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// This program implements a Covid lookup service
// over TCP or Unix Data Socket. It loads CSV Covid Dataset
// information using package lib (see above) and uses a simple
// text-based protocol to interact with the client and send
// the data.
//
// Clients send covid dataset search requests as a textual command in the form:
// Open new Terminal:
// $ go run serertxt.go
// Open another Terminal:
// $ nc localhost 4040
// $ {"query": {"region": "Sindh"}}
// $ {"query": {"date": "4/4/2020"}}
// for query It's mendatory to follow the given JSOn Structure as it is given above.
//
// When the server receives the request, it is parsed and is then used
// to search the list of covid Dataset. The search result is then printed
// JSON Format dataset to the client.
//
// Focus:
// This version of the server uses TCP sockets (or UDS) to implement a simple
// text-based application-level protocol. There are no streaming strategy
// employed for the read/write operations. Buffers are read in one shot
// creating opportunities for missing data during read.
//
// Testing:
// Netcat or telnet can be used to test this server by connecting and
// sending command using the format described above.
//
// Usage: server [options]
// options:
//   -e host endpoint, default ":4040"
//   -n network protocol [tcp,unix], default "tcp"


                                    Here is complete overview of this tcp server
            
            
(Golang): This tasks is designed to help you work with concepts frequently used in backend systems development. 

## Programming Language
[Go v1.14](https://golang.org/)


## Task

Write a **TCP Server** that loads dataset from a **CSV file** and provide interface to query the dataset. TCP server will expose port **4040**.


### Dataset

You will be required to download **Corona Virus Pakistan Dataset 2020** from the **OpenData.com.pk**, convert the dataset into a CSV file and use this file to load data into the server.

- Download `COVID_FINAL_DATA.xlsx` from [OpenData.com.pk](https://opendata.com.pk/dataset/corona-virus-pakistan-dataset-2020)
- Convert first sheet "TimeSeries_KeyIndicators" into a CSV file
- Place the CSV file into the repository

Following columns are required in CSV:
- Cumulative Test Positive
- Cumulative Tests Performed
- Date
- Discharged
- Expired
- Admitted
- Region

### Server Communication

User should be able to connect to the server using **NetCat** `nc localhost 4040` command on Linux/Unix based systems.

Once connected to TCP, user should be able communicate with the application by sending queries in JSON format.

```
{
	"query": {
		"region": "Sindh"
	}
}
```

```
{
	"query": {
		"date": "20/3/2020"
	}
}
```

User can query data based on two fields: Region and Date.

In response, server will return a **list** of records that will match query. An individual record's JSON format will look like:

```
{
   "date": "2020-03-11",
   "positive": 2,
   "tests": 171,
   "expired": 0,
   "admitted": 13,
   "discharged": 0,
   "region": "Sindh"
}
```


## Query Examples

```
> nc localhost 4040
> {"query": {"region": "Sindh"}}
> {"response": [
   {
	   "date": "11/03/2020",
	   "positive": 2,
	   "tests": 171,
	   "expired": 0,
	   "admitted": 13,
	   "discharged": 0,
	   "region": "Sindh"
   },
   {
	   "date": "12/3/2020",
	   "positive": 14,
	   "tests": 324,
	   "expired": 0,
	   "admitted": 13,
	   "discharged": 0,
	   "region": "Sindh"
   },
   {
	   "date": "2020-03-13",
	   "positive": 43,
	   "tests": 324,
	   "expired": 0,
	   "admitted": 12,
	   "discharged": 0,
	   "region": "Sindh"
   }
  ]}
```

```
> nc localhost 4040
> {"query": {"date": "2020-03-20"}}
> {"response": [
   {
	   "date": "2020-03-20",
	   "positive": 2,
	   "tests": 171,
	   "expired": 0,
	   "admitted": 13,
	   "discharged": 0,
	   "region": "Sindh"
   },
   {
	   "date": "2020-03-20",
	   "positive": 14,
	   "tests": 324,
	   "expired": 0,
	   "admitted": 13,
	   "discharged": 0,
	   "region": "Punjab"
   },
   {
	   "date": "2020-03-20",
	   "positive": 43,
	   "tests": 324,
	   "expired": 0,
	   "admitted": 12,
	   "discharged": 0,
	   "region": "KP"
   }
  ]}
```



## Learning Resources

[Effective Go](https://golang.org/doc/effective_go.html)

[Reading a simple CSV in Go](https://medium.com/@ankurraina/reading-a-simple-csv-in-go-36d7a269cecd)

[Read a CSV File into a Struct](https://golangcode.com/how-to-read-a-csv-file-into-a-struct/)

[Go by Example: JSON](https://gobyexample.com/json)

[Network Programming with Go: A TCP Server with a Custom Protocol](https://www.youtube.com/watch?v=yW1ltZidh7g)

[How to Use Netcat Commands: Examples and Cheat Sheets](https://www.varonis.com/blog/netcat-commands/)