Stage 5 — Team Mode (3v3)

[KineticTactic]

What this is: Extending the room engine for teams with multiple users per side. A 3v3 match is a standard room with 2 Teams, each containing 3 Users. Does not touch the tournament layer.

Owner: Can be a second developer working in parallel with Stage 6A–6B.

Tasks

1. ContestTeam multi-user logic

   • Room creation with teamSize: 3: accept teams: [{ name, members: [userId, userId, userId] }].
   • Validate team sizes (1 or 3 per team, consistent within a contest).
   • Populate team:<teamId>:users Set with all member userId values.
   • In the cf_sync_queue worker: resolve userId → teamId by checking team:<teamId>:users membership before updating room:<id>:scores.

2. Team score aggregation

   • Any team member's AC increments the team's score: ZINCRBY room:<id>:scores <points> <teamId>.
   • Individual attribution is preserved in ContestSubmission via the userId field.
   • Activity appended to room:<id>:submissions stream: { userId, teamId, problemId, ... }.

3. Arena team claim

   • A problem is locked by teamId when any member of the team claims it.
   • Lua claim script uses teamId|cfTimestamp as the lock value (not userId|cfTimestamp).

4. Ready check for teams

   • All members of all teams must POST /api/contests/rooms/:id/ready.
   • If any member fails to ready within 60s, their entire team is withdrawn as a unit.

Testing Gate

• 3v3 Blitz: 6 real CF accounts, two teams of 3. Any team member's AC increments the team score in room:<id>:scores. Verify ContestTeam.score in MongoDB after room end.
• 3v3 Arena claim: A member of Team 1 and a member of Team 2 race for a problem. Earlier CF timestamp wins the claim for their respective team.
• Regression: all Stage 3 and Stage 4 1v1 tests still pass after team mode changes.

Handoff Contract

• Team and 1v1 modes work without conflict. Full Stage 3 + Stage 4 regression passes.
• ContestTeam schema works for both standalone rooms and knockout tournament context (nullable roundId, contestId fields).

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