[レポート]「API Gateway Unleashed: A Hands-on Journey to API Excellence」というセッションに参加しました #API303 #AWSreInvent

AWSTemplateFormatVersion: '2010-09-09'
Transform: AWS::Serverless-2016-10-31
Description: >
  Sample SAM Template for BMI Calculator API

Globals:
    # Enable Logs
    Api:
        MethodSettings:
            - ResourcePath: "/*"
              HttpMethod: "*"
              DataTraceEnabled: True
              LoggingLevel: INFO
              MetricsEnabled: True
    Function:
        Timeout: 3
        Runtime: nodejs18.x

Resources:

    # REST API
    BmiAPI:
        Type: AWS::Serverless::Api
        Properties:
            StageName: dev
            OpenApiVersion: 3.0.3
            DefinitionBody:
                "Fn::Transform":
                    Name: "AWS::Include"
                    Parameters:
                        Location: "s3://technical-review/openapi.yaml" # 任意の場所に置く
            EndpointConfiguration:
                Type: REGIONAL

    # Lambda functions
    BmiCalculator:
        Type: AWS::Serverless::Function
        Properties:
            CodeUri: s3://technical-review/lambda/source.zip # 任意の場所に置く
            Handler: bmi-calculator.BmiCalculator

    # Execution Role
    LambdaExecutionRole:
        Type: AWS::IAM::Role
        Properties:
            AssumeRolePolicyDocument:
                Version: "2012-10-17"
                Statement:
                  - Effect: Allow
                    Principal:
                      Service:
                        - apigateway.amazonaws.com
                    Action:
                      - 'sts:AssumeRole'
            Policies:
                - PolicyName: AllowLambdaExec
                  PolicyDocument:
                    Version: "2012-10-17"
                    Statement:
                      - Effect: Allow
                        Action: 'lambda:InvokeFunction'
                        Resource: !GetAtt BmiCalculator.Arn

Outputs:
  BmiAPI:
    Description: "API Gateway endpoint URL for BMI Calculator API"
    Value: !Sub "https://${BmiAPI}.execute-api.${AWS::Region}.amazonaws.com/dev/"

openapi: "3.0.1"
info:
   title: "bmi-calculator-api"
   description: "BMI Calculator API with IaC example"
   version: "1.0"

paths:

    /bmi:
        post:
            consumes:
            - "application/json"
            produces:
            - "application/json"
            responses:
                "200":
                    description: "200 response"
            x-amazon-apigateway-integration:
                httpMethod: "POST"
                credentials:
                    Fn::GetAtt: [LambdaExecutionRole, Arn]
                uri:
                  Fn::Sub: "arn:aws:apigateway:${AWS::Region}:lambda:path/2015-03-31/functions/${BmiCalculator.Arn}/invocations"
                responses:
                    default:
                        statusCode: "200"
                passthroughBehavior: "when_no_match"
                type: "aws"

/**
 * このファイルには、BMI計算APIで使用されるLambda関数のソースコードが含まれます
 */

  module.exports.BmiCalculator = async (event) => {
    try {
      // Check if event is null or undefined and throw an error if it is
      if (!event) {
        throw new Error('Event object is undefined or empty');
      }

      // Use optional chaining to set default values for properties that may not exist
      const { height, weight, unit } = event ?? {};

      // バリデーション: 必須パラメータチェック
      if (!height || !weight) {
        throw new Error('Missing required parameters: height and weight');
      }

      // 数値変換とバリデーション
      const heightNum = parseFloat(height);
      const weightNum = parseFloat(weight);

      if (isNaN(heightNum) || isNaN(weightNum)) {
        throw new Error('Height and weight must be valid numbers');
      }

      if (heightNum <= 0 || weightNum <= 0) {
        throw new Error('Height and weight must be positive numbers');
      }

      // 身長をメートルに変換（デフォルトはcm）
      const heightInMeters = unit === 'm' ? heightNum : heightNum / 100;

      if (heightInMeters > 3.0 || heightInMeters < 0.5) {
        throw new Error('Height is out of valid range');
      }

      // BMI計算
      const bmi = (weightNum / (heightInMeters * heightInMeters)).toFixed(1);

      // BMIカテゴリー判定
      const category = getBmiCategory(parseFloat(bmi));

      // Return a response object with a 200 status code and JSON body
      const response = {
        statusCode: 200,
        body: JSON.stringify({
          bmi: bmi.toString(),
          category: category,
          height: heightNum,
          weight: weightNum,
          unit: unit || 'cm'
        }),
        headers: {
          'X-Powered-By': 'AWS API Gateway & Lambda Serverless'
        },
        isBase64Encoded: false
      };

      return response;
    } catch (error) {
      // Log the error and return a response object with a 400 status code and an error message
      console.error('Error calculating BMI:', error.message);
      return {
        statusCode: 400,
        body: 'Error calculating BMI',
        headers: {
          'X-Powered-By': 'AWS API Gateway & Lambda Serverless'
        },
        isBase64Encoded: false
      };
    }
  };

  // Define a helper function to determine BMI category
  function getBmiCategory(bmi) {
      if (bmi < 18.5) {
          return 'Underweight';
      } else if (bmi >= 18.5 && bmi < 25.0) {
          return 'Normal weight';
      } else if (bmi >= 25.0 && bmi < 30.0) {
          return 'Overweight';
      } else {
          return 'Obese';
      }
  }