/**
 * Tournament engine tests — bracket generation, match scheduling,
 * elimination logic, and round progression.
 *
 * Uses vi.mock to swap the global db/schema/sqlite singleton with an
 * in-memory test database so every test gets a clean slate.
 */
import { describe, it, expect, beforeEach, vi } from 'vitest'
import { createTestDb, insertTestBot } from '../test-helpers/db.js'
import { nanoid } from 'nanoid'

// Swap the db module before tournament code imports it
let testDb: ReturnType<typeof createTestDb>

vi.mock('../db/index.js', () => {
  // Lazy — the actual testDb is assigned in beforeEach,
  // but the module proxy always dereferences the live binding.
  return {
    get db() { return testDb.db },
    get schema() { return testDb.schema },
    get sqlite() { return testDb.sqlite },
  }
})

// Import AFTER mock is registered so the module picks up the proxy
import {
  createTournament,
  joinTournament,
  startTournament,
  getTournamentBracket,
  listTournaments,
  getPendingMatches,
  linkFightToMatch,
  onFightFinished,
} from './tournaments.js'

import { eq, and } from 'drizzle-orm'

// ---------------------------------------------------------------------------
// helpers
// ---------------------------------------------------------------------------

/** Insert N bots with ascending ELO (1200, 1300, 1400 ...) */
function seedBots(count: number) {
  const bots = []
  for (let i = 0; i < count; i++) {
    const bot = insertTestBot(testDb.db, {
      id: `bot-${i}`,
      name: `Fighter-${i}`,
      eloRating: 1200 + i * 100,
    })
    bots.push(bot)
  }
  return bots
}

/** Create a tournament and fill it with bots, returning the tournament id and bot ids */
function createAndFill(size: 8 | 16 | 32, botCount: number) {
  const bots = seedBots(botCount)
  const tid = createTournament(`Test-${size}`, 'single_elim', size, 0)
  for (const bot of bots) {
    joinTournament(tid, bot.id)
  }
  return { tid, bots }
}

/**
 * Insert a fight record into the DB so FK constraints are satisfied
 * when linking fights to tournament matches.
 */
function insertFight(fightId: string, botAId: string, botBId: string) {
  testDb.db.insert(testDb.schema.fights).values({
    id: fightId,
    botAId,
    botBId,
    arena: 'test-arena',
    status: 'live',
    createdAt: new Date().toISOString(),
  }).run()
}

/**
 * Link a fight to a match with FK-safe fight insertion.
 * Creates the fight record, then links it to the match.
 */
function safeLink(matchId: string, fightId: string, botAId: string, botBId: string) {
  insertFight(fightId, botAId, botBId)
  linkFightToMatch(matchId, fightId)
}

// ---------------------------------------------------------------------------
// setup
// ---------------------------------------------------------------------------

beforeEach(() => {
  testDb = createTestDb()
})

// ---------------------------------------------------------------------------
// createTournament
// ---------------------------------------------------------------------------

describe('createTournament', () => {
  it('creates tournament with correct defaults', () => {
    const id = createTournament('Halvening Cup', 'single_elim', 8, 500)

    const all = listTournaments()
    expect(all).toHaveLength(1)

    const t = all[0]
    expect(t.id).toBe(id)
    expect(t.name).toBe('Halvening Cup')
    expect(t.format).toBe('single_elim')
    expect(t.size).toBe(8)
    expect(t.entrySats).toBe(500)
    expect(t.prizeSats).toBe(4000) // 500 * 8
    expect(t.status).toBe('open')
    expect(t.currentRound).toBe(0)
  })

  it('creates free tournament (zero entry fee)', () => {
    createTournament('Free Arena', 'single_elim', 16)

    const all = listTournaments()
    expect(all[0].entrySats).toBe(0)
    expect(all[0].prizeSats).toBe(0)
  })

  it('listTournaments filters by status', () => {
    createTournament('Open1', 'single_elim', 8)
    createTournament('Open2', 'single_elim', 8)

    expect(listTournaments('open')).toHaveLength(2)
    expect(listTournaments('active')).toHaveLength(0)
    expect(listTournaments('finished')).toHaveLength(0)
  })
})

// ---------------------------------------------------------------------------
// joinTournament
// ---------------------------------------------------------------------------

describe('joinTournament', () => {
  it('adds bot entry', () => {
    const bots = seedBots(1)
    const tid = createTournament('Join Test', 'single_elim', 8)

    const entryId = joinTournament(tid, bots[0].id)
    expect(entryId).toBeTruthy()

    const bracket = getTournamentBracket(tid)!
    expect(bracket.entries).toHaveLength(1)
    expect(bracket.entries[0].botId).toBe(bots[0].id)
  })

  it('rejects duplicate entry', () => {
    const bots = seedBots(1)
    const tid = createTournament('Dup Test', 'single_elim', 8)
    joinTournament(tid, bots[0].id)

    expect(() => joinTournament(tid, bots[0].id))
      .toThrow('Bot already entered in this tournament')
  })

  it('rejects entry to nonexistent tournament', () => {
    const bots = seedBots(1)
    expect(() => joinTournament('fake-id', bots[0].id))
      .toThrow('Tournament not found')
  })

  it('rejects entry when tournament is full', () => {
    const { tid } = createAndFill(8, 8)
    const extra = insertTestBot(testDb.db, { id: 'bot-extra', name: 'ExtraBot' })

    expect(() => joinTournament(tid, extra.id))
      .toThrow('Tournament is full')
  })

  it('rejects entry to non-open tournament', () => {
    const { tid } = createAndFill(8, 4)
    startTournament(tid)

    const extra = insertTestBot(testDb.db, { id: 'bot-late', name: 'LateBot' })
    expect(() => joinTournament(tid, extra.id))
      .toThrow('Tournament is not accepting entries')
  })
})

// ---------------------------------------------------------------------------
// startTournament & bracket generation
// ---------------------------------------------------------------------------

describe('startTournament', () => {
  it('requires at least 2 entries', () => {
    const bots = seedBots(1)
    const tid = createTournament('Tiny', 'single_elim', 8)
    joinTournament(tid, bots[0].id)

    expect(() => startTournament(tid)).toThrow('Need at least 2 entries')
  })

  it('rejects double-start', () => {
    const { tid } = createAndFill(8, 4)
    startTournament(tid)

    expect(() => startTournament(tid)).toThrow('Tournament already started')
  })

  it('sets status to active and currentRound >= 1', () => {
    const { tid } = createAndFill(8, 8)
    startTournament(tid)

    const bracket = getTournamentBracket(tid)!
    expect(bracket.tournament.status).toBe('active')
    expect(bracket.tournament.currentRound).toBeGreaterThanOrEqual(1)
    expect(bracket.tournament.startedAt).toBeTruthy()
  })
})

describe('bracket generation — 8 bots (full bracket)', () => {
  it('generates 4 round-1 matches for 8 bots', () => {
    const { tid } = createAndFill(8, 8)
    startTournament(tid)

    const bracket = getTournamentBracket(tid)!
    const r1 = bracket.matches.filter(m => m.round === 1)
    expect(r1).toHaveLength(4)
  })

  it('seeds by ELO: highest vs lowest', () => {
    const { tid } = createAndFill(8, 8)
    startTournament(tid)

    const bracket = getTournamentBracket(tid)!
    const r1 = bracket.matches.filter(m => m.round === 1).sort((a, b) => a.matchIndex - b.matchIndex)

    // Seed 1 (highest ELO = bot-7) vs Seed 8 (lowest = bot-0) in match 0
    expect(r1[0].botAId).toBe('bot-7')
    expect(r1[0].botBId).toBe('bot-0')

    // Seed 2 (bot-6) vs Seed 7 (bot-1) in match 1
    expect(r1[1].botAId).toBe('bot-6')
    expect(r1[1].botBId).toBe('bot-1')
  })

  it('all round-1 matches are pending (no byes)', () => {
    const { tid } = createAndFill(8, 8)
    startTournament(tid)

    const bracket = getTournamentBracket(tid)!
    const r1 = bracket.matches.filter(m => m.round === 1)
    expect(r1.every(m => m.status === 'pending')).toBe(true)
  })
})

describe('bracket generation — 4 bots in size-8 bracket (with byes)', () => {
  it('generates 4 round-1 matches, all byes auto-advance', () => {
    const { tid } = createAndFill(8, 4)
    startTournament(tid)

    const bracket = getTournamentBracket(tid)!
    const r1 = bracket.matches.filter(m => m.round === 1)
    expect(r1).toHaveLength(4)

    // 4 bots fill seeded slots [0..3], slots [4..7] are null.
    // Matches pair seeded[i] vs seeded[7-i], so every match is bot vs null = bye.
    // All 4 round-1 matches should be finished (auto-advanced).
    const byeMatches = r1.filter(m => m.status === 'finished')
    expect(byeMatches).toHaveLength(4)

    // Round 2 should already be generated with the 4 winners
    const r2 = bracket.matches.filter(m => m.round === 2)
    expect(r2.length).toBeGreaterThanOrEqual(2)
  })

  it('bye matches have a winner set', () => {
    const { tid } = createAndFill(8, 4)
    startTournament(tid)

    const bracket = getTournamentBracket(tid)!
    const byeMatches = bracket.matches.filter(m => m.round === 1 && m.status === 'finished')

    for (const m of byeMatches) {
      expect(m.winnerId).toBeTruthy()
      // Winner should be the non-null bot
      if (m.botAId && !m.botBId) expect(m.winnerId).toBe(m.botAId)
      if (m.botBId && !m.botAId) expect(m.winnerId).toBe(m.botBId)
    }
  })
})

describe('bracket generation — 16 bots', () => {
  it('generates 8 round-1 matches for full 16-bot bracket', () => {
    const { tid } = createAndFill(16, 16)
    startTournament(tid)

    const bracket = getTournamentBracket(tid)!
    const r1 = bracket.matches.filter(m => m.round === 1)
    expect(r1).toHaveLength(8)
    expect(r1.every(m => m.status === 'pending')).toBe(true)
  })
})

// ---------------------------------------------------------------------------
// getPendingMatches & linkFightToMatch
// ---------------------------------------------------------------------------

describe('getPendingMatches', () => {
  it('returns matches where both bots are present', () => {
    const { tid } = createAndFill(8, 8)
    startTournament(tid)

    const pending = getPendingMatches(tid)
    expect(pending.length).toBe(4)
    for (const m of pending) {
      expect(m.botAId).toBeTruthy()
      expect(m.botBId).toBeTruthy()
      expect(m.status).toBe('pending')
    }
  })
})

describe('linkFightToMatch', () => {
  it('sets fight ID and status to live', () => {
    const { tid } = createAndFill(8, 8)
    startTournament(tid)

    const pending = getPendingMatches(tid)
    const match = pending[0]
    safeLink(match.id, 'fight-xyz', match.botAId!, match.botBId!)

    const updated = testDb.db.select().from(testDb.schema.tournamentMatches)
      .where(eq(testDb.schema.tournamentMatches.id, match.id))
      .get()!

    expect(updated.fightId).toBe('fight-xyz')
    expect(updated.status).toBe('live')
  })
})

// ---------------------------------------------------------------------------
// onFightFinished — elimination & round progression
// ---------------------------------------------------------------------------

describe('onFightFinished — elimination logic', () => {
  it('marks loser as eliminated', () => {
    const { tid } = createAndFill(8, 8)
    startTournament(tid)

    const pending = getPendingMatches(tid)
    const match = pending[0]
    safeLink(match.id, 'fight-elim-1', match.botAId!, match.botBId!)

    onFightFinished('fight-elim-1', match.botAId!)

    // Loser (botB) should be eliminated
    const entry = testDb.db.select().from(testDb.schema.tournamentEntries)
      .where(and(
        eq(testDb.schema.tournamentEntries.tournamentId, tid),
        eq(testDb.schema.tournamentEntries.botId, match.botBId!),
      ))
      .get()!

    // SQLite stores boolean as 0/1 via raw query; drizzle may return number
    expect(entry.eliminated).toBeTruthy()
  })

  it('updates match with winner and finished status', () => {
    const { tid } = createAndFill(8, 8)
    startTournament(tid)

    const pending = getPendingMatches(tid)
    const match = pending[0]
    safeLink(match.id, 'fight-elim-2', match.botAId!, match.botBId!)

    onFightFinished('fight-elim-2', match.botAId!)

    const updated = testDb.db.select().from(testDb.schema.tournamentMatches)
      .where(eq(testDb.schema.tournamentMatches.id, match.id))
      .get()!

    expect(updated.winnerId).toBe(match.botAId)
    expect(updated.status).toBe('finished')
  })

  it('ignores draw (null winnerId)', () => {
    const { tid } = createAndFill(8, 8)
    startTournament(tid)

    const pending = getPendingMatches(tid)
    safeLink(pending[0].id, 'fight-draw', pending[0].botAId!, pending[0].botBId!)

    // onFightFinished early-returns on falsy winnerId, so no-op
    onFightFinished('fight-draw', null as unknown as string)
  })

  it('ignores non-tournament fights', () => {
    // No tournament context — should not throw
    onFightFinished('random-fight-id', 'some-bot')
  })
})

// ---------------------------------------------------------------------------
// round progression — full tournament lifecycle
// ---------------------------------------------------------------------------

describe('round progression', () => {
  it('advances to round 2 when all round-1 matches finish', () => {
    const { tid } = createAndFill(8, 8)
    startTournament(tid)

    const pending = getPendingMatches(tid)
    expect(pending).toHaveLength(4)

    // Finish all round 1 matches — botA always wins
    for (const match of pending) {
      safeLink(match.id, `fight-r1-${match.matchIndex}`, match.botAId!, match.botBId!)
      onFightFinished(`fight-r1-${match.matchIndex}`, match.botAId!)
    }

    const bracket = getTournamentBracket(tid)!
    expect(bracket.tournament.currentRound).toBe(2)

    // Round 2 should have 2 matches
    const r2 = bracket.matches.filter(m => m.round === 2)
    expect(r2).toHaveLength(2)
  })

  it('full 8-bot tournament completes in 3 rounds (8 -> 4 -> 2 -> 1)', () => {
    const { tid } = createAndFill(8, 8)
    startTournament(tid)

    // Round 1: 4 matches
    let pending = getPendingMatches(tid)
    expect(pending).toHaveLength(4)
    for (const m of pending) {
      safeLink(m.id, `fight-${m.round}-${m.matchIndex}`, m.botAId!, m.botBId!)
      onFightFinished(`fight-${m.round}-${m.matchIndex}`, m.botAId!)
    }

    // Round 2: 2 matches
    pending = getPendingMatches(tid)
    expect(pending).toHaveLength(2)
    for (const m of pending) {
      safeLink(m.id, `fight-${m.round}-${m.matchIndex}`, m.botAId!, m.botBId!)
      onFightFinished(`fight-${m.round}-${m.matchIndex}`, m.botAId!)
    }

    // Round 3 (final): 1 match
    pending = getPendingMatches(tid)
    expect(pending).toHaveLength(1)
    const finalMatch = pending[0]
    safeLink(finalMatch.id, 'fight-final', finalMatch.botAId!, finalMatch.botBId!)
    onFightFinished('fight-final', finalMatch.botAId!)

    // Tournament should be finished
    const bracket = getTournamentBracket(tid)!
    expect(bracket.tournament.status).toBe('finished')
    expect(bracket.tournament.finishedAt).toBeTruthy()
  })

  it('partial round completion does not advance', () => {
    const { tid } = createAndFill(8, 8)
    startTournament(tid)

    const pending = getPendingMatches(tid)

    // Only finish 2 out of 4 matches
    for (let i = 0; i < 2; i++) {
      safeLink(pending[i].id, `fight-partial-${i}`, pending[i].botAId!, pending[i].botBId!)
      onFightFinished(`fight-partial-${i}`, pending[i].botAId!)
    }

    const bracket = getTournamentBracket(tid)!
    // Still in round 1 — not all matches finished
    expect(bracket.tournament.currentRound).toBe(1)

    // No round 2 matches generated yet
    const r2 = bracket.matches.filter(m => m.round === 2)
    expect(r2).toHaveLength(0)
  })
})

// ---------------------------------------------------------------------------
// getTournamentBracket
// ---------------------------------------------------------------------------

describe('getTournamentBracket', () => {
  it('returns null for unknown tournament', () => {
    expect(getTournamentBracket('fake-id')).toBeNull()
  })

  it('includes bot names in match data', () => {
    const { tid } = createAndFill(8, 8)
    startTournament(tid)

    const bracket = getTournamentBracket(tid)!
    const r1 = bracket.matches.filter(m => m.round === 1)

    for (const m of r1) {
      if (m.botAId) expect(m.botAName).toBeTruthy()
      if (m.botBId) expect(m.botBName).toBeTruthy()
    }
  })

  it('entries show seed numbers after start', () => {
    const { tid } = createAndFill(8, 8)
    startTournament(tid)

    const bracket = getTournamentBracket(tid)!
    const seeds = bracket.entries.map(e => e.seed).sort((a, b) => a - b)
    expect(seeds).toEqual([1, 2, 3, 4, 5, 6, 7, 8])
  })

  it('highest ELO gets seed 1', () => {
    const { tid } = createAndFill(8, 8)
    startTournament(tid)

    const bracket = getTournamentBracket(tid)!
    // bot-7 has highest ELO (1200 + 7*100 = 1900)
    const topSeed = bracket.entries.find(e => e.seed === 1)!
    expect(topSeed.botId).toBe('bot-7')
  })

  it('tracks eliminated status', () => {
    const { tid } = createAndFill(8, 8)
    startTournament(tid)

    // Before any fights, nobody eliminated
    let bracket = getTournamentBracket(tid)!
    expect(bracket.entries.every(e => !e.eliminated)).toBe(true)

    // Finish one match
    const pending = getPendingMatches(tid)
    safeLink(pending[0].id, 'fight-track', pending[0].botAId!, pending[0].botBId!)
    onFightFinished('fight-track', pending[0].botAId!)

    bracket = getTournamentBracket(tid)!
    const eliminated = bracket.entries.filter(e => e.eliminated)
    expect(eliminated).toHaveLength(1)
    expect(eliminated[0].botId).toBe(pending[0].botBId)
  })
})