import { Form, redirect, useLoaderData, useActionData, useNavigation } from 'react-router';
import type { Route } from './+types/admin.sports-seasons.$id.elo-ratings';

import { logger } from '~/lib/logger';
import { findSportsSeasonById, updateSportsSeason } from '~/models/sports-season';
import { findParticipantsBySportsSeasonId } from '~/models/season-participant';
import {
  getAllParticipantEVsForSeason,
  batchSaveSourceElos,
  batchUpsertParticipantEVs,
} from '~/models/participant-expected-value';
import { batchUpsertParticipantEvSnapshots } from '~/models/ev-snapshot';
import { getSimulator, type SimulatorType } from '~/services/simulations/registry';
import { calculateEV } from '~/services/ev-calculator';
import { DEFAULT_SCORING_RULES } from '~/lib/scoring-types';
import { recalculateStandings } from '~/models/scoring-calculator';
import { database } from '~/database/context';
import * as schema from '~/database/schema';
import { eq } from 'drizzle-orm';
import { Button } from '~/components/ui/button';
import { Input } from '~/components/ui/input';
import { Label } from '~/components/ui/label';
import { Textarea } from '~/components/ui/textarea';
import {
  Card,
  CardContent,
  CardDescription,
  CardHeader,
  CardTitle,
} from '~/components/ui/card';
import { useState } from 'react';
import { Loader2, CheckCircle2, AlertCircle } from 'lucide-react';
import { normalizeName } from '~/lib/fuzzy-match';
import { getSimulatorConfig, supportsProjectedWins } from '~/services/simulations/simulator-config';
import {
  eloToProjectedTablePoints,
  eloToProjectedWins,
  projectedTablePointsToElo,
  projectedWinsToElo,
} from '~/services/probability-engine';

// Simulator types that use worldRanking in addition to sourceElo
const RANKING_SIMULATOR_TYPES = new Set(['darts_bracket', 'cs2_major_qualifying_points']);

function rankingLabel(simulatorType: string | null | undefined): string {
  if (simulatorType === 'cs2_major_qualifying_points') return 'HLTV Rank';
  return 'World Rank';
}

export function meta({ data }: Route.MetaArgs): Route.MetaDescriptors {
  return [{ title: `Elo Ratings — ${data?.sportsSeason?.name ?? "Sports Season"} - Brackt Admin` }];
}

export async function loader({ params }: Route.LoaderArgs) {
  const sportsSeasonId = params.id;

  const sportsSeason = await findSportsSeasonById(sportsSeasonId);

  if (!sportsSeason) {
    throw new Response('Sports season not found', { status: 404 });
  }

  const participants = await findParticipantsBySportsSeasonId(sportsSeasonId);
  const existingEVs = await getAllParticipantEVsForSeason(sportsSeasonId);

  const existingData: Record<string, { elo: number | null; ranking: number | null }> = {};
  for (const ev of existingEVs) {
    existingData[ev.participantId] = {
      elo: ev.sourceElo ?? null,
      ranking: ev.worldRanking ?? null,
    };
  }

  const usesRanking = RANKING_SIMULATOR_TYPES.has(sportsSeason.sport?.simulatorType ?? '');

  const simulatorConfig = sportsSeason.sport?.simulatorType
    ? getSimulatorConfig(sportsSeason.sport.simulatorType as SimulatorType)
    : null;
  const canUseProjectedWins = sportsSeason.sport?.simulatorType
    ? supportsProjectedWins(sportsSeason.sport.simulatorType as SimulatorType)
    : false;

  return { sportsSeason, participants, existingData, usesRanking, simulatorConfig, canUseProjectedWins };
}

interface ActionData {
  success?: boolean;
  message?: string;
}

export async function action({ request, params }: Route.ActionArgs) {
  const sportsSeasonId = params.id;
  const formData = await request.formData();

  const sportsSeason = await findSportsSeasonById(sportsSeasonId);
  if (!sportsSeason) {
    return { success: false, message: 'Sports season not found' };
  }

  const participants = await findParticipantsBySportsSeasonId(sportsSeasonId);
  const usesRanking = RANKING_SIMULATOR_TYPES.has(sportsSeason.sport?.simulatorType ?? '');
  const rawMode = formData.get('inputMode');
  const inputMode = rawMode === 'projectedWins' ? 'projectedWins' : 'elo';

  const eloInputs: Array<{ participantId: string; sportsSeasonId: string; sourceElo: number; worldRanking?: number | null }> = [];

  if (inputMode === 'projectedWins' && sportsSeason.sport?.simulatorType) {
    const config = getSimulatorConfig(sportsSeason.sport.simulatorType as SimulatorType);
    if (!config) {
      return { success: false, message: 'This sport does not support projection input.' };
    }

    for (const participant of participants) {
      const winsVal = formData.get(`wins_${participant.id}`) as string;
      if (winsVal && winsVal.trim() !== '') {
        const projectedWins = parseFloat(winsVal);
        const projectionMax = config.projectionInput === 'tablePoints' ? config.seasonGames * 3 : config.seasonGames;
        if (!isNaN(projectedWins) && projectedWins >= 0 && projectedWins <= projectionMax) {
          const elo = config.projectionInput === 'tablePoints'
            ? projectedTablePointsToElo(projectedWins, config.seasonGames, config.parityFactor, config.averageOpponentElo)
            : projectedWinsToElo(projectedWins, config.seasonGames, config.parityFactor, config.averageOpponentElo);
          eloInputs.push({ participantId: participant.id, sportsSeasonId, sourceElo: elo });
        }
      }
    }
  } else {
    for (const participant of participants) {
      const eloVal = formData.get(`elo_${participant.id}`) as string;
      const rankVal = formData.get(`rank_${participant.id}`) as string;

      if (eloVal && eloVal.trim() !== '') {
        const elo = Number(eloVal);
        if (!isNaN(elo) && elo > 0) {
          if (usesRanking) {
            const ranking = rankVal && rankVal.trim() !== '' ? Number(rankVal) : null;
            eloInputs.push({
              participantId: participant.id,
              sportsSeasonId,
              sourceElo: elo,
              worldRanking: ranking && !isNaN(ranking) && ranking > 0 ? ranking : null,
            });
          } else {
            eloInputs.push({ participantId: participant.id, sportsSeasonId, sourceElo: elo });
          }
        }
      }
    }
  }

  if (eloInputs.length === 0) {
    return { success: false, message: inputMode === 'projectedWins'
      ? 'Please enter projections for at least one participant'
      : 'Please enter an Elo rating for at least one participant' };
  }

  if (!sportsSeason.sport?.simulatorType) {
    return { success: false, message: 'This sport has no simulator type configured. Set one on the sport in the admin panel.' };
  }

  if (sportsSeason.simulationStatus === 'running') {
    return { success: false, message: 'A simulation is already running. Please wait.' };
  }

  await batchSaveSourceElos(eloInputs);

  await updateSportsSeason(sportsSeasonId, { simulationStatus: 'running' });

  try {
    const simulator = getSimulator(sportsSeason.sport.simulatorType as SimulatorType);
    const results = await simulator.simulate(sportsSeasonId);

    if (results.length === 0) {
      throw new Error('Simulation returned no results.');
    }

    const simulatedIds = new Set(results.map(r => r.participantId));
    const ZERO_PROBS = {
      probFirst: 0, probSecond: 0, probThird: 0, probFourth: 0,
      probFifth: 0, probSixth: 0, probSeventh: 0, probEighth: 0,
    };
    const evInputs = [
      ...results.map(r => ({
        participantId: r.participantId,
        sportsSeasonId,
        probabilities: r.probabilities,
        scoringRules: DEFAULT_SCORING_RULES,
        source: 'elo_simulation' as const,
      })),
      ...participants
        .filter(p => !simulatedIds.has(p.id))
        .map(p => ({
          participantId: p.id,
          sportsSeasonId,
          probabilities: ZERO_PROBS,
          scoringRules: DEFAULT_SCORING_RULES,
          source: 'elo_simulation' as const,
        })),
    ];

    await batchUpsertParticipantEVs(evInputs);

    const seasonSports = await database().query.seasonSports.findMany({
      where: eq(schema.seasonSports.sportsSeasonId, sportsSeasonId),
    });
    await Promise.all(seasonSports.map(({ seasonId }) => recalculateStandings(seasonId)));

    const today = new Date().toISOString().slice(0, 10);
    await batchUpsertParticipantEvSnapshots(
      results.map(r => ({
        participantId: r.participantId,
        sportsSeasonId,
        snapshotDate: today,
        probFirst: r.probabilities.probFirst,
        probSecond: r.probabilities.probSecond,
        probThird: r.probabilities.probThird,
        probFourth: r.probabilities.probFourth,
        probFifth: r.probabilities.probFifth,
        probSixth: r.probabilities.probSixth,
        probSeventh: r.probabilities.probSeventh,
        probEighth: r.probabilities.probEighth,
        calculatedEV: calculateEV(r.probabilities, DEFAULT_SCORING_RULES),
        source: r.source,
      }))
    );

    await updateSportsSeason(sportsSeasonId, { simulationStatus: 'idle' });
  } catch (error) {
    await updateSportsSeason(sportsSeasonId, { simulationStatus: 'failed' });
    logger.error('Error running simulation:', error);
    return {
      success: false,
      message: error instanceof Error ? error.message : 'Simulation failed',
    };
  }

  return redirect(`/admin/sports-seasons/${sportsSeasonId}/expected-values`);
}

export default function AdminSportsSeasonEloRatings() {
  const { sportsSeason, participants, existingData, usesRanking, simulatorConfig, canUseProjectedWins } = useLoaderData<typeof loader>();
  const actionData = useActionData<ActionData>();
  const navigation = useNavigation();

  const [inputMode, setInputMode] = useState<'elo' | 'projectedWins'>('elo');
  const projectionLabel = simulatorConfig?.projectionInput === 'tablePoints' ? 'Projected Points' : 'Projected Wins';
  const projectionUnit = simulatorConfig?.projectionInput === 'tablePoints' ? 'points' : 'wins';
  const projectionMax = simulatorConfig
    ? simulatorConfig.projectionInput === 'tablePoints'
      ? simulatorConfig.seasonGames * 3
      : simulatorConfig.seasonGames
    : 0;

  const [eloValues, setEloValues] = useState<Record<string, string>>(() => {
    const initial: Record<string, string> = {};
    participants.forEach(p => {
      const d = existingData[p.id];
      if (d?.elo !== null && d?.elo !== undefined) initial[p.id] = d.elo.toString();
    });
    return initial;
  });

  const [rankValues, setRankValues] = useState<Record<string, string>>(() => {
    const initial: Record<string, string> = {};
    participants.forEach(p => {
      const d = existingData[p.id];
      if (d?.ranking !== null && d?.ranking !== undefined) initial[p.id] = d.ranking.toString();
    });
    return initial;
  });

  const [winsValues, setWinsValues] = useState<Record<string, string>>(() => {
    const initial: Record<string, string> = {};
    if (simulatorConfig) {
      participants.forEach(p => {
        const d = existingData[p.id];
        if (d?.elo !== null && d?.elo !== undefined) {
          initial[p.id] = (simulatorConfig.projectionInput === 'tablePoints'
            ? eloToProjectedTablePoints(d.elo, simulatorConfig.seasonGames, simulatorConfig.parityFactor, simulatorConfig.averageOpponentElo)
            : eloToProjectedWins(d.elo, simulatorConfig.seasonGames, simulatorConfig.parityFactor, simulatorConfig.averageOpponentElo)
          ).toFixed(1);
        }
      });
    }
    return initial;
  });

  const [bulkText, setBulkText] = useState('');
  const [parseResults, setParseResults] = useState<{
    matched: Array<{ participantId: string; name: string; elo: number; ranking: number | null; inputName: string }>;
    unmatched: Array<{ inputName: string; elo: number; ranking: number | null }>;
  } | null>(null);

  function findParticipantMatch(inputName: string) {
    const normalizedInput = normalizeName(inputName);
    const normalized = participants.map(p => ({ p, n: normalizeName(p.name) }));

    const exact = normalized.find(({ n }) => n === normalizedInput);
    if (exact) return exact.p;

    const contains = normalized.find(({ n }) => n.includes(normalizedInput) || normalizedInput.includes(n));
    if (contains) return contains.p;

    const inputWords = normalizedInput.split(' ').filter(w => w.length > 2);
    const overlap = normalized.find(({ n }) => {
      const pWords = n.split(' ').filter(w => w.length > 2);
      const shared = inputWords.filter(w => pWords.includes(w));
      return shared.length > 0 && shared.length >= Math.min(inputWords.length, pWords.length) * 0.5;
    });

    return overlap?.p ?? null;
  }

  function parseBulkText() {
    const lines = bulkText.split('\n');
    const matched: Array<{ participantId: string; name: string; elo: number; ranking: number | null; inputName: string }> = [];
    const unmatched: Array<{ inputName: string; elo: number; ranking: number | null }> = [];
    const seen = new Set<string>();

    for (const line of lines) {
      const trimmed = line.trim();
      if (!trimmed) continue;

      if (inputMode === 'projectedWins' && simulatorConfig) {
        const match = /^(.+?)[\s,:\t]+(\d+(?:\.\d+)?)\s*$/.exec(trimmed);
        if (!match) continue;

        const inputName = match[1].trim();
        const projectedWins = parseFloat(match[2]);

        if (isNaN(projectedWins) || projectedWins < 0 || projectedWins > projectionMax) continue;

        const elo = simulatorConfig.projectionInput === 'tablePoints'
          ? projectedTablePointsToElo(projectedWins, simulatorConfig.seasonGames, simulatorConfig.parityFactor, simulatorConfig.averageOpponentElo)
          : projectedWinsToElo(projectedWins, simulatorConfig.seasonGames, simulatorConfig.parityFactor, simulatorConfig.averageOpponentElo);

        const participant = findParticipantMatch(inputName);
        if (participant && !seen.has(participant.id)) {
          seen.add(participant.id);
          matched.push({ participantId: participant.id, name: participant.name, elo, ranking: null, inputName });
        } else if (!participant) {
          unmatched.push({ inputName, elo, ranking: null });
        }
      } else {
        const match = usesRanking
          ? /^(.+?)[\s,:\t]+(\d{3,5})(?:[\s,:\t]+(\d{1,3}))?\s*$/.exec(trimmed)
          : /^(.+?)[\s,:\t]+(\d{3,5})\s*$/.exec(trimmed);
        if (!match) continue;

        const inputName = match[1].trim();
        const elo = parseInt(match[2], 10);
        const ranking = usesRanking && match[3] ? parseInt(match[3], 10) : null;

        if (isNaN(elo) || elo < 500 || elo > 5000) continue;

        const participant = findParticipantMatch(inputName);
        if (participant && !seen.has(participant.id)) {
          seen.add(participant.id);
          matched.push({ participantId: participant.id, name: participant.name, elo, ranking, inputName });
        } else if (!participant) {
          unmatched.push({ inputName, elo, ranking });
        }
      }
    }

    setParseResults({ matched, unmatched });
  }

  function applyMatches() {
    if (!parseResults) return;
    const newElos = { ...eloValues };
    const newRanks = { ...rankValues };
    const newWins = { ...winsValues };
    for (const m of parseResults.matched) {
      newElos[m.participantId] = m.elo.toString();
      if (m.ranking !== null) newRanks[m.participantId] = m.ranking.toString();
      if (inputMode === 'projectedWins' && simulatorConfig) {
        newWins[m.participantId] = (simulatorConfig.projectionInput === 'tablePoints'
          ? eloToProjectedTablePoints(m.elo, simulatorConfig.seasonGames, simulatorConfig.parityFactor, simulatorConfig.averageOpponentElo)
          : eloToProjectedWins(m.elo, simulatorConfig.seasonGames, simulatorConfig.parityFactor, simulatorConfig.averageOpponentElo)
        ).toFixed(1);
      }
    }
    setEloValues(newElos);
    setRankValues(newRanks);
    setWinsValues(newWins);
    setParseResults(null);
    setBulkText('');
  }

  const isSubmitting = navigation.state === 'submitting';
  const simulatorType = sportsSeason.sport?.simulatorType ?? null;
  const rankLabel = rankingLabel(simulatorType);

  // When ranking is available, sort by rank ascending, then unranked alphabetically
  const sortedParticipants = usesRanking
    ? [...participants].toSorted((a, b) => {
        const rankA = rankValues[a.id] ? parseInt(rankValues[a.id], 10) : null;
        const rankB = rankValues[b.id] ? parseInt(rankValues[b.id], 10) : null;
        if (rankA !== null && rankB !== null) return rankA - rankB;
        if (rankA !== null) return -1;
        if (rankB !== null) return 1;
        return a.name.localeCompare(b.name);
      })
    : participants;

  return (
    <div className="container mx-auto py-8">
      <div className="mb-8">
        <h1 className="text-3xl font-bold mb-2">Elo Ratings</h1>
        <p className="text-muted-foreground">
          {sportsSeason.sport.name} — {sportsSeason.name}
        </p>
      </div>

      {/* Input Mode Toggle */}
      {canUseProjectedWins && !usesRanking && (
        <div className="mb-6 flex gap-2">
          <Button
            type="button"
            variant={inputMode === 'elo' ? 'default' : 'outline'}
            onClick={() => setInputMode('elo')}
          >
            Elo Ratings
          </Button>
          <Button
            type="button"
            variant={inputMode === 'projectedWins' ? 'default' : 'outline'}
            onClick={() => setInputMode('projectedWins')}
          >
            {projectionLabel}
          </Button>
        </div>
      )}

      {/* Bulk Import */}
      <Card className="mb-6">
        <CardHeader>
          <CardTitle>Bulk Import</CardTitle>
          <CardDescription>
            {inputMode === 'projectedWins' && simulatorConfig ? (
              <>
                Paste projected season {projectionUnit} one per line. Format: <code>Team Name, {simulatorConfig.projectionInput === 'tablePoints' ? '76.5' : '15.6'}</code>.
                Projections are automatically converted to Elo ratings using {simulatorConfig.seasonGames} total games
                and parity factor {simulatorConfig.parityFactor}. Names are fuzzy-matched to participants.
              </>
            ) : usesRanking ? (
              <>
                Paste one entry per line. Format:{' '}
                <code>Name, Elo, {rankLabel}</code> (ranking is optional — omit it and the simulator
                will use Elo order for seeding). Names are fuzzy-matched to participants.
              </>
            ) : (
              <>
                Paste Elo ratings one per line. Format: <code>Player Name, 2450</code>. Player names
                are fuzzy-matched to participants.
              </>
            )}
          </CardDescription>
        </CardHeader>
        <CardContent className="space-y-4">
          <Textarea
            placeholder={
              inputMode === 'projectedWins'
                ? simulatorConfig?.projectionInput === 'tablePoints'
                  ? `Team Name, 76.5\nTeam Name, 68.0\nTeam Name, 54.5`
                  : `Team Name, 15.6\nTeam Name, 14.5\nTeam Name, 13.8`
                : usesRanking
                  ? simulatorType === 'cs2_major_qualifying_points'
                    ? `Natus Vincere, 1850, 1\nFaZe Clan, 1820, 2\nVitality, 1810, 3`
                    : `Luke Littler, 2099, 1\nMichael van Gerwen, 1950, 2\nLuke Humphries, 1947, 3`
                  : `Judd Trump, 2594\nRonnie O'Sullivan, 2441\nMark Selby, 2432`
            }
            value={bulkText}
            onChange={e => { setBulkText(e.target.value); setParseResults(null); }}
            rows={8}
            className="font-mono text-sm"
          />
          <Button type="button" variant="outline" onClick={parseBulkText} disabled={!bulkText.trim()}>
            Parse Ratings
          </Button>

          {parseResults && (
            <div className="space-y-3">
              {parseResults.matched.length > 0 && (
                <div>
                  <div className="flex items-center gap-2 text-sm font-medium text-emerald-400 mb-2">
                    <CheckCircle2 className="h-4 w-4" />
                    Matched ({parseResults.matched.length})
                  </div>
                  <div className="rounded-md border border-emerald-500/30 bg-emerald-500/10 divide-y divide-emerald-500/20 text-sm">
                    {parseResults.matched.map(m => (
                      <div key={m.participantId} className="flex justify-between px-3 py-1.5">
                        <span className="text-muted-foreground">{m.inputName}</span>
                        <span className="font-medium">
                          {m.name} &rarr; Elo {m.elo}
                          {usesRanking && m.ranking !== null ? `, ${rankLabel} #${m.ranking}` : ''}
                        </span>
                      </div>
                    ))}
                  </div>
                </div>
              )}

              {parseResults.unmatched.length > 0 && (
                <div>
                  <div className="flex items-center gap-2 text-sm font-medium text-amber-700 mb-2">
                    <AlertCircle className="h-4 w-4" />
                    Not matched ({parseResults.unmatched.length}) — enter manually below
                  </div>
                  <div className="rounded-md border border-amber-200 bg-amber-50 divide-y divide-amber-100 text-sm">
                    {parseResults.unmatched.map(u => (
                      <div key={u.inputName} className="flex justify-between px-3 py-1.5">
                        <span>{u.inputName}</span>
                        <span className="font-medium">
                          Elo {u.elo}
                          {usesRanking && u.ranking !== null ? `, ${rankLabel} #${u.ranking}` : ''}
                        </span>
                      </div>
                    ))}
                  </div>
                </div>
              )}

              {parseResults.matched.length > 0 && (
                <Button type="button" onClick={applyMatches}>
                  Apply {parseResults.matched.length} matched ratings to form
                </Button>
              )}
            </div>
          )}
        </CardContent>
      </Card>

      <div className="grid gap-6 lg:grid-cols-2">
        <Card>
          <CardHeader>
            <CardTitle>
              {inputMode === 'projectedWins'
                ? `${projectionLabel} (out of ${projectionMax || '?'})`
                : usesRanking
                  ? `Player Elo & ${rankLabel}s`
                  : 'Player Elo Ratings'}
            </CardTitle>
            <CardDescription>
              {inputMode === 'projectedWins'
                ? `Enter each team's projected total season ${projectionUnit}. Converted to Elo automatically. Saving will run the simulation and update expected values.`
                : usesRanking
                  ? `Enter each player's Elo and ${rankLabel}. Saving will automatically run the simulation and update expected values.`
                  : 'Enter each player\'s current Elo rating. Saving will automatically run the simulation and update expected values.'}
            </CardDescription>
          </CardHeader>
          <CardContent>
            <Form method="post" className="space-y-4">
              <input type="hidden" name="inputMode" value={inputMode} />
              {usesRanking && inputMode === 'elo' && (
                <div className="grid grid-cols-[1fr_100px_90px] gap-x-3 gap-y-1 items-center text-xs font-medium text-muted-foreground">
                  <span>Player</span>
                  <span>Elo</span>
                  <span>{rankLabel} #</span>
                </div>
              )}
              {inputMode === 'projectedWins' && (
                <div className="grid grid-cols-[1fr_100px] gap-x-3 gap-y-1 items-center text-xs font-medium text-muted-foreground">
                  <span>Team</span>
                  <span>{simulatorConfig?.projectionInput === 'tablePoints' ? 'Proj Pts' : 'Proj Wins'}</span>
                </div>
              )}
              <div className="space-y-2">
                {sortedParticipants.map(participant => {
                  if (inputMode === 'projectedWins' && simulatorConfig) {
                    return (
                      <div key={participant.id} className="grid grid-cols-[1fr_100px] gap-x-3 items-center">
                        <Label htmlFor={`wins_${participant.id}`} className="truncate text-sm">
                          {participant.name}
                        </Label>
                        <Input
                          type="number"
                          step="0.1"
                          id={`wins_${participant.id}`}
                          name={`wins_${participant.id}`}
                          placeholder={`${(projectionMax / 2).toFixed(1)}`}
                          value={winsValues[participant.id] ?? ''}
                          onChange={e =>
                            setWinsValues(prev => ({ ...prev, [participant.id]: e.target.value }))
                          }
                          className="h-8 text-sm"
                        />
                      </div>
                    );
                  }

                  return (
                    <div
                      key={participant.id}
                      className={usesRanking
                        ? 'grid grid-cols-[1fr_100px_90px] gap-x-3 items-center'
                        : 'grid grid-cols-2 gap-4 items-center'}
                    >
                      <Label htmlFor={`elo_${participant.id}`} className="truncate text-sm">
                        {participant.name}
                      </Label>
                      <Input
                        type="number"
                        id={`elo_${participant.id}`}
                        name={`elo_${participant.id}`}
                        placeholder={usesRanking ? '1800' : '2450'}
                        value={eloValues[participant.id] ?? ''}
                        onChange={e =>
                          setEloValues(prev => ({ ...prev, [participant.id]: e.target.value }))
                        }
                        className={usesRanking ? 'h-8 text-sm' : undefined}
                      />
                      {usesRanking && (
                        <Input
                          type="number"
                          name={`rank_${participant.id}`}
                          placeholder="—"
                          value={rankValues[participant.id] ?? ''}
                          onChange={e =>
                            setRankValues(prev => ({ ...prev, [participant.id]: e.target.value }))
                          }
                          className="h-8 text-sm"
                        />
                      )}
                    </div>
                  );
                })}
              </div>

              {actionData && !actionData.success && actionData.message && (
                <div className="text-sm text-destructive">{actionData.message}</div>
              )}

              <Button type="submit" disabled={isSubmitting}>
                {isSubmitting && <Loader2 className="mr-2 h-4 w-4 animate-spin" />}
                {isSubmitting ? 'Saving & Running Simulation...' : 'Save Ratings & Run Simulation'}
              </Button>
            </Form>
          </CardContent>
        </Card>

        <Card>
          <CardHeader>
            <CardTitle>How It Works</CardTitle>
          </CardHeader>
          <CardContent className="text-sm space-y-2">
            {inputMode === 'projectedWins' ? (
              <ol className="list-decimal list-inside space-y-2">
                <li>Enter each team's projected total season {projectionUnit}</li>
                <li>Projections are converted to Elo ratings using the inverse Elo formula</li>
                <li>Elo ratings are saved and the simulation runs automatically</li>
                <li>Results: probability distributions across 1st–8th place buckets</li>
                <li>Expected fantasy value is calculated per team</li>
              </ol>
            ) : (
              <ol className="list-decimal list-inside space-y-2">
                <li>Save Elo ratings{usesRanking ? ` and ${rankLabel}s` : ''} for all participants</li>
                <li>Compute per-game win probability from Elo difference</li>
                <li>Compute match win probability using the Bernoulli model for each round's format</li>
                <li>Run Monte Carlo simulations of the full event</li>
                <li>Distribute probabilities across 1st–8th place buckets</li>
                <li>Calculate expected fantasy value per player</li>
              </ol>
            )}
            {usesRanking && inputMode === 'elo' && (
              <div className="mt-4 text-muted-foreground text-xs">
                {rankLabel} is optional — if omitted, the simulator uses Elo order for seeding.
              </div>
            )}
            {inputMode === 'projectedWins' && simulatorConfig && (
              <div className="mt-4 text-muted-foreground text-xs">
                Conversion: Elo = {simulatorConfig.averageOpponentElo} &minus; {simulatorConfig.parityFactor} &times; log&#8321;&#8320;((1 &minus; rate) / rate),
                where rate = projection / {projectionMax}.
              </div>
            )}
          </CardContent>
        </Card>
      </div>
    </div>
  );
}
