API.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.Json;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Extensions.Logging;
using Saunter.Attributes;

namespace StreetlightsAPI
{
    public class Streetlight
    {
        /// <summary>
        /// Id of the streetlight.
        /// </summary>
        public int Id { get; set; }
        
        /// <summary>
        /// Lat-Long coordinates of the streetlight.
        /// </summary>
        public double[] Position { get; set; }

        /// <summary>
        /// History of light intensity measurements
        /// </summary>
        public List<KeyValuePair<DateTime, int>> LightIntensity { get; set; }
    }

    public class LightMeasuredEvent
    {
        /// <summary>
        /// Id of the streetlight.
        /// </summary>
        public int Id { get; set; }

        /// <summary>
        /// Light intensity measured in lumens.
        /// </summary>
        public int Lumens { get; set; }

        /// <summary>
        /// Light intensity measured in lumens.
        /// </summary>
        public DateTime SentAt { get; set; }
    }

    [AsyncApi]
    [ApiController]
    [Route("")]
    public class StreetlightsController
    {
        private const string PublishLightMeasuredTopic = "publish/light/measured";


        // Simulate a database of streetlights
        private static int StreetlightSeq = 2;
        private static readonly List<Streetlight> StreetlightDatabase = new List<Streetlight>
        {
            new Streetlight { Id = 1, Position = new [] { -36.320320, 175.485986 }, LightIntensity = new() },
        };
        
        private readonly IStreetlightMessageBus _streetlightMessageBus;
        private readonly ILogger _logger;

        public StreetlightsController(IStreetlightMessageBus streetlightMessageBus, ILoggerFactory loggerFactory)
        {
            _streetlightMessageBus = streetlightMessageBus;
            _logger = loggerFactory.CreateLogger<StreetlightsController>();
        }
        
        /// <summary>
        /// Get all streetlights
        /// </summary>
        [HttpGet]
        [Route("api/streetlights")]
        public IEnumerable<Streetlight> Get() => StreetlightDatabase;

        /// <summary>
        /// Add a new streetlight
        /// </summary>
        [HttpPost]
        [Route("api/streetlights")]
        public Streetlight Add([FromBody] Streetlight streetlight)
        {
            streetlight.Id = StreetlightSeq++;
            StreetlightDatabase.Add(streetlight);
            return streetlight;
        }

        /// <summary>
        /// Inform about environmental lighting conditions for a particular streetlight.
        /// </summary>
        [Channel(PublishLightMeasuredTopic, Servers = new []{"webapi"}, XParams = new[] { "key1=value1", "key2=value2" })]
        [PublishOperation(typeof(LightMeasuredEvent), "Light")]
        [HttpPost]
        [Route(PublishLightMeasuredTopic)]
        public void MeasureLight([FromBody] LightMeasuredEvent lightMeasuredEvent)
        {
            lightMeasuredEvent.SentAt = DateTime.Now;

            var payload = JsonSerializer.Serialize(lightMeasuredEvent);

            _logger.LogInformation("Received message on {Topic} with payload {Payload} ", PublishLightMeasuredTopic, payload);

            var streetlight = StreetlightDatabase.SingleOrDefault(s => s.Id == lightMeasuredEvent.Id);
            if (streetlight != null)
            {
                streetlight.LightIntensity.Add(new(lightMeasuredEvent.SentAt, lightMeasuredEvent.Lumens));

                // Re-publish messages we receive
                _streetlightMessageBus.PublishLightMeasurement(lightMeasuredEvent);
            }
        }
    }
}