Arduino code for ESP8266/ESP32 for fetching future electricity prices from the nordic energy price market "Nordpool" using Vattenfall's API

Nordpool.h

// MIT License
//
// Copyright (c) 2022 freol35241
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.

#ifndef NORDPOOL_H
#define NORDPOOL_H

// Expects the time.h to be updated via a NTP server
// For example:
//  #include <time.h>
//  configTime(3600, 3600, "pool.ntp.org");
//
// Requires:
//  ArduinoJson (https://arduinojson.org/)
//  DebugLog (https://github.com/hideakitai/DebugLog)

#include "Arduino.h"
#include "time.h"
#include <HTTPClient.h>
#include <DebugLog.h>
#include <ArduinoJson.h>

namespace Nordpool
{

    String url_to_fetch(const String &area, tm *time_info)
    {

        char today[12]; // should be enough
        strftime(today, sizeof(today), "%Y-%m-%d", time_info);

        String url = "https://www.vattenfall.se/api/price/spot/pricearea/";
        url += today;
        url += "/";
        url += "2099-12-31";
        url += "/";
        url += area;

        return url;
    }

    int fetch_upcoming_prices(const String &area, float *prices)
    {
        HTTPClient client;

        tm time_info;
        if (!getLocalTime(&time_info))
        {
            LOG_ERROR("Failed to get local date and time!");
            return -1;
        }

        String url = url_to_fetch(area, &time_info);

        client.begin(url.c_str());

        int rc = client.GET();

        LOG_INFO("Http response code: ", rc);

        if (rc != 200)
        {
            LOG_ERROR("Failed to fetch prices using: ", url);
            return -1;
        }

        DynamicJsonDocument doc(12288);

        DeserializationError error = deserializeJson(doc, client.getStream());

        if (error)
        {
            LOG_ERROR("deserializeJson() failed: ", error.c_str());
            return -1;
        }

        bool start_found = false;
        int ix = 0;

        for (JsonObject item : doc.as<JsonArray>())
        {

            if (!start_found)
            {
                uint8_t hour = String((const char *)item["TimeStampHour"]).substring(0, 2).toInt();
                if (hour == time_info.tm_hour)
                {
                    start_found = true;
                }
                else
                {
                    continue;
                }
            }

            prices[ix++] = item["Value"];
        }

        return ix;
    }

}

#endif