This is a REST API written in Go (Golang). The underlying database is PostgreSQL.
Daily weather data is available for 3 cities: Vienna, Sopron, Budapest - from 1980-01-01 to 2023-09-15. Forecast functionality for one day is also available.

There are two ways to interact with the API: with API-key and without.
In a real-life scenario, there could be two roles: a basic user and a data analyst. If you do not use an API key, limited information is available. By using API-key, all the data is available for data analysts.

The architecture of the application is the following:

Docker and Docker Compose. You need to install both on your computer.

Create a .env.secret file with the following environment variables:

POSTGRES_USER={YOUR_PG_USER}
POSTGRES_PASS={YOUR_PG_PASS}
POSTGRES_DB={YOUR_PG_DB}
POSTGRES_HOST=localhost
POSTGRES_PORT={YOUR_PG_PORT}
API_KEY={SUPERSECRET_API_KEY}
API_PORT={YOUR_API_PORT}

Afterwards go into the project folder and start the application and initialize the database:
docker compose --env-file .env.secret up -d

Make sure both services are available (database and application) and running on the defined ports:
docker ps

There are three endpoints for normal users and data analysts:

1. Limited data for normal users:
   localhost:{8080}/api/city={CITY[Sopron,Vienna or Budapest]}&date={YYYY-MM-DD}
   For example:
   https://localhost:8080/api/city=Sopron&date=2021-01-03
   Response:

{  
  "city": "Sopron",  
  "date": "2021-01-03T00:00:00Z",  
  "temperature_2m_mean": 3.9,  
  "precipitation_sum": 1.4  
}

2. Extended data for data analysts:
   localhost:{API_PORT}/api/city={CITY[Sopron,Vienna or Budapest]}&date={YYYY-MM-DD}
   API key sent as "api-key" value in header (or in frontend it can be provided in the form). For example:
   Response:

{  
  "city": "Sopron",  
  "date": "2021-01-03T00:00:00Z",  
  "temperature_2m_max": 6.4,  
  "temperature_2m_min": 1.6,  
  "temperature_2m_mean": 3.9,  
  "sunrise": "2021-01-03T08:42:00Z",  
  "sunset": "2021-01-03T17:14:00Z",  
  "precipitation_sum": 1.4,  
  "rain_sum": 1.4,  
  "snowfall_sum": 0,  
  "precipitation_hours": 7,  
  "windspeed_10m_max": 14.8,  
  "winddirection_10m_dominant": 156  
}

For the full data, you need to attach your {API_KEY} as a value to the key: api-key into the HTTP request header.

3. Basic forecast data for normal users: localhost:{API_PORT}/api/forecast/city={CITY[Sopron,Vienna or Budapest]}&date={YYYY-MM-DD} API key is not needed for forecast.

For example:
https://localhost:8080/api/forecast/city=Sopron&date=2021-01-03
Response:

{  
  "city": "Sopron",  
  "temperature_2m_mean": 3.9,  
  "precipitation_sum": 1.4  
}

docker compose --env-file .env.secret down --rmi all -v Delete wapi_pgdata folder (this is the persistent volume of the Postgres container).

Credits to open-meteo.com Historical Weather API for the data.