/**
 * Phase 2 one-off backfill: populate canonical tables
 * (`tournaments`, `participants`, `tournament_results`,
 * `participant_surface_elos`) from existing per-window data.
 *
 * See CLAUDE.md and the Phase 2 plan docs. Rules that this script
 * MUST obey:
 *   - Never copy `qualifying_points_awarded` from `event_results` to
 *     `tournament_results`. QP stays per-window.
 *   - Never touch `season_participant_qualifying_totals`.
 *   - Abort loud (collect into `report.errors`) if two windows disagree
 *     on a canonical participant's surface-Elo values.
 *
 * `dryRun: true` means: run every read, compute every count, but never
 * issue an `insert()` or `update()`.
 */

import { eq, and, isNull } from "drizzle-orm";

import { database } from "~/database/context";
import * as schema from "~/database/schema";

import { extractTournamentIdentity } from "./backfill/match-tournament";

export interface BackfillOptions {
  dryRun: boolean;
  sportId?: string;
}

export interface BackfillReport {
  tournamentsCreated: number;
  /** Count of scoring_events whose tournament_id was (or would be) set. */
  tournamentsLinked: number;
  participantsCreated: number;
  /** Count of season_participants whose participant_id was (or would be) set. */
  participantsLinked: number;
  tournamentResultsCreated: number;
  surfaceElosCreated: number;
  warnings: string[];
  errors: string[];
}

type Db = ReturnType<typeof database>;
type SportsSeasonRow = typeof schema.sportsSeasons.$inferSelect;
type ScoringEventRow = typeof schema.scoringEvents.$inferSelect;
type SeasonParticipantRow = typeof schema.seasonParticipants.$inferSelect;
type EventResultRow = typeof schema.eventResults.$inferSelect;
type SeasonParticipantSurfaceEloRow =
  typeof schema.seasonParticipantSurfaceElos.$inferSelect;
type TournamentRow = typeof schema.tournaments.$inferSelect;
type ParticipantRow = typeof schema.participants.$inferSelect;
type TournamentResultRow = typeof schema.tournamentResults.$inferSelect;
type ParticipantSurfaceEloRow =
  typeof schema.participantSurfaceElos.$inferSelect;

export async function runBackfill(
  opts: BackfillOptions,
): Promise<BackfillReport> {
  const report: BackfillReport = {
    tournamentsCreated: 0,
    tournamentsLinked: 0,
    participantsCreated: 0,
    participantsLinked: 0,
    tournamentResultsCreated: 0,
    surfaceElosCreated: 0,
    warnings: [],
    errors: [],
  };

  const db = database();

  // 1. Load qualifying-points seasons (optionally filtered by sport).
  const whereClauses = [
    eq(schema.sportsSeasons.scoringPattern, "qualifying_points"),
  ];
  if (opts.sportId) {
    whereClauses.push(eq(schema.sportsSeasons.sportId, opts.sportId));
  }

  const seasons = (await db
    .select()
    .from(schema.sportsSeasons)
    .where(and(...whereClauses))) as SportsSeasonRow[];

  for (const season of seasons) {
    await backfillSeason(db, season, opts, report);
  }

  return report;
}

async function backfillSeason(
  db: Db,
  season: SportsSeasonRow,
  opts: BackfillOptions,
  report: BackfillReport,
): Promise<void> {
  // ─── a. Tournament linking ────────────────────────────────────────────────
  const unlinkedEvents = (await db
    .select()
    .from(schema.scoringEvents)
    .where(
      and(
        eq(schema.scoringEvents.sportsSeasonId, season.id),
        isNull(schema.scoringEvents.tournamentId),
      ),
    )) as ScoringEventRow[];

  for (const ev of unlinkedEvents) {
    let identity;
    try {
      identity = extractTournamentIdentity({
        name: ev.name,
        eventDate: ev.eventDate,
        eventType: ev.eventType,
      });
    } catch (e) {
      report.warnings.push(
        `skip scoring_event ${ev.id} (${ev.name}): ${(e as Error).message}`,
      );
      continue;
    }

    // Look up existing canonical tournament.
    const [existing] = (await db
      .select()
      .from(schema.tournaments)
      .where(
        and(
          eq(schema.tournaments.sportId, season.sportId),
          eq(schema.tournaments.name, identity.name),
          eq(schema.tournaments.year, identity.year),
        ),
      )
      .limit(1)) as TournamentRow[];

    let tournamentId: string | undefined = existing?.id;

    if (!existing) {
      const startsAt = ev.eventDate ? new Date(ev.eventDate) : null;
      const status =
        startsAt && startsAt.getTime() < Date.now() ? "completed" : "scheduled";

      if (!opts.dryRun) {
        const [inserted] = (await db
          .insert(schema.tournaments)
          .values({
            sportId: season.sportId,
            name: identity.name,
            year: identity.year,
            startsAt,
            status,
          })
          .returning()) as TournamentRow[];
        tournamentId = inserted.id;
      }
      report.tournamentsCreated += 1;
    }

    if (!opts.dryRun && tournamentId) {
      await db
        .update(schema.scoringEvents)
        .set({ tournamentId, updatedAt: new Date() })
        .where(eq(schema.scoringEvents.id, ev.id));
    }
    report.tournamentsLinked += 1;
  }

  // ─── b. Participant linking ───────────────────────────────────────────────
  const unlinkedParticipants = (await db
    .select()
    .from(schema.seasonParticipants)
    .where(
      and(
        eq(schema.seasonParticipants.sportsSeasonId, season.id),
        isNull(schema.seasonParticipants.participantId),
      ),
    )) as SeasonParticipantRow[];

  for (const sp of unlinkedParticipants) {
    const [existing] = (await db
      .select()
      .from(schema.participants)
      .where(
        and(
          eq(schema.participants.sportId, season.sportId),
          eq(schema.participants.name, sp.name),
        ),
      )
      .limit(1)) as ParticipantRow[];

    let participantId: string | undefined = existing?.id;

    if (!existing) {
      if (!opts.dryRun) {
        const [inserted] = (await db
          .insert(schema.participants)
          .values({
            sportId: season.sportId,
            name: sp.name,
          })
          .returning()) as ParticipantRow[];
        participantId = inserted.id;
      }
      report.participantsCreated += 1;
    }

    if (!opts.dryRun && participantId) {
      await db
        .update(schema.seasonParticipants)
        .set({ participantId, updatedAt: new Date() })
        .where(eq(schema.seasonParticipants.id, sp.id));
    }
    report.participantsLinked += 1;
  }

  // ─── c. Tournament results (copy completed event_results) ────────────────
  // Refetch events — they may now have tournamentId set (if !dryRun).
  const allEvents = (await db
    .select()
    .from(schema.scoringEvents)
    .where(
      eq(schema.scoringEvents.sportsSeasonId, season.id),
    )) as ScoringEventRow[];

  for (const ev of allEvents) {
    if (!ev.tournamentId) {
      // In dry-run we may not have a tournamentId yet; skip result copy.
      continue;
    }

    const results = (await db
      .select()
      .from(schema.eventResults)
      .where(
        eq(schema.eventResults.scoringEventId, ev.id),
      )) as EventResultRow[];

    for (const r of results) {
      // Only copy rows with real placement/rawScore data.
      if (r.placement == null && r.rawScore == null) {
        continue;
      }

      // Look up the season_participants row to get canonical participantId.
      const [sp] = (await db
        .select()
        .from(schema.seasonParticipants)
        .where(
          eq(schema.seasonParticipants.id, r.seasonParticipantId),
        )
        .limit(1)) as SeasonParticipantRow[];

      if (!sp || !sp.participantId) {
        // Link step should have handled this; skip defensively.
        continue;
      }

      // Check if a tournament_results row already exists.
      const [existingResult] = (await db
        .select()
        .from(schema.tournamentResults)
        .where(
          and(
            eq(schema.tournamentResults.tournamentId, ev.tournamentId),
            eq(schema.tournamentResults.participantId, sp.participantId),
          ),
        )
        .limit(1)) as TournamentResultRow[];

      if (existingResult) {
        continue;
      }

      if (!opts.dryRun) {
        // NOTE: intentionally do NOT copy qualifyingPointsAwarded.
        await db.insert(schema.tournamentResults).values({
          tournamentId: ev.tournamentId,
          participantId: sp.participantId,
          placement: r.placement,
          rawScore: r.rawScore,
        });
      }
      report.tournamentResultsCreated += 1;
    }
  }

  // ─── d. Surface Elo (per-window → canonical) ─────────────────────────────
  const elos = (await db
    .select()
    .from(schema.seasonParticipantSurfaceElos)
    .where(
      eq(schema.seasonParticipantSurfaceElos.sportsSeasonId, season.id),
    )) as SeasonParticipantSurfaceEloRow[];

  for (const elo of elos) {
    const [sp] = (await db
      .select()
      .from(schema.seasonParticipants)
      .where(
        eq(schema.seasonParticipants.id, elo.participantId),
      )
      .limit(1)) as SeasonParticipantRow[];

    if (!sp || !sp.participantId) {
      continue;
    }

    const canonicalParticipantId = sp.participantId;

    const [existingElo] = (await db
      .select()
      .from(schema.participantSurfaceElos)
      .where(
        eq(
          schema.participantSurfaceElos.participantId,
          canonicalParticipantId,
        ),
      )
      .limit(1)) as ParticipantSurfaceEloRow[];

    if (existingElo) {
      // Conflict detection: compare eloHard/eloClay/eloGrass/worldRanking.
      const fields: Array<keyof ParticipantSurfaceEloRow> = [
        "eloHard",
        "eloClay",
        "eloGrass",
        "worldRanking",
      ];
      const mismatches: string[] = [];
      for (const f of fields) {
        if (existingElo[f] !== elo[f as keyof SeasonParticipantSurfaceEloRow]) {
          mismatches.push(
            `${f}: existing=${String(existingElo[f])} vs incoming=${String(elo[f as keyof SeasonParticipantSurfaceEloRow])}`,
          );
        }
      }
      if (mismatches.length > 0) {
        report.errors.push(
          `conflict for participant ${canonicalParticipantId} (season ${season.id}): ${mismatches.join(", ")}`,
        );
      }
      // Do not overwrite.
      continue;
    }

    if (!opts.dryRun) {
      await db.insert(schema.participantSurfaceElos).values({
        participantId: canonicalParticipantId,
        eloHard: elo.eloHard,
        eloClay: elo.eloClay,
        eloGrass: elo.eloGrass,
        worldRanking: elo.worldRanking,
      });
    }
    report.surfaceElosCreated += 1;
  }
}