import { database } from "~/database/context";
import * as schema from "~/database/schema";
import { eq } from "drizzle-orm";
import { DEFAULT_SCORING_RULES, type ScoringRules } from "~/lib/scoring-types";

// Re-export for convenience
export { DEFAULT_SCORING_RULES, type ScoringRules };

/**
 * Get scoring rules for a season
 */
export async function getScoringRules(
  seasonId: string,
  providedDb?: ReturnType<typeof database>
): Promise<ScoringRules | null> {
  const db = providedDb || database();

  const season = await db.query.seasons.findFirst({
    where: eq(schema.seasons.id, seasonId),
  });

  if (!season) {
    return null;
  }

  return {
    pointsFor1st: season.pointsFor1st,
    pointsFor2nd: season.pointsFor2nd,
    pointsFor3rd: season.pointsFor3rd,
    pointsFor4th: season.pointsFor4th,
    pointsFor5th: season.pointsFor5th,
    pointsFor6th: season.pointsFor6th,
    pointsFor7th: season.pointsFor7th,
    pointsFor8th: season.pointsFor8th,
  };
}

/**
 * Update scoring rules for a season
 */
export async function updateScoringRules(
  seasonId: string,
  rules: Partial<ScoringRules>,
  providedDb?: ReturnType<typeof database>
): Promise<ScoringRules> {
  const db = providedDb || database();

  const [updated] = await db
    .update(schema.seasons)
    .set(rules)
    .where(eq(schema.seasons.id, seasonId))
    .returning({
      pointsFor1st: schema.seasons.pointsFor1st,
      pointsFor2nd: schema.seasons.pointsFor2nd,
      pointsFor3rd: schema.seasons.pointsFor3rd,
      pointsFor4th: schema.seasons.pointsFor4th,
      pointsFor5th: schema.seasons.pointsFor5th,
      pointsFor6th: schema.seasons.pointsFor6th,
      pointsFor7th: schema.seasons.pointsFor7th,
      pointsFor8th: schema.seasons.pointsFor8th,
    });

  return updated;
}

/**
 * Calculate fantasy points for a given placement based on season scoring rules
 */
export function calculateFantasyPoints(
  placement: number,
  rules: ScoringRules
): number {
  const pointsMap: Record<number, number> = {
    1: rules.pointsFor1st,
    2: rules.pointsFor2nd,
    3: rules.pointsFor3rd,
    4: rules.pointsFor4th,
    5: rules.pointsFor5th,
    6: rules.pointsFor6th,
    7: rules.pointsFor7th,
    8: rules.pointsFor8th,
  };

  return pointsMap[placement] || 0;
}

/**
 * Calculate averaged points for shared placements (e.g., playoff ties)
 * Used when multiple participants share positions
 *
 * Example: 4 teams lose in quarterfinals, they share positions 5-8
 * Average = (25 + 25 + 15 + 15) / 4 = 20 points each
 *
 * The result is rounded to the nearest whole point, matching the published rule
 * on the /rules page: "the points for all tied positions are combined and split
 * equally among them, rounded to the nearest whole point". That page's own
 * example rounds down — a three-way tie for 6th–8th is (25 + 15 + 15) / 3 =
 * 18.33 → 18 — so this is nearest, not ceiling. Season point values are integer
 * columns, so this averaging is the only place fractional points can arise.
 */
export function calculateAveragedPoints(
  placements: number[],
  rules: ScoringRules
): number {
  if (placements.length === 0) return 0;

  const total = placements.reduce((sum, placement) => {
    return sum + calculateFantasyPoints(placement, rules);
  }, 0);

  // Epsilon guard mirrors roundQualifyingPoints — keeps values that are exactly
  // representable-adjacent (e.g. 18.499999999999996) from rounding the wrong way.
  return Math.round(total / placements.length + Number.EPSILON);
}

/**
 * Calculate points for participants sharing a standings placement.
 *
 * Example: two participants tied for 2nd share 2nd and 3rd place points.
 * If a tie extends beyond the scoring range, the extra slots contribute 0.
 */
export function calculateSharedPlacementPoints(
  startPlacement: number,
  tiedParticipants: number,
  rules: ScoringRules
): number {
  if (startPlacement <= 0 || tiedParticipants <= 0) return 0;

  const placements = Array.from(
    { length: tiedParticipants },
    (_, index) => startPlacement + index
  );

  return calculateAveragedPoints(placements, rules);
}

/**
 * Tier definitions for brackets where positions 5–8 split into two separate pairs.
 *
 * Most brackets (standard single-elimination) have ONE tier covering positions 5–8:
 * four QF losers all tie and share the combined prize pool → avg([5,6,7,8]).
 *
 * AFL is different: it has TWO distinct tiers in the 5–8 zone:
 *   - T5-T6: Semi-Finals losers (positions 5 and 6) → avg([5,6])
 *   - T7-T8: Elimination Finals losers (positions 7 and 8) → avg([7,8])
 *
 * LLWS has the same shape from its two elimination brackets:
 *   - T5-T6: Elimination Final losers (one per side) → avg([5,6])
 *   - T7-T8: Elimination Round 4 losers (one per side) → avg([7,8])
 */
const SPLIT_5678_TEMPLATE_IDS = new Set(["afl_10", "llws_20"]);

/**
 * Brackets with a real 3rd place game, meaning positions 3 and 4 are distinct
 * (not averaged). Standard brackets average them because both SF losers tie.
 *
 * llws_20's Consolation Third Place game decides 3rd and 4th head-to-head between
 * the two side runners-up.
 */
const DISTINCT_34_TEMPLATE_IDS = new Set(["fifa_48", "llws_20"]);

/**
 * Calculate fantasy points for a bracket placement, averaging tied positions.
 *
 * Standard single-elimination bracket tiers:
 *   1st: solo winner
 *   2nd: solo finalist
 *   3rd-4th: two SF losers share these positions → averaged
 *   5th-8th: four QF losers share these positions → averaged
 *
 * AFL bracket tiers (afl_10):
 *   5th-6th: Semi-Finals losers → averaged separately from 7th-8th
 *   7th-8th: Elimination Finals losers → averaged separately from 5th-6th
 *
 * Use this instead of calculateFantasyPoints for playoff_bracket scoring.
 */
export function calculateBracketPoints(
  finalPosition: number,
  rules: ScoringRules,
  bracketTemplateId?: string | null
): number {
  if (finalPosition <= 0) return 0;
  if (finalPosition === 1) return rules.pointsFor1st;
  if (finalPosition === 2) return rules.pointsFor2nd;
  if (finalPosition === 3 || finalPosition === 4) {
    if (bracketTemplateId && DISTINCT_34_TEMPLATE_IDS.has(bracketTemplateId))
      return finalPosition === 3 ? rules.pointsFor3rd : rules.pointsFor4th;
    return calculateAveragedPoints([3, 4], rules);
  }
  if (finalPosition >= 5 && finalPosition <= 8) {
    if (bracketTemplateId && SPLIT_5678_TEMPLATE_IDS.has(bracketTemplateId)) {
      // AFL-style: two separate 2-team tiers within 5–8
      if (finalPosition <= 6) return calculateAveragedPoints([5, 6], rules);
      return calculateAveragedPoints([7, 8], rules);
    }
    // Standard: all four QF losers share one tier
    return calculateAveragedPoints([5, 6, 7, 8], rules);
  }
  return 0;
}

/**
 * Fantasy points earned by a single drafted participant, for any scoring pattern.
 *
 * This is the ONE place the bracket / qualifying_points / default cascade lives.
 * It previously existed as a hand-rolled if/else at six call sites, two of which
 * were missing the qualifying_points arm entirely — that divergence is what made
 * a tied golfer worth 15 points on the team page and draft board but 7.5 in the
 * standings. Every caller must route through here.
 *
 * @param finalPosition - Placement in the sports season (1-8 scores, 0 = none).
 * @param scoringPattern - The sports season's scoringPattern column.
 * @param rules - The fantasy season's point values.
 * @param opts.bracketTemplateId - Required for playoff_bracket to pick the right
 *   tier structure (e.g. AFL/LLWS split 5–8 into two pairs).
 * @param opts.tiedParticipants - Required for qualifying_points: how many
 *   participants share this finalPosition across the WHOLE sports season, not
 *   just the ones that were drafted. Defaults to 1 (no tie).
 */
export function calculatePickPoints(
  finalPosition: number,
  scoringPattern: string | null | undefined,
  rules: ScoringRules,
  opts?: { bracketTemplateId?: string | null; tiedParticipants?: number }
): number {
  if (scoringPattern === "playoff_bracket") {
    return calculateBracketPoints(finalPosition, rules, opts?.bracketTemplateId ?? null);
  }
  if (scoringPattern === "qualifying_points") {
    return calculateSharedPlacementPoints(
      finalPosition,
      opts?.tiedParticipants ?? 1,
      rules
    );
  }
  return calculateFantasyPoints(finalPosition, rules);
}

/**
 * Get points array as a simple ordered list [1st, 2nd, 3rd, ..., 8th]
 * Useful for display purposes
 */
export function getScoringRulesArray(rules: ScoringRules): number[] {
  return [
    rules.pointsFor1st,
    rules.pointsFor2nd,
    rules.pointsFor3rd,
    rules.pointsFor4th,
    rules.pointsFor5th,
    rules.pointsFor6th,
    rules.pointsFor7th,
    rules.pointsFor8th,
  ];
}