# NLL Box Lacrosse Simulator Implementation Plan

## Goal

Implement National Lacrosse League (NLL) box lacrosse as a preseason-draftable sport. Brackt leagues should be able to draft NLL teams before the regular season starts, while the simulator projects both:

1. the 18-game regular season and top-eight playoff qualification; and
2. the NLL playoff bracket: single-elimination Quarterfinals followed by best-of-three Semifinals and best-of-three NLL Finals.

This is **not** a playoff-only MVP. The simulator must support all NLL teams in preseason and in-season states, then converge naturally to bracket-only behavior once the playoff field is known.

## Current NLL format assumptions

Use these assumptions until the league changes format or an admin overrides season config:

- NLL uses unified single-table standings.
- The league has 14 franchises.
- Each team plays an 18-game regular season.
- Top eight teams qualify for the playoffs.
- Quarterfinal matchups are `1 vs 8`, `2 vs 7`, `3 vs 6`, and `4 vs 5`.
- Quarterfinals are single elimination.
- Semifinals and NLL Finals are best-of-three series.
- Bracket arms should be fixed as `(1 vs 8) winner vs (4 vs 5) winner` and `(2 vs 7) winner vs (3 vs 6) winner`, matching the published NLL bracket layout.

References checked May 12, 2026:

- Official NLL playoff bracket page: <https://www.nll.com/playoff-bracket/>
- Official 2026 playoff schedule/format announcement: <https://www.nll.com/news/national-lacrosse-league-unveils-2026-playoff-schedule-and-quarterfinal-matchups/>
- Official unified standings/playoff structure announcement: <https://www.nll.com/news/nll-adopts-unified-standings-format-and-updated-playoff-structure-for-the-2023-24-season/>
- Official NLL standings page: <https://www.nll.com/standings/>

## Architecture fit

Follow the simulator guide:

- Add a dedicated `nll_bracket` `simulatorType`.
- Keep mutable season inputs in `season_participant_simulator_inputs`; do not hardcode current teams, current standings, odds, seeds, or ratings in the simulator.
- Query simulator config and inputs through the simulator model/runner pathways already used by admin routes.
- Use the existing input-policy system so direct Elo can be derived from projected wins or futures odds.
- Return the standard top-eight probability columns used by expected values.

## Data model and config changes

### Simulator type

Add `nll_bracket` in all simulator type locations:

- `database/schema.ts` `simulatorTypeEnum`
- `app/services/simulations/registry.ts` `SIMULATOR_TYPES`
- `app/services/simulations/registry.ts` registry entry
- `app/services/simulations/manifest.ts` profile map
- `app/services/simulations/simulator-config.ts` projected-wins config

Generate the enum migration with `npm run db:generate`; never hand-write migration SQL.

### Manifest profile

Recommended profile:

```ts
nll_bracket: {
  defaultConfig: {
    iterations: 50_000,
    seasonGames: 18,
    parityFactor: 400,
    bracketSize: 8,
    playoffTeams: 8,
    regularSeasonTeamCount: 14,
    regularSeasonMode: "project_remaining_games",
    regularSeasonNoise: 0.9,
    homeFieldElo: 0,
  },
  requiredInputs: ["sourceElo"],
  optionalInputs: ["projectedWins", "sourceOdds", "seed"],
  derivableInputs: { sourceElo: ["projectedWins", "sourceOdds"] },
  setupSections: ["participants", "eloRatings", "regularStandings", "bracket"],
}
```

`projectedWins` is the preferred preseason admin input. Direct `sourceElo` should override it, and futures odds can remain a fallback/alternative.

### Simulator config

Add `nll_bracket` to `app/services/simulations/simulator-config.ts`:

```ts
nll_bracket: {
  seasonGames: 18,
  parityFactor: 400,
  averageOpponentElo: 1500,
}
```

This enables generic projected-wins-to-Elo handling in admin setup.

## Simulator algorithm

Create `app/services/simulations/nll-simulator.ts` with an `NLLSimulator implements Simulator`.

### Inputs loaded per run

Load:

- all `seasonParticipants` for the sports season;
- resolved `sourceElo` values from simulator inputs / EV compatibility bridge;
- optional `projectedWins` for preseason regular-season projection;
- optional `seed` values for known playoff seeds;
- regular-season standings from the existing regular standings table when available;
- playoff bracket event/matches/games when available.

Fail readiness through the manifest/input policy if required Elo cannot be resolved for every participant that can affect the playoff field. Do not silently assign Elo unless the season config explicitly enables an input-policy fallback.

### Mode selection

The simulator should choose the most complete available state:

1. **Bracket-aware mode**: if a populated NLL playoff bracket exists, honor it.
   - Use completed match winners/losers.
   - Use completed game rows inside best-of-three matches when present.
   - Simulate unresolved games/matches.
2. **Known-seed mode**: if no bracket exists but eight teams have seeds 1-8, simulate the playoff bracket directly from those seeds.
3. **Regular-season projection mode**: otherwise, simulate the full regular season each iteration, derive top-eight seeds, then simulate playoffs.

Regular-season projection mode is required for preseason draftability.

### Regular-season projection mode

For each Monte Carlo iteration:

1. Start each team from current standings if present:
   - `wins`, `losses`, and `gamesPlayed` from the regular standings table;
   - if standings are absent, start all teams at `0-0`.
2. Determine remaining games:
   - `remainingGames = max(0, seasonGames - gamesPlayed)`.
3. Convert Elo to game win probability against an average opponent:
   - `p = 1 / (1 + 10 ** ((averageOpponentElo - teamElo) / parityFactor))`.
4. Project additional wins:
   - preseason/default option: sample `remainingGames` Bernoulli trials at `p`;
   - if `projectedWins` exists, calibrate the team's mean final wins toward that projection by blending Elo-derived win rate with projected-win rate;
   - preserve current wins as a floor, so projected final wins cannot fall below already-earned wins.
5. Rank all teams by simulated final wins, with random tiebreaker for teams tied on wins.
6. Take the top eight as seeds 1-8.
7. Simulate the playoff bracket for those seeds.

Recommended projection blend for phase one:

```ts
projectedRate = projectedWins / seasonGames
eloRate = eloGameWinProbability(teamElo, averageOpponentElo, parityFactor)
regularSeasonWinRate = projectedWins == null
  ? eloRate
  : 0.65 * projectedRate + 0.35 * eloRate
```

Keep `0.65` configurable as `projectedWinsWeight` if added to `defaultConfig`.

### Playoff simulation

For playoff games, use team-vs-team Elo probability:

```ts
pA = 1 / (1 + 10 ** ((eloB - eloA) / parityFactor))
```

Then simulate:

- Quarterfinals: one game.
- Semifinals: best of three, first team to two wins.
- Finals: best of three, first team to two wins.

Export small helpers for testability:

- `nllGameWinProbability(eloA, eloB, parityFactor)`
- `simulateNllGame(teamA, teamB, parityFactor)`
- `simulateBestOfThree(teamA, teamB, parityFactor, existingWins?)`
- `buildNllBracketFromSeeds(seedEntries)`
- `simulateNllPlayoffs(seedEntries, options)`
- `simulateRegularSeasonSeeds(teams, options)`

### Completed results and partial series

When a playoff bracket exists:

- A completed match with `winnerId` should be deterministic.
- For best-of-three matches, completed `playoff_match_games` rows should set current series wins.
- If a team already has two series wins, treat the series as complete even if `playoffMatches.isComplete` has not yet been toggled.
- If only one game is complete, simulate the remaining game(s) from the current 1-0 state.

### Probability mapping

Map each iteration to Brackt's standard top-eight shape:

- champion: `probFirst`
- finalist: `probSecond`
- two semifinal losers: split evenly across `probThird` and `probFourth`
- four quarterfinal losers: split evenly across `probFifth`, `probSixth`, `probSeventh`, `probEighth`
- non-playoff teams in a given iteration receive no placement count for that iteration

Across all participants:

- `probFirst` sums to 1;
- `probSecond` sums to 1;
- `probThird` and `probFourth` each sum to 1;
- `probFifth` through `probEighth` each sum to 1.

## Admin and data setup

### Preseason setup workflow

1. Create the NLL sport with `simulatorType = "nll_bracket"`.
2. Create the NLL sports season with all 14 teams as participants.
3. Import preseason `projectedWins` for every team through the generic simulator CSV importer.
4. Optionally import championship futures odds.
5. Run the simulator before draft rooms open; all 14 teams should receive EV based on playoff qualification and bracket outcomes.

### In-season workflow

1. Sync or manually update regular standings.
2. Re-run the simulator as standings change.
3. `projectedWins` can remain a preseason prior, but current standings should increasingly dominate as games are played.

### Playoff workflow

1. Once seeds are final, enter seeds or create the bracket.
2. If bracket exists, the simulator should stop projecting regular-season qualification and use bracket-aware mode.
3. As playoff games complete, update match/game results and re-run the simulator.

## Testing plan

Add `app/services/simulations/__tests__/nll-simulator.test.ts`.

Required tests:

- projected-wins-to-Elo readiness works for `nll_bracket`;
- regular-season projection can run from a preseason `0-0` state with 14 teams;
- higher projected wins increase playoff qualification and title probability;
- only eight teams qualify in each simulated iteration;
- seed ordering builds fixed bracket arms correctly: `(1,8)/(4,5)` and `(2,7)/(3,6)`;
- Quarterfinals are single-game;
- Semifinals and Finals are best-of-three;
- partial best-of-three state is honored;
- completed matches are deterministic;
- all output probability columns sum correctly;
- manifest, registry, and schema enum stay in sync.

Run at minimum:

```bash
npm run typecheck
npm run lint
npm run test:run
```

## Implementation task breakdown

1. Add schema enum and migration for `nll_bracket`.
2. Add manifest/config/registry entries.
3. Implement pure NLL simulator helpers.
4. Implement regular-season projection mode.
5. Implement known-seed playoff mode.
6. Implement bracket-aware mode with completed match/game support.
7. Add unit tests and readiness/manifest regression coverage.
8. Seed/create admin data for the NLL sport and current season outside of production code.
9. Run required checks.
10. Verify `/admin/simulators` shows actionable setup state and can run preseason NLL seasons.

## Explicit non-goals

- Do not hardcode current NLL standings, team Elo values, futures odds, or playoff seeds into production simulator code.
- Do not make NLL playoff-only; preseason draftability requires regular-season simulation.
- Do not add route-level Drizzle queries for simulator setup; use model/service layers.
- Do not create migration SQL manually.