Merge pull request #101 from bartoszclapinski/sprint2/phase2.C.3-error-handling-#93

feat(error-handling): complete phase 2.c.3 cleanup (#93)

Author: bartoszclapinski

.ai/sprints/sprint2/cleanup-plan.md

@@ -67,14 +67,14 @@ After completing Sprint 2 (GitHub Integration & Background Jobs), this cleanup p
 **Goal**: Improve error handling with user-friendly messages
 
 #### Tasks:
-- [ ] Create custom exception types (NotFoundException, ValidationException, etc.)
-- [ ] Add global exception handler middleware
-- [ ] Return user-friendly error messages from API endpoints
-- [ ] Add validation to DTOs (FluentValidation)
-- [ ] Handle GitHub API rate limit errors gracefully
-- [ ] Add retry logic for transient failures (Polly)
-- [ ] Display error messages in Blazor components
-- [ ] Add error logging to Application Insights/Serilog
+- [x] Create custom exception types (NotFoundException, ValidationException, etc.)
+- [x] Add global exception handler middleware
+- [x] Return user-friendly error messages from API endpoints
+- [x] Add validation to DTOs (FluentValidation)
+- [x] Handle GitHub API rate limit errors gracefully
+- [x] Add retry logic for transient failures (Polly)
+- [x] Display error messages in Blazor components
+- [x] Add error logging to Application Insights/Serilog
 
 **Time Estimate**: 1 day
 

.ai/sprints/sprint2/sprint-log.md

@@ -1276,6 +1276,67 @@ Integrate with GitHub to fetch and sync developer metrics with background proces
 
 ---
 
+### Day 12 - November 16, 2025
+**Focus**:
+- Phase 2.C.3 task “Display error messages in Blazor components” (Issue #93)
+
+**Highlights**:
+- Created reusable `HttpResponseMessageExtensions.ReadProblemDetailsMessageAsync()` in Web layer to hydrate RFC 7807 payloads (reused across components and forms).
+- Updated `Home.razor`, `Repositories.razor`, and `PullRequests.razor` to call the helper and surface API failures via `ISnackbar` and existing alert panels, instead of silent failures or generic strings.
+- Refined `Login.razor` and `Register.razor` to show validation/business error details coming from the new global exception pipeline.
+- Added `_Imports.razor` import so every component can access the helper without extra directives.
+
+**Testing**:
+- `dotnet build` (root solution) — succeeds with 0 warnings/errors.
+
+**Notes / Next Steps**:
+- Remaining 2.C.3 items are resiliency related (Polly retry + GitHub rate-limit handling) and structured logging.
+- Once resiliency work lands we can close issue #93 and move to Phase 2.C.4 (Caching).
+
+---
+
+### Day 13 - November 17, 2025
+**Focus**:
+- Phase 2.C.3 tasks “Handle GitHub API rate limit errors gracefully” + “Add retry logic for transient failures (Polly)” (Issue #93)
+
+**Highlights**:
+- Added `Polly` dependency plus internal `GitHubResiliencePolicies` helper that gives every Octokit call a 3-attempt exponential backoff with jitter for `ApiException`, `HttpRequestException`, and `TaskCanceledException`.
+- Centralized rate-limit messaging through `GitHubExceptionHelper`, mapping Octokit’s `RateLimitExceededException` to our `ExternalServiceException` with a human-readable retry ETA.
+- Updated `GitHubRepositoryService`, `GitHubCommitsService`, and `GitHubPullRequestService` to:
+  - Execute through the shared retry policy (with cancellation support),
+  - Throw domain exceptions (`NotFoundException`, `UnauthorizedAccessException`, `ExternalServiceException`) so the global handler can respond consistently,
+  - Log transient retries vs terminal failures separately.
+- Confirmed background job + controllers automatically benefit (they already bubble exceptions), so UI now gets friendly “rate limit” snackbars without special casing.
+
+**Testing**:
+- `dotnet build`
+- `dotnet test tests/DevMetricsPro.Infrastructure.Tests/DevMetricsPro.Infrastructure.Tests.csproj`
+
+**Notes / Next Steps**:
+- Final open Phase 2.C.3 item is structured logging/Application Insights hook-up; once done we can close Issue #93 and move ahead to caching (2.C.4).
+
+---
+
+### Day 14 - November 17, 2025 (later)
+**Focus**:
+- Phase 2.C.3 task “Add error logging to Application Insights/Serilog” (Issue #93)
+
+**Highlights**:
+- Added `Microsoft.ApplicationInsights.AspNetCore` + `Serilog.Sinks.ApplicationInsights`, surfaced configuration knobs in `appsettings*.json`, and wired telemetry registration to only activate when a connection string is provided (so devs aren’t forced to provision AI locally).
+- Updated `Program.cs` to:
+  - Bootstrap Serilog early, then rebuild the pipeline via `UseSerilog` with DI/Configuration.
+  - Forward console + rolling file logs, and conditionally fan out to Application Insights using `TelemetryConverter.Traces`.
+  - Enable `UseSerilogRequestLogging()` for per-request diagnostics.
+- Confirmed solution builds cleanly with new telemetry references.
+
+**Testing**:
+- `dotnet build`
+
+**Notes / Next Steps**:
+- Phase 2.C.3 is now fully green (Issue #93 ready to close once branch is reviewed/merged). Next phase in the cleanup plan: 2.C.4 Caching Layer.
+
+---
+
 ### Sprint 2 Completion Summary
 
 ---

src/DevMetricsPro.Application/DevMetricsPro.Application.csproj

@@ -4,6 +4,10 @@
     <ProjectReference Include="..\DevMetricsPro.Core\DevMetricsPro.Core.csproj" />
   </ItemGroup>
 
+  <ItemGroup>
+    <PackageReference Include="FluentValidation" Version="12.1.0" />
+  </ItemGroup>
+
   <PropertyGroup>
     <TargetFramework>net9.0</TargetFramework>
     <ImplicitUsings>enable</ImplicitUsings>

src/DevMetricsPro.Application/Validators/GitHubCallbackRequestValidator.cs

@@ -0,0 +1,13 @@
+using DevMetricsPro.Application.DTOs.GitHub;
+using FluentValidation;
+
+namespace DevMetricsPro.Application.Validators;
+
+public class GitHubCallbackRequestValidator : AbstractValidator<GitHubCallbackRequest>
+{
+    public GitHubCallbackRequestValidator()
+    {
+        RuleFor(x => x.Code).NotEmpty();
+        RuleFor(x => x.State).NotEmpty();
+    }
+}

src/DevMetricsPro.Application/Validators/LoginRequestValidator.cs

@@ -0,0 +1,18 @@
+using DevMetricsPro.Application.DTOs.Auth;
+using FluentValidation;
+
+namespace DevMetricsPro.Application.Validators;
+
+public class LoginRequestValidator : AbstractValidator<LoginRequest>
+{
+    public LoginRequestValidator()
+    {
+        RuleFor(x => x.Email)
+            .NotEmpty().WithMessage("Email is required")
+            .EmailAddress().WithMessage("Invalid email format");
+
+        RuleFor(x => x.Password)
+            .NotEmpty().WithMessage("Password is required");
+    }
+}
+

src/DevMetricsPro.Application/Validators/RegisterRequestValidator.cs

@@ -0,0 +1,27 @@
+using DevMetricsPro.Application.DTOs.Auth;
+using FluentValidation;
+
+namespace DevMetricsPro.Application.Validators;
+
+public class RegisterRequestValidator : AbstractValidator<RegisterRequest>
+{
+    public RegisterRequestValidator()
+    {
+        RuleFor(x => x.Email)
+            .NotEmpty().WithMessage("Email is required")
+            .EmailAddress().WithMessage("Invalid email format");
+
+        RuleFor(x => x.Password)
+            .NotEmpty().WithMessage("Password is required")
+            .MinimumLength(8).WithMessage("Password must be at least 8 characters long");
+
+        RuleFor(x => x.ConfirmPassword)
+            .NotEmpty().WithMessage("Password confirmation is required")
+            .Equal(x => x.Password).WithMessage("Passwords do not match");
+
+        RuleFor(x => x.DisplayName)
+            .MaximumLength(100).WithMessage("Display name cannot exceed 100 characters")
+            .When(x => !string.IsNullOrWhiteSpace(x.DisplayName));
+    }
+}
+

src/DevMetricsPro.Core/Exceptions/BusinessRuleException.cs

@@ -0,0 +1,8 @@
+namespace DevMetricsPro.Core.Exceptions;
+
+public class BusinessRuleException : Exception
+{    
+    public BusinessRuleException(string message) : base(message) {}
+
+    public BusinessRuleException(string message, Exception? innerException) : base(message, innerException) {}
+}

src/DevMetricsPro.Core/Exceptions/ExternalServiceException.cs

@@ -0,0 +1,8 @@
+namespace DevMetricsPro.Core.Exceptions;
+
+public class ExternalServiceException : Exception
+{
+    public ExternalServiceException(string message) : base(message) {}
+
+    public ExternalServiceException(string message, Exception? innerException) : base(message, innerException) {}
+}

src/DevMetricsPro.Core/Exceptions/NotFoundException.cs

@@ -0,0 +1,8 @@
+namespace DevMetricsPro.Core.Exceptions;
+
+public class NotFoundException : Exception
+{
+    public NotFoundException(string message) : base(message) {}
+
+    public NotFoundException(string message, Exception? innerException) : base(message, innerException) {}
+}

src/DevMetricsPro.Core/Exceptions/ValidationException.cs

@@ -0,0 +1,8 @@
+namespace DevMetricsPro.Core.Exceptions;
+
+public class ValidationException : Exception
+{
+    public ValidationException(string message) : base(message) {}
+
+    public ValidationException(string message, Exception? innerException) : base(message, innerException) {}
+}