Coins were always 1:10 of XP. Now they have their own event log + a
helper that dedups by reason within a configurable window.
Backend:
• migration 032 creates coin_log (user_id, amount, reason, created_at)
with indices for the 'fired today?' check
• awardCoins now records into coin_log on every call (reason defaults
to 'xp_bonus' for the legacy XP-proportional path)
• awardCoinsOnce(userId, amount, reason, window) — fires the bonus
only if no row matches in the window:
'day' → DATE(created_at) = today
'week' → ISO week match
'forever' → never twice
Wired events (Phase 4 subset of the plan):
• Daily login — 10 coins, once/day. Hooked in updateStreak so the
bonus rides on the existing 'daily_activity' XP trigger.
• Daily goal completion — 15/25/40 coins (easy/medium/hard), once/day.
Sits next to the existing tier XP bonus in updateDailyGoal.
• Variant clear — 30 coins, once per (user, variant) forever. Fires
from the exam-prep attempts endpoint when the user's final correct
answer fills out a math9 variant.
Deferred (need invasive trigger hooks): weekly goal, paragraph close,
boss defeated, referral.
Verified end-to-end: awardCoinsOnce returns true→false on repeated
calls, coin_log records the first, coins balance moves once.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Recent-attempts widget on /exam-prep/:examKey was showing raw LaTeX
like '\dfrac{7}{9}' because stripPreview only removed HTML tags.
Now it also converts common LaTeX to readable unicode (fractions →
a/b, \sqrt → √, \cdot → ·, comparisons → ≤≥≠, Greek letters, etc.)
before truncating.
KaTeX rendering would be overkill for a 100-char preview row; this
just makes the existing text legible.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Practice (random) now picks tasks by ascending difficulty so the first
slot is always level 1 and the session ramps up. Adds ?exclude= to drop
specific subtopics from the random pool, with a per-section checkbox
modal in the UI.
Each task carries a topic_ref (textbook chapter + paragraph) shown as
a 'Учить тему · §N' button next to the solution, deep-linking to the
right section of /textbook/<slug>. Mapping seeded for all 15 math9
subtopics in migration 028.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Maxim Dolgolyov