# dynamodb-repository

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DynamoDB repository for key-value indexed tables. Designed for Lambda use. Handles niceties like created and updated timestamps and default id creation.

## Install

`$ npm install @setho/dynamodb-repository --save`

## Usage

### TypeScript/ES6

```typescript
import { KeyValueRepository } from '@setho/dynamodb-repository';

const myRepo = new KeyValueRepository({
  tableName: 'Items', // Required
  keyName: 'id', // Required
  idOptions: {
    // Optional
    prefix: 'ITEM_', // Default is empty string
  },
  documentClient, // Required - V3 DynamoDBDocumentClient from @aws-sdk/lib-dynamodb
});
```

### JavaScript

```javascript
const { KeyValueRepository } = require('@setho/dynamodb-repository');

const myRepo = new KeyValueRepository({
  tableName: 'Items', // Required
  keyName: 'id', // Required
  idOptions: {
    // Optional
    prefix: 'ITEM#', // Default is empty string
  },
  documentClient, // Required - V3 DynamoDBDocumentClient from @aws-sdk/lib-dynamodb
});
```

#### Constructor

Use the optional `idOptions` constructor parameter to set an optional `prefix` to give your ids some human-readable context. The remainder of the key is a ULID, which is both unique and lexicographically sortable. See an explanation of and motivation for ULIDs [here](https://github.com/ulid/spec).

## Create

- Requires action `dynamodb:PutItem`
- Automatically adds a string key (this will overwrite any you may try to provide). Use constructor options to specify length and optional prefix.
- Automatically provides a `createdAt` and `updatedAt` timestamp in ISO-8601
- Returns what was saved; does not mutate the item passed in.

```javascript
const mySavedItem = await myRepo.create(myItem);
mySavedItem.id; // itm_a4d02890b7174730b4bbbc
mySavedItem.createdAt; // 1979-11-04T09:00:00.000Z
mySavedItem.updatedAt; // 1979-11-04T09:00:00.000Z
```

## Get by Key

- Requires action `dynamodb:GetItem`.
- Throws `404` if item not found using [http-errors](https://npmjs.com/package/http-errors).

```javascript
const myItem = await myRepo.get(id);
```

## Get Many

- Requires action `dynamodb:Scan`
- Accepts optional parameter fields `limit` and `cursor`
  - `limit` defaults to 100
- Returns object with `items` (Array) and `cursor` (String)
  - `items` will always be an array; if nothing found, it will be empty
  - `cursor` will be present if there are more items to fetch, otherwise it will be undefined

```javascript
// Example to pull 100 at time until you have all items
const allItems = [];
const getAllItems = async ({ limit, cursor = null }) => {
  const getResult = await myRepo.getMany({ limit, cursor });
  allItems.push(...getResult.items);
  if (getResult.cursor) {
    await getAllItems({ cursor: getResult.cursor });
  }
};
await getAllItems();
// The array allItems now has all your items. Go nuts.
```

## Remove by Key

- Requires action `dynamodb:DeleteItem`

```javascript
await myRepo.remove(id);
```

## Update

- Requires `dynamodb:UpdateItem`
- Honors revision check; it will only update if the revision on disk is the one you are updating. Will return a `409` if the revision has changed underneath you.
- Will perform a partial update if you don't pass in all properties. Think of this as a "patch" vs. a replacement update. The `key` and `revision` properties are always required.
- Returns the entire entity, including both new and unchanged properties

```js
const person = await myRepo.create({
  name: 'Joe',
  age: 28,
  favoriteColor: 'blue',
});
// Full item update
person.favoriteColor = 'teal';
const newPerson1 = await myRepo.update(person);
console.log(newPerson1.favoriteColor); // 'teal'

// Partial update
const partial = {
  favoriteColor: 'aquamarine',
  key: person.key,
  revision: newPerson1.revision,
};
const newPerson2 = await myRepo.update(partial);
console.log(newPerson2.favoriteColor); // 'aquamarine'
console.log(newPerson2.age); // 28
```

// More Coming Soon...