use argon2::{Argon2, PasswordHasher, PasswordVerifier};

pub fn hash_password(password: &str) -> Result<String> {
    let salt = SaltString::generate(&mut OsRng);
    let argon2 = Argon2::default();
    let hash = argon2.hash_password(password.as_bytes(), &salt)?;
    Ok(hash.to_string())
}

pub fn verify_password(password: &str, hash: &str) -> Result<bool> {
    let parsed = PasswordHash::new(hash)?;
    Ok(Argon2::default()
        .verify_password(password.as_bytes(), &parsed)
        .is_ok())
}

use subtle::ConstantTimeEq;

fn validate_password(provided: &str, expected: &str) -> bool {
    // Constant-time comparison prevents timing attacks
    // Attackers cannot infer password length/content from response times
    provided.as_bytes().ct_eq(expected.as_bytes()).into()
}

const MAX_AUTH_FAILURES: u32 = 10;
const AUTH_LOCKOUT_SECONDS: u64 = 60;

impl ClientState {
    /// Check if AUTH is currently blocked
    pub fn auth_is_blocked(&self) -> Option<u64> {
        let lockout_until = self.auth_lockout_until.load(Ordering::Relaxed);
        let now = current_timestamp_secs();
        if now < lockout_until {
            Some(lockout_until - now)  // Seconds remaining
        } else {
            None
        }
    }

    /// Record a failed AUTH attempt
    pub fn auth_record_failure(&self) -> bool {
        let failures = self.auth_failures.fetch_add(1, Ordering::Relaxed) + 1;
        if failures >= MAX_AUTH_FAILURES {
            let lockout_until = current_timestamp_secs() + AUTH_LOCKOUT_SECONDS;
            self.auth_lockout_until.store(lockout_until, Ordering::Relaxed);
            true  // Now locked out
        } else {
            false
        }
    }

    /// Reset on successful auth
    pub fn auth_reset_failures(&self) {
        self.auth_failures.store(0, Ordering::Relaxed);
        self.auth_lockout_until.store(0, Ordering::Relaxed);
    }
}

pub struct AclUser {
    /// Username
    name: String,

    /// Argon2id password hash
    password_hash: Option<String>,

    /// Account enabled
    enabled: bool,

    /// Command permissions
    commands: CommandPermissions,

    /// Key access patterns
    keys: KeyPatterns,

    /// Pub/Sub channel patterns
    channels: ChannelPatterns,
}

pub struct CommandPermissions {
    /// Explicitly allowed commands
    allowed: HashSet<String>,

    /// Explicitly denied commands
    denied: HashSet<String>,

    /// Allowed categories (@read, @write, @admin, etc.)
    categories: HashSet<String>,
}

pub struct TlsConfig {
    /// Server certificate chain
    cert_chain: Vec<Certificate>,

    /// Private key
    private_key: PrivateKey,

    /// CA for client verification (optional)
    client_ca: Option<RootCertStore>,

    /// Require client certificates
    require_client_auth: bool,
}

const ALLOWED_GLOBALS: &[&str] = &[
    // Redis API
    "redis", "KEYS", "ARGV",

    // Safe standard library
    "string", "table", "math",
    "tonumber", "tostring", "type",
    "pairs", "ipairs", "next",
    "unpack", "select", "error",
    "pcall", "assert",

    // Constants
    "cjson", "cmsgpack",
];

// REMOVED (dangerous)
// os, io, debug, loadfile, dofile, require, package

pub struct LuaSandbox {
    /// Maximum memory usage (bytes)
    memory_limit: usize,

    /// Maximum instructions before timeout
    instruction_limit: u64,

    /// Execution timeout
    timeout: Duration,
}

fn sha1_hash(script: &str) -> String {
    use sha1::{Sha1, Digest};
    let mut hasher = Sha1::new();
    hasher.update(script.as_bytes());
    let result = hasher.finalize();
    result.iter().map(|b| format!("{:02x}", b)).collect()
}

const KEYS_WARN_THRESHOLD: usize = 10_000;
const KEYS_MAX_RETURN: usize = 100_000;

pub fn cmd_keys(...) -> Result<Frame> {
    let db_size = db.len();

    // Warn on large databases
    if db_size > KEYS_WARN_THRESHOLD {
        tracing::warn!(
            "KEYS command on large database ({} keys). Consider SCAN instead.",
            db_size
        );
    }

    // Collect with limit
    let keys: Vec<_> = db.keys()
        .filter(|k| pattern.matches(k))
        .take(KEYS_MAX_RETURN)
        .collect();

    Ok(Frame::Array(keys))
}

pub struct ConnectionLimits {
    /// Maximum concurrent connections
    max_clients: usize,

    /// Maximum input buffer size per client
    max_input_buffer: usize,

    /// Maximum output buffer size per client
    max_output_buffer: usize,

    /// Connection timeout (idle)
    timeout: Duration,
}

pub struct RateLimiter {
    /// Requests per second per IP
    requests_per_second: u32,

    /// Burst allowance
    burst_size: u32,

    /// Current state per IP
    state: DashMap<IpAddr, TokenBucket>,
}