# CypherD - Backend

## Prerequisites
- Understand Nestjs - a typescript based Backend MVC Framework [Module](https://docs.nestjs.com/modules) , [Controllers](https://docs.nestjs.com/controllers) , [Providers](https://docs.nestjs.com/providers) , [Validations](https://docs.nestjs.com/techniques/validation)
- Understand [local-db](https://lenn.gitbook.io/db-local/) - A simple alternative to database with simple JSON.
- Understand REST Architecture, HTTP Verbs and Response Codes

### Points to Consider:

- API endpoints must follow REST Architectural Patterns and Guidelines (https://www.codecademy.com/article/what-is-rest )
- Variable Names , Function Names, Class Names should be Meaningful.

## Problem Statement: Create a RESTful API

### 1. An Endpoint to Get the aggregate token balances of an address in the following chains: Ethereum, Fantom, and Polygon.

- [ ] Integrate with CovalentHq - https://api.covalenthq.com/v1/1/address/0x52114fb7396dbe19096ffa343d18830f5d77b6c6/balances_v2/?key=<your_api_key>

Sample Input:

	 0x52114fb7396dbe19096ffa343d18830f5d77b6c6 

Sample Output :

{
	address: "0x52114fb7396dbe19096ffa343d18830f5d77b6c6",
	balances: {
		eth: [
		{
			name: '',
			symbol:'',
			decimals:'',
			contractAddress:'',
			contractDeicmals:'',
			logo:'',
			balance: xx,
			balanceInUSD: xx,
		}
		],
		polygon:[],
		fantom:[],
	},
	totalBalanceInUSD: XXX
}

### 2. Watchlist Management Feature

#### 2.1 An Endpoint to Get Master Coin list - Coingecko Integration

- [ ] Integrate with following API to generate the master list of tokens https://api.coingecko.com/api/v3/coins/list
- [ ] `id` field in the response should be used in upcoming APIs to track these coins through the watchlist

Sample Output:

{
	coins:
	[
		{
			"id": "matic-network",
			"symbol": "matic",
			"name": "Polygon"
		},
	
	]
}

#### 2.2 An Endpoint to Create Watchlist with a name
Validation : name should be alphanumeric with minimum of 5 characters and maximum of 20
Sample Input :

{
	name: "vitalikWatchlist"
}

Sample Output :

{
	id: "24cf68e1-3ef1-403b-9851-44a90cb32816",
	name: "vitalikWatchlist", 
	tokens: []
}
 

#### 2.3 Add tokens to Watchlist
Validation :
- `tokensToBeAdded` list should be validated with Coingecko List with the `id` field.
- should ignore duplicates

Sample Input :

{
	tokensToBeAdded: [ "matic-network"] 
}

Sample Output:

{
	id: "24cf68e1-3ef1-403b-9851-44a90cb32816",
	name: "vitalikWatchlist", 
	tokens: ["matic-network"]
}

#### 2.4 Delete tokens from Watchlist
Sample Input

{
	tokensToBeDeleted: ["matic-network""] 
}

Sample Output

{
	id: "24cf68e1-3ef1-403b-9851-44a90cb32816",
	name: "vitalikWatchlist", 
	tokens: []
}

#### 2.5 An Endpoint to Get Watchlist by its id

Sample Output

{
	id: "24cf68e1-3ef1-403b-9851-44a90cb32816",
	name: "vitalikWatchlist", 
	tokens: ["matic-network", "gravity-finance"]
}

#### 2.6 An Endpoint to Delete Watchlist by its id

### References :

https://www.coingecko.com/en/api/documentation

https://www.covalenthq.com/platform/#/auth/register/ - For Api key generation

https://www.covalenthq.com/docs/api - CovalentHQ Docs

https://www.codecademy.com/article/what-is-rest

| chain | id |
|--|--|
| ethereum | 1 |
| polygon | 137 |
| fantom | 250 |