2.1 Configuration POCOs (Mqtt, Storage, UrlFetch, ApiKey)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

IMPLEMENTATION.md

@@ -71,7 +71,7 @@ Each type lives in `src/FrameProcessor/Domain/`. Tests in `tests/FrameProcessor.
 
 ## Phase 2 — Configuration binding
 
-### [ ] 2.1 `MqttOptions`, `StorageOptions`, `UrlFetchOptions`, `ApiKeyOptions`
+### [x] 2.1 `MqttOptions`, `StorageOptions`, `UrlFetchOptions`, `ApiKeyOptions`
 - POCOs in `src/FrameProcessor/Configuration/`.
 - Bound from `appsettings.json` via `builder.Services.Configure<T>(...)`.
 - Validate on startup (`ValidateOnStart` + `IValidateOptions<T>` or DataAnnotations).

src/FrameProcessor/Configuration/ApiKeyOptions.cs

@@ -0,0 +1,20 @@
+using System.ComponentModel.DataAnnotations;
+using FrameProcessor.Domain;
+
+namespace FrameProcessor.Configuration;
+
+/// <summary>
+/// Wraps the shared API key from <c>appsettings.json</c>. The configured value is bound
+/// from the top-level <c>ApiKey</c> key (which is a plain string in the JSON schema —
+/// see SPEC.md §6.1) into <see cref="Value"/>; consumers should call <see cref="ToApiKey"/>
+/// to obtain the constant-time-comparing <see cref="ApiKey"/> value type.
+/// </summary>
+public sealed class ApiKeyOptions
+{
+    public const string SectionName = "ApiKey";
+
+    [Required(AllowEmptyStrings = false)]
+    public string Value { get; set; } = string.Empty;
+
+    public ApiKey ToApiKey() => new(Value);
+}

src/FrameProcessor/Configuration/MqttOptions.cs

@@ -0,0 +1,35 @@
+using System.ComponentModel.DataAnnotations;
+
+namespace FrameProcessor.Configuration;
+
+/// <summary>
+/// Bound from the <c>Mqtt</c> section of <c>appsettings.json</c>. See SPEC.md §6.1.
+/// </summary>
+public sealed class MqttOptions
+{
+    public const string SectionName = "Mqtt";
+
+    [Required(AllowEmptyStrings = false)]
+    public string Host { get; set; } = string.Empty;
+
+    [Range(1, 65535)]
+    public int Port { get; set; } = 1883;
+
+    [Required(AllowEmptyStrings = false)]
+    public string ClientId { get; set; } = string.Empty;
+
+    public string? Username { get; set; }
+
+    public string? Password { get; set; }
+
+    public bool UseTls { get; set; }
+
+    [Required(AllowEmptyStrings = false)]
+    public string BaseTopic { get; set; } = "frames";
+
+    [Range(0, 2)]
+    public int PublishQos { get; set; } = 1;
+
+    [MinLength(1)]
+    public int[] RetryBackoffSeconds { get; set; } = Array.Empty<int>();
+}

src/FrameProcessor/Configuration/StorageOptions.cs

@@ -0,0 +1,14 @@
+using System.ComponentModel.DataAnnotations;
+
+namespace FrameProcessor.Configuration;
+
+/// <summary>
+/// Bound from the <c>Storage</c> section of <c>appsettings.json</c>. See SPEC.md §6.1, §7.
+/// </summary>
+public sealed class StorageOptions
+{
+    public const string SectionName = "Storage";
+
+    [Required(AllowEmptyStrings = false)]
+    public string ImageDirectory { get; set; } = string.Empty;
+}

src/FrameProcessor/Configuration/UrlFetchOptions.cs

@@ -0,0 +1,20 @@
+using System.ComponentModel.DataAnnotations;
+
+namespace FrameProcessor.Configuration;
+
+/// <summary>
+/// Bound from the <c>UrlFetch</c> section of <c>appsettings.json</c>. See SPEC.md §6.1, §8.
+/// </summary>
+public sealed class UrlFetchOptions
+{
+    public const string SectionName = "UrlFetch";
+
+    [Range(1, long.MaxValue)]
+    public long MaxBytes { get; set; } = 52_428_800L;
+
+    [Range(1, int.MaxValue)]
+    public int TimeoutSeconds { get; set; } = 30;
+
+    [Range(0, int.MaxValue)]
+    public int MaxRedirects { get; set; } = 3;
+}

src/FrameProcessor/Program.cs

@@ -1,7 +1,29 @@
+using FrameProcessor.Configuration;
+
 var builder = WebApplication.CreateBuilder(args);
 
 builder.Services.AddControllers();
 
+builder.Services.AddOptions<MqttOptions>()
+    .Bind(builder.Configuration.GetSection(MqttOptions.SectionName))
+    .ValidateDataAnnotations()
+    .ValidateOnStart();
+
+builder.Services.AddOptions<StorageOptions>()
+    .Bind(builder.Configuration.GetSection(StorageOptions.SectionName))
+    .ValidateDataAnnotations()
+    .ValidateOnStart();
+
+builder.Services.AddOptions<UrlFetchOptions>()
+    .Bind(builder.Configuration.GetSection(UrlFetchOptions.SectionName))
+    .ValidateDataAnnotations()
+    .ValidateOnStart();
+
+builder.Services.AddOptions<ApiKeyOptions>()
+    .Configure<IConfiguration>((opts, cfg) => opts.Value = cfg[ApiKeyOptions.SectionName] ?? string.Empty)
+    .ValidateDataAnnotations()
+    .ValidateOnStart();
+
 var app = builder.Build();
 
 app.MapControllers();