Add server-side ELO ratings

api/QuestionsApi/Controllers/QuestionsController.cs

@@ -13,11 +13,13 @@ public class QuestionsController : ControllerBase
 {
     private readonly QuestionStore _questions;
     private readonly QuestionAttemptStore _attempts;
+    private readonly RatingStore _ratings;
 
-    public QuestionsController(QuestionStore questions, QuestionAttemptStore attempts)
+    public QuestionsController(QuestionStore questions, QuestionAttemptStore attempts, RatingStore ratings)
     {
         _questions = questions;
         _attempts = attempts;
+        _ratings = ratings;
     }
 
     [HttpGet("systems")]
@@ -34,10 +36,11 @@ public class QuestionsController : ControllerBase
     {
         var questions = await _questions.SearchAsync(req, User.IsInRole("SUPER"));
         var percentages = await _attempts.GetPercentagesByQuestionAsync(questions.Select(q => q.ExternalId));
+        var questionElos = await _ratings.GetQuestionElosAsync(questions.Select(q => q.ExternalId));
         return Ok(questions.Select(q =>
         {
             percentages.TryGetValue(q.ExternalId, out var questionPercentages);
-            return QuestionResponse.FromModel(q, questionPercentages);
+            return QuestionResponse.FromModel(q, questionPercentages, questionElos.GetValueOrDefault(q.ExternalId, 1000));
         }).ToList());
     }
 
@@ -50,7 +53,8 @@ public class QuestionsController : ControllerBase
             return NotFound();
 
         var percentages = await _attempts.GetPercentagesForQuestionAsync(question.ExternalId);
-        return Ok(QuestionResponse.FromModel(question, percentages));
+        var questionElo = await _ratings.GetQuestionEloAsync(question.ExternalId);
+        return Ok(QuestionResponse.FromModel(question, percentages, questionElo));
     }
 
     [HttpPost("attempts/first")]
@@ -75,18 +79,60 @@ public class QuestionsController : ControllerBase
         if (string.IsNullOrWhiteSpace(userId))
             return Unauthorized();
 
-        await _attempts.RecordFirstAttemptAsync(
+        var wasFirstAttempt = await _attempts.RecordFirstAttemptAsync(
             question.ExternalId,
             userId,
             req.ChoiceId.Trim(),
             req.ChoiceId.Trim() == question.CorrectChoiceId);
+        var rating = await _ratings.ApplyFirstResultAsync(
+            userId,
+            question,
+            req.ChoiceId.Trim() == question.CorrectChoiceId,
+            wasFirstAttempt);
 
         return Ok(new FirstQuestionAttemptResponse
         {
             QuestionExternalId = question.ExternalId,
             ChoiceSelectionPercentages = QuestionResponse.BuildChoiceSelectionPercentages(
                 question,
-                await _attempts.GetPercentagesForQuestionAsync(question.ExternalId))
+                await _attempts.GetPercentagesForQuestionAsync(question.ExternalId)),
+            QuestionElo = rating.QuestionElo,
+            Rating = rating
+        });
+    }
+
+    [HttpPost("{externalId}/skip")]
+    [Authorize(Roles = "USER,SUPER")]
+    public async Task<IActionResult> Skip(string externalId)
+    {
+        if (string.IsNullOrWhiteSpace(externalId))
+            return BadRequest("externalId required");
+
+        var question = await _questions.GetByExternalIdAsync(externalId.Trim());
+        if (question is null || (!question.IsPublished && !User.IsInRole("SUPER")))
+            return NotFound();
+
+        var userId = CurrentUserId();
+        if (string.IsNullOrWhiteSpace(userId))
+            return Unauthorized();
+
+        var wasFirstAttempt = await _attempts.RecordFirstAttemptAsync(
+            question.ExternalId,
+            userId,
+            "",
+            false,
+            true);
+        var rating = await _ratings.ApplyFirstResultAsync(userId, question, false, wasFirstAttempt);
+
+        return Ok(new SkipQuestionResponse
+        {
+            QuestionExternalId = question.ExternalId,
+            CorrectChoiceId = question.CorrectChoiceId,
+            ChoiceSelectionPercentages = QuestionResponse.BuildChoiceSelectionPercentages(
+                question,
+                await _attempts.GetPercentagesForQuestionAsync(question.ExternalId)),
+            QuestionElo = rating.QuestionElo,
+            Rating = rating
         });
     }
 
@@ -183,4 +229,10 @@ public class QuestionsController : ControllerBase
 
         return null;
     }
+
+    private string CurrentUserId() =>
+        User.FindFirstValue(ClaimTypes.NameIdentifier)
+        ?? User.FindFirstValue(ClaimTypes.Name)
+        ?? User.Identity?.Name
+        ?? "";
 }

api/QuestionsApi/Controllers/RatingsController.cs

@@ -0,0 +1,32 @@
+using Microsoft.AspNetCore.Authorization;
+using Microsoft.AspNetCore.Mvc;
+using QuestionsApi.Services;
+using System.Security.Claims;
+
+namespace QuestionsApi.Controllers;
+
+[ApiController]
+[Route("api/[controller]")]
+public class RatingsController : ControllerBase
+{
+    private readonly RatingStore _ratings;
+
+    public RatingsController(RatingStore ratings)
+    {
+        _ratings = ratings;
+    }
+
+    [HttpGet("me")]
+    [Authorize(Roles = "USER,SUPER")]
+    public async Task<IActionResult> Me()
+    {
+        var userId = User.FindFirstValue(ClaimTypes.NameIdentifier)
+            ?? User.FindFirstValue(ClaimTypes.Name)
+            ?? User.Identity?.Name
+            ?? "";
+        if (string.IsNullOrWhiteSpace(userId))
+            return Unauthorized();
+
+        return Ok(await _ratings.GetProfileAsync(userId));
+    }
+}