template.yaml

---
# Look at https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-template-resource-type-ref.html
# and https://github.com/awslabs/serverless-application-model/blob/master/versions/2016-10-31.md
# for information on how to use this template
AWSTemplateFormatVersion: 2010-09-09        # Defines this YAMl as a cloudformation template
Transform: AWS::Serverless-2016-10-31       # Integrates SAM into the template
Description: Boilerplate SAM template.
Parameters:                                 # Parameters that you can set outside of your template to pass values to it
  DomainName:
    Type: String
    Description: Domain name for things
    Default: domain.com
  Certificate:                              # The ARN of your certificate, should look something like:
    Type: String                  # arn:aws:acm:eu-west-1:867530202211:certificate/658a382b-563e-40bb-8098-e073385310bf
    Description: Certificate for custom domain
    Default: arn:aws:acm:region:numbers:certificate/uuid
  Subdomain:
    Type: String
    Description: Subdomain of your site
    Default: api.
Globals:
    Api:
      Cors:                                 # Use if you want CORS otherwise remove this
        AllowMethods: "'*'"                 # CORS has caused me headaches in the past so it might be worth
        AllowHeaders: "'*'"                 # it to remove this entirely
        AllowOrigin: !Sub "'https://${DomainName}'"

Resources:
  route53Domain:                            # Creates a domain in Route53 with api as the prefix e.g. api.domain.com
    Type: AWS::Route53::RecordSetGroup      # This guide assumes you have a Route53 domain to use
    Properties:
      HostedZoneName: !Sub ${DomainName}.
      RecordSets:
        - Name: !Join
          - ''
          - - !Ref Subdomain                # Change this if you want a different sub-domain
            - !Ref DomainName
            - '.'
          Type: A
          AliasTarget:
            HostedZoneId: !GetAtt ApiDomainName.DistributionHostedZoneId
            DNSName: !GetAtt ApiDomainName.DistributionDomainName

  BasePathMapping:                          # Creates a API Gateway stage called prod
    Type: AWS::ApiGateway::BasePathMapping
    Properties:
      DomainName: !Sub ${Subdomain}${DomainName}
      RestApiId:
        Ref: RestApi
      Stage: prod
    DependsOn: RestApiprodStage

  ApiDomainName:                            # Assigns the domain's certificate to API Gateway
    Type: AWS::ApiGateway::DomainName
    Properties:
      DomainName: !Sub ${Subdomain}${DomainName}
      CertificateArn: !Ref Certificate

  RestApi:                                  # Creates an API with stage Prod
    Type: AWS::Serverless::Api
    Properties:
      Name: RestApi
      StageName: prod

  lambdaFunction:                           # Creates a lambda function
    Type: AWS::Serverless::Function
    Properties:
      CodeUri: src/index.js                 # Specify where in your directory the code is
      Handler: index.handler              # Specify the name of lambda's entry function
      Role: !GetAtt lambdaRole.Arn          # A role defined in the template
      Runtime: nodejs8.10                   # Change runtime to whatever language you are suing e.g. python3.6
      Events:
        lambdaAPI:
          Type: Api                         # Assigns the lambda function an API call
          Properties:
            Path: /lambdafunction           # Put your path here! e.g. api.domain.com/lambdafunction
            Method: get                     # Put your method here! e.g. post, get, put, delete...
            RestApiId: !Ref RestApi

  lambdaRole:
    Type: AWS::IAM::Role
    Properties:
      ManagedPolicyArns:
        - arn:aws:iam::aws:policy/service-role/AWSLambdaBasicExecutionRole
      AssumeRolePolicyDocument:
        Version: 2012-10-17
        Statement:
          - Effect: Allow
            Principal:
              Service:
                - lambda.amazonaws.com
            Action:
              - sts:AssumeRole
      Policies:                             # Put your policy documents here. What follows is an
        - PolicyName: s3GetPutPolicy        # example of a policy that allows GetObject access to all objects
          PolicyDocument:                   # in a particular bucket, defined later in this template
            Version: 2012-10-17
            Statement:
              - Effect: Allow
                Action:
                  - s3:GetObject
                Resource:
                  - !GetAtt fileServerBucket.Arn
                  - !Sub ${fileServerBucket.Arn}/*

  fileServerBucket:                         # Sample bucket, only necessary if you want a bucket
    Type: AWS::S3::Bucket