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

import { logger } from '~/lib/logger';
import { findSportsSeasonById, updateSportsSeason } from '~/models/sports-season';
import { findParticipantsBySportsSeasonId, createParticipant } from '~/models/participant';
import {
  batchUpsertParticipantEVs,
} from '~/models/participant-expected-value';
import { batchUpsertParticipantEvSnapshots } from '~/models/ev-snapshot';
import { getSurfaceElosForSeason, batchUpsertSurfaceElos } from '~/models/surface-elo';
import { getSimulator, type SimulatorType } from '~/services/simulations/registry';
import { calculateEV, type ScoringRules } from '~/services/ev-calculator';
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 { useEffect, useRef, useState } from 'react';
import { Loader2, CheckCircle2, AlertCircle, UserPlus } from 'lucide-react';

const DEFAULT_SCORING_RULES: ScoringRules = {
  pointsFor1st: 100,
  pointsFor2nd: 70,
  pointsFor3rd: 45,
  pointsFor4th: 45,
  pointsFor5th: 20,
  pointsFor6th: 20,
  pointsFor7th: 20,
  pointsFor8th: 20,
};

export function meta({ data }: Route.MetaArgs): Route.MetaDescriptors {
  return [{ title: `Surface Elo — ${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 existingElos = await getSurfaceElosForSeason(sportsSeasonId);

  const eloMap: Record<string, { ranking: number | null; hard: number | null; clay: number | null; grass: number | null }> = {};
  for (const r of existingElos) {
    eloMap[r.participantId] = {
      ranking: r.worldRanking,
      hard: r.eloHard,
      clay: r.eloClay,
      grass: r.eloGrass,
    };
  }

  return { sportsSeason, participants, eloMap };
}

type ActionData =
  | { intent: 'create-participant'; success: true; participant: { id: string; name: string } }
  | { intent: 'create-participant'; success: false; message: string }
  | { success?: boolean; message?: string };

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

  // Handle participant creation separately
  if (intent === 'create-participant') {
    const name = (formData.get('name') as string)?.trim();
    if (!name) {
      return { intent: 'create-participant', success: false, message: 'Name is required' } satisfies ActionData;
    }
    const participant = await createParticipant({ sportsSeasonId, name });
    return {
      intent: 'create-participant',
      success: true,
      participant: { id: participant.id, name: participant.name },
    } satisfies ActionData;
  }

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

  if (!sportsSeason.sport?.simulatorType) {
    return { success: false, message: 'This sport has no simulator type configured.' };
  }

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

  const participants = await findParticipantsBySportsSeasonId(sportsSeasonId);

  // Parse surface Elos from form fields: ranking_{id}, hard_{id}, clay_{id}, grass_{id}
  const surfaceEloInputs = participants
    .map((p) => {
      const ranking = parseIntOrNull(formData.get(`ranking_${p.id}`) as string);
      const hard    = parseIntOrNull(formData.get(`hard_${p.id}`) as string);
      const clay    = parseIntOrNull(formData.get(`clay_${p.id}`) as string);
      const grass   = parseIntOrNull(formData.get(`grass_${p.id}`) as string);
      return { participantId: p.id, sportsSeasonId, worldRanking: ranking, eloHard: hard, eloClay: clay, eloGrass: grass };
    })
    .filter((r) => r.worldRanking !== null || r.eloHard !== null || r.eloClay !== null || r.eloGrass !== null);

  if (surfaceEloInputs.length === 0) {
    return { success: false, message: 'Please enter at least one Elo rating.' };
  }

  await batchUpsertSurfaceElos(surfaceEloInputs);

  // Auto-run simulation
  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);

    // Refresh projected points in team standings
    const seasonSports = await database().query.seasonSports.findMany({
      where: eq(schema.seasonSports.sportsSeasonId, sportsSeasonId),
    });
    await Promise.all(seasonSports.map(({ seasonId }) => recalculateStandings(seasonId)));

    // EV snapshot
    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 tennis simulation:', error);
    return {
      success: false,
      message: error instanceof Error ? error.message : 'Simulation failed',
    };
  }

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

function parseIntOrNull(val: string | null | undefined): number | null {
  if (!val || val.trim() === '') return null;
  const n = Math.round(parseFloat(val.trim()));
  return isNaN(n) || n <= 0 ? null : n;
}

function normalizeName(name: string): string {
  return name.toLowerCase().replace(/[^a-z0-9\s]/g, '').replace(/\s+/g, ' ').trim();
}

// Bigram Dice coefficient for fuzzy name matching
function bigrams(s: string): string[] {
  const result: string[] = [];
  for (let i = 0; i < s.length - 1; i++) result.push(s.slice(i, i + 2));
  return result;
}

function diceCoefficient(a: string, b: string): number {
  if (a === b) return 1;
  if (a.length < 2 || b.length < 2) return 0;
  const bigA = bigrams(a);
  const bigB = new Set(bigrams(b));
  const intersection = bigA.filter((bg) => bigB.has(bg)).length;
  return (2 * intersection) / (bigA.length + bigB.size);
}

type EloValues = Record<string, { ranking: string; hard: string; clay: string; grass: string }>;

interface MatchedItem {
  participantId: string;
  name: string;
  ranking: number;
  hard: number;
  clay: number;
  grass: number;
  inputName: string;
}

interface Suggestion {
  participantId: string;
  name: string;
  score: number;
}

interface UnmatchedItem {
  inputName: string;
  ranking: number;
  hard: number;
  clay: number;
  grass: number;
  suggestions: Suggestion[];
}

interface ParseResults {
  matched: MatchedItem[];
  unmatched: UnmatchedItem[];
}

type LocalParticipant = { id: string; name: string };

export default function AdminSportsSeasonSurfaceElo() {
  const { sportsSeason, participants: loaderParticipants, eloMap } = useLoaderData<typeof loader>();
  const actionData = useActionData<ActionData>();
  const navigation = useNavigation();
  const createFetcher = useFetcher<ActionData>();

  const [localParticipants, setLocalParticipants] = useState<LocalParticipant[]>(loaderParticipants);

  const [eloValues, setEloValues] = useState<EloValues>(() => {
    const initial: EloValues = {};
    loaderParticipants.forEach((p) => {
      const existing = eloMap[p.id];
      initial[p.id] = {
        ranking: existing !== undefined && existing.ranking !== null ? String(existing.ranking) : '',
        hard:    existing !== undefined && existing.hard    !== null ? String(existing.hard)    : '',
        clay:    existing !== undefined && existing.clay    !== null ? String(existing.clay)    : '',
        grass:   existing !== undefined && existing.grass   !== null ? String(existing.grass)   : '',
      };
    });
    return initial;
  });

  // Bulk import state: "Player Name, ranking, hardElo, clayElo, grassElo" one per line
  const [bulkText, setBulkText] = useState('');
  const [parseResults, setParseResults] = useState<ParseResults | null>(null);

  // Store pending Elo values for participants being created
  const pendingElosByName = useRef<Map<string, { ranking: number; hard: number; clay: number; grass: number }>>(new Map());

  // When a participant is created, apply their Elos and remove from unmatched
  useEffect(() => {
    if (
      createFetcher.state !== 'idle' ||
      !createFetcher.data ||
      !('intent' in createFetcher.data) ||
      createFetcher.data.intent !== 'create-participant' ||
      !createFetcher.data.success
    ) return;

    const { participant } = createFetcher.data as Extract<ActionData, { intent: 'create-participant'; success: true }>;

    // Add to local participants list
    setLocalParticipants((prev) => {
      if (prev.some((p) => p.id === participant.id)) return prev;
      return [...prev, participant];
    });

    // Apply pending Elo values
    const pending = pendingElosByName.current.get(participant.name);
    if (pending) {
      setEloValues((prev) => ({
        ...prev,
        [participant.id]: {
          ranking: String(pending.ranking),
          hard:    String(pending.hard),
          clay:    String(pending.clay),
          grass:   String(pending.grass),
        },
      }));
      pendingElosByName.current.delete(participant.name);
    }

    // Remove from unmatched
    setParseResults((prev) => {
      if (!prev) return prev;
      return {
        ...prev,
        unmatched: prev.unmatched.filter((u) => u.inputName !== participant.name),
      };
    });
  }, [createFetcher.state, createFetcher.data]);

  function findParticipantMatch(inputName: string, pool: LocalParticipant[]) {
    const normalizedInput = normalizeName(inputName);
    const normalized = pool.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 getFuzzySuggestions(inputName: string, pool: LocalParticipant[], exclude: Set<string>): Suggestion[] {
    const normalizedInput = normalizeName(inputName);
    return pool
      .filter((p) => !exclude.has(p.id))
      .map((p) => ({ participantId: p.id, name: p.name, score: diceCoefficient(normalizedInput, normalizeName(p.name)) }))
      .filter((s) => s.score >= 0.3)
      .toSorted((a, b) => b.score - a.score)
      .slice(0, 3);
  }

  function parseBulkText() {
    const lines = bulkText.split('\n');
    const matched: MatchedItem[] = [];
    const unmatched: UnmatchedItem[] = [];
    const seen = new Set<string>();

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

      const match = /^(.+?)[,\t]\s*(\d{1,4})[,\t]\s*(\d{3,5}(?:\.\d+)?)[,\t]\s*(\d{3,5}(?:\.\d+)?)[,\t]\s*(\d{3,5}(?:\.\d+)?)\s*$/.exec(trimmed);
      if (!match) continue;

      const inputName = match[1].trim();
      const ranking = parseInt(match[2], 10);
      const hard    = Math.round(parseFloat(match[3]));
      const clay    = Math.round(parseFloat(match[4]));
      const grass   = Math.round(parseFloat(match[5]));

      const participant = findParticipantMatch(inputName, localParticipants);
      if (participant && !seen.has(participant.id)) {
        seen.add(participant.id);
        matched.push({ participantId: participant.id, name: participant.name, ranking, hard, clay, grass, inputName });
      } else {
        // No match found, or the matched participant was already claimed by an earlier line
        const suggestions = getFuzzySuggestions(inputName, localParticipants, seen);
        unmatched.push({ inputName, ranking, hard, clay, grass, suggestions });
      }
    }

    setParseResults({ matched, unmatched });
  }

  function assignSuggestion(item: UnmatchedItem, suggestion: Suggestion) {
    setParseResults((prev) => {
      if (!prev) return prev;
      return {
        matched: [
          ...prev.matched,
          {
            participantId: suggestion.participantId,
            name: suggestion.name,
            ranking: item.ranking,
            hard: item.hard,
            clay: item.clay,
            grass: item.grass,
            inputName: item.inputName,
          },
        ],
        unmatched: prev.unmatched.filter((u) => u.inputName !== item.inputName),
      };
    });
  }

  function handleCreateParticipant(item: UnmatchedItem) {
    pendingElosByName.current.set(item.inputName, {
      ranking: item.ranking,
      hard: item.hard,
      clay: item.clay,
      grass: item.grass,
    });
    const fd = new FormData();
    fd.set('intent', 'create-participant');
    fd.set('name', item.inputName);
    createFetcher.submit(fd, { method: 'post' });
  }

  function applyMatches() {
    if (!parseResults) return;
    const newValues = { ...eloValues };
    for (const m of parseResults.matched) {
      newValues[m.participantId] = {
        ranking: String(m.ranking),
        hard:    String(m.hard),
        clay:    String(m.clay),
        grass:   String(m.grass),
      };
    }
    setEloValues(newValues);
    setParseResults(null);
    setBulkText('');
  }

  const setField = (participantId: string, field: 'ranking' | 'hard' | 'clay' | 'grass', value: string) => {
    setEloValues((prev) => ({
      ...prev,
      [participantId]: { ...prev[participantId], [field]: value },
    }));
  };

  const isSubmitting = navigation.state === 'submitting';

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

      {/* Bulk Import */}
      <Card className="mb-6">
        <CardHeader>
          <CardTitle>Bulk Import</CardTitle>
          <CardDescription>
            Paste ratings one per line. Format:{' '}
            <code>Player Name, ranking, hardElo, clayElo, grassElo</code>. Player names are
            fuzzy-matched to participants. Rankings are ATP/WTA (1 = world #1). Typical tennis
            Elo ranges: 1400–2200.
          </CardDescription>
        </CardHeader>
        <CardContent className="space-y-4">
          <Textarea
            placeholder={`Carlos Alcaraz, 1, 2180, 2200, 2100\nJannik Sinner, 2, 2190, 2050, 2080\nNovak Djokovic, 3, 2120, 2150, 2090`}
            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 gap-4">
                        <span className="text-muted-foreground">{m.inputName}</span>
                        <span className="font-medium">
                          {m.name} &rarr; #{m.ranking} H:{m.hard} / C:{m.clay} / G:{m.grass}
                        </span>
                      </div>
                    ))}
                  </div>
                </div>
              )}

              {parseResults.unmatched.length > 0 && (
                <div>
                  <div className="flex items-center gap-2 text-sm font-medium text-amber-400 mb-2">
                    <AlertCircle className="h-4 w-4" />
                    Not matched ({parseResults.unmatched.length})
                  </div>
                  <div className="rounded-md border border-amber-500/30 bg-amber-500/10 divide-y divide-amber-500/20 text-sm">
                    {parseResults.unmatched.map((u) => {
                      const isCreating =
                        createFetcher.state !== 'idle' &&
                        pendingElosByName.current.has(u.inputName);
                      return (
                        <div key={u.inputName} className="px-3 py-2 space-y-2">
                          <div className="font-medium text-amber-300">{u.inputName}</div>
                          {u.suggestions.length > 0 ? (
                            <div className="space-y-1">
                              <div className="text-xs text-muted-foreground">Did you mean…</div>
                              {u.suggestions.map((s) => (
                                <div key={s.participantId} className="flex items-center gap-2">
                                  <Button
                                    type="button"
                                    size="sm"
                                    variant="outline"
                                    className="h-6 text-xs px-2"
                                    onClick={() => assignSuggestion(u, s)}
                                  >
                                    Use this
                                  </Button>
                                  <span className="text-muted-foreground">{s.name}</span>
                                  <span className="text-xs text-muted-foreground/60">
                                    ({Math.round(s.score * 100)}% match)
                                  </span>
                                </div>
                              ))}
                              <Button
                                type="button"
                                size="sm"
                                variant="ghost"
                                className="h-6 text-xs px-2 text-amber-400 hover:text-amber-300"
                                disabled={isCreating}
                                onClick={() => handleCreateParticipant(u)}
                              >
                                {isCreating ? (
                                  <><Loader2 className="mr-1 h-3 w-3 animate-spin" /> Creating…</>
                                ) : (
                                  <><UserPlus className="mr-1 h-3 w-3" /> Create new participant</>
                                )}
                              </Button>
                            </div>
                          ) : (
                            <div className="flex items-center gap-2">
                              <span className="text-xs text-muted-foreground">No close matches found.</span>
                              <Button
                                type="button"
                                size="sm"
                                variant="outline"
                                className="h-6 text-xs px-2"
                                disabled={isCreating}
                                onClick={() => handleCreateParticipant(u)}
                              >
                                {isCreating ? (
                                  <><Loader2 className="mr-1 h-3 w-3 animate-spin" /> Creating…</>
                                ) : (
                                  <><UserPlus className="mr-1 h-3 w-3" /> Create participant</>
                                )}
                              </Button>
                            </div>
                          )}
                        </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-3">
        <div className="lg:col-span-2">
          <Card>
            <CardHeader>
              <CardTitle>Player Surface Elo Ratings</CardTitle>
              <CardDescription>
                Enter Elo ratings per surface. Saving will run the simulation and update expected
                values. Leave blank for any surface if you don't have a rating — a fallback of
                1500 will be used.
              </CardDescription>
            </CardHeader>
            <CardContent>
              <Form method="post" className="space-y-4">
                <div className="space-y-1">
                  {/* Header row */}
                  <div className="grid grid-cols-5 gap-3 text-xs font-semibold text-muted-foreground uppercase tracking-wide pb-1 border-b">
                    <span>Player</span>
                    <span>Rank</span>
                    <span>Hard</span>
                    <span>Clay</span>
                    <span>Grass</span>
                  </div>

                  {localParticipants.map((p) => (
                    <div key={p.id} className="grid grid-cols-5 gap-3 items-center py-1">
                      <Label htmlFor={`ranking_${p.id}`} className="truncate text-sm">
                        {p.name}
                      </Label>
                      <Input
                        type="number"
                        id={`ranking_${p.id}`}
                        name={`ranking_${p.id}`}
                        placeholder="1"
                        value={eloValues[p.id]?.ranking ?? ''}
                        onChange={(e) => setField(p.id, 'ranking', e.target.value)}
                        className="h-8 text-sm"
                      />
                      {(['hard', 'clay', 'grass'] as const).map((surface) => (
                        <Input
                          key={surface}
                          type="number"
                          name={`${surface}_${p.id}`}
                          placeholder="1750"
                          value={eloValues[p.id]?.[surface] ?? ''}
                          onChange={(e) => setField(p.id, surface, e.target.value)}
                          className="h-8 text-sm"
                        />
                      ))}
                    </div>
                  ))}
                </div>

                {actionData && !('intent' in 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>
        </div>

        <Card>
          <CardHeader>
            <CardTitle>How It Works</CardTitle>
          </CardHeader>
          <CardContent className="text-sm space-y-2 text-muted-foreground">
            <ol className="list-decimal list-inside space-y-2">
              <li>Enter surface-specific Elo ratings for all players</li>
              <li>For each of 10,000 simulations, simulate all 4 Grand Slams using the appropriate surface Elo</li>
              <li>Top 32 by world ranking are seeded; remaining 96 are drawn randomly</li>
              <li>Per-match win probability: p = 1 / (1 + 10^(−ΔElo/400))</li>
              <li>QP per round: Winner 20, Finalist 14, SF 9, QF 4, R16 1.5</li>
              <li>Players are ranked by total QP across all 4 majors</li>
              <li>Placement probabilities (1st–8th) determine expected fantasy value</li>
            </ol>
            <div className="mt-4 text-xs space-y-1">
              <div className="font-medium text-foreground">Grand Slam surfaces:</div>
              <div>Australian Open — Hard</div>
              <div>French Open — Clay</div>
              <div>Wimbledon — Grass</div>
              <div>US Open — Hard</div>
            </div>
          </CardContent>
        </Card>
      </div>
    </div>
  );
}
