Add API documentation and implement sample todos endpoint

.instructions.md

@@ -0,0 +1,89 @@
+# WebAPI Code Review Guidelines
+
+## API Documentation
+
+This is a todo management REST API built with ASP.NET Core 10 using the minimal APIs pattern.
+
+### Current Endpoints
+
+#### GET /todos
+- **Name**: GetTodos
+- **Description**: Retrieves all todo items
+- **Response**: Array of `Todo` objects
+- **Status Codes**: 200 OK
+
+#### GET /todos/{id}
+- **Name**: GetTodoById
+- **Description**: Retrieves a specific todo item by ID
+- **Path Parameters**: `id` (int) - The todo item ID
+- **Response**: `Todo` object if found, 404 if not found
+- **Status Codes**: 200 OK, 404 Not Found
+
+#### POST /todos
+- **Name**: CreateTodo
+- **Description**: Creates a new todo item
+- **Request Body**: Plain string - the todo title
+- **Response**: Created `Todo` object with generated ID
+- **Status Codes**: 201 Created
+- **Location Header**: `/todos/{newId}` pointing to the newly created resource
+
+### Data Model
+
+```csharp
+public record Todo(
+    int Id,
+    string? Title,
+    DateOnly? DueBy = null,
+    bool IsComplete = false
+);
+```
+
+- **Id**: Unique identifier (auto-generated on creation)
+- **Title**: The todo item description
+- **DueBy**: Optional due date
+- **IsComplete**: Completion status (default: false)
+
+## Code Review Checklist
+
+When reviewing changes to this API, ensure:
+
+### Endpoint Design
+- [ ] New endpoints follow the `MapGet/MapPost/MapPut/MapDelete` pattern with the `/todos` group
+- [ ] All endpoints have meaningful `WithName()` identifiers
+- [ ] HTTP status codes are appropriate (201 for creation, 404 for not found, etc.)
+- [ ] POST endpoints use `TypedResults.Created()` and return the created resource
+
+### Data Handling
+- [ ] New IDs are generated correctly (current logic: `Max(t => t.Id) + 1`)
+- [ ] All todo items are properly serialized/deserialized with `AppJsonSerializerContext`
+- [ ] Optional fields are properly nullable (`DateOnly?`, `string?`)
+
+### In-Memory Storage
+- [ ] The `sampleTodos` list is a `List<Todo>` (mutable for POST/PUT/DELETE operations)
+- [ ] Data operations maintain data integrity
+- [ ] Consider future migration to a database when needed
+
+### API Contract
+- [ ] All new endpoints are documented with `WithName()`
+- [ ] OpenAPI/Swagger documentation is accurate (enable with `app.MapOpenApi()` in Development)
+- [ ] Request/response types align with the `Todo` record definition
+
+### Testing Considerations
+- [ ] POST endpoint should test ID generation with multiple creates
+- [ ] GET endpoints should handle both existing and non-existent IDs
+- [ ] Consider testing edge cases (empty lists, max int IDs, etc.)
+
+## Technology Stack
+
+- **.NET**: 10.0
+- **Framework**: ASP.NET Core (Minimal APIs)
+- **Serialization**: System.Text.Json
+- **API Documentation**: OpenAPI (Swagger) support enabled
+
+## Future Enhancement Areas
+
+- Implement DELETE and PUT endpoints for updating and deleting todos
+- Add database persistence (Entity Framework Core)
+- Add input validation (title length, date validation)
+- Implement filtering/pagination for GET /todos
+- Add async database operations

Program.cs

@@ -18,14 +18,14 @@
     app.MapOpenApi();
 }
 
-Todo[] sampleTodos =
-[
-    new(1, "Walk the dog"),
-    new(2, "Do the dishes", DateOnly.FromDateTime(DateTime.Now)),
-    new(3, "Do the laundry", DateOnly.FromDateTime(DateTime.Now.AddDays(1))),
-    new(4, "Clean the bathroom"),
-    new(5, "Clean the car", DateOnly.FromDateTime(DateTime.Now.AddDays(2)))
-];
+var sampleTodos = new List<Todo>
+{
+    new Todo(1, "Walk the dog"),
+    new Todo(2, "Do the dishes", DateOnly.FromDateTime(DateTime.Now)),
+    new Todo(3, "Do the laundry", DateOnly.FromDateTime(DateTime.Now.AddDays(1))),
+    new Todo(4, "Clean the bathroom"),
+    new Todo(5, "Clean the car", DateOnly.FromDateTime(DateTime.Now.AddDays(2)))
+};
 
 var todosApi = app.MapGroup("/todos");
 todosApi.MapGet("/", () => sampleTodos)
@@ -37,6 +37,15 @@
         : TypedResults.NotFound())
     .WithName("GetTodoById");
 
+todosApi.MapPost("/", (string title) =>
+{
+    var newId = sampleTodos.Max(t => t.Id) + 1;
+    var newTodo = new Todo(newId, title);
+    sampleTodos.Add(newTodo);
+    return TypedResults.Created($"/todos/{newId}", newTodo);
+})
+    .WithName("CreateTodo");
+
 app.Run();
 
 public record Todo(int Id, string? Title, DateOnly? DueBy = null, bool IsComplete = false);