Round 3 - Machine Round Question Question

task.txt

Write a TCP server that provides the following functionality:

1. Be able to communicate over TCP with a client such as `nc` (netcat),
`telnet`, or a custom TCP client.
2. Provide echo functionality:
Command: "ECHO <string>"
Expected response: "<string>"
3. Allow data to be stored:
Command: "SET <key> <value>"

Expected response: "!200"
Errors:
- if store is full: "!500"
- if syntax error: "!400"
4. Allow data to be retrieved:
Command: "GET <key>"
Expected response: "<value>"
Errors:
- if key not found (ie., not previously set): "!404"
- if syntax error: "!400"
5. Allow setting tags with keys:
Command: "SET <key> <value> <tag1> <tag2> <...tagN>"
Expected behaviour is same as (3)
6. Allow data to be retrieved with tags:
Command: "GETWITHTAGS <key>"
Expected response: "<value> [<tag1> <tag2> <...tagN>]"
Other behaviour similar to (4)
7. Load into your datastore a file _on the server_:
Extra: Save datastore to filename
#json and think something else
Command: "LOAD <filename>"
Example: "LOAD scores.db"
Expected response: "!200" if load succeeds. "!500" if an error occurs
8. List keys with a specific tag:
Command: "LISTKEYSWITHTAG EXACT <tagname>"
Expected response: "[<key1> <key2> <...key3>]"
Errors:
- if tag not found (or there exists no keys with that tag): "!404"
9. Aggregation functionality:
Support COUNT, MAX, MIN, AVG, SUM.
Command: "COUNT TAG <tag>"
Response: "<result-value>", where result-value is the result of the
aggregation function.
For example, if the current state of the datastore was:

---
key1 30 tagR
key2 40 tagQ
key3 20 tagR
---
then "AVG TAG tagR" would respond with "25".
### Notes
1. It isn't necessary to preserve the values in the datastore
2. You will find a command called `checker.py` that will test
your code. You will be able to test your code by running the command,
`./checker.py <port>`, where the <port> is the port number where your
TCP server is currently listening.
3. Ensure that your program follows the spec below exactly since the
checker is automated.
4. Test often.
5. Listen for instructions on the Zoom call.

### Table of control codes
| meaning | control code|
| -------- | -------- |
| generic error | 500 |
| invalid input or parsing error | 400 |
| input too large | 413 |
| key not found | 404 |
| error loading .db - no such file? | 404 |
| OK (but no data response) | 200 |