/**
 * LLWS 20-team double-elimination routing — the pure half of the bracket.
 *
 * Lives in lib/ rather than models/ because the renderer needs it: models/playoff-match
 * pulls in the database context and drizzle, which must not reach the browser bundle.
 * models/playoff-match re-exports everything here, so server-side callers are unchanged.
 */

import { llwsMatchNumber, llwsSideAndLocal } from "~/lib/bracket-templates";

/**
 * Where one participant goes after an LLWS match: a round, a side-local match number,
 * and which slot to fill. `null` means eliminated (or, for winners, no further game).
 */
interface LLWSDestination {
  round: string;
  localMatch: number;
  slot: "participant1Id" | "participant2Id";
}

/**
 * LLWS advancement map, in SIDE-LOCAL match numbers.
 *
 * Keyed by round, then by the local match number of the completed game. Each entry
 * says where the winner goes and where the loser goes (null = eliminated).
 *
 * Verified game-by-game against the official 2026 LLBWS bracket. Note the deliberate
 * cross-overs — the elimination bracket does NOT feed straight across:
 *   Elim R1:  L(Opening m2) v L(Opening m3)  and  L(Opening m1) v L(Opening m4)
 *   Elim R3:  L(Semi m1) v W(Elim R2 m2)     and  L(Semi m2) v W(Elim R2 m1)
 *   Elim R4:  W(Elim R3 m1) v W(Elim R3 m2)
 *
 * A loss in the winners bracket routes into the elimination bracket rather than
 * eliminating the team; a loss in the elimination bracket is final.
 */
const LLWS_ADVANCEMENT: Record<
  string,
  Record<number, { winner: LLWSDestination | null; loser: LLWSDestination | null }>
> = {
  "Opening Round": {
    1: {
      winner: { round: "Winners Round 2", localMatch: 1, slot: "participant2Id" },
      loser: { round: "Elimination Round 1", localMatch: 2, slot: "participant1Id" },
    },
    2: {
      winner: { round: "Winners Round 2", localMatch: 2, slot: "participant2Id" },
      loser: { round: "Elimination Round 1", localMatch: 1, slot: "participant1Id" },
    },
    3: {
      winner: { round: "Winners Semifinals", localMatch: 1, slot: "participant1Id" },
      loser: { round: "Elimination Round 1", localMatch: 1, slot: "participant2Id" },
    },
    4: {
      winner: { round: "Winners Semifinals", localMatch: 2, slot: "participant2Id" },
      loser: { round: "Elimination Round 1", localMatch: 2, slot: "participant2Id" },
    },
  },
  "Winners Round 2": {
    1: {
      winner: { round: "Winners Semifinals", localMatch: 1, slot: "participant2Id" },
      loser: { round: "Elimination Round 2", localMatch: 1, slot: "participant1Id" },
    },
    2: {
      winner: { round: "Winners Semifinals", localMatch: 2, slot: "participant1Id" },
      loser: { round: "Elimination Round 2", localMatch: 2, slot: "participant1Id" },
    },
  },
  "Winners Semifinals": {
    1: {
      winner: { round: "Winners Final", localMatch: 1, slot: "participant1Id" },
      loser: { round: "Elimination Round 3", localMatch: 1, slot: "participant1Id" },
    },
    2: {
      winner: { round: "Winners Final", localMatch: 1, slot: "participant2Id" },
      loser: { round: "Elimination Round 3", localMatch: 2, slot: "participant1Id" },
    },
  },
  "Winners Final": {
    1: {
      winner: { round: "Bracket Championship", localMatch: 1, slot: "participant1Id" },
      // A winners-bracket final loss is not an elimination — it drops to the
      // Elimination Final for a second chance at the side championship.
      loser: { round: "Elimination Final", localMatch: 1, slot: "participant1Id" },
    },
  },
  "Elimination Round 1": {
    1: {
      winner: { round: "Elimination Round 2", localMatch: 1, slot: "participant2Id" },
      loser: null,
    },
    2: {
      winner: { round: "Elimination Round 2", localMatch: 2, slot: "participant2Id" },
      loser: null,
    },
  },
  "Elimination Round 2": {
    // Cross-over: R2 m1's winner meets the OTHER semifinal loser.
    1: {
      winner: { round: "Elimination Round 3", localMatch: 2, slot: "participant2Id" },
      loser: null,
    },
    2: {
      winner: { round: "Elimination Round 3", localMatch: 1, slot: "participant2Id" },
      loser: null,
    },
  },
  "Elimination Round 3": {
    // The later game (m2) is printed on top: G32 = W28 v W26, G31 = W27 v W25.
    1: {
      winner: { round: "Elimination Round 4", localMatch: 1, slot: "participant2Id" },
      loser: null,
    },
    2: {
      winner: { round: "Elimination Round 4", localMatch: 1, slot: "participant1Id" },
      loser: null,
    },
  },
  "Elimination Round 4": {
    1: {
      winner: { round: "Elimination Final", localMatch: 1, slot: "participant2Id" },
      loser: null,
    },
  },
  "Elimination Final": {
    1: {
      winner: { round: "Bracket Championship", localMatch: 1, slot: "participant2Id" },
      loser: null,
    },
  },
};

/** Rounds whose losers drop into the elimination bracket instead of going out. */
export const LLWS_LOSER_ADVANCES_ROUNDS = new Set([
  "Opening Round",
  "Winners Round 2",
  "Winners Semifinals",
]);

/** A resolved LLWS destination, in global (not side-local) match numbers. */
export interface LLWSResolvedDestination {
  round: string;
  matchNumber: number;
  slot: "participant1Id" | "participant2Id";
}

/**
 * Resolve where the winner and loser of a completed LLWS match go, in global match
 * numbers. `null` means that participant has no further game (eliminated, or the
 * tournament is over for them).
 *
 * Pure — no DB access — so the whole 38-game routing can be verified against the
 * official bracket in tests. advanceLLWSWinner is a thin writer on top of this.
 */
export function resolveLLWSAdvancement(
  round: string,
  matchNumber: number
): { winner: LLWSResolvedDestination | null; loser: LLWSResolvedDestination | null } {
  // Terminal rounds — nobody advances.
  if (round === "Consolation Third Place" || round === "World Championship") {
    return { winner: null, loser: null };
  }

  // Bracket Championship is the crossover: the winner goes to the World Championship
  // and the loser to the Consolation game. The side fixes the slot in both (U.S. takes
  // participant1, International participant2), so the two sides can't collide.
  if (round === "Bracket Championship") {
    const { side } = llwsSideAndLocal("Bracket Championship", matchNumber);
    const slot: "participant1Id" | "participant2Id" =
      side === 0 ? "participant1Id" : "participant2Id";
    return {
      winner: { round: "World Championship", matchNumber: 1, slot },
      loser: { round: "Consolation Third Place", matchNumber: 1, slot },
    };
  }

  const roundMap = LLWS_ADVANCEMENT[round];
  if (!roundMap) {
    throw new Error(`Round '${round}' is not part of the LLWS bracket`);
  }

  const { side, localMatch } = llwsSideAndLocal(round, matchNumber);
  const routes = roundMap[localMatch];
  if (!routes) {
    throw new Error(`No LLWS advancement defined for ${round} match ${matchNumber}`);
  }

  // Winner and loser stay on their own side, so the same side offset applies to both.
  const toGlobal = (d: LLWSDestination | null): LLWSResolvedDestination | null =>
    d === null
      ? null
      : { round: d.round, matchNumber: llwsMatchNumber(d.round, side, d.localMatch), slot: d.slot };

  return { winner: toGlobal(routes.winner), loser: toGlobal(routes.loser) };
}