

  return response;
};

const del = async function (event, context) {
  if (!event.queryStringParameters || !event.queryStringParameters.id) {
    return {
      statusCode: 400,
      body: "'id' query parameter is required"
    };
  }
  let response;

  try {
    await deleteYourObjectHere(
      event.queryStringParameters.id
    );

    response = {
      statusCode: 200
    };
  } catch (err) {
    console.error(err);
    response = {
      statusCode: 500,
      body: err.toString()
    };
  }

  return response;
}

const _routes = {
  get,
  post,
  put,
  delete: del
};

exports.adapter = async function (event, context, options) {
  let response = {};
  try {
    if(options.routes) {
      Object.keys(options.routes).forEach(r => {
        _routes[r] = options.routes[r]
      })
    }
    if (_routes[event.httpMethod.toLowerCase()]) {
      response = await _routes[event.httpMethod.toLowerCase()](event, context);
    } else {
      response = {
        statusCode: 404
      };
    }

    if(!response.headers) {
      response.headers = {
        'Access-Control-Allow-Origin': '*'
      }
    } else {
      response.headers['Access-Control-Allow-Origin'] = '*'
    }

    return response;
  } catch (err) {
    console.error(err)
    return {
      statusCode: 500,
      body: err.toString()
    };
  }
};