use bcrypt::{hash, verify, DEFAULT_COST};
use rusqlite::Connection;
use std::collections::HashMap;

use crate::blackjack::BlackjackState;
use crate::server::database;
use crate::server::games::blackjack::{BlackjackGame, BlackjackHand};
use crate::server::games::registry::GameRegistry;
use crate::server::games::session::SessionManager;
use crate::server::games::traits::{GameError, GamePhase, GameState};

#[derive(Debug, Default)]
pub struct ConnectionState {
    user: Option<String>,
}

impl ConnectionState {
    pub fn user(&self) -> Option<&str> {
        self.user.as_deref()
    }
}

pub struct ServerCore {
    conn: Connection,
    sessions: SessionManager,
    registry: GameRegistry,
    bcrypt_cost: u32,
    blackjack: BlackjackGame,
}

impl ServerCore {
    pub fn new(conn: Connection) -> Self {
        Self::with_registry(conn, GameRegistry::with_defaults(), DEFAULT_COST)
    }

    pub fn with_registry(
        conn: Connection,
        registry: GameRegistry,
        bcrypt_cost: u32,
    ) -> Self {
        Self {
            conn,
            sessions: SessionManager::new(),
            registry,
            bcrypt_cost,
            blackjack: BlackjackGame::new(),
        }
    }

    /// Test/utility hook: use a fixed shoe for the next hand(s).
    pub fn with_blackjack_deck(mut self, deck: Vec<String>) -> Self {
        self.blackjack = BlackjackGame::with_deck(deck);
        self
    }

    pub fn open(path: &str) -> rusqlite::Result<Self> {
        let conn = Connection::open(path)?;
        database::init_db(&conn);
        Ok(Self::new(conn))
    }

    pub fn handle_message(&mut self, state: &mut ConnectionState, msg: &str) -> String {
        let parts: Vec<&str> = msg.splitn(5, ' ').collect();
        match parts[0] {
            "GAME_LIST" => {
                let mut games = self.registry.list_games();
                games.sort();
                let info: Vec<String> = games
                    .iter()
                    .filter_map(|game_type| {
                        self.registry
                            .get_game(game_type)
                            .map(|game| format!("{}:{}", game_type, game.get_name()))
                    })
                    .collect();
                if info.is_empty() {
                    "ERROR No games available".to_string()
                } else {
                    format!("GAME_LIST {}", info.join(","))
                }
            }
            "GAME_INFO" => {
                if parts.len() != 2 {
                    "ERROR Invalid GAME_INFO format. Usage: GAME_INFO <game_type>"
                        .to_string()
                } else {
                    match self.registry.get_game(parts[1]) {
                        Some(game) => format!(
                            "GAME_INFO {} {} {}",
                            parts[1],
                            game.get_name(),
                            game.get_description()
                        ),
                        None => format!("ERROR Unknown game type: {}", parts[1]),
                    }
                }
            }
            "PLAY_START" => {
                if parts.len() == 3 && parts[1] == "blackjack" {
                    self.handle_blackjack_start(state, parts[2])
                } else if parts.len() != 3 && parts.len() != 4 {
                    "ERROR Invalid PLAY_START format. Usage: PLAY_START <game_type> <bet_amount> [payload]"
                        .to_string()
                } else {
                    self.handle_play_start(state, parts[1], parts[2], parts.get(3).copied())
                }
            }
            "BLACKJACK_ACTION" => {
                if parts.len() != 3 {
                    "ERROR Invalid BLACKJACK_ACTION format. Usage: BLACKJACK_ACTION <session> <action>"
                        .to_string()
                } else {
                    self.handle_blackjack_action(state, parts[1], parts[2])
                }
            }
            "REGISTER" => {
                if parts.len() != 3 {
                    "ERROR Invalid REGISTER format".to_string()
                } else {
                    self.handle_register(parts[1], parts[2])
                }
            }
            "AUTH" => {
                if parts.len() != 3 {
                    "ERROR Invalid AUTH format".to_string()
                } else {
                    self.handle_auth(state, parts[1], parts[2])
                }
            }
            "PING" => "PONG".to_string(),
            "INFO" => self.handle_info(state),
            _ => msg.to_string(),
        }
    }

    fn handle_register(&mut self, username: &str, credential: &str) -> String {
        if database::get_hashed_password(&self.conn, username).is_some() {
            return "ERROR User already exists".to_string();
        }

        let hashed = match hash(credential, self.bcrypt_cost) {
            Ok(hashed) => hashed,
            Err(error) => {
                eprintln!("bcrypt failed for {username}: {error}");
                return "ERROR Could not hash password".to_string();
            }
        };

        match database::add_user(&self.conn, username, &hashed) {
            Ok(()) => format!("REGISTERED {}", username),
            Err(_) => "ERROR User already exists".to_string(),
        }
    }

    fn handle_auth(
        &mut self,
        state: &mut ConnectionState,
        username: &str,
        credential: &str,
    ) -> String {
        let Some(stored) = database::get_hashed_password(&self.conn, username) else {
            return "ERROR User not found".to_string();
        };

        let valid = if stored.starts_with("$2") {
            verify(credential, &stored).unwrap_or(false)
        } else if stored == credential {
            // Legacy unsalted SHA-256 row: accept once, then upgrade in place.
            match hash(credential, self.bcrypt_cost) {
                Ok(upgraded) => {
                    if let Err(error) =
                        database::set_hashed_password(&self.conn, username, &upgraded)
                    {
                        eprintln!("failed to upgrade password for {username}: {error}");
                    }
                }
                Err(error) => eprintln!("bcrypt failed for {username}: {error}"),
            }
            true
        } else {
            false
        };

        if valid {
            state.user = Some(username.to_string());
            format!("OK {}", username)
        } else {
            "ERROR Invalid credentials".to_string()
        }
    }

    fn handle_info(&self, state: &ConnectionState) -> String {
        let Some(user) = state.user.as_deref() else {
            return "ERROR Not logged in".to_string();
        };

        match (
            database::get_account_id(&self.conn, user),
            database::get_balance(&self.conn, user),
        ) {
            (Some(id), Some(balance)) => format!("INFO {} {} {}", user, id, balance),
            _ => "ERROR Error retrieving user info".to_string(),
        }
    }

    fn handle_blackjack_start(&mut self, state: &ConnectionState, bet_str: &str) -> String {
        let Some(user) = state.user.as_deref() else {
            return "ERROR Not logged in".to_string();
        };
        if self
            .sessions
            .get_user_sessions(user)
            .iter()
            .any(|session| session.game_type == "blackjack")
        {
            return "ERROR Blackjack hand already in progress".to_string();
        }
        let bet: i64 = match bet_str.parse() {
            Ok(bet) => bet,
            Err(_) => return "ERROR Invalid bet amount".to_string(),
        };
        if bet <= 0 {
            return "ERROR Invalid bet amount".to_string();
        }
        let Some(balance) = database::get_balance(&self.conn, user) else {
            return "ERROR Could not retrieve balance".to_string();
        };
        if balance < bet {
            return "ERROR Insufficient balance".to_string();
        }
        let balance = match database::debit(&mut self.conn, user, bet) {
            Ok(balance) => balance,
            Err(_) => return "ERROR Insufficient balance".to_string(),
        };

        let hand = self.blackjack.deal(bet as u64);
        let session_id = self.create_blackjack_session(user, &hand);
        self.blackjack_response(user, &session_id, hand, balance)
    }

    fn create_blackjack_session(&mut self, user: &str, hand: &BlackjackHand) -> String {
        let mut data = HashMap::new();
        data.insert("hand".to_string(), hand.to_json());
        let game_state = GameState {
            session_id: String::new(),
            game_type: "blackjack".to_string(),
            bet_amount: hand.bet,
            phase: GamePhase::Playing,
            data,
        };
        self.sessions
            .create_session(user, "blackjack".to_string(), game_state)
    }

    fn handle_blackjack_action(
        &mut self,
        state: &ConnectionState,
        session_id: &str,
        action: &str,
    ) -> String {
        let Some(user) = state.user.as_deref() else {
            return "ERROR Not logged in".to_string();
        };
        let Ok(session) = self.sessions.get_session(session_id) else {
            return "ERROR Session not found".to_string();
        };
        if session.username != user || session.game_type != "blackjack" {
            return "ERROR Invalid session".to_string();
        }
        let Some(raw) = session.state.data.get("hand") else {
            return "ERROR Missing hand".to_string();
        };
        let Ok(mut hand) = BlackjackHand::from_json(raw) else {
            return "ERROR Invalid hand".to_string();
        };
        if hand.is_done() {
            return "ERROR Hand is over".to_string();
        }

        let balance = database::get_balance(&self.conn, user).unwrap_or(0);
        match action {
            "hit" => {
                if let Err(error) = hand.hit() {
                    return format!("ERROR {error}");
                }
            }
            "stand" => hand.stand(),
            "double" => {
                if hand.player.len() != 2 {
                    return "ERROR Double is only allowed on the first two cards".to_string();
                }
                if database::debit(&mut self.conn, user, hand.base_bet as i64).is_err() {
                    return "ERROR Insufficient balance".to_string();
                }
                if let Err(error) = hand.double() {
                    let _ = database::credit(&mut self.conn, user, hand.base_bet as i64);
                    return format!("ERROR {error}");
                }
            }
            "cancel" => {
                let refund = session.bet_amount as i64;
                let balance = database::credit(&mut self.conn, user, refund).unwrap_or(balance);
                let _ = self.sessions.remove_session(session_id);
                hand.cancel();
                let state = hand.state(session_id, balance);
                return blackjack_wire(&state);
            }
            _ => return "ERROR Unknown action".to_string(),
        }

        let balance = database::get_balance(&self.conn, user).unwrap_or(balance);
        self.blackjack_response(user, session_id, hand, balance)
    }

    fn blackjack_response(
        &mut self,
        user: &str,
        session_id: &str,
        hand: BlackjackHand,
        balance: i64,
    ) -> String {
        if hand.is_done() {
            let state = hand.state(session_id, balance);
            let details = serde_json::to_string(&state).unwrap_or_else(|_| "{}".to_string());
            let balance = match database::settle_play(
                &mut self.conn,
                session_id,
                user,
                "blackjack",
                hand.bet as i64,
                hand.winnings as i64,
                &details,
            ) {
                Ok(balance) => balance,
                Err(error) => {
                    eprintln!("Blackjack settlement failed for {user}: {error}");
                    let _ = self.sessions.remove_session(session_id);
                    return "ERROR Failed to update balance".to_string();
                }
            };
            let _ = self.sessions.remove_session(session_id);
            let state = hand.state(session_id, balance);
            blackjack_wire(&state)
        } else {
            if let Ok(mut session) = self.sessions.get_session(session_id) {
                session.state.bet_amount = hand.bet;
                session
                    .state
                    .data
                    .insert("hand".to_string(), hand.to_json());
                let _ = self.sessions.update_session(session_id, session.state);
            }
            let state = hand.state(session_id, balance);
            blackjack_wire(&state)
        }
    }

    fn handle_play_start(
        &mut self,
        state: &ConnectionState,
        game_type: &str,
        bet_amount_str: &str,
        payload: Option<&str>,
    ) -> String {
        let Some(user) = state.user.as_deref() else {
            return "ERROR Not logged in".to_string();
        };

        let bet_amount: i64 = match bet_amount_str.parse() {
            Ok(amount) => amount,
            Err(_) => return "ERROR Invalid bet amount".to_string(),
        };
        if bet_amount <= 0 {
            return "ERROR Invalid bet amount".to_string();
        }

        let Some(game) = self.registry.get_game(game_type) else {
            return format!("ERROR Unknown game type: {}", game_type);
        };

        let Some(balance) = database::get_balance(&self.conn, user) else {
            return "ERROR Could not retrieve balance".to_string();
        };
        if balance < 0 {
            return "ERROR Invalid balance".to_string();
        }

        if let Err(error) = game.validate_bet(bet_amount as u64, balance as u64) {
            return game_error(error);
        }

        let game_state = game.prepare_state(user, bet_amount as u64);
        let params: Vec<&str> = payload.into_iter().collect();
        let new_state = match game.process_action(&game_state, "spin", &params) {
            Ok(state) => state,
            Err(error) => return game_error(error),
        };
        let result = match game.calculate_result(&new_state) {
            Ok(result) => result,
            Err(error) => return game_error(error),
        };

        // The session is the audit guard for the deduction and is created
        // before the balance changes. The durable audit row is `plays`.
        let session_id =
            self.sessions
                .create_session(user, game_type.to_string(), new_state.clone());

        let winnings = match i64::try_from(result.winnings) {
            Ok(winnings) => winnings,
            Err(_) => {
                let _ = self.sessions.remove_session(&session_id);
                return "ERROR Winnings out of range".to_string();
            }
        };

        let details =
            serde_json::to_string(&result.result_data).unwrap_or_else(|_| "{}".to_string());

        match database::apply_play(
            &mut self.conn,
            &session_id,
            user,
            game_type,
            bet_amount,
            winnings,
            &details,
        ) {
            Ok(new_balance) => {
                let _ = self.sessions.remove_session(&session_id);
                if game_type == "roulette" {
                    let number = result
                        .result_data
                        .get("number")
                        .cloned()
                        .unwrap_or_default();
                    let color = result
                        .result_data
                        .get("color")
                        .cloned()
                        .unwrap_or_default();
                    let bets = result
                        .result_data
                        .get("bets")
                        .cloned()
                        .unwrap_or_else(|| "{}".to_string());
                    format!(
                        "ROULETTE_RESULT {session_id} {winnings} {bet_amount} {new_balance} {number} {color} {bets}"
                    )
                } else {
                    let reels = result
                        .result_data
                        .get("reels")
                        .cloned()
                        .unwrap_or_default();
                    let win_type = result
                        .result_data
                        .get("win_type")
                        .cloned()
                        .unwrap_or_default();
                    let win_lines = result
                        .result_data
                        .get("win_lines")
                        .cloned()
                        .unwrap_or_else(|| "-".to_string());
                    let win_cells = result
                        .result_data
                        .get("win_cells")
                        .cloned()
                        .unwrap_or_else(|| "-".to_string());
                    format!(
                        "GAME_RESULT {session_id} {winnings} {bet_amount} {new_balance} {reels} {win_type} {win_lines} {win_cells}"
                    )
                }
            }
            Err(error) => {
                let _ = self.sessions.remove_session(&session_id);
                eprintln!("Balance transaction failed for {user}: {error}");
                "ERROR Failed to update balance".to_string()
            }
        }
    }

    pub fn disconnect(&mut self, state: &ConnectionState) {
        if let Some(user) = state.user.as_deref() {
            for session in self.sessions.get_user_sessions(user) {
                if session.game_type == "blackjack" {
                    let _ = database::credit(&mut self.conn, user, session.bet_amount as i64);
                }
                let _ = self.sessions.remove_session(&session.session_id);
            }
        }
    }

    pub fn balance(&self, username: &str) -> Option<i64> {
        database::get_balance(&self.conn, username)
    }

    pub fn play_count(&self, username: &str) -> i64 {
        database::count_plays(&self.conn, username)
    }

    pub fn session_count(&self) -> usize {
        self.sessions.len()
    }
}

fn game_error(error: GameError) -> String {
    match error {
        GameError::InsufficientBalance => "ERROR Insufficient balance".to_string(),
        GameError::InvalidBet => "ERROR Invalid bet amount".to_string(),
        GameError::InvalidAction(message) => format!("ERROR {message}"),
        GameError::GameOver => "ERROR Game over".to_string(),
        GameError::SessionNotFound => "ERROR Session not found".to_string(),
        GameError::InternalError(message) => format!("ERROR {message}"),
    }
}

fn blackjack_wire(state: &BlackjackState) -> String {
    format!(
        "BLACKJACK_STATE {}",
        serde_json::to_string(state).unwrap_or_else(|_| "{}".to_string())
    )
}