firestore.rules

rules_version = '2';

service cloud.firestore {
  match /databases/{database}/documents {

    // ── postbox collection ──────────────────────────────────────────────────
    // Authenticated users may read postbox data. Only server-side (Cloud
    // Functions admin SDK) may write postbox documents.
    match /postbox/{postboxId} {
      allow read: if request.auth != null;
      allow write: if false;
    }

    // ── claims collection ───────────────────────────────────────────────────
    // Claims are written exclusively by Cloud Functions (admin SDK).
    // Authenticated users may read their own claims only.
    match /claims/{claimId} {
      allow read: if request.auth != null && resource.data.userid == request.auth.uid;
      allow write: if false;
    }

    // ── users collection ────────────────────────────────────────────────────
    // Profile fields (displayName, streak, lastClaimDate, createdAt) are
    // written exclusively by Cloud Functions (Admin SDK) — this prevents
    // clients from bypassing the profanity filter by writing displayName
    // directly. The friends array is the only field clients may modify.
    match /users/{uid} {
      allow read: if request.auth != null;
      // The friends array, notificationPrefs map, and mapColor string are the
      // only fields clients may modify on their own document. All other fields
      // (displayName, streak, lastClaimDate, createdAt, points) are written by
      // Cloud Functions using the Admin SDK, which bypasses these rules. FCM
      // tokens live in the separate fcmTokens/{uid} collection to avoid
      // exposure here.
      // friends is capped at 200 entries to prevent O(n) leaderboard read abuse.
      // notificationPrefs must be a map (type-validated to prevent garbage writes).
      // mapColor must be a short string (palette key) when present; deletion
      // (FieldValue.delete()) is also allowed since the diff only fires on
      // present fields.
      allow update: if request.auth != null && request.auth.uid == uid
        && request.resource.data.diff(resource.data).affectedKeys()
              .hasOnly(['friends', 'notificationPrefs', 'mapColor'])
        && (!request.resource.data.diff(resource.data).affectedKeys()
                .hasAny(['friends'])
            || (request.resource.data.friends is list
                && request.resource.data.friends.size() <= 200))
        && (!request.resource.data.diff(resource.data).affectedKeys()
                .hasAny(['notificationPrefs'])
            || request.resource.data.notificationPrefs is map)
        && (!request.resource.data.diff(resource.data).affectedKeys()
                .hasAny(['mapColor'])
            || !('mapColor' in request.resource.data)
            || (request.resource.data.mapColor is string
                && request.resource.data.mapColor.size() <= 32));
      // Create and all other writes are handled by Cloud Functions.
      allow create: if false;
    }

    // Per-county lifetime stats kept under users/{uid}/countyStats/{slug}.
    // Readable by any signed-in user (matches the parent users/{uid} rule
    // used by friend-profile views); written only by Cloud Functions.
    match /users/{uid}/countyStats/{countySlug} {
      allow read: if request.auth != null;
      allow write: if false;
    }

    // ── leaderboards collection ─────────────────────────────────────────────
    // Leaderboard documents are written by Cloud Functions only.
    // Authenticated users may read them.
    match /leaderboards/{period} {
      allow read: if request.auth != null;
      allow write: if false;
    }

    // Per-county lifetime leaderboards live under
    // leaderboards/lifetime_by_county/counties/{countySlug}. Same access
    // pattern as the period docs above.
    match /leaderboards/lifetime_by_county/counties/{countySlug} {
      allow read: if request.auth != null;
      allow write: if false;
    }

    // ── meta collection ──────────────────────────────────────────────────────
    // Read-only aggregate stats (e.g. meta/stats.totalPostboxes) used to
    // compute lifetime leaderboard percentages. Written by import scripts only.
    match /meta/{docId} {
      allow read: if request.auth != null;
      allow write: if false;
    }

    // ── reports collection ───────────────────────────────────────────────────
    // User-submitted reports about postbox data problems. Created and reviewed
    // exclusively by Cloud Functions (submitReport / reviewReport, Admin SDK).
    // A reporter may read their own reports; users with the `admin` custom
    // claim may read all of them (the in-app admin review interface).
    match /reports/{reportId} {
      allow read: if request.auth != null
        && (resource.data.reporterUid == request.auth.uid
            || request.auth.token.admin == true);
      allow write: if false;
    }

    // ── reportQuotas collection ──────────────────────────────────────────────
    // Per-user daily counter enforcing the submitReport rate limit. Written
    // (and only ever read) by the submitReport Cloud Function (Admin SDK);
    // clients have no business reading or writing it.
    match /reportQuotas/{uid} {
      allow read, write: if false;
    }

    // ── fcmTokens collection ─────────────────────────────────────────────────
    // Stores FCM device tokens separate from the world-readable users collection
    // so that tokens are not exposed to other authenticated users. Written
    // exclusively by the registerFcmToken Cloud Function (Admin SDK).
    // Users may only read their own token document.
    match /fcmTokens/{uid} {
      allow read: if request.auth != null && request.auth.uid == uid;
      allow write: if false;
    }

    // ── moderationFlags collection ───────────────────────────────────────────
    // Shadow-mode abuse-detection flags, written exclusively by the
    // onClaimCreated Cloud Function (Admin SDK) and updated by reviewFlag.
    // Readable only by users with the `admin` custom claim (the in-app abuse
    // review interface). No client writes.
    match /moderationFlags/{flagId} {
      allow read: if request.auth != null && request.auth.token.admin == true;
      allow write: if false;
    }

    // ── trustScores collection ───────────────────────────────────────────────
    // Per-user server-only trust score decayed by the abuse detector. Never
    // client-readable (kept out of the world-readable users/{uid} doc so it
    // can't leak) and never client-writable — Cloud Functions (Admin SDK) only.
    match /trustScores/{uid} {
      allow read, write: if false;
    }

    // ── deletions collection ─────────────────────────────────────────────────
    // Per-London-day account-deletion audit counter, written by the
    // onUserDeleted Cloud Function (Admin SDK). Server-only; clients have no
    // business reading or writing it.
    match /deletions/{docId} {
      allow read, write: if false;
    }

  }
}