import { eq, and } from "drizzle-orm";
import { database } from "~/database/context";
import * as schema from "~/database/schema";
import type { BracketTemplate } from "~/lib/bracket-templates";
import { getBracketTemplate } from "~/lib/bracket-templates";

export type PlayoffMatch = typeof schema.playoffMatches.$inferSelect;
export type NewPlayoffMatch = typeof schema.playoffMatches.$inferInsert;

export async function createPlayoffMatch(
  data: NewPlayoffMatch
): Promise<PlayoffMatch> {
  const db = database();
  const [match] = await db
    .insert(schema.playoffMatches)
    .values(data)
    .returning();
  return match;
}

export async function createManyPlayoffMatches(
  data: NewPlayoffMatch[]
): Promise<PlayoffMatch[]> {
  const db = database();
  return await db
    .insert(schema.playoffMatches)
    .values(data)
    .returning();
}

export async function findPlayoffMatchById(
  id: string
): Promise<PlayoffMatch | undefined> {
  const db = database();
  return await db.query.playoffMatches.findFirst({
    where: eq(schema.playoffMatches.id, id),
    with: {
      scoringEvent: true,
      participant1: true,
      participant2: true,
      winner: true,
      loser: true,
    },
  });
}

export async function findPlayoffMatchesByEventId(
  eventId: string
): Promise<PlayoffMatch[]> {
  const db = database();
  return await db.query.playoffMatches.findMany({
    where: eq(schema.playoffMatches.scoringEventId, eventId),
    orderBy: (matches, { asc }) => [asc(matches.matchNumber)],
    with: {
      participant1: true,
      participant2: true,
      winner: true,
      loser: true,
    },
  });
}

export async function findPlayoffMatchesByEventIdAndRound(
  eventId: string,
  round: string
): Promise<PlayoffMatch[]> {
  const db = database();
  return await db.query.playoffMatches.findMany({
    where: and(
      eq(schema.playoffMatches.scoringEventId, eventId),
      eq(schema.playoffMatches.round, round)
    ),
    orderBy: (matches, { asc }) => [asc(matches.matchNumber)],
    with: {
      participant1: true,
      participant2: true,
      winner: true,
      loser: true,
    },
  });
}

export async function updatePlayoffMatch(
  id: string,
  data: Partial<NewPlayoffMatch>
): Promise<PlayoffMatch> {
  const db = database();
  const [match] = await db
    .update(schema.playoffMatches)
    .set({ ...data, updatedAt: new Date() })
    .where(eq(schema.playoffMatches.id, id))
    .returning();
  return match;
}

export async function deletePlayoffMatch(id: string): Promise<void> {
  const db = database();
  await db.delete(schema.playoffMatches).where(eq(schema.playoffMatches.id, id));
}

export async function deletePlayoffMatchesByEventId(
  eventId: string
): Promise<void> {
  const db = database();
  await db
    .delete(schema.playoffMatches)
    .where(eq(schema.playoffMatches.scoringEventId, eventId));
}

/**
 * Set the winner of a playoff match
 */
export async function setMatchWinner(
  matchId: string,
  winnerId: string,
  loserId: string,
  participant1Score?: number,
  participant2Score?: number
): Promise<PlayoffMatch> {
  const db = database();
  const [match] = await db
    .update(schema.playoffMatches)
    .set({
      winnerId,
      loserId,
      isComplete: true,
      participant1Score: participant1Score?.toString(),
      participant2Score: participant2Score?.toString(),
      updatedAt: new Date(),
    })
    .where(eq(schema.playoffMatches.id, matchId))
    .returning();
  return match;
}

/**
 * Generate a standard single elimination bracket structure
 */
export async function generateSingleEliminationBracket(
  eventId: string,
  participantIds: string[]
): Promise<PlayoffMatch[]> {
  const db = database();
  const numParticipants = participantIds.length;

  // Validate that we have 4 or 8 participants for standard bracket
  if (numParticipants !== 4 && numParticipants !== 8) {
    throw new Error("Single elimination bracket requires 4 or 8 participants");
  }

  const matches: NewPlayoffMatch[] = [];

  if (numParticipants === 8) {
    // Quarterfinals (4 matches)
    for (let i = 0; i < 4; i++) {
      matches.push({
        scoringEventId: eventId,
        round: "Quarterfinals",
        matchNumber: i + 1,
        participant1Id: participantIds[i * 2],
        participant2Id: participantIds[i * 2 + 1],
        isComplete: false,
      });
    }

    // Semifinals (2 matches)
    for (let i = 0; i < 2; i++) {
      matches.push({
        scoringEventId: eventId,
        round: "Semifinals",
        matchNumber: i + 1,
        participant1Id: null,
        participant2Id: null,
        isComplete: false,
      });
    }
  } else if (numParticipants === 4) {
    // Semifinals (2 matches)
    for (let i = 0; i < 2; i++) {
      matches.push({
        scoringEventId: eventId,
        round: "Semifinals",
        matchNumber: i + 1,
        participant1Id: participantIds[i * 2],
        participant2Id: participantIds[i * 2 + 1],
        isComplete: false,
      });
    }
  }

  // Finals (1 match)
  matches.push({
    scoringEventId: eventId,
    round: "Finals",
    matchNumber: 1,
    participant1Id: null,
    participant2Id: null,
    isComplete: false,
  });

  return await createManyPlayoffMatches(matches);
}

/**
 * Advance the winner of a match to the next round
 * Uses deterministic slot assignment to maintain bracket structure
 */
export async function advanceWinner(
  matchId: string,
  winnerId: string
): Promise<void> {
  const db = database();

  // Get the match
  const match = await findPlayoffMatchById(matchId);
  if (!match) throw new Error("Match not found");

  // Determine which round this is and where to advance
  const eventId = match.scoringEventId;
  let nextRound: string;
  let nextMatchNumber: number;
  let participantSlot: 'participant1Id' | 'participant2Id';

  if (match.round === "Quarterfinals") {
    nextRound = "Semifinals";
    // Match 1,2 -> SF1, Match 3,4 -> SF2
    nextMatchNumber = match.matchNumber <= 2 ? 1 : 2;
    // Odd matches (1, 3) -> participant1, Even matches (2, 4) -> participant2
    participantSlot = match.matchNumber % 2 === 1 ? 'participant1Id' : 'participant2Id';
  } else if (match.round === "Semifinals") {
    nextRound = "Finals";
    nextMatchNumber = 1;
    // SF Match 1 -> Finals participant1, SF Match 2 -> Finals participant2
    participantSlot = match.matchNumber === 1 ? 'participant1Id' : 'participant2Id';
  } else {
    // Finals - no advancement needed
    return;
  }

  // Find the next match
  const nextMatches = await findPlayoffMatchesByEventIdAndRound(eventId, nextRound);
  const nextMatch = nextMatches.find(m => m.matchNumber === nextMatchNumber);

  if (!nextMatch) throw new Error("Next match not found");

  // Check if the slot is already filled
  if (nextMatch[participantSlot]) {
    throw new Error(`Next match ${participantSlot} is already filled`);
  }

  // Fill the determined slot
  await updatePlayoffMatch(nextMatch.id, { [participantSlot]: winnerId });
}

/**
 * Generate standard tournament seeding matchups
 * Returns pairs of seed indices for proper bracket balance
 *
 * Examples:
 * - 4 teams: [[0,3], [1,2]] = 1v4, 2v3
 * - 8 teams: [[0,7], [3,4], [1,6], [2,5]] = 1v8, 4v5, 2v7, 3v6
 * - 16 teams: [[0,15], [7,8], [4,11], [3,12], [5,10], [2,13], [6,9], [1,14]]
 *            = 1v16, 8v9, 5v12, 4v13, 6v11, 3v14, 7v10, 2v15
 */
function generateStandardSeeding(teamCount: number): [number, number][] {
  if (![4, 8, 16, 32].includes(teamCount)) {
    // For non-standard sizes (like NCAA 68, NFL 14), return sequential for now
    // Those will need custom seeding logic in their respective phases
    const pairs: [number, number][] = [];
    for (let i = 0; i < teamCount; i += 2) {
      pairs.push([i, i + 1]);
    }
    return pairs;
  }

  // Standard balanced bracket seeding
  const rounds = Math.log2(teamCount);
  let seeds = [0, 1]; // Start with 1 vs 2

  // Build up seeding by adding rounds
  for (let round = 1; round < rounds; round++) {
    const newSeeds: number[] = [];
    const maxSeed = Math.pow(2, round + 1) - 1;

    for (const seed of seeds) {
      newSeeds.push(seed);
      newSeeds.push(maxSeed - seed);
    }
    seeds = newSeeds;
  }

  // Convert to pairs (odd indices vs even indices)
  const pairs: [number, number][] = [];
  for (let i = 0; i < seeds.length; i += 2) {
    pairs.push([seeds[i], seeds[i + 1]]);
  }

  return pairs;
}

/**
 * Generate a bracket from a template
 * Phase 2.6: Template-based bracket generation
 * Phase 2.7: Added proper tournament seeding
 *
 * @param eventId - The scoring event ID
 * @param templateId - The bracket template ID (e.g., "simple_16", "ncaa_68")
 * @param participantIds - Array of participant IDs to assign to the bracket (optional, can be assigned later)
 * @returns Array of created playoff matches
 */
export async function generateBracketFromTemplate(
  eventId: string,
  templateId: string,
  participantIds?: string[]
): Promise<PlayoffMatch[]> {
  const template = getBracketTemplate(templateId);
  if (!template) {
    throw new Error(`Bracket template '${templateId}' not found`);
  }

  // Validate participant count if provided
  if (participantIds && participantIds.length !== template.totalTeams) {
    throw new Error(
      `Template '${templateId}' requires ${template.totalTeams} participants, but ${participantIds.length} were provided`
    );
  }

  const matches: NewPlayoffMatch[] = [];

  // Generate matches for each round in the template
  for (const round of template.rounds) {
    // Only assign participants to the first round if participantIds provided
    let seedingPairs: [number, number][] = [];

    if (participantIds && round === template.rounds[0]) {
      const firstRoundTeams = round.matchCount * 2;
      seedingPairs = generateStandardSeeding(firstRoundTeams);
    }

    for (let i = 0; i < round.matchCount; i++) {
      let participant1Id: string | null = null;
      let participant2Id: string | null = null;
      let seedInfo: string | null = null;

      if (participantIds && round === template.rounds[0] && seedingPairs[i]) {
        const [seed1Index, seed2Index] = seedingPairs[i];
        participant1Id = participantIds[seed1Index] || null;
        participant2Id = participantIds[seed2Index] || null;

        // Store seed info for display (1-indexed for users)
        seedInfo = `${seed1Index + 1} vs ${seed2Index + 1}`;
      }

      matches.push({
        scoringEventId: eventId,
        round: round.name,
        matchNumber: i + 1,
        participant1Id,
        participant2Id,
        isComplete: false,
        isScoring: round.isScoring,
        templateRound: round.name,
        seedInfo,
      });
    }
  }

  return await createManyPlayoffMatches(matches);
}

/**
 * Advance winner to next round using template-based logic
 * Works with any bracket template
 */
export async function advanceWinnerTemplate(
  matchId: string,
  winnerId: string,
  template: BracketTemplate
): Promise<void> {
  const db = database();

  // Get the match
  const match = await findPlayoffMatchById(matchId);
  if (!match) throw new Error("Match not found");

  // Find current round in template
  const currentRoundIndex = template.rounds.findIndex(
    (r) => r.name === match.round
  );
  if (currentRoundIndex === -1) {
    throw new Error(`Round '${match.round}' not found in template`);
  }

  const currentRound = template.rounds[currentRoundIndex];

  // Check if there's a next round
  if (!currentRound.feedsInto) {
    // Championship game - no advancement needed
    return;
  }

  const nextRound = template.rounds.find((r) => r.name === currentRound.feedsInto);
  if (!nextRound) {
    throw new Error(`Next round '${currentRound.feedsInto}' not found in template`);
  }

  // Determine next match number and slot
  // This uses the same logic as before: matches advance in sequential pairs
  const nextMatchNumber = Math.ceil(match.matchNumber / 2);
  const participantSlot: 'participant1Id' | 'participant2Id' =
    match.matchNumber % 2 === 1 ? 'participant1Id' : 'participant2Id';

  // Find the next match
  const nextMatches = await findPlayoffMatchesByEventIdAndRound(
    match.scoringEventId,
    nextRound.name
  );
  const nextMatch = nextMatches.find((m) => m.matchNumber === nextMatchNumber);

  if (!nextMatch) {
    throw new Error(
      `Next match not found: round=${nextRound.name}, matchNumber=${nextMatchNumber}`
    );
  }

  // Check if the slot is already filled
  if (nextMatch[participantSlot]) {
    throw new Error(`Next match ${participantSlot} is already filled`);
  }

  // Fill the determined slot
  await updatePlayoffMatch(nextMatch.id, { [participantSlot]: winnerId });
}