import { v4 as uuidv4 } from 'uuid';
import { League } from '../../domain/entities/League';
import { Season } from '../../domain/entities/Season';
import type { ILeagueRepository } from '../../domain/repositories/ILeagueRepository';
import type { ISeasonRepository } from '../../domain/repositories/ISeasonRepository';
import type { ILeagueScoringConfigRepository } from '../../domain/repositories/ILeagueScoringConfigRepository';
import type { LeagueScoringConfig } from '../../domain/entities/LeagueScoringConfig';
import type { AsyncUseCase } from '@gridpilot/shared/application';
import type {
  LeagueScoringPresetProvider,
  LeagueScoringPresetDTO,
} from '../ports/LeagueScoringPresetProvider';
import {
  LeagueVisibility,
  MIN_RANKED_LEAGUE_DRIVERS,
} from '../../domain/value-objects/LeagueVisibility';

/**
 * League visibility/ranking mode.
 * - 'ranked' (or legacy 'public'): Competitive, public, affects driver ratings. Min 10 drivers.
 * - 'unranked' (or legacy 'private'): Casual with friends, no rating impact.
 */
export type LeagueVisibilityInput = 'ranked' | 'unranked' | 'public' | 'private';

export interface CreateLeagueWithSeasonAndScoringCommand {
  name: string;
  description?: string;
  /**
   * League visibility/ranking mode.
   * - 'ranked' (or legacy 'public'): Competitive, public, affects ratings. Requires min 10 drivers.
   * - 'unranked' (or legacy 'private'): Casual with friends, no rating impact.
   */
  visibility: LeagueVisibilityInput;
  ownerId: string;
  gameId: string;
  maxDrivers?: number;
  maxTeams?: number;
  enableDriverChampionship: boolean;
  enableTeamChampionship: boolean;
  enableNationsChampionship: boolean;
  enableTrophyChampionship: boolean;
  scoringPresetId?: string;
}

export interface CreateLeagueWithSeasonAndScoringResultDTO {
  leagueId: string;
  seasonId: string;
  scoringPresetId?: string;
  scoringPresetName?: string;
}

export class CreateLeagueWithSeasonAndScoringUseCase
  implements AsyncUseCase<CreateLeagueWithSeasonAndScoringCommand, CreateLeagueWithSeasonAndScoringResultDTO> {
  constructor(
    private readonly leagueRepository: ILeagueRepository,
    private readonly seasonRepository: ISeasonRepository,
    private readonly leagueScoringConfigRepository: ILeagueScoringConfigRepository,
    private readonly presetProvider: LeagueScoringPresetProvider,
  ) {}

  async execute(
    command: CreateLeagueWithSeasonAndScoringCommand,
  ): Promise<CreateLeagueWithSeasonAndScoringResultDTO> {
    this.validate(command);

    const leagueId = uuidv4();

    const league = League.create({
      id: leagueId,
      name: command.name,
      description: command.description ?? '',
      ownerId: command.ownerId,
      settings: {
        // Presets are attached at scoring-config level; league settings use a stable points system id.
        pointsSystem: 'custom',
        ...(command.maxDrivers !== undefined ? { maxDrivers: command.maxDrivers } : {}),
      },
    });

    await this.leagueRepository.create(league);

    const seasonId = uuidv4();
    const season = Season.create({
      id: seasonId,
      leagueId: league.id,
      gameId: command.gameId,
      name: `${command.name} Season 1`,
      year: new Date().getFullYear(),
      order: 1,
      status: 'active',
      startDate: new Date(),
      endDate: new Date(),
    });

    await this.seasonRepository.create(season);

    const presetId = command.scoringPresetId ?? 'club-default';
    const preset: LeagueScoringPresetDTO | undefined =
      this.presetProvider.getPresetById(presetId);

    if (!preset) {
      throw new Error(`Unknown scoring preset: ${presetId}`);
    }

    const scoringConfig: LeagueScoringConfig = {
      id: uuidv4(),
      seasonId,
      scoringPresetId: preset.id,
      championships: [],
    };

    // For the initial alpha slice, we keep using the preset's config shape from the in-memory registry.
    // The preset registry is responsible for building the full LeagueScoringConfig; we only attach the preset id here.
    const fullConfigFactory = (await import(
      '../../infrastructure/repositories/InMemoryScoringRepositories'
    )) as typeof import('../../infrastructure/repositories/InMemoryScoringRepositories');

    const presetFromInfra = fullConfigFactory.getLeagueScoringPresetById(
      preset.id,
    );
    if (!presetFromInfra) {
      throw new Error(`Preset registry missing preset: ${preset.id}`);
    }

    const infraConfig = presetFromInfra.createConfig({ seasonId });
    const finalConfig: LeagueScoringConfig = {
      ...infraConfig,
      scoringPresetId: preset.id,
    };

    await this.leagueScoringConfigRepository.save(finalConfig);

    return {
      leagueId: league.id,
      seasonId,
      scoringPresetId: preset.id,
      scoringPresetName: preset.name,
    };
  }

  private validate(command: CreateLeagueWithSeasonAndScoringCommand): void {
    if (!command.name || command.name.trim().length === 0) {
      throw new Error('League name is required');
    }
    if (!command.ownerId || command.ownerId.trim().length === 0) {
      throw new Error('League ownerId is required');
    }
    if (!command.gameId || command.gameId.trim().length === 0) {
      throw new Error('gameId is required');
    }
    if (!command.visibility) {
      throw new Error('visibility is required');
    }
    if (command.maxDrivers !== undefined && command.maxDrivers <= 0) {
      throw new Error('maxDrivers must be greater than 0 when provided');
    }

    // Validate visibility-specific constraints
    const visibility = LeagueVisibility.fromString(command.visibility);
    
    if (visibility.isRanked()) {
      // Ranked (public) leagues require minimum 10 drivers for competitive integrity
      const driverCount = command.maxDrivers ?? 0;
      if (driverCount < MIN_RANKED_LEAGUE_DRIVERS) {
        throw new Error(
          `Ranked leagues require at least ${MIN_RANKED_LEAGUE_DRIVERS} drivers. ` +
          `Current setting: ${driverCount}. ` +
          `For smaller groups, consider creating an Unranked (Friends) league instead.`
        );
      }
    }
  }
}