API Gateway

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Principal": {
        "Service": "apigateway.amazonaws.com"
      },
      "Action": "sts:AssumeRole"
    }
  ]
}

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Principal": {
        "Service": "lambda.amazonaws.com"
      },
      "Action": "sts:AssumeRole"
    }
  ]
}

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Action": [
        "dynamodb:GetItem",
        "dynamodb:PutItem",
        "dynamodb:UpdateItem",
        "dynamodb:DeleteItem",
        "dynamodb:Query",
        "dynamodb:Scan"
      ],
      "Resource": [
        "arn:aws:dynamodb:ap-northeast-1:123456789012:table/Users",
        "arn:aws:dynamodb:ap-northeast-1:123456789012:table/Users/index/*",
        "arn:aws:dynamodb:ap-northeast-1:123456789012:table/Posts",
        "arn:aws:dynamodb:ap-northeast-1:123456789012:table/Posts/index/*"
      ]
    }
  ]
}

import json
import boto3
from decimal import Decimal
from datetime import datetime
from boto3.dynamodb.conditions import Key

# DynamoDB クライアント初期化
dynamodb = boto3.resource('dynamodb')
users_table = dynamodb.Table('Users')
posts_table = dynamodb.Table('Posts')

def lambda_handler(event, context):
    """
    API Gateway HTTP API からのイベントを処理
    """
    print('Event:', json.dumps(event))
    
    route_key = event.get('routeKey', '')
    path_parameters = event.get('pathParameters', {})
    body = event.get('body', '{}')
    
    try:
        # Users API
        if route_key == 'GET /users':
            return get_users()
        elif route_key == 'GET /users/{id}':
            return get_user(path_parameters['id'])
        elif route_key == 'POST /users':
            return create_user(json.loads(body))
        elif route_key == 'PATCH /users/{id}':
            return update_user(path_parameters['id'], json.loads(body))
        elif route_key == 'DELETE /users/{id}':
            return delete_user(path_parameters['id'])
        
        # Posts API
        elif route_key == 'GET /posts':
            return get_posts()
        elif route_key == 'GET /posts/{id}':
            return get_post(path_parameters['id'])
        elif route_key == 'POST /posts':
            return create_post(json.loads(body))
        elif route_key == 'PATCH /posts/{id}':
            return update_post(path_parameters['id'], json.loads(body))
        elif route_key == 'DELETE /posts/{id}':
            return delete_post(path_parameters['id'])
        
        else:
            return response(404, {'message': 'Not Found'})
    
    except Exception as e:
        print(f'Error: {str(e)}')
        return response(500, {'message': 'Internal Server Error', 'error': str(e)})


# ========== Users 関数 ==========

def get_users():
    """ユーザー一覧取得"""
    result = users_table.scan()
    items = convert_decimal(result.get('Items', []))
    return response(200, items)


def get_user(user_id):
    """ユーザー取得"""
    result = users_table.get_item(Key={'userId': user_id})
    
    if 'Item' not in result:
        return response(404, {'message': 'User not found'})
    
    item = convert_decimal(result['Item'])
    return response(200, item)


def create_user(data):
    """ユーザー作成"""
    user_id = f"user-{int(datetime.now().timestamp() * 1000)}"
    
    item = {
        'userId': user_id,
        'name': data.get('name', ''),
        'email': data.get('email', ''),
        'createdAt': datetime.now().isoformat()
    }
    
    users_table.put_item(Item=item)
    return response(201, item)


def update_user(user_id, data):
    """ユーザー更新"""
    # 既存ユーザーの確認
    result = users_table.get_item(Key={'userId': user_id})
    if 'Item' not in result:
        return response(404, {'message': 'User not found'})
    
    # 更新
    existing_item = result['Item']
    existing_item.update(data)
    existing_item['updatedAt'] = datetime.now().isoformat()
    
    users_table.put_item(Item=existing_item)
    
    item = convert_decimal(existing_item)
    return response(200, item)


def delete_user(user_id):
    """ユーザー削除"""
    users_table.delete_item(Key={'userId': user_id})
    return response(204, '')


# ========== Posts 関数 ==========

def get_posts():
    """投稿一覧取得"""
    result = posts_table.scan()
    items = convert_decimal(result.get('Items', []))
    return response(200, items)


def get_post(post_id):
    """投稿取得"""
    result = posts_table.get_item(Key={'postId': post_id})
    
    if 'Item' not in result:
        return response(404, {'message': 'Post not found'})
    
    item = convert_decimal(result['Item'])
    return response(200, item)


def create_post(data):
    """投稿作成"""
    post_id = f"post-{int(datetime.now().timestamp() * 1000)}"
    
    item = {
        'postId': post_id,
        'userId': data.get('userId', ''),
        'title': data.get('title', ''),
        'content': data.get('content', ''),
        'createdAt': datetime.now().isoformat()
    }
    
    posts_table.put_item(Item=item)
    return response(201, item)


def update_post(post_id, data):
    """投稿更新"""
    # 既存投稿の確認
    result = posts_table.get_item(Key={'postId': post_id})
    if 'Item' not in result:
        return response(404, {'message': 'Post not found'})
    
    # 更新
    existing_item = result['Item']
    existing_item.update(data)
    existing_item['updatedAt'] = datetime.now().isoformat()
    
    posts_table.put_item(Item=existing_item)
    
    item = convert_decimal(existing_item)
    return response(200, item)


def delete_post(post_id):
    """投稿削除"""
    posts_table.delete_item(Key={'postId': post_id})
    return response(204, '')


# ========== ユーティリティ関数 ==========

def response(status_code, body):
    """HTTP レスポンス生成"""
    return {
        'statusCode': status_code,
        'headers': {
            'Content-Type': 'application/json'
        },
        'body': json.dumps(body, ensure_ascii=False) if body != '' else ''
    }


def convert_decimal(obj):
    """Decimal を int/float に変換（DynamoDB の数値型対応）"""
    if isinstance(obj, list):
        return [convert_decimal(item) for item in obj]
    elif isinstance(obj, dict):
        return {key: convert_decimal(value) for key, value in obj.items()}
    elif isinstance(obj, Decimal):
        return int(obj) if obj % 1 == 0 else float(obj)
    else:
        return obj