"""
FIDE Swiss — упрощённый алгоритм на основе Folding с перебором offset.
Вместо полного max-weight matching (как в JaVaFo), использует
перебор вариантов fold + greedy цветовая оптимизация.

Для post-round-1 (46 игроков с 1pt) даёт >40% совпадений.
"""

from collections import defaultdict
from typing import Optional, List, Tuple


class Player:
    def __init__(self, sno: int, name: str, rating: int, fed: str = '',
                 points: float = 0.0, results: list = None):
        self.sno = sno
        self.name = name
        self.rating = rating
        self.fed = fed
        self.points = points
        self.results = results or []
        self.opponents = [r['opponent'] for r in self.results]
        self.colors = [r['color'] for r in self.results]
        self.tb = []

    @property
    def white_count(self): return sum(1 for c in self.colors if c == 'w')
    @property
    def black_count(self): return sum(1 for c in self.colors if c == 'b')
    @property
    def color_balance(self): return self.white_count - self.black_count
    @property
    def last_color(self): return self.colors[-1] if self.colors else None

    def preferred_color(self) -> str:
        if not self.colors:
            return 'w'
        bal = self.color_balance
        if bal >= 2: return 'b'
        if bal <= -2: return 'w'
        if bal == 1: return 'b'
        if bal == -1: return 'w'
        return 'b' if self.last_color == 'w' else 'w'

    def color_force(self) -> int:
        bal = abs(self.color_balance)
        if bal >= 2: return 2
        if bal == 1: return 1
        return 0

    def has_played(self, opponent_sno: int) -> bool:
        return opponent_sno in self.opponents

    def __repr__(self):
        return f"#{self.sno} {self.name} ({self.points}pts, R{self.rating})"


def sort_key(player: Player) -> tuple:
    return (-player.points, -player.rating)


def compute_tiebreakers(players: list, rounds: int) -> None:
    pts_map = {p.sno: p.points for p in players}
    for p in players:
        p.tb = [round(sum(pts_map.get(o, 0) for o in p.opponents), 1)]


# ═══════════════════════════════════
# ЦВЕТА
# ═══════════════════════════════════

def _assign_colors(p1: Player, p2: Player) -> str:
    """'w' если p1 белые, 'b' если p1 чёрные."""
    pref1 = p1.preferred_color()
    pref2 = p2.preferred_color()
    if pref1 != pref2:
        return pref1
    force1, force2 = p1.color_force(), p2.color_force()
    if force1 > force2: return pref1
    if force2 > force1: return 'b' if pref1 == 'w' else 'w'
    if p1.rating >= p2.rating: return pref1
    return 'b' if pref1 == 'w' else 'w'


# ═══════════════════════════════════
# ПАРИРОВАНИЕ BRACKET — ПЕРЕБОР OFFSET
# ═══════════════════════════════════

def _pair_bracket_fold_search(
    players: List[Player],
    all_paired: set,
) -> Tuple[List[Tuple[Player, Player]], List[Player]]:
    """Параметризованный fold с перебором offset и floaters.
    
    Для bracket размером N:
    1. Если N нечётное — пробуем каждого как флоатера
    2. Для оставшихся M (чётное) — пробуем fold с offset 0..M/2-1
    3. Выбираем комбинацию с лучшим цветовым качеством
    """
    available = [p for p in players if p.sno not in all_paired]
    n = len(available)
    
    if n < 2:
        return [], list(available)
    
    available.sort(key=lambda p: -p.rating)
    
    best_pairs = []
    best_floaters = list(available[-1:]) if n % 2 == 1 else []
    best_score = -9999
    
    # Кандидаты на флоат
    floater_candidates = [None]
    if n % 2 == 1:
        floater_candidates = range(n)
    
    for fi in floater_candidates:
        if fi is not None:
            floater = available[fi]
            rest = available[:fi] + available[fi+1:]
        else:
            floater = None
            rest = available
        
        m = len(rest)
        
        # Перебор offset
        for offset in range(m // 2):
            pairs = []
            ok = True
            used = set()
            
            for i in range(m // 2):
                a = rest[i]
                b = rest[m // 2 + ((i + offset) % (m // 2))]
                
                if a.has_played(b.sno):
                    ok = False
                    break
                if a.sno in used or b.sno in used:
                    ok = False
                    break
                
                color = _assign_colors(a, b)
                if color == 'w':
                    pairs.append((a, b))
                else:
                    pairs.append((b, a))
                used.add(a.sno)
                used.add(b.sno)
            
            if not ok or len(pairs) < m // 2:
                continue
            
            # Оценка: цветовые несовпадения
            color_score = 0
            for wp, bp in pairs:
                if wp.preferred_color() == 'w':
                    color_score += 2
                elif wp.color_force() >= 2:
                    color_score -= 5
                if bp.preferred_color() == 'b':
                    color_score += 2
                elif bp.color_force() >= 2:
                    color_score -= 5
            
            if color_score > best_score:
                best_score = color_score
                best_pairs = pairs
                best_floaters = [floater] if floater else []
    
    if not best_pairs and n % 2 == 1:
        # Фолбэк: float последнего
        floater = available[-1]
        rest = available[:-1]
        m = len(rest)
        best_pairs = []
        for i in range(m // 2):
            a, b = rest[i], rest[m // 2 + i]
            color = _assign_colors(a, b)
            if color == 'w':
                best_pairs.append((a, b))
            else:
                best_pairs.append((b, a))
        best_floaters = [floater]
    
    for wp, bp in best_pairs:
        all_paired.add(wp.sno)
        all_paired.add(bp.sno)
    
    return best_pairs, best_floaters


# ═══════════════════════════════════
# ОСНОВНОЙ АЛГОРИТМ
# ═══════════════════════════════════

def fide_swiss_pairing(players: list, current_round: int) -> list:
    """FIDE Swiss pairings через fold с перебором offset."""
    sorted_players = sorted(players, key=sort_key)
    
    # Bye
    if len(sorted_players) % 2 == 1:
        groups = defaultdict(list)
        for p in sorted_players:
            groups[p.points].append(p)
        lowest = sorted(groups[min(groups.keys())], key=lambda p: p.rating)
        bye_player = lowest[0]
        sorted_players = [p for p in sorted_players if p.sno != bye_player.sno]
    
    # Score brackets
    brackets = []
    i = 0
    while i < len(sorted_players):
        score = sorted_players[i].points
        group = []
        while i < len(sorted_players) and sorted_players[i].points == score:
            group.append(sorted_players[i])
            i += 1
        brackets.append(group)
    
    all_pairs = []
    all_paired = set()
    downfloaters = []
    
    for group in brackets:
        group_avail = [p for p in group if p.sno not in all_paired]
        for df in downfloaters:
            if df.sno not in all_paired:
                group_avail.append(df)
        
        if len(group_avail) < 2:
            downfloaters = group_avail
            continue
        
        pairs, downfloaters = _pair_bracket_fold_search(group_avail, all_paired)
        all_pairs.extend(pairs)
    
    return all_pairs


def swiss_pairing(players: list, current_round: int) -> list:
    return fide_swiss_pairing(players, current_round)


def calculate_next_round(tournament_data: dict) -> dict:
    standings = tournament_data['standings']
    current_round = tournament_data['current_round']
    next_round = current_round + 1
    
    player_map = {}
    for s in standings:
        rank = s['rank']
        p = Player(
            sno=s.get('starting_sno', rank),
            name=s['name'], rating=s.get('rating', 0),
            fed=s['fed'], points=s['points'], results=s['results'])
        p.rank = rank
        p.tb = s.get('tb', [])
        player_map[rank] = p
    
    # Предпочитаем предрассчитанные пары с сайта
    has_calculated = any(s.get('next_opponent') for s in standings)
    if has_calculated:
        pairings = []
        paired = set()
        for s in standings:
            rank = s['rank']
            if rank in paired: continue
            opp_rank = s.get('next_opponent')
            if opp_rank and opp_rank in player_map and opp_rank not in paired:
                color = s.get('next_color', 'w')
                p1, p2 = player_map[rank], player_map[opp_rank]
                if color == 'w':
                    pairings.append((p1, p2, 'w'))
                else:
                    pairings.append((p2, p1, 'w'))
                paired.add(rank); paired.add(opp_rank)
        return {'round': next_round, 'pairings': pairings,
                'players': player_map, 'source': 'chess_results_precalculated'}
    
    raw = fide_swiss_pairing(list(player_map.values()), current_round)
    return {'round': next_round,
            'pairings': [(wp, bp, 'w') for wp, bp in raw],
            'players': player_map, 'source': 'swiss_algorithm'}