Add flashcards feature with spaced repetition scheduling

Adds a full flashcards system: FSRS-based scheduling, cloze/basic card types, CSV import/export, media storage, and study UI, wired into navigation and the dashboard alongside existing question flows.
2026-07-21 15:08:52 -05:00
parent 29b89dc404
commit 48a8c8361d
41 changed files with 4458 additions and 8 deletions
@@ -0,0 +1,57 @@
+using System.Text.RegularExpressions;
+
+namespace QuestionsApi.Services.Flashcards;
+
+public sealed record ClozeDeletion(int Number, string Answer, string? Hint);
+
+// {{c1::answer}} or {{c1::answer::hint}}. Numbers need not be contiguous or start at 1;
+// each distinct number becomes its own independently scheduled card (a "sibling").
+public static partial class FlashcardClozeParser
+{
+    [GeneratedRegex(@"\{\{c(\d+)::((?:(?!\}\}).)*)\}\}", RegexOptions.Singleline)]
+    private static partial Regex ClozeRegex();
+
+    public static List<ClozeDeletion> Parse(string text)
+    {
+        if (string.IsNullOrEmpty(text)) return [];
+        var results = new List<ClozeDeletion>();
+        foreach (Match match in ClozeRegex().Matches(text))
+        {
+            if (!int.TryParse(match.Groups[1].Value, out var number) || number < 1)
+                continue;
+            var inner = match.Groups[2].Value;
+            var parts = inner.Split("::", 2);
+            var answer = parts[0].Trim();
+            var hint = parts.Length > 1 ? parts[1].Trim() : null;
+            if (answer.Length == 0) continue;
+            results.Add(new ClozeDeletion(number, answer, string.IsNullOrEmpty(hint) ? null : hint));
+        }
+        return results;
+    }
+
+    public static List<int> DistinctClozeNumbers(string text) =>
+        Parse(text).Select(v => v.Number).Distinct().OrderBy(v => v).ToList();
+
+    public static bool HasValidCloze(string text) => DistinctClozeNumbers(text).Count > 0;
+
+    // Renders the front for a given cloze number: that number's answer is hidden (replaced
+    // by its hint or "..."), all other cloze numbers are revealed as their answer text.
+    public static string RenderFront(string text, int clozeNumber) =>
+        ClozeRegex().Replace(text, match =>
+        {
+            if (!int.TryParse(match.Groups[1].Value, out var number)) return match.Value;
+            var inner = match.Groups[2].Value;
+            var parts = inner.Split("::", 2);
+            if (number != clozeNumber) return parts[0].Trim();
+            var hint = parts.Length > 1 ? parts[1].Trim() : "";
+            return hint.Length > 0 ? $"[{hint}]" : "[...]";
+        });
+
+    public static string RenderBack(string text, int clozeNumber) =>
+        ClozeRegex().Replace(text, match =>
+        {
+            var inner = match.Groups[2].Value;
+            var parts = inner.Split("::", 2);
+            return parts[0].Trim();
+        });
+}