This solution demonstrates Golang HTTP server capable of accept specific JSON structures and store them. It also can return stored values. Solution uses simple in-memory storage.

Challenges:

• some variability possible in provided JSONs.

Code highlights:

• gorilla/mux as HTTP server router (internal/api/server/server.go)
• application-specific handler format (see 'AppHandler' type and 'toHandler' func).
• custom JSON marshalling (see 'RawTemperature' and 'RawTime' types)
• end-to-end HTTP tests (see internal/api/server/server_test.go)
• in-memory storage is designed to be replaceable (internal/storage/repo.go)

Assumptions made:

• Application can accept data in different formats. But outputs only the single format for each type
  • for time this is "2006-01-02T15:04:05.999Z07:00"
  • for temperature - float with Celsius value
• if timezone is unknown, assume GMT0
• invalid json in the demo data (no comma after "HDDSpace"): assume json is valid
• assume that InternalTemp is allowed to have 'c' too (no such case in demo data)

Go 1.18 is required to be installed locally and added to the PATH.

Use makefile's shortcuts to build, test and run the project.

• "make build" : builds the project and places the binary result "sample_server" to the project root
• "make test" : runs all unit tests
• "make run" : builds and executes the binary with debug configuration

Application can be configured with certain environment variables. To get the list of them - run "make help_env" or simply "./sample_server --help". E.g. to run app with custom port run "SAMPLE_SERVER_SERVER_ADDR=:3999 ./sample_server"

Once application executed, it's api is accessible. Default port is 4000.

Api contains two endpoints

Curl example:

curl --header "Content-Type: application/json" \
  --request POST \
  --data '{
    "machineId": 12345,
    "stats": {
        "cpuTemp": 90.1,
        "fanSpeed": 400,
        "HDDSpace": 800,
        "internalTemp": "72c"
    },
    "lastLoggedIn": "admin/Paul",
    "sysTime": "2022-04-23T18:25:43.511Z"
}' \
  http://localhost:4000/

Fields cpuTemp and internalTemp could be both

• number (integer or float) or
• string containing number with letter 'c' in the end

Allowed time formats:

• "2006-01-02T15:04:05Z07:00"
• "Mon 2006-01-02 15:04:05" (UTC assume timezone)

curl 127.0.0.1:4000 

It returns an json array of objects. Object structure is close to previous api, but has additional ID field. This json uses only one sysTime format and always use numeric temperatures.

[
    {
        "id": "632ce4f2-4bd7-4ea5-94ca-5e6c9c06eed2",
        "machineId": 12345,
        "stats": {
            "cpuTemp": 90.1,
            "fanSpeed": 400,
            "HDDSpace": 800,
            "internalTemp": 72
        },
        "lastLoggedIn": "admin/Paul",
        "sysTime": "2022-04-23T18:25:43.511Z"
    }
]