package tournament

import (
	"context"
	"database/sql"
	"fmt"
)

// TournamentSummary is a lightweight summary for the tournament lobby view.
type TournamentSummary struct {
	ID             string  `json:"id"`
	Name           string  `json:"name"`
	Status         string  `json:"status"`
	PlayerCount    int     `json:"player_count"`
	ActivePlayers  int     `json:"active_players"`
	CurrentLevel   int     `json:"current_level"`
	SmallBlind     int64   `json:"small_blind"`
	BigBlind       int64   `json:"big_blind"`
	RemainingMs    int64   `json:"remaining_ms"`
	TotalElapsedMs int64   `json:"total_elapsed_ms"`
	PrizePool      int64   `json:"prize_pool"`
	StartedAt      *int64  `json:"started_at,omitempty"`
	CreatedAt      int64   `json:"created_at"`
}

// MultiManager manages multiple simultaneous tournaments.
// It provides lobby views and tournament switching.
// Independence guarantee: every piece of state (clock, players, tables,
// financials) is scoped by tournament_id. No global singletons.
type MultiManager struct {
	service *Service
}

// NewMultiManager creates a new multi-tournament manager.
func NewMultiManager(service *Service) *MultiManager {
	return &MultiManager{service: service}
}

// ListActiveTournaments returns all tournaments with active statuses
// (registering, running, paused, final_table) for the lobby view.
// This powers the multi-tournament switching UI (MULTI-02).
func (m *MultiManager) ListActiveTournaments(ctx context.Context) ([]TournamentSummary, error) {
	rows, err := m.service.db.QueryContext(ctx,
		`SELECT t.id, t.name, t.status, t.current_level, t.clock_state,
		        t.clock_remaining_ns, t.total_elapsed_ns,
		        t.started_at, t.created_at,
		        (SELECT COUNT(*) FROM tournament_players tp
		         WHERE tp.tournament_id = t.id) as player_count,
		        (SELECT COUNT(*) FROM tournament_players tp
		         WHERE tp.tournament_id = t.id AND tp.status = 'active') as active_players,
		        COALESCE(
		          (SELECT SUM(amount) FROM transactions tx
		           WHERE tx.tournament_id = t.id
		           AND tx.type IN ('buyin', 'rebuy', 'addon', 'reentry')
		           AND tx.undone = 0), 0
		        ) -
		        COALESCE(
		          (SELECT SUM(amount) FROM transactions tx
		           WHERE tx.tournament_id = t.id
		           AND tx.type = 'rake'
		           AND tx.undone = 0), 0
		        ) as prize_pool
		 FROM tournaments t
		 WHERE t.status IN ('created', 'registering', 'running', 'paused', 'final_table')
		 ORDER BY t.created_at DESC`)
	if err != nil {
		return nil, fmt.Errorf("tournament: list active: %w", err)
	}
	defer rows.Close()

	return m.scanSummaries(ctx, rows)
}

// ListAllTournaments returns all tournaments (active + recent completed) for display.
func (m *MultiManager) ListAllTournaments(ctx context.Context) ([]TournamentSummary, error) {
	rows, err := m.service.db.QueryContext(ctx,
		`SELECT t.id, t.name, t.status, t.current_level, t.clock_state,
		        t.clock_remaining_ns, t.total_elapsed_ns,
		        t.started_at, t.created_at,
		        (SELECT COUNT(*) FROM tournament_players tp
		         WHERE tp.tournament_id = t.id) as player_count,
		        (SELECT COUNT(*) FROM tournament_players tp
		         WHERE tp.tournament_id = t.id AND tp.status = 'active') as active_players,
		        COALESCE(
		          (SELECT SUM(amount) FROM transactions tx
		           WHERE tx.tournament_id = t.id
		           AND tx.type IN ('buyin', 'rebuy', 'addon', 'reentry')
		           AND tx.undone = 0), 0
		        ) -
		        COALESCE(
		          (SELECT SUM(amount) FROM transactions tx
		           WHERE tx.tournament_id = t.id
		           AND tx.type = 'rake'
		           AND tx.undone = 0), 0
		        ) as prize_pool
		 FROM tournaments t
		 ORDER BY t.created_at DESC
		 LIMIT 50`)
	if err != nil {
		return nil, fmt.Errorf("tournament: list all: %w", err)
	}
	defer rows.Close()

	return m.scanSummaries(ctx, rows)
}

// GetTournamentSummary returns a lightweight summary for a single tournament.
func (m *MultiManager) GetTournamentSummary(ctx context.Context, id string) (*TournamentSummary, error) {
	row := m.service.db.QueryRowContext(ctx,
		`SELECT t.id, t.name, t.status, t.current_level, t.clock_state,
		        t.clock_remaining_ns, t.total_elapsed_ns,
		        t.started_at, t.created_at,
		        (SELECT COUNT(*) FROM tournament_players tp
		         WHERE tp.tournament_id = t.id) as player_count,
		        (SELECT COUNT(*) FROM tournament_players tp
		         WHERE tp.tournament_id = t.id AND tp.status = 'active') as active_players,
		        COALESCE(
		          (SELECT SUM(amount) FROM transactions tx
		           WHERE tx.tournament_id = t.id
		           AND tx.type IN ('buyin', 'rebuy', 'addon', 'reentry')
		           AND tx.undone = 0), 0
		        ) -
		        COALESCE(
		          (SELECT SUM(amount) FROM transactions tx
		           WHERE tx.tournament_id = t.id
		           AND tx.type = 'rake'
		           AND tx.undone = 0), 0
		        ) as prize_pool
		 FROM tournaments t
		 WHERE t.id = ?`, id)

	summary, err := m.scanSingleSummary(ctx, row)
	if err == sql.ErrNoRows {
		return nil, ErrTournamentNotFound
	}
	if err != nil {
		return nil, fmt.Errorf("tournament: get summary: %w", err)
	}

	return summary, nil
}

func (m *MultiManager) scanSummaries(ctx context.Context, rows *sql.Rows) ([]TournamentSummary, error) {
	var summaries []TournamentSummary
	for rows.Next() {
		var ts TournamentSummary
		var clockState string
		var clockRemainingNs, totalElapsedNs int64
		var startedAt sql.NullInt64
		var playerCount, activePlayers int
		var prizePool int64

		if err := rows.Scan(
			&ts.ID, &ts.Name, &ts.Status, &ts.CurrentLevel, &clockState,
			&clockRemainingNs, &totalElapsedNs,
			&startedAt, &ts.CreatedAt,
			&playerCount, &activePlayers,
			&prizePool,
		); err != nil {
			return nil, fmt.Errorf("tournament: scan summary: %w", err)
		}

		ts.PlayerCount = playerCount
		ts.ActivePlayers = activePlayers
		ts.RemainingMs = clockRemainingNs / 1_000_000
		ts.TotalElapsedMs = totalElapsedNs / 1_000_000
		ts.PrizePool = prizePool
		if startedAt.Valid {
			ts.StartedAt = &startedAt.Int64
		}

		// Get live clock data from registry if available
		if engine := m.service.registry.Get(ts.ID); engine != nil {
			snap := engine.Snapshot()
			ts.RemainingMs = snap.RemainingMs
			ts.TotalElapsedMs = snap.TotalElapsedMs
			ts.CurrentLevel = snap.CurrentLevel
			ts.SmallBlind = snap.Level.SmallBlind
			ts.BigBlind = snap.Level.BigBlind
		}

		summaries = append(summaries, ts)
	}
	return summaries, rows.Err()
}

func (m *MultiManager) scanSingleSummary(ctx context.Context, row *sql.Row) (*TournamentSummary, error) {
	ts := &TournamentSummary{}
	var clockState string
	var clockRemainingNs, totalElapsedNs int64
	var startedAt sql.NullInt64
	var playerCount, activePlayers int
	var prizePool int64

	if err := row.Scan(
		&ts.ID, &ts.Name, &ts.Status, &ts.CurrentLevel, &clockState,
		&clockRemainingNs, &totalElapsedNs,
		&startedAt, &ts.CreatedAt,
		&playerCount, &activePlayers,
		&prizePool,
	); err != nil {
		return nil, err
	}

	ts.PlayerCount = playerCount
	ts.ActivePlayers = activePlayers
	ts.RemainingMs = clockRemainingNs / 1_000_000
	ts.TotalElapsedMs = totalElapsedNs / 1_000_000
	ts.PrizePool = prizePool
	if startedAt.Valid {
		ts.StartedAt = &startedAt.Int64
	}

	// Get live clock data from registry if available
	if engine := m.service.registry.Get(ts.ID); engine != nil {
		snap := engine.Snapshot()
		ts.RemainingMs = snap.RemainingMs
		ts.TotalElapsedMs = snap.TotalElapsedMs
		ts.CurrentLevel = snap.CurrentLevel
		ts.SmallBlind = snap.Level.SmallBlind
		ts.BigBlind = snap.Level.BigBlind
	}

	return ts, nil
}