"""Matchmaking Engine for ServeSync"""
from sqlalchemy.orm import Session
from app.models.match import Match, MatchPlayer, MatchStage, MatchStatus, MatchType
from app.models.court import Court
from app.models.player import Player
from app.models.booking import Booking, BookingStatus
from app.services.elo import calculate_elo_change, get_elo_range, is_valid_match
from datetime import datetime, timedelta
from typing import Optional, List


def create_open_match(db: Session, title: str, match_type: MatchType = MatchType.DOUBLES) -> Match:
    """Stage 1: Create an open match lobby - no restrictions"""
    max_players = 4 if match_type == MatchType.DOUBLES else 2
    match = Match(
        stage=MatchStage.OPEN,
        match_type=match_type,
        status=MatchStatus.LOBBY,
        title=title,
        max_players=max_players,
    )
    db.add(match)
    db.commit()
    db.refresh(match)
    return match


def create_skill_match(
    db: Session,
    title: str,
    creator_elo: float,
    match_type: MatchType = MatchType.DOUBLES,
    tolerance: float = 200,
) -> Match:
    """Stage 2: Create a skill-based match with ELO constraints"""
    min_elo, max_elo = get_elo_range(creator_elo, tolerance)
    max_players = 4 if match_type == MatchType.DOUBLES else 2
    match = Match(
        stage=MatchStage.SKILL_BASED,
        match_type=match_type,
        status=MatchStatus.LOBBY,
        title=title,
        max_players=max_players,
        min_elo=min_elo,
        max_elo=max_elo,
    )
    db.add(match)
    db.commit()
    db.refresh(match)
    return match


def join_match(db: Session, match_id: int, player_id: int, team: int) -> Optional[MatchPlayer]:
    """Add a player to a match lobby"""
    match = db.query(Match).filter(Match.id == match_id).first()
    if not match or match.status != MatchStatus.LOBBY:
        return None

    player = db.query(Player).filter(Player.id == player_id).first()
    if not player:
        return None

    # Check player count
    current_players = db.query(MatchPlayer).filter(MatchPlayer.match_id == match_id).count()
    if current_players >= match.max_players:
        return None

    # Check if already joined
    existing = db.query(MatchPlayer).filter(
        MatchPlayer.match_id == match_id,
        MatchPlayer.player_id == player_id
    ).first()
    if existing:
        return existing

    # For skill-based matches, check ELO constraint
    if match.stage == MatchStage.SKILL_BASED:
        if match.min_elo and match.max_elo:
            if not is_valid_match(player.elo_rating, match.min_elo, match.max_elo):
                return None

    mp = MatchPlayer(
        match_id=match_id,
        player_id=player_id,
        team=team,
        elo_before=player.elo_rating,
    )
    db.add(mp)
    db.commit()
    db.refresh(mp)
    return mp


def start_match(db: Session, match_id: int) -> Optional[Match]:
    """Start a match - auto-assign court if available"""
    match = db.query(Match).filter(Match.id == match_id).first()
    if not match:
        return None

    players = db.query(MatchPlayer).filter(MatchPlayer.match_id == match_id).count()
    if players < match.max_players:
        return None

    # Auto-assign an available court
    if not match.court_id:
        court = find_available_court(db)
        if court:
            match.court_id = court.id
            # Create booking
            now = datetime.utcnow()
            booking = Booking(
                player_id=db.query(MatchPlayer).filter(MatchPlayer.match_id == match_id).first().player_id,
                court_id=court.id,
                start_time=now,
                end_time=now + timedelta(hours=1),
                duration_hours=1.0,
                total_cost=court.hourly_rate,
                status=BookingStatus.IN_PROGRESS,
                is_match_booking=True,
            )
            db.add(booking)

    match.status = MatchStatus.IN_PROGRESS
    match.started_at = datetime.utcnow()
    db.commit()
    db.refresh(match)
    return match


def find_available_court(db: Session) -> Optional[Court]:
    """Find an available court not currently in use"""
    from sqlalchemy import and_
    busy_court_ids = db.query(Match.court_id).filter(
        Match.status == MatchStatus.IN_PROGRESS,
        Match.court_id.isnot(None)
    ).all()
    busy_ids = [c[0] for c in busy_court_ids]

    court = db.query(Court).filter(
        Court.is_active == True,
        Court.id.notin_(busy_ids)
    ).first()
    return court


def complete_match(db: Session, match_id: int, team1_score: int, team2_score: int) -> Optional[Match]:
    """Complete a match and update ELO ratings"""
    match = db.query(Match).filter(Match.id == match_id).first()
    if not match or match.status != MatchStatus.IN_PROGRESS:
        return None

    match.status = MatchStatus.COMPLETED
    match.team1_score = team1_score
    match.team2_score = team2_score
    match.ended_at = datetime.utcnow()

    winner_team = 1 if team1_score > team2_score else 2

    # Get players
    team1_players = db.query(MatchPlayer).filter(
        MatchPlayer.match_id == match_id, MatchPlayer.team == 1
    ).all()
    team2_players = db.query(MatchPlayer).filter(
        MatchPlayer.match_id == match_id, MatchPlayer.team == 2
    ).all()

    # Calculate average ELO
    team1_avg = sum(p.elo_before or p.player.elo_rating for p in team1_players) / len(team1_players)
    team2_avg = sum(p.elo_before or p.player.elo_rating for p in team2_players) / len(team2_players)

    if winner_team == 1:
        w_change, l_change = calculate_elo_change(team1_avg, team2_avg)
    else:
        l_change, w_change = calculate_elo_change(team2_avg, team1_avg)
        w_change, l_change = -l_change, -w_change

    # Update player ELOs
    for mp in team1_players:
        is_winner = (winner_team == 1)
        change = w_change if is_winner else l_change
        mp.is_winner = is_winner
        mp.elo_change = change
        mp.elo_after = (mp.elo_before or mp.player.elo_rating) + change
        mp.player.elo_rating += change
        if is_winner:
            mp.player.wins += 1
        else:
            mp.player.losses += 1
        mp.player.total_matches += 1

    for mp in team2_players:
        is_winner = (winner_team == 2)
        change = w_change if is_winner else l_change
        mp.is_winner = is_winner
        mp.elo_change = change
        mp.elo_after = (mp.elo_before or mp.player.elo_rating) + change
        mp.player.elo_rating += change
        if is_winner:
            mp.player.wins += 1
        else:
            mp.player.losses += 1
        mp.player.total_matches += 1

    db.commit()
    db.refresh(match)
    return match


def get_lobby_matches(db: Session, stage: Optional[MatchStage] = None) -> List[Match]:
    """Get all lobby matches, optionally filtered by stage"""
    query = db.query(Match).filter(Match.status == MatchStatus.LOBBY)
    if stage:
        query = query.filter(Match.stage == stage)
    return query.order_by(Match.created_at.desc()).all()