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nxtgauge-ai-assistant/docs/ASK_ASH_IMPLEMENTATION_PLAN.md
Ashwin Kumar Sivakumar 4e3180745f
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docs: add Ask Ash billing architecture and implementation plan docs
2026-08-15 22:32:13 +05:30

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Ask Ash — Remaining Implementation Plan

Status as of 2026-07-06. This is an execution checklist, not a redesign — it assumes the architecture in ASK_ASH_BILLING_ARCHITECTURE.md and the code already built (Section "Done" below). Each remaining item lists exact file paths, function signatures, and DB shapes so it can be implemented without re-deriving design decisions. Once implemented, hand back for testing/bug-hunting the same way prior phases were verified (real DB, real HTTP, real edge cases — not just cargo check).

0. What's already done (don't redo)

  • Wallet + ledger: crates/db/src/models/ai_credits.rs — AiCreditsRepository with ensure_wallet, try_reserve_credits, try_capture_reservation, try_release_reservation, add_purchased_credits, admin_adjust_credits. Row-locked, idempotent, tested (crates/db/tests/ai_credits.rs, ai_credits_reaper.rs).
  • Schema: migrations 20260703210000_ai_credits_wallet, 20260703220000_ai_credits_seed_features, 20260705110000_ai_credit_packages in crates/db/migrations/.
  • Charge helper: apps/users/src/ai_credits.rs::charge_ai_feature — reserve → work closure → capture/release, writes ai_usage_logs.
  • HTTP (user-facing): apps/users/src/handlers/ai_credits.rs — GET /api/ai-credits/wallet, POST /api/ai-credits/charge, GET /api/ai/usage/summary, GET /api/ai/usage/logs.
  • HTTP (purchase, PayU): apps/payments/src/ai_credits.rs + apps/payments/src/payu.rs — GET /api/ai-credits (packages), POST /api/ai-credits/order, POST /api/ai-credits/verify. Real PayU HMAC-SHA512 hash, cross-verified against an independent Python implementation. Also fixed: TraceCoins' /api/payments/create-order/verify (was calling a Beeceptor mock, not any real gateway; also had a broken amount vs amount_inr column bug).
  • Admin package CRUD (payments): apps/payments/src/ai_credits.rs::admin_router() — GET/POST /api/admin/ai-credits/packages, PATCH /api/admin/ai-credits/packages/{id}. Nested in apps/payments/src/main.rs. Not yet nested into the gateway routing test suite for the users-side admin endpoints below — those don't exist yet.
  • Admin credit adjustment primitive: AiCreditsRepository::admin_adjust_credits(pool, user_id, amount, is_add, reason, actor_id, idempotency_key) in crates/db/src/models/ai_credits.rs — ADD grants bonus credits, DEDUCT consumes bonus→monthly→purchased in order, mandatory reason, ledger entry types admin_adjustment_credit/admin_adjustment_debit. HTTP handler not yet written (see Task 2 below).
  • Gateway routing: apps/gateway/src/main.rs — fixed a real bug where /api/ai-credits/* (order/verify/packages, hosted in payments) silently fell through to the generic /api/ai → users rule and would have 404'd in production. Added /api/admin/ai-credits/packages → payments routing. Both covered by #[cfg(test)] mod tests in the same file — extend this test module when adding the users-side admin routes in Task 2.
  • Cron jobs: apps/cron/src/tasks/ai_credits.rs — sweep_expired_reservation_holds (every 2 min), reset_stale_daily_ai_usage (hourly). Verified against the real running binary.
  • JWT crypto fix: crates/auth/Cargo.toml + crates/contracts/Cargo.toml — added features = ["rust_crypto"] to the jsonwebtoken dependency. Was causing every authenticated request to panic its worker thread.
  • Real features wired to credits: apps/users/src/handlers/ai.rs::ai_generate_job_field (title/description/skills/category — all four, one handler) and ::ai_generate_cover_letter, both migrated off the old company_ai_usage/job_seeker_ai_usage daily-counter onto charge_ai_feature. Fixed a real bug found while testing this: try_release_reservation wasn't rolling back daily_actions_used/daily_credits_used, so a failed request permanently burned daily quota even with no charge — fixed, regression-tested.
  • Frontend fixes: nxtgauge-frontend-solid/src/lib/payu.ts split into submitPayuCheckout (takes an already-built order) + openPayuCheckout (creates a TraceCoins order, then delegates) — fixes a bug where CreditsPage.tsx's AI-credit checkout was silently creating a second, mismatched order. CompanyJobsPage.tsx's description/skills buttons fixed to call the one real /api/ai/generate-job-field endpoint instead of two nonexistent ones.

Known pre-existing gap, not caused by this work, not yet fixed: nxtgauge-admin-solid's existing TraceCoins credit-adjustment page (src/routes/admin/credit.tsx) calls /api/admin/credits/{adjust,ledger,reconcile,balance} — none of these exist anywhere in the backend. That admin feature doesn't work today, independent of AI credits. Not in scope here unless you want it added — flagging so it's a conscious decision, not a surprise.

Task 1 — Finish the admin endpoints for AI credits wallet (users service)

Files: apps/users/src/handlers/ai_credits.rs (add handlers), apps/users/src/handlers/mod.rs (already has ai_credits registered), apps/users/src/main.rs (nest a new admin router).

Add to apps/users/src/handlers/ai_credits.rs:

pub fn admin_router() -> Router<AppState> {
    Router::new()
        .route("/balance", get(admin_balance))
        .route("/ledger", get(admin_ledger))
        .route("/adjust", post(admin_adjust))
        .route("/reconcile", get(admin_reconcile))
}
  • GET /balance?userId=<uuid> — require_admin(&auth) gate (same pattern as apps/payments/src/ai_credits.rs::admin_list_packages). Parse userId query param, call AiCreditsRepository::ensure_wallet, return the same WalletDto shape already defined in this file (reuse it, don't redefine).
  • GET /ledger?userId=<uuid>&page=&limit= — paginated query against ai_credit_ledger WHERE wallet_id = (SELECT id FROM user_ai_subscriptions WHERE user_id = $1) ORDER BY created_at DESC. Response shape { data: [...], total: i64 } to match the existing TraceCoins ledger UI pattern in nxtgauge-admin-solid/src/routes/admin/credit.tsx (GET /api/admin/credits/ledger?userId=).
  • POST /adjust — body { user_id: Uuid, amount: i32, type: "ADD" | "DEDUCT", reason: String, reference_id: Option<Uuid> } (exact shape of the existing, already-defined-but-backend-missing TraceCoins contract in credit.tsx line ~103 — reuse the field names so the admin UI's fetch call is identical apart from the URL). Validate reason is non-empty (return 400 INVALID_REASON if blank — this is deliberately mandatory, not optional, per the architecture doc's "every admin-issued credit change must be explained" rule). Call AiCreditsRepository::admin_adjust_credits(pool, body.user_id, body.amount, body.type == "ADD", &body.reason, auth.user_id, idempotency_key). Generate a server-side idempotency key if the client doesn't send one (e.g. format!("admin-adjust:{}:{}", auth.user_id, uuid::Uuid::new_v4())) — or better, require the frontend to send one so a double-click can't double-adjust (recommended: frontend generates a UUID per form submission attempt, resent unchanged on retry).
  • GET /reconcile?from=<date>&to=<date> — sums ai_credit_ledger.credits grouped by entry_type within the date range, plus a per-wallet drift check: for a sample (or all, if the table is still small) of wallets touched in the range, recompute SUM(credits) FROM ai_credit_ledger WHERE wallet_id = X and compare to the wallet's derived available_credits() — flag any mismatch. This is the concrete "ledger is the source of truth, reconcile against it" mechanism from the architecture doc's Section 5.

Error handling: reuse credits_error_response already in this file; add any new error codes needed (e.g. a 400 for missing/invalid userId query param — just return (StatusCode::BAD_REQUEST, Json(json!({"error": "..."}))) inline, no need for a new AiCreditsError variant for pure request-parsing issues).

Wire it up in apps/users/src/main.rs:

.nest("/api/admin/ai-credits", handlers::ai_credits::admin_router())

Place this near the existing .nest("/api/ai-credits", handlers::ai_credits::router()) line.

Gateway: no gateway change needed — /api/admin/ai-credits/balance etc. don't match the /api/admin/ai-credits/packages rule just added, so they correctly fall through to the existing generic /api/admin/ → users_url catch-all. But add test cases to apps/gateway/src/main.rs's existing #[cfg(test)] mod tests confirming this (the pattern is already there — admin_ai_credits_routes_split_correctly already asserts /api/admin/ai-credits/balance etc. route to users — just make sure the real handlers now exist to back that assumption).

Verification checklist (mirror how every prior phase was tested — spin up a throwaway Postgres+Redis via Docker, run migrations, start the real binary, hit it with curl + a minted JWT):

  • Admin balance for a user with no wallet yet auto-provisions Free plan (same as the user-facing endpoint).
  • Ledger pagination returns newest-first, respects page/limit.
  • Adjust ADD: bonus_credits_total increases, ledger row entry_type='admin_adjustment_credit', credits > 0.
  • Adjust DEDUCT: consumes bonus→monthly→purchased in that order (write a test wallet with credits in multiple pools and confirm the split), rejects with InsufficientCredits if amount exceeds available_credits().
  • Adjust with blank reason → 400, no DB write.
  • Adjust twice with the same idempotency key → second call is a no-op (wallet unchanged, no second ledger row) — this exact behavior is already implemented in admin_adjust_credits, just confirm the HTTP layer passes the key through correctly.
  • Reconcile flags a deliberately-introduced drift (e.g. manually UPDATE ai_credit_ledger SET credits = credits + 999 on one row in a test DB, confirm the endpoint reports the mismatch).

Task 2 — Admin UI: AI credits tabs in nxtgauge-admin-solid

Files: src/routes/admin/pricing.tsx (add a tab), src/routes/admin/credit.tsx (add a tab). Do not create new route files or new sidebar entries — the existing sidebar entries for "Pricing" and "Credits" (src/components/AdminSidebar.tsx lines ~237-248) already navigate to these files; adding a tab is enough.

2a. pricing.tsx — "AI Credit Packages" tab

Add a third tab value alongside the existing view signal's "packages" | "create" (check the exact signal name/values in the file — described as "two tabs... via local view signal" in the research). New tab: "ai_packages".

  • List view: GET /api/admin/ai-credits/packages (admin-scoped, shows inactive too) → render as a table, same .data-table/.table-card classes as the existing TraceCoins package table. Columns: Name, Credits, Price (₹, convert from paise: price_inr / 100), Active toggle, Edit.
  • Create form: Name*, Description, Credits*, Price (₹)* → convert rupees to paise before POST /api/admin/ai-credits/packages (body { name, description, credits, price_inr }).
  • Inline edit / toggle active: PATCH /api/admin/ai-credits/packages/{id} with whichever fields changed (all optional in the body per Task 1's UpdatePackageRequest shape — { name?, description?, credits?, price_inr?, is_active? }).
  • Auth: same authHeaders() helper already in this file (sessionStorage.getItem('nxtgauge_admin_access_token')).

2b. credit.tsx — "AI Credits" tab

Add a fourth tab alongside the existing ledger | adjust | reconcile (activeTab signal). New tab: "ai_credits", itself with the same three sub-views (or just reuse three separate tab entries prefixed "AI " — whichever reads more naturally in the existing tab bar; the file already copy-pastes the tab-bar markup between sections, so follow that convention).

  • Balance & Ledger: GET /api/admin/ai-credits/balance?userId=, GET /api/admin/ai-credits/ledger?userId=. Same User ID input field as the existing TraceCoins version.
  • Reward/Deduct: same form fields as the existing TraceCoins "Reward/Deduct" tab (User ID, Amount, Type ADD/DEDUCT, Reason required, Reference ID optional) → POST /api/admin/ai-credits/adjust. This is deliberately a copy of the existing form's shape, just pointed at a new endpoint — reuse the component/markup, don't redesign it.
  • Reconcile: GET /api/admin/ai-credits/reconcile?from=&to=.

Do not touch the existing TraceCoins tabs/endpoints in either file — those stay exactly as they are (including the fact that their backend doesn't exist yet, per the known gap noted in Section 0; that's explicitly out of scope here).

Verification: once Task 1's backend is live, click through every button in both new tabs against a real running admin-solid dev server + real backend (not just a TypeScript compile check) — create a package, edit its price, deactivate it, look up a real user's AI wallet, adjust their credits, confirm the ledger updates.

Task 3 — Ollama security hardening

Context already gathered, don't re-research: nxtgauge-gitops/apps/ollama/base/ — deployment.yaml (OLLAMA_HOST=0.0.0.0:11434, resource limits cpu: 1000m / memory: 1500Mi, no auth env vars — Ollama has no built-in auth), service.yaml (ClusterIP, not internet-exposed — no ingress.yaml present), no NetworkPolicy anywhere restricting which pods can reach it. Cluster is Flux-managed (confirmed via existing NetworkPolicy resources in the flux-system/data namespaces) — changes must go into the nxtgauge-gitops repo and be committed/reconciled through Flux, never applied directly via kubectl apply against the live cluster.

Concrete work items, roughly in priority order:

  1. NetworkPolicy restricting ingress to the ollama Service in nxtgauge-gitops/apps/ollama/base/networkpolicy.yaml (new file, add to kustomization.yaml's resources: list). Restrict to pods with labels matching the users, payments, and nxtgauge-ai-assistant deployments (check their actual pod labels in nxtgauge-gitops/apps/*/base/deployment.yaml before writing the selector — don't guess label values). Confirm the cluster's CNI actually enforces NetworkPolicy (k3s ships an optional lightweight controller; this needs verifying against the live cluster, not assumed) before treating this as a real control rather than a documentation-only artifact.
  2. Application-layer prompt/response length caps, enforced in apps/users/src/handlers/ai.rs before calling call_ollama_inline — use ai_feature_costs.max_input_tokens/max_output_tokens (already columns in the schema, currently unenforced anywhere) as a character-count approximation (e.g. max_chars ≈ max_tokens * 4) since a real tokenizer isn't wired up. Reject oversized requests with 400 before spending a reservation.
  3. Truncated prompt/response audit logging — add prompt_preview/response_preview columns to ai_usage_logs (new migration, short varchar, e.g. first 200 chars), populate in apps/users/src/ai_credits.rs::log_usage. Mirrors the pattern already used (but currently dead) in the broken apps/companies/src/handlers/ai.rs stub — same idea, done for real this time.
  4. TLS between services and Ollama — recommend but treat as a separate, heavier infra task (cert-manager + Ollama TLS termination or a service mesh); don't block the above items on this.
  5. Health-check + circuit breaker for Ollama outages — already flagged as an open item in the architecture doc's Section 8; implement as a periodic GET {OLLAMA_BASE_URL}/ poll (Ollama's root path responds 200 when healthy) feeding a simple in-memory circuit-breaker state in apps/users, returning a fast "AI temporarily unavailable" instead of every request timing out individually.

Task 4 — Wire remaining real AI features to credits

Before writing any code, audit which of these have a real (non-404) backend handler — several already-shipped frontend buttons turned out to call nonexistent endpoints (found twice now: CompanyJobsPage.tsx's description/skills buttons, and the entire pre-existing admin/credits/* page). Grep apps/users/src/handlers/*.rs for actual .route(...) registrations, don't trust frontend fetch() calls as evidence a backend exists.

Candidates from the original feature list: AI Chat, Help Center Assistant, Knowledge Base Search, Resume Improvement, Professional Profile Improvement, AI Suggestions, AI Form Filling, Requirement Analysis, Ticket Summaries, Admin Insights.

For each real handler found, migrate it the same way ai_generate_job_field/ai_generate_cover_letter were migrated:

  1. Identify what daily-quota/rate-limit mechanism it currently uses (if any).
  2. Seed a feature cost row in ai_feature_costs if one doesn't already exist for it (4 exist today: help_answer, jd_generate, cover_letter_generate, resume_improve — check crates/db/migrations/20260703220000_ai_credits_seed_features.up.sql).
  3. Wrap the existing generation call (call_ollama_inline or equivalent) in crate::ai_credits::charge_ai_feature(...), following the exact pattern in ai_generate_job_field.
  4. Test the failure path specifically (point OLLAMA_BASE_URL at an unreachable host, confirm the reservation releases and daily counters roll back — this exact bug was found and fixed once already; don't assume the fix generalizes without testing each new call site).

Task 5 — Refund architecture

New table (migration): ai_refunds — id, user_id, ledger_debit_entry_id (FK ai_credit_ledger.id), credits_refunded, reason (provider_failure|timeout|validation_failure|manual), initiated_by (system|admin|user_dispute), status (pending|approved|rejected|completed), created_at, resolved_at.

Two paths:

  • Automatic: triggered from charge_ai_feature's error path — currently a failed request just releases the reservation (never charged in the first place, so nothing to refund). A genuine refund is needed only if a charge was captured and the feature then failed asynchronously after the fact (e.g., a downstream step fails after the LLM call succeeded and credits were captured) — audit whether this can currently happen anywhere; if not, automatic refunds may not be needed yet and this table exists for the manual path only.
  • Manual (admin): new endpoint POST /api/admin/ai-credits/refunds — body { user_id, ledger_debit_entry_id, reason, notes? }, looks up the original debit ledger entry, credits back via a new ledger entry entry_type='refund' (extend AiCreditsRepository with a refund_credits function mirroring admin_adjust_credits's ADD path but tagged distinctly), writes an ai_refunds row, requires require_admin.

Task 6 — Coupons, promotions, referral, admin-issued credits

New tables (one migration): ai_coupons (id, code UNIQUE, discount_type, value, applicable_package_ids UUID[], applicable_plan_codes TEXT[], max_redemptions, redemptions_used, valid_from, valid_until, is_active), ai_coupon_redemptions (coupon_id, user_id, redeemed_at, UNIQUE(coupon_id, user_id) — enforces single-use-per-user at the DB level, not just application logic), ai_promotions (id, name, trigger_type, bonus_credits, applicable_plan_codes TEXT[], valid_from, valid_until, is_active), ai_bonus_credits (id, user_id, source_type, source_reference_id, credits, expires_at, ledger_entry_id FK).

Coupon redemption at purchase time: extend apps/payments/src/ai_credits.rs::create_order to accept an optional coupon_code, validate against ai_coupons (active, not expired, redemption count under max, not already redeemed by this user via ai_coupon_redemptions), apply the discount to the PayU order amount, and only insert into ai_coupon_redemptions after verify_order confirms payment success (not at order-creation time, to avoid burning a redemption on an abandoned checkout).

Task 7 — Subscription lifecycle

New table: ai_subscription_history (id, user_id, from_plan_id, to_plan_id, change_type (upgrade|downgrade|cancel|renew), proration_credits, effective_at, created_by, created_at).

Add columns to user_ai_subscriptions (already has billing_cycle, auto_renew from the initial migration — check before adding duplicates): confirm status supports active|past_due|cancelled|expired (currently only 'active' is ever written).

Logic (new module, e.g. apps/users/src/ai_subscription.rs):

  • Upgrade: immediate — set new plan_id, new monthly_credits_total, compute prorated bonus (remaining_days / days_in_period × (new_monthly - old_monthly)), grant via a new ledger entry type subscription_grant, write ai_subscription_history.
  • Downgrade: don't change plan_id immediately — write ai_subscription_history with effective_at = current_period_end, and have the (currently-hourly) cron reset job also check for and apply due downgrades when it rolls a wallet into a new period.
  • Trial plans: add is_trial, trial_days columns to ai_plans; on trial expiry (checked in the same cron job), auto-downgrade to free unless the user has since upgraded/purchased.

Task 8 — Credit expiration enforcement

user_ai_subscriptions.purchased_credits_expire_at already exists as a column but nothing sets or checks it.

  1. Set it in apps/payments/src/ai_credits.rs::verify_order when granting purchased credits (e.g. NOW() + INTERVAL '12 months' — confirm the actual policy with whoever owns pricing; the architecture doc recommends this but doesn't mandate a specific duration).
  2. Add expiry-first consumption order to try_capture_reservation/admin_adjust_credits's DEDUCT path — currently consumption order is bonus → monthly → purchased; per the architecture doc's Section 4.1, it should be expiring-soonest-first across whichever pools have an expiry, which today only purchased_credits does. Given only one pool expires, the existing order (bonus → monthly → purchased) already happens to leave purchased-with-expiry for last, which is backwards — purchased credits closest to expiring should be spent before they're lost. This needs revisiting once expiry is actually set.
  3. New cron task in apps/cron/src/tasks/ai_credits.rs: sweep wallets where purchased_credits_expire_at < NOW() and purchased_credits_total > purchased_credits_used, write a ledger entry entry_type='expiration' for the unused remainder, zero out the expired portion.

Task 9 — Token cost engine / provider cost / margin tracking

ai_usage_logs already has cached_tokens, provider_reported_cost, internal_cost, credit_unit_price_at_time columns (added in the Phase 1 migration) — none are populated.

  1. New table ai_model_cost_config: model_alias, cost_per_1k_input_tokens, cost_per_1k_output_tokens, cost_basis ('compute_amortized'|'provider_metered'), effective_from.
  2. In apps/users/src/ai_credits.rs::charge_ai_feature/log_usage, after the LLM call, compute internal_cost = tokens_used × cost_per_1k(model, cost_basis) / 1000 using the config table, and store it. provider_reported_cost stays NULL until a real per-token-billed provider is added to LiteLLM (self-hosted Ollama has no real per-request cost signal today).
  3. Margin (credits_charged × credit_unit_price − internal_cost) is a read-time analytics computation for the admin dashboard (Task 2/reconcile-adjacent), not stored per-row.

Task 10 — Observability

Per the architecture doc's explicit recommendation: do not add Prometheus/Grafana — this cluster doesn't run them (confirmed: only an OpenTelemetry Collector shipping to OpenObserve exists in nxtgauge-gitops). Add OTel metrics (ai_ledger_writes_total, ai_reservation_holds_active, ai_charge_latency_ms) emitted from apps/users/apps/payments via whatever OTel Rust crate is already used elsewhere in this workspace (check for one before adding a new dependency), feeding the existing collector pipeline.

Suggested order

  1. Task 1 + 2 (finish the admin dashboard you're already partway through) — no design decisions left, just execution.
  2. Task 3 (Ollama security) — real, currently-open vulnerability.
  3. Task 4 (wire remaining features) — mostly mechanical once the audit is done, directly increases how much of the system is actually load-bearing.
  4. Tasks 5–9 in whatever order matches business priority — none block each other.
  5. Task 10 last — needs the others to exist before there's anything meaningful to instrument.