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 +1,64 @@
+using System.Text;
+
+namespace QuestionsApi.Services.Flashcards;
+
+// Minimal RFC 4180 CSV reader/writer (quoted fields, embedded commas/newlines, "" escaping).
+// UTF-8, text-only, matches the flashcard CSV contract exactly.
+public static class FlashcardCsv
+{
+    public static readonly string[] Headers =
+        ["stable_id", "deck", "type", "prompt", "answer", "extra", "tags", "source_question_external_id"];
+
+    public static List<string[]> ParseRows(string text)
+    {
+        var rows = new List<string[]>();
+        var field = new StringBuilder();
+        var row = new List<string>();
+        var inQuotes = false;
+        var i = 0;
+        var n = text.Length;
+
+        while (i < n)
+        {
+            var c = text[i];
+            if (inQuotes)
+            {
+                if (c == '"')
+                {
+                    if (i + 1 < n && text[i + 1] == '"') { field.Append('"'); i += 2; continue; }
+                    inQuotes = false; i++; continue;
+                }
+                field.Append(c); i++; continue;
+            }
+
+            switch (c)
+            {
+                case '"':
+                    inQuotes = true; i++; break;
+                case ',':
+                    row.Add(field.ToString()); field.Clear(); i++; break;
+                case '\r':
+                    i++; break;
+                case '\n':
+                    row.Add(field.ToString()); field.Clear();
+                    rows.Add(row.ToArray()); row = [];
+                    i++; break;
+                default:
+                    field.Append(c); i++; break;
+            }
+        }
+        if (field.Length > 0 || row.Count > 0)
+        {
+            row.Add(field.ToString());
+            rows.Add(row.ToArray());
+        }
+        return rows;
+    }
+
+    public static string WriteRow(IEnumerable<string> fields) => string.Join(",", fields.Select(Escape));
+
+    private static string Escape(string field) =>
+        field.IndexOfAny(['"', ',', '\n', '\r']) >= 0
+            ? "\"" + field.Replace("\"", "\"\"") + "\""
+            : field;
+}