Adding our Serverless API

billing.js

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+import stripePackage from "stripe";
+import handler from "./libs/handler-lib";
+import { calculateCost } from "./libs/billing-lib";
+
+export const main = handler(async (event, context) => {
+  const { storage, source } = JSON.parse(event.body);
+  const amount = calculateCost(storage);
+  const description = "Scratch charge";
+
+  // Load our secret key from the  environment variables
+  const stripe = stripePackage(process.env.stripeSecretKey);
+
+  await stripe.charges.create({
+    source,
+    amount,
+    description,
+    currency: "usd"
+  });
+  return { status: true };
+});

create.js

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+import * as uuid from "uuid";
+import handler from "./libs/handler-lib";
+import dynamoDb from "./libs/dynamodb-lib";
+
+export const main = handler(async (event, context) => {
+  const data = JSON.parse(event.body);
+  const params = {
+    TableName: process.env.tableName,
+    // 'Item' contains the attributes of the item to be created
+    // - 'userId': user identities are federated through the
+    //             Cognito Identity Pool, we will use the identity id
+    //             as the user id of the authenticated user
+    // - 'noteId': a unique uuid
+    // - 'content': parsed from request body
+    // - 'attachment': parsed from request body
+    // - 'createdAt': current Unix timestamp
+    Item: {
+      userId: event.requestContext.identity.cognitoIdentityId,
+      noteId: uuid.v1(),
+      content: data.content,
+      attachment: data.attachment,
+      createdAt: Date.now()
+    }
+  };
+
+  await dynamoDb.put(params);
+
+  return params.Item;
+});

delete.js

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+import handler from "./libs/handler-lib";
+import dynamoDb from "./libs/dynamodb-lib";
+
+export const main = handler(async (event, context) => {
+  const params = {
+    TableName: process.env.tableName,
+    // 'Key' defines the partition key and sort key of the item to be removed
+    // - 'userId': Identity Pool identity id of the authenticated user
+    // - 'noteId': path parameter
+    Key: {
+      userId: event.requestContext.identity.cognitoIdentityId,
+      noteId: event.pathParameters.id
+    }
+  };
+
+  await dynamoDb.delete(params);
+
+  return { status: true };
+});

get.js

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+import handler from "./libs/handler-lib";
+import dynamoDb from "./libs/dynamodb-lib";
+
+export const main = handler(async (event, context) => {
+  const params = {
+    TableName: process.env.tableName,
+    // 'Key' defines the partition key and sort key of the item to be retrieved
+    // - 'userId': Identity Pool identity id of the authenticated user
+    // - 'noteId': path parameter
+    Key: {
+      userId: event.requestContext.identity.cognitoIdentityId,
+      noteId: event.pathParameters.id
+    }
+  };
+
+  const result = await dynamoDb.get(params);
+  if ( ! result.Item) {
+    throw new Error("Item not found.");
+  }
+
+  // Return the retrieved item
+  return result.Item;
+});

libs/billing-lib.js

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+export function calculateCost(storage) {
+  const rate = storage <= 10
+    ? 4
+    : storage <= 100
+      ? 2
+      : 1;
+
+  return rate * storage * 100;
+}

libs/dynamodb-lib.js

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+import AWS from "aws-sdk";
+
+const client = new AWS.DynamoDB.DocumentClient();
+
+export default {
+  get   : (params) => client.get(params).promise(),
+  put   : (params) => client.put(params).promise(),
+  query : (params) => client.query(params).promise(),
+  update: (params) => client.update(params).promise(),
+  delete: (params) => client.delete(params).promise(),
+};

libs/handler-lib.js

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+export default function handler(lambda) {
+  return function (event, context) {
+    return Promise.resolve()
+      // Run the Lambda
+      .then(() => lambda(event, context))
+      // On success
+      .then((responseBody) => [200, responseBody])
+      // On failure
+      .catch((e) => {
+        return [500, { error: e.message }];
+      })
+      // Return HTTP response
+      .then(([statusCode, body]) => ({
+        statusCode,
+        headers: {
+          "Access-Control-Allow-Origin": "*",
+          "Access-Control-Allow-Credentials": true,
+        },
+        body: JSON.stringify(body),
+      }));
+  };
+}

list.js

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+import handler from "./libs/handler-lib";
+import dynamoDb from "./libs/dynamodb-lib";
+
+export const main = handler(async (event, context) => {
+  const params = {
+    TableName: process.env.tableName,
+    // 'KeyConditionExpression' defines the condition for the query
+    // - 'userId = :userId': only return items with matching 'userId'
+    //   partition key
+    // 'ExpressionAttributeValues' defines the value in the condition
+    // - ':userId': defines 'userId' to be Identity Pool identity id
+    //   of the authenticated user
+    KeyConditionExpression: "userId = :userId",
+    ExpressionAttributeValues: {
+      ":userId": event.requestContext.identity.cognitoIdentityId
+    }
+  };
+
+  const result = await dynamoDb.query(params);
+
+  // Return the matching list of items in response body
+  return result.Items;
+});

mocks/billing-event.json

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+{
+  "body": "{\"source\":\"tok_visa\",\"storage\":21}",
+  "requestContext": {
+    "identity": {
+      "cognitoIdentityId": "USER-SUB-1234"
+    }
+  }
+}

mocks/create-event.json

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+{
+  "body": "{\"content\":\"hello world\",\"attachment\":\"hello.jpg\"}",
+  "requestContext": {
+    "identity": {
+      "cognitoIdentityId": "USER-SUB-1234"
+    }
+  }
+}

mocks/delete-event.json

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+{
+  "pathParameters": {
+    "id": "2b82e2c0-793f-11ea-9602-6d514f529482"
+  },
+  "requestContext": {
+    "identity": {
+      "cognitoIdentityId": "USER-SUB-1234"
+    }
+  }
+}

mocks/get-event.json

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+{
+  "pathParameters": {
+    "id": "2b82e2c0-793f-11ea-9602-6d514f529482"
+  },
+  "requestContext": {
+    "identity": {
+      "cognitoIdentityId": "USER-SUB-1234"
+    }
+  }
+}

mocks/list-event.json

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+{
+  "requestContext": {
+    "identity": {
+      "cognitoIdentityId": "USER-SUB-1234"
+    }
+  }
+}

mocks/update-event.json

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+{
+  "body": "{\"content\":\"new world\",\"attachment\":\"new.jpg\"}",
+  "pathParameters": {
+    "id": "2b82e2c0-793f-11ea-9602-6d514f529482"
+  },
+  "requestContext": {
+    "identity": {
+      "cognitoIdentityId": "USER-SUB-1234"
+    }
+  }
+}