feat: add CSV import for student event rankings

Let advisors load preference ranks from a converted CSV with fuzzy matching, known aliases, and a parse-preview-save page instead of relying on the ranking editor.

Co-authored-by: Cursor <cursoragent@cursor.com>

WebApp/Services/StudentEventRankingSaveService.cs

@@ -0,0 +1,111 @@
+using Core.Entities;
+using Core.Models;
+using Data;
+using Microsoft.EntityFrameworkCore;
+
+namespace WebApp.Services;
+
+/// <summary>
+/// Replaces event rankings for students present in a successful ranking import.
+/// </summary>
+public class StudentEventRankingSaveService : IStudentEventRankingSaveService
+{
+    private readonly AppDbContext _context;
+    private readonly ILogger<StudentEventRankingSaveService> _logger;
+
+    public StudentEventRankingSaveService(AppDbContext context, ILogger<StudentEventRankingSaveService> logger)
+    {
+        _context = context;
+        _logger = logger;
+    }
+
+    /// <inheritdoc />
+    public async Task<IReadOnlyList<string>> GetStudentsWithExistingRankingsAsync(
+        StudentEventRankingParseResult parseResult,
+        CancellationToken cancellationToken = default)
+    {
+        var studentIds = GetStudentIds(parseResult);
+        if (studentIds.Count == 0)
+            return [];
+
+        return await _context.Students
+            .AsNoTracking()
+            .Where(s => studentIds.Contains(s.Id) && s.EventRankings.Any())
+            .OrderBy(s => s.LastName)
+            .ThenBy(s => s.FirstName)
+            .Select(s => s.FirstName + " " + s.LastName)
+            .ToListAsync(cancellationToken);
+    }
+
+    /// <inheritdoc />
+    public async Task<StudentEventRankingSaveResult> SaveAsync(
+        StudentEventRankingParseResult parseResult,
+        CancellationToken cancellationToken = default)
+    {
+        var studentIds = GetStudentIds(parseResult);
+        if (studentIds.Count == 0)
+            return new StudentEventRankingSaveResult();
+
+        var students = await _context.Students
+            .Include(s => s.EventRankings)
+            .Where(s => studentIds.Contains(s.Id))
+            .ToListAsync(cancellationToken);
+
+        var eventIds = parseResult.Matches
+            .Select(m => m.Ranking.EventDefinition.Id)
+            .Where(id => id != 0)
+            .Distinct()
+            .ToList();
+
+        var events = await _context.Events
+            .Where(e => eventIds.Contains(e.Id))
+            .ToDictionaryAsync(e => e.Id, cancellationToken);
+
+        var matchesByStudent = parseResult.Matches
+            .Where(m => m.Ranking.Student.Id != 0)
+            .GroupBy(m => m.Ranking.Student.Id)
+            .ToDictionary(g => g.Key, g => g.ToList());
+
+        var rankingsSaved = 0;
+        foreach (var student in students)
+        {
+            if (!matchesByStudent.TryGetValue(student.Id, out var matches))
+                continue;
+
+            student.EventRankings.Clear();
+            foreach (var match in matches.OrderBy(m => m.Ranking.Rank))
+            {
+                if (!events.TryGetValue(match.Ranking.EventDefinition.Id, out var eventDefinition))
+                {
+                    _logger.LogWarning(
+                        "Skipping ranking for student {StudentId}: event {EventId} was not found",
+                        student.Id,
+                        match.Ranking.EventDefinition.Id);
+                    continue;
+                }
+
+                student.EventRankings.Add(new StudentEventRanking
+                {
+                    Student = student,
+                    EventDefinition = eventDefinition,
+                    Rank = match.Ranking.Rank
+                });
+                rankingsSaved++;
+            }
+        }
+
+        await _context.SaveChangesAsync(cancellationToken);
+
+        return new StudentEventRankingSaveResult
+        {
+            StudentsUpdated = students.Count,
+            RankingsSaved = rankingsSaved
+        };
+    }
+
+    private static List<int> GetStudentIds(StudentEventRankingParseResult parseResult) =>
+        [.. parseResult.Matches
+            .Select(m => m.Ranking.Student.Id)
+            .Where(id => id != 0)
+            .Distinct()];
+}