galaxy-game/gateway/PLAN.md

Edge Gateway Implementation Plan

Summary

This plan breaks implementation into small, reviewable phases. Each phase has a single primary goal, clear deliverables, explicit dependencies, acceptance criteria, and focused tests.

The intended v1 architecture is:

• unauthenticated public ingress over REST/JSON;
• authenticated ingress over gRPC on HTTP/2;
• FlatBuffers payloads for authenticated business commands;
• protobuf-based gRPC control envelopes;
• authenticated server-streaming push through gRPC;
• separate public traffic classes and isolated anti-abuse counters.

Assumptions and Defaults

• message_type is the stable downstream routing key.
• protocol_version covers transport and envelope compatibility, not business payload schema compatibility.
• FlatBuffers are used for business payload bytes only.
• Browser bootstrap and asset traffic are within gateway scope, even when backed by a pluggable proxy or handler.
• Long-polling is out of scope for v1.

Phase 1. Module Skeleton

Goal: create the runnable gateway process skeleton.

Artifacts:

• cmd/gateway
• internal/app
• base configuration types
• startup and shutdown wiring

Dependencies: none.

Acceptance criteria:

• the process starts with config;
• the process shuts down cleanly on signal;
• lifecycle wiring is testable.

Targeted tests:

• startup with valid config;
• shutdown without leaked goroutines.

Phase 2. Public REST Server

Goal: add the unauthenticated HTTP server shell.

Artifacts:

• public REST listener
• GET /healthz
• GET /readyz
• base error serialization
• request classification hook

Dependencies: Phase 1.

Acceptance criteria:

• health endpoints respond deterministically;
• public requests are classified at least into public_auth and browser_*.

Targeted tests:

• health endpoint responses;
• request classification smoke tests.

Phase 3. Public Auth REST Handlers

Goal: expose unauthenticated auth commands through REST/JSON.

Artifacts:

• POST /api/v1/public/auth/send-email-code
• POST /api/v1/public/auth/confirm-email-code
• request and response DTOs
• adapter calls into AuthServiceClient

Dependencies: Phase 2.

Acceptance criteria:

• no session authentication is required for these routes;
• handlers delegate only through the auth service adapter.

Targeted tests:

• success and validation errors for both routes;
• no session lookup on public auth paths.

Phase 4. Public Traffic Classification

Goal: isolate public traffic into stable anti-abuse classes.

Artifacts:

• PublicTrafficClassifier
• classes public_auth, browser_bootstrap, browser_asset, public_misc
• isolated rate-limit bucket keys

Dependencies: Phase 2.

Acceptance criteria:

• browser traffic does not share buckets with public auth;
• auth counters remain unaffected by asset bursts.

Targeted tests:

• per-class routing tests;
• bucket isolation tests.

Phase 5. Public REST Anti-Abuse

Goal: add coarse protection to unauthenticated REST traffic.

Artifacts:

• body size limits
• method allow-lists
• malformed request counters
• per-class rate-limit thresholds

Dependencies: Phase 4.

Acceptance criteria:

• first-load browser bursts are not marked hostile because of burst pattern alone;
• malformed or oversized requests are rejected predictably.

Targeted tests:

• bootstrap burst stays outside auth abuse counters;
• invalid methods and oversized bodies are rejected.

Phase 6. gRPC Server and Public Contracts

Goal: bring up authenticated transport over gRPC and HTTP/2.

Artifacts:

• gRPC listener
• protobuf service definitions
• ExecuteCommand
• SubscribeEvents

Dependencies: Phase 1.

Acceptance criteria:

• unary and server-streaming RPCs are reachable;
• the server runs only over HTTP/2.

Targeted tests:

• unary transport smoke test;
• stream transport smoke test.

Phase 7. Envelope Parsing and Protocol Gate

Goal: validate the gRPC control envelope before security checks continue.

Artifacts:

• envelope parser
• required-field validation
• protocol version gate

Dependencies: Phase 6.

Acceptance criteria:

• unsupported or malformed envelopes are rejected before routing.

Targeted tests:

• missing field rejection;
• unsupported protocol_version rejection.

Phase 8. Session Cache Lookup

Goal: resolve authenticated identity from cache.

Artifacts:

• SessionCache
• session lookup pipeline
• revoked versus active session handling

Dependencies: Phase 7.

Acceptance criteria:

• unknown and revoked sessions are blocked before signature verification.

Targeted tests:

• cache hit with active session;
• cache miss reject;
• revoked session reject.

Phase 9. Payload Hash and Signing Input

Goal: verify payload integrity before signature verification.

Artifacts:

• payload_hash verification
• canonical signing input builder

Dependencies: Phase 8.

Acceptance criteria:

• changing payload bytes or envelope fields breaks the signing input.

Targeted tests:

• payload hash mismatch reject;
• canonical bytes differ when signed fields change.

Phase 10. Client Signature Verification

Goal: authenticate the request origin using the session public key.

Artifacts:

• signature verifier
• deterministic auth reject mapping

Dependencies: Phase 9.

Acceptance criteria:

• wrong key and invalid signature produce stable rejects.

Targeted tests:

• success case with valid signature;
• bad signature reject;
• wrong-key reject.

Phase 11. Freshness and Anti-Replay

Goal: enforce transport freshness and replay protection.

Artifacts:

• timestamp freshness window
• ReplayStore
• replay reservation and rejection logic

Dependencies: Phase 10.

Acceptance criteria:

• stale requests and duplicate request_id values are rejected.

Targeted tests:

• stale timestamp reject;
• replay reject for same session and request ID;
• distinct sessions do not collide.

Phase 12. Authenticated Rate Limits and Policy

Goal: apply edge policy after transport authenticity is established.

Artifacts:

• rate-limit keys for IP, session, user, and message class
• authenticated policy evaluation hook

Dependencies: Phase 11.

Acceptance criteria:

• authenticated buckets are independent from public REST buckets.

Targeted tests:

• per-dimension throttling;
• bucket isolation from public traffic.

Phase 13. Internal Authenticated Command and Routing

Goal: forward only verified context to downstream services.

Artifacts:

• AuthenticatedCommand
• DownstreamRouter
• DownstreamClient

Dependencies: Phase 12.

Acceptance criteria:

• downstream services receive verified context only;
• raw transport details do not leak as authoritative input.

Targeted tests:

• route selection by message_type;
• downstream receives the expected authenticated context.

Phase 14. Signed Unary Responses

Goal: return verifiable server responses to authenticated clients.

Artifacts:

• response envelope builder
• payload hash generation
• ResponseSigner

Dependencies: Phase 13.

Acceptance criteria:

• unary responses always carry the original request_id, payload_hash, and server signature.

Targeted tests:

• response correlation test;
• server signature generation test.

Phase 15. Session Update and Revocation Events

Goal: keep gateway session state current without synchronous hot-path lookups.

Artifacts:

• EventSubscriber
• session update handlers
• session revoke handlers

Dependencies: Phase 8.

Acceptance criteria:

• session updates change gateway behavior without per-request sync calls to the auth service.

Targeted tests:

• cache update from event;
• revocation event invalidates cached session.

Phase 16. Authenticated Push Stream

Goal: open a verified server-streaming channel for client-facing delivery.

Artifacts:

• SubscribeEvents handler
• stream binding to user_id and device_session_id
• initial server time event

Dependencies: Phase 15.

Acceptance criteria:

• the stream opens only after the full auth pipeline succeeds.

Targeted tests:

• authorized stream open;
• rejected stream open for invalid session;
• first event contains server time.

Phase 17. Event Fan-Out

Goal: deliver client-facing events from internal pub/sub to active streams.

Artifacts:

• PushHub
• event fan-out logic
• user and session targeting rules

Dependencies: Phase 16.

Acceptance criteria:

• events are delivered to the correct active streams only.

Targeted tests:

• single-session delivery;
• multi-device delivery for one user;
• unrelated sessions do not receive the event.

Phase 18. Revocation-Driven Stream Teardown

Goal: terminate active delivery channels when a session is revoked.

Artifacts:

• stream teardown on revoke
• connection cleanup logic

Dependencies: Phase 17.

Acceptance criteria:

• revocation blocks new unary requests and closes active streams for the same session.

Targeted tests:

• revoke closes active stream;
• revoked session cannot reopen the stream.

Phase 19. Observability and Shutdown Hardening

Goal: make the service operable in production.

Artifacts:

• structured logs
• metrics
• trace propagation
• timeout budgets
• graceful shutdown for unary and streaming traffic

Dependencies: Phase 18.

Acceptance criteria:

• shutdown is deterministic;
• logs and metrics expose stable edge outcomes without leaking secrets.

Targeted tests:

• shutdown closes listeners and active streams;
• secret and signature values are not logged.

Phase 20. Acceptance Pass

Goal: reconcile implementation, documentation, and regression coverage.

Artifacts:

• updated README and PLAN
• final protocol and interface review
• focused regression test run

Dependencies: Phases 1 through 19.

Acceptance criteria:

• implementation matches documented contracts and ordering guarantees;
• docs describe the actual gateway behavior.

Targeted tests:

• run focused package tests for gateway packages;
• rerun cross-cutting regression scenarios.

Cross-Cutting Regression Scenarios

• send_email_code and confirm_email_code are available without session auth and are still limited by public auth policy.
• Public browser bootstrap and asset bursts do not increase auth abuse counters and are not rejected as hostile because of intensity alone.
• Any gRPC command without a valid session is rejected before routing.
• Unknown and revoked sessions are handled predictably and consistently where policy requires identical behavior.
• Signature verification fails when payload_bytes, payload_hash, message_type, request_id, or the signing key changes.
• payload_hash is verified before downstream execution.
• Requests outside the freshness window are rejected.
• Reused request_id values are rejected within the session replay window.
• Public REST and authenticated gRPC traffic use independent buckets and independent abuse telemetry.
• Downstream services receive AuthenticatedCommand, not raw REST or gRPC transport requests.
• Unary responses preserve request_id correlation and are server-signed.
• Streaming connections open only after the auth pipeline and close on revoke.
• Session cache updates from events change gateway behavior without synchronous auth-service lookups per request.
• Graceful shutdown terminates unary and streaming traffic cleanly.