feat(api): ✨ add flat query option for device endpoints

Added support for a "flat" query parameter to device API endpoints,
allowing device data to be returned as flattened key-value pairs.
Endpoints now provide more informative NotFound responses, listing
available device serial numbers.

Author: caunt

src/EcoFlow.Mqtt.Api/EntryPoint.cs

@@ -3,10 +3,12 @@
 using EcoFlow.Mqtt.Api.Extensions;
 using EcoFlow.Mqtt.Api.Services;
 using Microsoft.AspNetCore.Builder;
+using Microsoft.AspNetCore.Http;
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Logging;
 using Microsoft.Extensions.Options;
 using System.Text;
+using System.Text.Json;
 
 Console.OutputEncoding = Encoding.UTF8;
 
@@ -48,5 +50,18 @@
 foreach (var device in devices)
     await mqttApi.SubscribeDeviceAsync(session, mqttConfiguration, device);
 
-app.MapGet("/", () => mqttApi.Devices);
+app.MapGet("/", (HttpRequest httpRequest) =>
+    httpRequest.Query.ContainsKey("flat")
+        ? Results.Text(string.Join('\n', JsonSerializer.SerializeToNode(mqttApi.Devices).Flatten()))
+        : Results.Json(mqttApi.Devices));
+
+app.MapGet("/{serialNumber}", (HttpRequest httpRequest, string serialNumber) =>
+    mqttApi.Devices.TryGetValue(serialNumber, out var device)
+    ? httpRequest.Query.ContainsKey("flat")
+        ? Results.Text(string.Join('\n', JsonSerializer.SerializeToNode(mqttApi.Devices[serialNumber]).Flatten()))
+        : Results.Json(mqttApi.Devices[serialNumber])
+    : httpRequest.Query.ContainsKey("flat")
+        ? Results.NotFound(string.Join(',', mqttApi.Devices.Keys))
+        : Results.NotFound($"Device not found. Existing serial numbers: {string.Join(',', mqttApi.Devices.Keys)}"));
+
 app.Run();

src/EcoFlow.Mqtt.Api/Extensions/JsonExtensions.cs

@@ -39,5 +39,52 @@ public void Sort()
                     }
             }
         }
+
+        public IEnumerable<string> Flatten(string keySeparator = ".", string arrayFormat = "[{0}]")
+        {
+            foreach (var flattenedLine in Walk(node, string.Empty))
+                yield return flattenedLine;
+
+            IEnumerable<string> Walk(JsonNode? currentNode, string currentPath)
+            {
+                switch (currentNode)
+                {
+                    case JsonObject jsonObject:
+                        foreach (var jsonProperty in jsonObject)
+                        {
+                            var nextPath = string.IsNullOrEmpty(currentPath)
+                                ? jsonProperty.Key
+                                : currentPath + keySeparator + jsonProperty.Key;
+
+                            foreach (var flattenedLine in Walk(jsonProperty.Value, nextPath))
+                                yield return flattenedLine;
+                        }
+                        break;
+
+                    case JsonArray jsonArray:
+                        var arrayIndex = 0;
+
+                        foreach (var jsonArrayItem in jsonArray)
+                        {
+                            var nextPath = currentPath + string.Format(arrayFormat, arrayIndex);
+
+                            foreach (var flattenedLine in Walk(jsonArrayItem, nextPath))
+                                yield return flattenedLine;
+
+                            arrayIndex++;
+                        }
+                        break;
+
+                    case JsonValue jsonValue:
+                        var valueAsString = jsonValue.ToString() ?? string.Empty;
+                        yield return $"{currentPath}={valueAsString}";
+                        break;
+
+                    case null:
+                        yield return $"{currentPath}=";
+                        break;
+                }
+            }
+        }
     }
 }