Add ranking metric expansion tasks

ai/tasks/pending/TASK-185-add-ranking-extra-metrics-backend-support.md

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+---
+id: TASK-185-add-ranking-extra-metrics-backend-support
+title: Add ranking extra metrics backend support
+status: pending
+type: backend
+team: Backend Senior
+supporting_teams:
+  - Arquitecto Python
+  - Arquitecto de Base de Datos
+roadmap_item: foundation
+priority: high
+---
+
+# TASK-185-add-ranking-extra-metrics-backend-support - Add ranking extra metrics backend support
+
+## Goal
+
+Add backend support for additional `Ranking global` metrics by reusing the existing RCON materialized read model, while preserving the current Ranking route and avoiding unsafe annual recomputation.
+
+## Context
+
+`TASK-183` confirmed that `GET /api/ranking` currently supports only `metric=kills`, with weekly/monthly reading from the RCON materialized leaderboard and annual reading from snapshots. The next backend step is to extend metric support safely for weekly/monthly and keep annual constrained to snapshot-safe behavior only.
+
+Preserve the current product identity: Spanish-speaking HLL Vietnam community, military/Vietnam/tactical/sober visual direction and controlled repository evolution.
+
+## Steps
+
+1. Read the listed files first.
+2. Keep the public endpoint as:
+   - `GET /api/ranking?timeframe=weekly|monthly|annual&server_id=<server-or-all>&metric=<metric>&limit=<limit>&year=<year>`
+3. Extend weekly/monthly support for:
+   - `kills`
+   - `deaths`
+   - `teamkills`
+   - `matches_considered`
+   - `kd_ratio`
+   - `kills_per_match`
+4. Preserve `metric=kills` behavior and compatibility for existing Ranking requests.
+5. Reuse the materialized RCON read model and avoid introducing a new ranking architecture.
+6. Keep annual support safe:
+   - support `kills`
+   - only support additional annual metrics if they are snapshot-backed without public full-year recomputation
+   - otherwise return a controlled `400` for unsupported annual metrics
+7. Update route validation and payload normalization only where necessary.
+8. Extend validation coverage for the new metrics and failure cases.
+
+## Files to Read First
+
+- `AGENTS.md`
+- `ai/repo-context.md`
+- `ai/architecture-index.md`
+- `docs/global-ranking-page-plan.md`
+- `backend/app/routes.py`
+- `backend/app/payloads.py`
+- `backend/app/rcon_historical_leaderboards.py`
+- `backend/app/rcon_annual_rankings.py`
+- `scripts/run-stats-validation.ps1`
+- `scripts/run-integration-tests.ps1`
+- `ai/tasks/done/TASK-183-review-global-ranking-implementation.md`
+- `ai/tasks/done/TASK-184-define-ranking-metric-expansion-contract.md`
+
+## Expected Files to Modify
+
+- `backend/app/rcon_historical_leaderboards.py`
+- `backend/app/routes.py`
+- `backend/app/payloads.py`
+- `backend/app/rcon_annual_rankings.py`
+- `scripts/run-stats-validation.ps1`
+- `ai/tasks/done/TASK-185-add-ranking-extra-metrics-backend-support.md`
+
+## Constraints
+
+- Do not create migrations.
+- Do not introduce a new architecture.
+- Do not recalculate the annual full-year ranking on public requests.
+- Do not reactivate Elo/MMR.
+- Do not reintroduce Comunidad Hispana #03.
+- Do not use public scoreboard as the normal primary source.
+- Do not modify frontend files.
+- Do not break Stats endpoints.
+- Do not break the existing Ranking route for `metric=kills`.
+
+## Validation
+
+Before completing the task ensure:
+
+- `powershell -ExecutionPolicy Bypass -File scripts/run-stats-validation.ps1`
+- `powershell -ExecutionPolicy Bypass -File scripts/run-integration-tests.ps1`
+- validate `GET /api/ranking` for:
+  - `timeframe=weekly&metric=kills`
+  - `timeframe=weekly&metric=deaths`
+  - `timeframe=weekly&metric=teamkills`
+  - `timeframe=weekly&metric=matches_considered`
+  - `timeframe=weekly&metric=kd_ratio`
+  - `timeframe=weekly&metric=kills_per_match`
+  - `timeframe=monthly&metric=kd_ratio`
+  - `timeframe=monthly&metric=kills_per_match`
+  - `timeframe=annual&metric=kills`
+  - unsupported metric
+  - unsupported timeframe
+  - `limit=3`
+  - `limit=101` or invalid limit according to the current contract
+- confirm annual behavior is still snapshot-safe
+- confirm `git diff --name-only` stays within scope
+
+## Outcome
+
+Document:
+
+- metrics added
+- formulas applied in backend ranking logic
+- annual metric behavior and limitations
+- validations executed
+- known limitations
+- recommended next task: expose the new metrics safely in Ranking frontend UX
+
+## Change Budget
+
+- Prefer fewer than 5 modified files.
+- Prefer changes under 200 lines when feasible.
+- Split the work into follow-up tasks if limits are exceeded.