import { DynamoDBClient } from "@aws-sdk/client-dynamodb";
import { QueryCommand, DynamoDBDocumentClient } from "@aws-sdk/lib-dynamodb";
import { getPaginatedResult, decodeCursor } from "dynamodb-paginator";

interface UserPet {
  userId: number; // partition key (hash)
  petId: number; // sort key (range)
}

const client = new DynamoDBClient({});
const docClient = DynamoDBDocumentClient.from(client);

const limit = 25;
const defaultInput = {
  TableName: "UserPets",
  Limit: limit,
  KeyConditionExpression: "userId = :userId",
  ExpressionAttributeValues: {
    ":userId": 1,
  },
  ConsistentRead: true,
};

// Could be a cursor from a previous paginated result
const cursor = undefined;
const paginationInput = decodeCursor(cursor) || defaultInput;

const command = new QueryCommand(paginationInput);

const response = await docClient.send(command);

// By default the cursors are encoded in base64, but you can supply your own encoding function
const paginatedResult = getPaginatedResult<UserPet>(
  paginationInput,
  limit,
  response
);

// Output:
// {
//     data: T[],
//     meta: {
//         limit: number,
//         hasMoreData: boolean,
//         cursor: string,
//         backCursor: string,
//         count: number
//     }
// }

import { randomBytes, createCipheriv, createDecipheriv } from "crypto";
import { getPaginatedResult, decodeCursor } from "dynamodb-paginator";

const ENC_KEY = randomBytes(32); // set random encryption key
const IV = randomBytes(16); // set random initialisation vector
const ALGORITHM = "aes-256-cbc";

const encrypt = (val) => {
  const cipher = createCipheriv(ALGORITHM, ENC_KEY, IV);
  let encrypted = cipher.update(JSON.stringify(val), "utf8", "base64");
  encrypted += cipher.final("base64");

  return encrypted;
};

const decrypt = (encrypted) => {
  const decipher = createDecipheriv(ALGORITHM, ENC_KEY, IV);
  const decrypted = decipher.update(encrypted, "base64", "utf8");

  return JSON.parse(decrypted + decipher.final("utf8"));
};

const limit = 2;
const params = { TableName: "UserPets", Limit: limit };
// Example DynamoDB Output
const result = {
  Count: 2,
  Items: [
    { userId: 1, petId: 1 },
    { userId: 1, petId: 2 },
  ],
  LastEvaluatedKey: { userId: 1, petId: 2 },
  ScannedCount: 2,
};

// Pass a custom encoding function
const paginatedResult = getPaginatedResult(params, limit, result, encrypt);

// Pass a custom decoding function
const decodedCursor = decodeCursor(paginatedResult.meta.cursor, decrypt);

console.log(decodedCursor);
// Output:
// {
//   TableName: 'UserPets',
//   Limit: 2,
//   ExclusiveStartKey: { userId: 1, petId: 2 },
//   previousKeys: [ { userId: 1, petId: 2 } ],
//   back: false
// }