fix: derive leaderboard stats from recorded activity instead of a seed (#671)

[MOHITKOURAV01]

Closes #671

The problem

Open the app for the first time and the Contributor Leaderboard tells you:

1 Verified Reports • 2 Submissions • 55 Quizzes Answered — Your Rank #5 — 125 pts

None of it happened.

return saved
  ? JSON.parse(saved)
  : { name: "You (Guest)", points: 125, reports: 2, verified: 1, quizzes: 55, avatar: "🌟" };

It is presented in the first person — "Your Rank", "(You)", "Current User" — with nothing marking it as a placeholder, and ranked against five fictional people using those figures. This repo has consistently treated invented values shown as measurements as bugs rather than acceptable placeholders (#499, #544, #546, #496). This is the same thing pointed at the user's own contribution history, where they have nothing to check it against.

It ignored the activity the app actually records

Leaderboard invented a storage key of its own, pollution-hub-user-points, that nothing else in the codebase ever writes to:

signal	where it already lives	read before	read now
community reports	pollution-community-reports	no	yes
challenge points	pollution_hub_total_points	no	yes
quiz completions	QUIZ_COMPLETED on the bus	no	yes

File a report in the Community Hub — total does not move. Earn 10 challenge points — does not move. The only thing that moved it was the simulator below.

The fix

src/utils/contributionStats.js derives the stats from the keys the rest of the app maintains, weighted by the POINT_SYSTEM the component already declared at the top of the file. The weights now live in the scoring module and the table renders from them, so the "How to Earn Points" legend and the arithmetic cannot drift apart.

Derived, not accumulated. A stored running total can drift from the activity it is meant to summarise, and once it has there is no way to tell.

One thing genuinely was not recorded anywhere: how many quiz questions have been answered. QUIZ_COMPLETED carries score and total but nothing persisted a count — achievementsStore only keeps the set of perfect quiz ids. The module maintains that counter itself, and it counts total rather than score: a 10-question quiz scored 3/10 is still 10 answers.

It self-registers on import, matching achievementsStore, and App.jsx imports it for the side effect — a quiz can be completed without the leaderboard ever having been mounted.

The simulator

{/* Developer Action Simulator for Testing */}
<button onClick={() => addPoints(50, "verified")}>+50 Verified Report</button>

No import.meta.env.DEV guard, no dev-mode check — these rendered for every visitor, at the bottom of the panel. Clicking one persisted a verified report that was never submitted. Between these and the seeded starting figures, no number on this panel corresponded to anything.

What remains is dev-only and writes through the same recording path the app uses, rather than incrementing a display total directly.

Four smaller defects in the same component

• key={user.name}. Names are not unique keys. A stored userStats.name matching a mock entry ("Priya Singh") produced duplicate React keys and one row silently won. Keyed on id.
• "Your Rank #0" on first paint — findIndex(...) + 1 on the empty array the state starts as. Renders — until there is a rank.
• localStorage.setItem inside a setState updater. Unguarded against quota errors, so the throw came from inside a React state update — and the updater was impure, so StrictMode ran it twice and wrote twice.
• The mock contributors were unlabelled, so the panel read as a real community ranking. They carry a sample chip now, and the panel says plainly that there is no shared backend behind the board yet ([Architecture]: Community Reports are localStorage-only — not actually shared between users; add backend + Hotspot Aggregation & Escalation #152).

Tests

src/utils/contributionStats.test.js (22) — each source counted and weighted, the combined total, Verified-prefixed statuses as CommunityHub actually writes them, corrupt/NaN/negative storage in every key, localStorage throwing, and the quiz listener counting questions rather than correct answers.

src/components/Leaderboard.test.jsx (13) — zeros for a new visitor, explicit assertions that the old seeded figures are gone, the ranking moving with a real total, sample labelling, a stable-key row count, and that the simulator is absent from a production build.

✓ src/utils/contributionStats.test.js (22 tests)
✓ src/components/Leaderboard.test.jsx  (13 tests)

Suite status

Re-verified against current main (575e33b), which now carries #672–#675: merges cleanly, 548 passed, 0 failed across 54 files.

(The earlier note here referred to 6 Commute.test.jsx failures inherited from main. #672 has since merged and fixed them.)

Migration

pollution-hub-user-points is no longer read or written, and is not migrated — the values in it were either the fabricated seed or simulator clicks, and there is no honest way to convert either into a real record. Existing reports and challenge points are picked up immediately. The quiz counter starts at zero, since nothing was ever stored to recover.

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[Aditya8369]

@MOHITKOURAV01 thanks for the contributions