Implemented Azure Redis Cache for weather data

handlenett-backend/web-api/HandlenettAPI/HandlenettAPI.csproj

@@ -30,6 +30,7 @@
     <PackageReference Include="Microsoft.Identity.Web.MicrosoftGraph" Version="3.1.0" />
     <PackageReference Include="Microsoft.Identity.Web.UI" Version="3.1.0" />
     <PackageReference Include="Microsoft.VisualStudio.Azure.Containers.Tools.Targets" Version="1.21.0" />
+    <PackageReference Include="StackExchange.Redis" Version="2.8.16" />
     <PackageReference Include="Swashbuckle.AspNetCore" Version="6.7.3" />
     <PackageReference Include="System.Net.Http" Version="4.3.4" />
   </ItemGroup>

handlenett-backend/web-api/HandlenettAPI/Models/Weather.cs

@@ -4,5 +4,6 @@ public class Weather
     {
         public string Temperature { get; set; }
         public Uri ImageUri { get; set; }
+        public DateTime LastUpdated { get; set; }
     }
 }

handlenett-backend/web-api/HandlenettAPI/Services/WeatherService.cs

@@ -1,19 +1,43 @@
-using HandlenettAPI.Models;
+using Azure.Identity;
+using HandlenettAPI.Models;
 using Newtonsoft.Json.Linq;
+using StackExchange.Redis;
+using System.Text.Json;
 
 namespace HandlenettAPI.Services
 {
     public class WeatherService
     {
         private readonly HttpClient _httpClient;
+        private readonly ConnectionMultiplexer _redis;
 
-        public WeatherService(HttpClient httpClient)
+        public WeatherService(HttpClient httpClient, IConfiguration config)
         {
             _httpClient = httpClient;
             _httpClient.DefaultRequestHeaders.Add("User-Agent", "Miles Haugesund Handlenett/1.0 ([email protected])");
+            _redis = ConnectionMultiplexer.Connect(config.GetConnectionString("AzureRedisCache"));
         }
 
         public async Task<Weather> GetWeatherByCoordinatesAsync(double latitude, double longitude)
+        {
+            Weather? weather = null;
+
+            var cachedValue = GetCacheValue("Weather");
+            if (cachedValue != null)
+            {
+                weather = JsonSerializer.Deserialize<Weather>(cachedValue.ToString());
+            }
+
+            if (weather == null || weather.LastUpdated <= DateTime.UtcNow.AddHours(-1))
+                {
+                    weather = await GetDataFromMet(latitude, longitude);
+                    weather.LastUpdated = DateTime.UtcNow;
+                    SetCacheValue("Weather", JsonSerializer.Serialize<Weather>(weather));
+                }
+            return weather;
+        }
+
+        private async Task<Weather> GetDataFromMet(double latitude, double longitude)
         {
             var returnModel = new Weather();
             var url = $"https://api.met.no/weatherapi/locationforecast/2.0/compact?lat={latitude}&lon={longitude}";
@@ -27,16 +51,29 @@ public async Task<Weather> GetWeatherByCoordinatesAsync(double latitude, double
 
                 returnModel.Temperature = json["properties"]["timeseries"][0]["data"]["instant"]["details"]["air_temperature"].ToString();
                 var symbol = json["properties"]["timeseries"][0]["data"]["next_1_hours"]["summary"]["symbol_code"].ToString();
+
+                //TODO: add icons for displaying weather in web app
                 //returnModel.ImageUri = new Uri($"https://api.met.no/weatherapi/weathericon/2.0/?symbol={symbol}&content_type=image/png");
                 //https://github.com/metno/weathericons
+
                 return returnModel;
             }
             else
             {
-                throw new Exception ("Unable to retrieve weather data from MET Norway.");
+                throw new Exception("Unable to retrieve weather data from MET Norway.");
             }
         }
 
+        private void SetCacheValue(string key, string value)
+        {
+            var db = _redis.GetDatabase();
+            db.StringSet(key, value);
+        }
 
+        private string? GetCacheValue(string key)
+        {
+            var db = _redis.GetDatabase();
+            return db.StringGet(key);
+        }
     }
 }