use super::traits::{Game, GameError, GamePhase, GameResult, GameState};
use crate::crash::{
    CrashState, SEED_LEN, commit_seed, crash_point_from_seed, payout, seed_to_uniform,
};
use rand::RngCore;
use serde::{Deserialize, Serialize};
use std::collections::{HashMap, VecDeque};
use std::sync::{Arc, Mutex};
use std::time::Instant;

/// Monotonic seconds. Injected so tests can drive a round without sleeping.
pub trait Clock: Send + Sync {
    fn now(&self) -> f64;
}

pub struct RealClock {
    origin: Instant,
}

impl RealClock {
    pub fn new() -> Self {
        Self {
            origin: Instant::now(),
        }
    }
}

impl Clock for RealClock {
    fn now(&self) -> f64 {
        self.origin.elapsed().as_secs_f64()
    }
}

/// A clock a test can move by hand. Clones share the same instant.
#[derive(Clone, Default)]
pub struct ManualClock {
    seconds: Arc<Mutex<f64>>,
}

impl ManualClock {
    pub fn new() -> Self {
        Self::default()
    }

    pub fn set(&self, seconds: f64) {
        *self.seconds.lock().unwrap() = seconds;
    }

    pub fn advance(&self, seconds: f64) {
        *self.seconds.lock().unwrap() += seconds;
    }

    pub fn seconds(&self) -> f64 {
        *self.seconds.lock().unwrap()
    }
}

impl Clock for ManualClock {
    fn now(&self) -> f64 {
        self.seconds()
    }
}

/// One crash round. Lives in the game session's `data` while it runs.
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct CrashRound {
    pub bet: u64,
    /// Drawn at start, revealed only when the round ends.
    pub crash_point: f64,
    /// The 32 random bytes the crash point commits to, hex encoded. Kept on
    /// the server until the round ends.
    pub seed: String,
    /// `sha256(seed)` in hex, sent with the start reply.
    pub commit: String,
    pub started_at: f64,
    /// Server Unix time at start, milliseconds, for clock sync.
    pub started_at_ms: u64,
    /// `running`, `cashed`, `crashed` or `forfeit`.
    pub phase: String,
    pub result: String,
    /// Live while running; frozen at the final value afterwards.
    pub multiplier: f64,
    pub payout: u64,
}

impl CrashRound {
    pub fn new(bet: u64, seed: [u8; SEED_LEN], started_at: f64, started_at_ms: u64) -> Self {
        let crash_point = crash_point_from_seed(&seed);
        Self {
            bet,
            crash_point,
            seed: seed_hex(&seed),
            commit: commit_seed(&seed),
            started_at,
            started_at_ms,
            phase: "running".to_string(),
            result: "playing".to_string(),
            multiplier: 1.0,
            payout: 0,
        }
    }

    pub fn is_running(&self) -> bool {
        self.phase == "running"
    }

    pub fn cash_out(&mut self, multiplier: f64) -> u64 {
        self.multiplier = multiplier;
        self.payout = payout(self.bet, multiplier);
        self.phase = "cashed".to_string();
        self.result = "cashed".to_string();
        self.payout
    }

    /// The round ended before the player could cash out.
    pub fn crash(&mut self) {
        self.multiplier = self.crash_point;
        self.payout = 0;
        self.phase = "crashed".to_string();
        self.result = "crashed".to_string();
    }

    pub fn forfeit(&mut self) {
        self.payout = 0;
        self.phase = "forfeit".to_string();
        self.result = "forfeit".to_string();
    }

    pub fn state(&self, session_id: &str, balance: i64) -> CrashState {
        CrashState {
            session_id: session_id.to_string(),
            phase: self.phase.clone(),
            bet: self.bet,
            balance,
            multiplier: self.multiplier,
            potential: payout(self.bet, self.multiplier),
            started_at: self.started_at_ms,
            crash_point: if self.is_running() {
                None
            } else {
                Some(self.crash_point)
            },
            payout: self.payout,
            result: self.result.clone(),
            commit: Some(self.commit.clone()),
            seed: if self.is_running() {
                None
            } else {
                Some(self.seed.clone())
            },
        }
    }

    pub fn to_json(&self) -> String {
        serde_json::to_string(self).unwrap_or_default()
    }

    pub fn from_json(raw: &str) -> Result<Self, serde_json::Error> {
        serde_json::from_str(raw)
    }
}

/// Crash-point generator. Tests queue fixed uniforms; production draws random
/// ones. The visible crash point stays hidden until `poll` or cashout ends the
/// round.
pub struct CrashGame {
    uniforms: VecDeque<f64>,
}

/// Hex encode a round seed. Lowercase, no separators.
fn seed_hex(seed: &[u8]) -> String {
    let mut out = String::with_capacity(seed.len() * 2);
    for byte in seed {
        use std::fmt::Write as _;
        let _ = write!(out, "{byte:02x}");
    }
    out
}

/// Draw a seed whose committed point matches a queued test uniform.
///
/// The first eight bytes are the big-endian integer closest to
/// `uniform * 2^64`; the remaining bytes are zero. This keeps the existing
/// deterministic crash-point tests meaningful while every round still has a
/// real seed.
fn seed_from_uniform(uniform: f64) -> [u8; SEED_LEN] {
    let uniform = if uniform.is_finite() {
        uniform.clamp(0.0, 0.999_999_999_999_999_9)
    } else {
        0.0
    };
    let value = (uniform * 18_446_744_073_709_551_616.0) as u64;
    let mut seed = [0u8; SEED_LEN];
    seed[..8].copy_from_slice(&value.to_be_bytes());
    seed
}

impl CrashGame {
    pub fn new() -> Self {
        Self {
            uniforms: VecDeque::new(),
        }
    }

    pub fn with_uniform(uniform: f64) -> Self {
        Self::with_uniforms([uniform])
    }

    pub fn with_uniforms(uniforms: impl IntoIterator<Item = f64>) -> Self {
        Self {
            uniforms: uniforms.into_iter().collect(),
        }
    }

    /// Draw the next round seed. Tests supply uniforms; production uses the
    /// operating system's random source.
    pub fn next_seed(&mut self) -> [u8; SEED_LEN] {
        if let Some(uniform) = self.uniforms.pop_front() {
            return seed_from_uniform(uniform);
        }
        let mut seed = [0u8; SEED_LEN];
        rand::thread_rng().fill_bytes(&mut seed);
        seed
    }

    /// Kept for callers that only need the point a queued uniform encodes.
    pub fn next_crash_point(&mut self) -> f64 {
        crash_point_from_seed(&self.next_seed())
    }

    /// The uniform encoded by a seed, exposed for verification tests.
    pub fn uniform_of(seed: &[u8; SEED_LEN]) -> f64 {
        seed_to_uniform(seed)
    }
}

impl Game for CrashGame {
    fn game_type(&self) -> &'static str {
        "crash"
    }

    fn get_name(&self) -> &'static str {
        "Crash"
    }

    fn get_description(&self) -> &'static str {
        "Crash: cash out before the multiplier crashes."
    }

    fn prepare_state(&self, _username: &str, bet_amount: u64) -> GameState {
        let mut data = HashMap::new();
        data.insert("status".to_string(), "ready".to_string());
        GameState {
            session_id: String::new(),
            game_type: "crash".to_string(),
            bet_amount,
            phase: GamePhase::WaitingToStart,
            data,
        }
    }

    fn process_action(
        &self,
        _state: &GameState,
        _action: &str,
        _params: &[&str],
    ) -> Result<GameState, GameError> {
        Err(GameError::InvalidAction(
            "Crash uses CRASH_CASHOUT and CRASH_FORFEIT".to_string(),
        ))
    }

    fn calculate_result(&self, _state: &GameState) -> Result<GameResult, GameError> {
        Err(GameError::InternalError(
            "Crash settles through CRASH_CASHOUT".to_string(),
        ))
    }
}