sendou.ink/app/modules/brackets-manager/find.ts

import type { Group, Match } from "~/modules/brackets-model";
import { BaseGetter } from "./base/getter";
import * as helpers from "./helpers";

export class Find extends BaseGetter {
  /**
   * Gets the upper bracket (the only bracket if single elimination or the winner bracket in double elimination).
   *
   * @param stageId ID of the stage.
   */
  public upperBracket(stageId: number): Group {
    const stage = this.storage.select("stage", stageId);
    if (!stage) throw Error("Stage not found.");

    switch (stage.type) {
      case "round_robin":
        throw Error("Round-robin stages do not have an upper bracket.");
      case "single_elimination":
      case "double_elimination":
        return this.getUpperBracket(stageId);
      default:
        throw Error("Unknown stage type.");
    }
  }

  /**
   * Gets the loser bracket.
   *
   * @param stageId ID of the stage.
   */
  public loserBracket(stageId: number): Group {
    const stage = this.storage.select("stage", stageId);
    if (!stage) throw Error("Stage not found.");

    switch (stage.type) {
      case "round_robin":
        throw Error("Round-robin stages do not have a loser bracket.");
      case "single_elimination":
        throw Error("Single elimination stages do not have a loser bracket.");
      case "double_elimination":
        // eslint-disable-next-line no-case-declarations
        const group = this.getLoserBracket(stageId);
        if (!group) throw Error("Loser bracket not found.");
        return group;
      default:
        throw Error("Unknown stage type.");
    }
  }

  /**
   * Returns the matches leading to the given match.
   *
   * If a `participantId` is given, the previous match _from their point of view_ is returned.
   *
   * @param matchId ID of the target match.
   * @param participantId Optional ID of the participant.
   */
  public previousMatches(matchId: number, participantId?: number): Match[] {
    const match = this.storage.select("match", matchId);
    if (!match) throw Error("Match not found.");

    const stage = this.storage.select("stage", match.stage_id);
    if (!stage) throw Error("Stage not found.");

    const group = this.storage.select("group", match.group_id);
    if (!group) throw Error("Group not found.");

    const round = this.storage.select("round", match.round_id);
    if (!round) throw Error("Round not found.");

    const matchLocation = helpers.getMatchLocation(stage.type, group.number);
    const previousMatches = this.getPreviousMatches(
      match,
      matchLocation,
      stage,
      round.number,
    );

    if (participantId !== undefined)
      return previousMatches.filter((m) =>
        helpers.isParticipantInMatch(m, participantId),
      );

    return previousMatches;
  }

  /**
   * Returns the matches following the given match.
   *
   * If a `participantId` is given:
   * - If the participant won, the next match _from their point of view_ is returned.
   * - If the participant is eliminated, no match is returned.
   *
   * @param matchId ID of the target match.
   * @param participantId Optional ID of the participant.
   */
  public nextMatches(matchId: number, participantId?: number): Match[] {
    const match = this.storage.select("match", matchId);
    if (!match) throw Error("Match not found.");

    const stage = this.storage.select("stage", match.stage_id);
    if (!stage) throw Error("Stage not found.");

    const group = this.storage.select("group", match.group_id);
    if (!group) throw Error("Group not found.");

    const { roundNumber, roundCount } = this.getRoundPositionalInfo(
      match.round_id,
    );
    const matchLocation = helpers.getMatchLocation(stage.type, group.number);

    const nextMatches = helpers.getNonNull(
      this.getNextMatches(match, matchLocation, stage, roundNumber, roundCount),
    );

    if (participantId !== undefined) {
      const loser = helpers.getLoser(match);
      if (stage.type === "single_elimination" && loser?.id === participantId)
        return []; // Eliminated.

      if (stage.type === "double_elimination") {
        const [upperBracketMatch, lowerBracketMatch] = nextMatches;

        if (loser?.id === participantId) {
          if (lowerBracketMatch) return [lowerBracketMatch];
          else return []; // Eliminated from lower bracket.
        }

        const winner = helpers.getWinner(match);
        if (winner?.id === participantId) return [upperBracketMatch];

        throw Error("The participant does not belong to this match.");
      }
    }

    return nextMatches;
  }

  /**
   * Finds a match in a given group. The match must have the given number in a round of which the number in group is given.
   *
   * **Example:** In group of id 1, give me the 4th match in the 3rd round.
   *
   * @param groupId ID of the group.
   * @param roundNumber Number of the round in its parent group.
   * @param matchNumber Number of the match in its parent round.
   */
  public match(
    groupId: number,
    roundNumber: number,
    matchNumber: number,
  ): Match {
    return this.findMatch(groupId, roundNumber, matchNumber);
  }
}