From b075b93f2a3acc750793738a54444baadae5171f Mon Sep 17 00:00:00 2001
From: Zareian <zareian.comp@gmail.com>
Date: Mon, 12 Oct 2026 12:18:46 +0330
Subject: [PATCH] Tutor/answers: bare subscripts (S_n, a_1) become Unicode;
 migration 0022 re-cleans DB text

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
---
 ai_tutor/tests_plain_history.py                  |  8 ++++++++
 .../migrations/0022_plain_math_messages_again.py | 16 ++++++++++++++++
 content/plain_math.py                            |  3 ++-
 content/seed/curriculum.json                     |  4 ++--
 rag/services/mathtext.py                         |  4 +++-
 5 files changed, 31 insertions(+), 4 deletions(-)
 create mode 100644 content/migrations/0022_plain_math_messages_again.py

diff --git a/ai_tutor/tests_plain_history.py b/ai_tutor/tests_plain_history.py
index f5b9c9f..9c80cac 100644
--- a/ai_tutor/tests_plain_history.py
+++ b/ai_tutor/tests_plain_history.py
@@ -23,3 +23,11 @@ class HistoryNeverShowsLatexTests(TestCase):
             self.assertNotIn('^', t)
             self.assertNotIn('$', t)
         self.assertIn('x²', texts[0])
+
+
+class ToPlainSubscriptTests(TestCase):
+    def test_bare_subscripts_are_unicode(self):
+        from rag.services.mathtext import to_plain
+        out = to_plain('S_n = n/2 × (a_1 + a_n)')
+        self.assertNotIn('_', out)
+        self.assertIn('Sₙ', out)
diff --git a/content/migrations/0022_plain_math_messages_again.py b/content/migrations/0022_plain_math_messages_again.py
new file mode 100644
index 0000000..29a6cba
--- /dev/null
+++ b/content/migrations/0022_plain_math_messages_again.py
@@ -0,0 +1,16 @@
+"""
+0021 پیش از تکمیلِ تبدیل (اندیسِ ساده‌ی S_n، a_1) اجرا شد؛ پیام‌های دستیار و متنِ سوال/درس را با نسخه‌ی کامل دوباره
+می‌گذراند. همان تبدیل، idempotent. `0021.forwards` عیناً دوباره اجرا می‌شود (تکراریِ سوال را هم پاک می‌کند).
+"""
+import importlib
+
+from django.db import migrations
+
+
+def forwards(apps, schema_editor):
+    importlib.import_module('content.migrations.0021_plain_math_everywhere').forwards(apps, schema_editor)
+
+
+class Migration(migrations.Migration):
+    dependencies = [('content', '0021_plain_math_everywhere')]
+    operations = [migrations.RunPython(forwards, migrations.RunPython.noop)]
diff --git a/content/plain_math.py b/content/plain_math.py
index cecae54..fdcccf4 100644
--- a/content/plain_math.py
+++ b/content/plain_math.py
@@ -99,7 +99,8 @@ def convert(text: str) -> str:
     s = re.sub(r'\^\(((?:[^()]|\([^()]*\))*)\)', lambda m: _try(m[1], _SUP) or f' به توانِ ({m[1].strip()}) ', s)
     s = re.sub(r'(?<=[A-Za-z0-9۰-۹\)₀-₉ₐ-ₜᵢⱼ])\^([A-Za-zα-ωΑ-Ω□▢])(?![A-Za-z0-9۰-۹])', lambda m: _try(m[1], _SUP) or f' به توانِ {m[1]} ', s)
     s = re.sub(r'\^([+\-−]?[0-9۰-۹]+)', lambda m: _try(m[1], _SUP) or m[0], s)
-    s =     s = re.sub(r'(?<=[A-Za-z\)∫Σ∏])_([0-9۰-۹]+|[A-Za-z]{1,4}[0-9۰-۹]?)', lambda m: ''.join(_SUB.get(ch, ch) for ch in m[1]), s)
+    s =     s = re.sub(r'((?<![A-Za-z0-9_])[A-Za-z]|log|ln|lim|[)∫Σ∏])_([0-9۰-۹]+[A-Za-z]?|[A-Za-z]{1,4}[0-9۰-۹]?)(?![A-Za-z0-9_])',
+               lambda m: (f'log پایه‌ی {m[2]}' if m[1] == 'log' and any(ch not in _SUB for ch in m[2]) else m[1] + ''.join(_SUB.get(ch, ch) for ch in m[2])), s)
     s = re.sub(r'log_([A-Za-z])(?![A-Za-z0-9])', lambda m: m[0] if m[1] in _SUB else f'log پایه‌ی {m[1]}', s)
     s = re.sub(r'(?<=\S) {2,}(?=\S)', ' ', s)
     s = re.sub(r'(?<=[A-Za-z])_\(([^()]*)\)', r'(\1)', s)
diff --git a/content/seed/curriculum.json b/content/seed/curriculum.json
index 12e615f..b8beeed 100644
--- a/content/seed/curriculum.json
+++ b/content/seed/curriculum.json
@@ -158704,7 +158704,7 @@
        "lessons": [
         {
          "title": "مقدارِ لگاریتم",
-         "introText": "logb(bᵏ) = k.",
+         "introText": "log پایه‌ی b(bᵏ) = k.",
          "example": "",
          "steps": []
         },
@@ -158716,7 +158716,7 @@
         },
         {
          "title": "معادله‌ی لگاریتمی",
-         "introText": "logb x = k ⇔ x = bᵏ.",
+         "introText": "log پایه‌ی b x = k ⇔ x = bᵏ.",
          "example": "",
          "steps": []
         },
diff --git a/rag/services/mathtext.py b/rag/services/mathtext.py
index d242ebf..36d5637 100644
--- a/rag/services/mathtext.py
+++ b/rag/services/mathtext.py
@@ -255,7 +255,9 @@ def _to_plain(text: str) -> str:
     text = _strip_markdown(text)
     text = re.sub(r'[ \t]+\n', '\n', text)
     text = re.sub(r'\n{3,}', '\n\n', text)
-    return text.strip()
+    # S_n، a_1، x^2 و توانِ پیچیده که بالا رد شد: همان تبدیلِ seed/دیتابیس (یک رفتار در همه‌جا).
+    from content.plain_math import convert as _plain
+    return _plain(text).strip()
 
 
 class StreamSanitizer: