Ilia Denisov
9f7c9099bc
Synchronous translation on read (Stage D) blocks the HTTP handler on translator I/O. Stage E switches to "send moments-fast, deliver when translated": recipients whose preferred_language differs from the detected body_lang are inserted with available_at=NULL, and an async worker turns them on once a LibreTranslate call materialises the cache row (or fails terminally after 5 retries). Schema delta on diplomail_recipients: available_at, translation_attempts, next_translation_attempt_at, plus a snapshot recipient_preferred_language so the worker queries do not need a join. Read paths (ListInbox, GetMessage, UnreadCount) filter on available_at IS NOT NULL. Push fan-out is moved from Service to the worker so the recipient only sees the toast when the inbox row is actually visible. Translator backend is now a configurable choice: empty BACKEND_DIPLOMAIL_TRANSLATOR_URL → noop (deliver original); populated → LibreTranslate HTTP client. Per-attempt timeout, max attempts, and worker interval all live in DiplomailConfig. The HTTP client itself is unit-tested via httptest (happy path, BCP47 normalisation, unsupported pair, 5xx, identical src/dst, missing URL); worker delivery + fallback paths are covered by the testcontainers-backed e2e tests in diplomail_e2e_test.go. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
174 lines
8.3 KiB
Markdown
174 lines
8.3 KiB
Markdown
# diplomail
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`diplomail` owns the diplomatic-mail subsystem of the Galaxy backend
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service. Messages live in the lobby-side domain (their storage and
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lifecycle are tied to a game), but they are surfaced inside the game UI
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— the lobby exposes only an unread-count badge per game.
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## Stages
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The package ships in four staged increments. Stage A is the surface
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described below; the remaining stages add admin / system mail,
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lifecycle hooks, paid-tier broadcast, multi-game broadcast, bulk
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purge, and the language-detection / translation cache.
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| Stage | Scope | Status |
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|-------|-------|--------|
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| A | Schema, personal single-recipient send / read / delete, unread badge, push event with body-language `und` | shipped |
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| B | Owner / admin sends + lifecycle hooks (paused, cancelled, kick); strict soft-access for kicked players | shipped |
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| C | Paid-tier personal broadcast + admin multi-game broadcast + bulk purge + admin observability | shipped |
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| D | Body-language detection (whatlanggo) + translation cache + lazy per-read translator dispatch | shipped |
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| E | LibreTranslate HTTP client + async translation worker with exponential backoff + delivery gating on translation completion | shipped |
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## Tables
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Three Postgres tables in the `backend` schema:
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- `diplomail_messages` — one row per send (personal, admin, or
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system). Captures `game_name` and IP at insert time so audit
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rendering survives renames and purges.
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- `diplomail_recipients` — one row per (message, recipient). Holds
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per-user `read_at`, `deleted_at`, `delivered_at`, `notified_at`
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state. Snapshot fields (`recipient_user_name`,
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`recipient_race_name`) are captured at insert time and survive
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membership revocation.
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- `diplomail_translations` — cached per (message, target_lang)
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rendering. One translation is reused across every recipient that
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asks for that language.
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## Permissions
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| Action | Caller | Pre-conditions |
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|--------|--------|----------------|
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| Send personal | user | active membership in game; recipient is active member |
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| Paid-tier broadcast | paid-tier user | active membership; recipients = every other active member |
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| Send admin (single user) | game owner OR site admin | recipient is any-status member of the game |
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| Send admin (broadcast) | game owner OR site admin | recipient scope ∈ `active` / `active_and_removed` / `all_members`; sender excluded |
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| Multi-game admin broadcast | site admin | scope `selected` (with `game_ids`) or `all_running` |
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| Bulk purge | site admin | `older_than_years >= 1`; targets games with terminal status finished more than N years ago |
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| Read message | the recipient | row exists in `diplomail_recipients(message_id, user_id)`; non-active members see admin-kind only |
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| Mark read | the recipient | row exists; idempotent if already marked |
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| Soft delete | the recipient | `read_at IS NOT NULL` (open-then-delete, item 10) |
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Stage D will add body-language detection (whatlanggo) and the
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translation cache + async worker.
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System mail is produced internally by lobby lifecycle hooks:
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`Service.transition()` emits `game.paused` / `game.cancelled` system
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mail to every active member; `Service.changeMembershipStatus` /
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`Service.AdminBanMember` emit `membership.removed` /
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`membership.blocked` system mail addressed to the affected user.
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## Content rules
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- Body is plain UTF-8 text. The server does **not** parse, sanitise,
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or escape HTML — the UI renders messages via `textContent`.
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- Body length is capped by `BACKEND_DIPLOMAIL_MAX_BODY_BYTES` (default
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4096). Subject length is capped by
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`BACKEND_DIPLOMAIL_MAX_SUBJECT_BYTES` (default 256). Both limits
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live in the service layer so they can be tuned without a schema
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migration.
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- `body_lang` is filled at send time by the configured
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`detector.LanguageDetector` (default: `whatlanggo`, body-only,
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≥ 25 runes; shorter bodies stay `und`).
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## Translation
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Stage D adds a lazy translation cache. When a recipient reads a
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message through `GET /api/v1/user/games/{game_id}/mail/messages/{id}`,
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the handler resolves the caller's `accounts.preferred_language` and
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asks `Service.GetMessage(…, targetLang)` to attach a translation:
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- on cache hit (row in `diplomail_translations`), the rendering is
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returned directly under `translated_subject` / `translated_body`;
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- on cache miss, the configured `translator.Translator` is invoked.
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A non-noop result is persisted and returned to the caller; the
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noop translator that ships with Stage D returns `engine == "noop"`,
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which is treated as "translation unavailable" and the caller falls
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back to the original body.
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The inbox listing (`/inbox`) reuses cached translations but never
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calls the translator on miss — bulk listings stay fast even when a
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real translator (LibreTranslate, SaaS engine) introduces I/O cost.
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Future work plugs a real `translator.Translator` (LibreTranslate
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HTTP client is the documented next step) without touching the rest
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of the system.
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## Async translation (Stage E)
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Stage E switches the translation pipeline from "lazy at read" to
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"async at send". The send path stays synchronous from the
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caller's perspective: the message and recipient rows are inserted
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in one transaction. What changes is delivery semantics:
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- Recipients whose `preferred_language` matches the detected
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`body_lang` (or whose body language is `und`) get
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`available_at = now()` straight away and the push event fires
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during the request.
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- Recipients whose `preferred_language` differs are inserted with
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`available_at IS NULL`. They are **not** visible in inbox, unread
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count, or push events until the worker translates the message.
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The worker (`internal/diplomail.Worker`, started as an
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`app.Component` in `cmd/backend/main`) ticks once every
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`BACKEND_DIPLOMAIL_WORKER_INTERVAL` (default `2s`). Each tick:
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1. Picks one distinct `(message_id, recipient_preferred_language)`
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pair from `diplomail_recipients` where `available_at IS NULL`
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and `next_translation_attempt_at` is unset or due.
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2. Loads the source message, checks the translation cache.
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3. On cache hit → marks every pending recipient of the pair
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delivered and emits push.
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4. On cache miss → asks the configured `Translator`:
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- success → caches the translation, marks delivered, push;
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- HTTP 400 (unsupported pair) → marks delivered without a
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translation (fallback to original);
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- other failure → bumps `translation_attempts`, schedules the
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retry via `next_translation_attempt_at`, leaves pending.
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5. After `BACKEND_DIPLOMAIL_TRANSLATOR_MAX_ATTEMPTS` (default `5`)
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the worker falls back to delivering the original body so a
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prolonged LibreTranslate outage does not strand messages.
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Retry backoff is exponential `1s → 2s → 4s → 8s → 16s` (capped at
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60s) per pair. Operators monitor the LibreTranslate dependency
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through standard OpenTelemetry export — translation outcomes
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surface in `diplomail.worker` logs at Info / Warn levels;
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Grafana / Prometheus dashboards live outside this package.
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## Push integration
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Every successful send emits a `diplomail.message.received` push
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intent through the existing notification pipeline. The catalog entry
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limits delivery to the push channel — email is intentionally absent;
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the inbox endpoint is the durable fallback for offline users. The
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payload includes the recipient's freshly recomputed unread count for
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the lobby badge and for the in-game header.
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## Lifecycle hooks (Stage B)
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The lobby module is the producer of system mail. Stage B will add a
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`DiplomailPublisher` collaborator on `lobby.Service` and call it on
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`paused` / `cancelled` transitions and on `BlockMembership` /
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`AdminBanMember`. The publisher constructs a
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`kind='admin', sender_kind='system'` message with a templated body;
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the recipient receives the durable copy in their inbox even after the
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membership is revoked.
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If a future stage adds inactivity-based player removal at the lobby
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sweeper, that path **must** call the same publisher so the kicked
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player has the explanation in their inbox.
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## Wiring
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`cmd/backend/main.go` constructs `*diplomail.Service` with three
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collaborators:
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- `*Store` over the shared Postgres pool;
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- `MembershipLookup` adapter that walks the lobby cache for the
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active `(game_id, user_id)` row and stitches in the immutable
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`accounts.user_name`;
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- `NotificationPublisher` adapter that translates each
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`DiplomailNotification` into a `notification.Intent` and routes it
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through `*notification.Service.Submit`.
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