deepslate 0.3.1

//! Configuration loaded from environment variables or a builder API.

use std::collections::HashMap;
use std::net::{Ipv4Addr, SocketAddr};
use std::time::Duration;

use thiserror::Error;

/// Errors returned when building proxy configuration.
#[derive(Debug, Error)]
pub enum ConfigError {
    /// A socket address could not be parsed.
    #[error(transparent)]
    AddrParse(#[from] std::net::AddrParseError),
    /// A numeric value could not be parsed.
    #[error(transparent)]
    ParseInt(#[from] std::num::ParseIntError),
    /// A required environment variable was missing.
    #[error("required environment variable {0} is not set")]
    MissingEnv(&'static str),
    /// An environment variable contained an invalid boolean value.
    #[error("invalid boolean for {key}: {value}")]
    InvalidBool {
        /// The environment variable name.
        key: &'static str,
        /// The invalid value.
        value: String,
    },
    /// The forwarding secret file could not be read.
    #[error("failed to read forwarding secret from {path}")]
    SecretFileRead {
        /// The path that was attempted.
        path: String,
        /// The underlying I/O error.
        #[source]
        source: std::io::Error,
    },
    /// The configured forwarding secret is empty.
    #[error("forwarding secret must not be empty")]
    MissingForwardingSecret,
    /// The configured compression level is invalid.
    #[error("invalid compression level {0}: must be 0-12")]
    InvalidCompressionLevel(i32),
    /// A connection limit was set to zero.
    #[error("{0} must be greater than zero")]
    InvalidConnectionLimit(&'static str),
}

/// Proxy configuration.
#[derive(Debug, Clone)]
pub struct Config {
    /// Address the proxy listens on for Minecraft clients.
    pub listen_addr: SocketAddr,
    /// Address the gRPC control plane listens on.
    #[cfg(feature = "grpc")]
    pub grpc_addr: SocketAddr,
    /// Optional bearer token for gRPC control plane authentication.
    ///
    /// When set, every gRPC request must include an `authorization: Bearer <token>`
    /// metadata header. When `None`, the control plane accepts unauthenticated
    /// requests.
    #[cfg(feature = "grpc")]
    pub grpc_auth_token: Option<String>,
    /// Whether online-mode (Mojang authentication) is enabled.
    pub online_mode: bool,
    /// HMAC secret for Velocity modern forwarding.
    pub forwarding_secret: Vec<u8>,
    /// Compression threshold in bytes (-1 to disable).
    pub compression_threshold: i32,
    /// Zlib compression level (0-12, where 1 is fastest and 12 is best).
    pub compression_level: i32,
    /// MOTD shown in the server list.
    pub motd: String,
    /// Maximum player count shown in the server list.
    pub max_players: i32,
    /// Read timeout for client and backend connections.
    pub read_timeout: Duration,
    /// Backend connection timeout.
    ///
    /// Limits how long the proxy waits for a TCP connection to a backend
    /// server. Without this, a firewall silently dropping SYN packets can
    /// block for the OS TCP timeout (typically 75–120 s on Linux).
    pub connect_timeout: Duration,
    /// Maximum number of concurrent connections the proxy will accept.
    ///
    /// When this limit is reached, new connections are immediately dropped.
    pub max_connections: u32,
    /// Maximum number of concurrent connections allowed from a single IP address.
    ///
    /// When this limit is reached for a given IP, additional connections from
    /// that IP are immediately dropped.
    pub max_connections_per_ip: u32,
    /// Ordered list of server IDs to try for initial connections.
    pub try_servers: Vec<String>,
    /// Map of hostnames to ordered server ID lists for forced-host routing.
    ///
    /// When a player connects using a hostname that matches a key in this map,
    /// the proxy tries the associated servers (in order) instead of the global
    /// [`try_servers`](Config::try_servers) list. Only applies to the initial
    /// connection, not server switches.
    pub forced_hosts: HashMap<String, Vec<String>>,
    /// Log level filter string.
    pub log_level: String,
    /// Whether to output logs as JSON.
    pub log_json: bool,
    /// How long to wait for active connections to drain on shutdown.
    pub shutdown_drain: Duration,
    /// Address the Prometheus metrics exporter listens on.
    #[cfg(feature = "metrics")]
    pub metrics_addr: SocketAddr,
}

impl Config {
    /// Load configuration from environment variables.
    ///
    /// # Errors
    ///
    /// Returns an error if a required variable is missing or a value is invalid.
    pub fn from_env() -> Result<Self, ConfigError> {
        let listen_addr = env_or("DEEPSLATE_ADDR", "0.0.0.0:25565").parse()?;
        #[cfg(feature = "grpc")]
        let grpc_addr = env_or("DEEPSLATE_GRPC_ADDR", "127.0.0.1:25577").parse()?;
        #[cfg(feature = "grpc")]
        let grpc_auth_token = grpc_auth_token_from_env()?;
        let online_mode = env_bool("DEEPSLATE_ONLINE_MODE", true)?;
        let forwarding_secret = forwarding_secret_from_env()?;
        let compression_threshold = env_or("DEEPSLATE_COMPRESSION_THRESHOLD", "256").parse()?;
        let compression_level: i32 = env_or("DEEPSLATE_COMPRESSION_LEVEL", "1").parse()?;
        let motd = env_or("DEEPSLATE_MOTD", "A Deepslate Proxy");
        let max_players = env_or("DEEPSLATE_MAX_PLAYERS", "500").parse()?;
        let read_timeout_ms: u64 = env_or("DEEPSLATE_READ_TIMEOUT_MS", "30000").parse()?;
        let connect_timeout_ms: u64 = env_or("DEEPSLATE_CONNECT_TIMEOUT_MS", "5000").parse()?;
        let max_connections = env_or("DEEPSLATE_MAX_CONNECTIONS", "10000").parse()?;
        let max_connections_per_ip = env_or("DEEPSLATE_MAX_CONNECTIONS_PER_IP", "3").parse()?;
        let try_servers = env_or("DEEPSLATE_TRY_SERVERS", "")
            .split(',')
            .map(str::trim)
            .filter(|s| !s.is_empty())
            .map(String::from)
            .collect();
        let forced_hosts = parse_forced_hosts(&env_or("DEEPSLATE_FORCED_HOSTS", ""));
        let log_level = env_or("DEEPSLATE_LOG_LEVEL", "info");
        let log_json = env_bool("DEEPSLATE_LOG_JSON", false)?;
        let shutdown_drain_ms: u64 = env_or("DEEPSLATE_SHUTDOWN_DRAIN_MS", "10000").parse()?;
        #[cfg(feature = "metrics")]
        let metrics_addr = env_or("DEEPSLATE_METRICS_ADDR", "127.0.0.1:9100").parse()?;

        Self {
            listen_addr,
            #[cfg(feature = "grpc")]
            grpc_addr,
            #[cfg(feature = "grpc")]
            grpc_auth_token,
            online_mode,
            forwarding_secret,
            compression_threshold,
            compression_level,
            motd,
            max_players,
            read_timeout: Duration::from_millis(read_timeout_ms),
            connect_timeout: Duration::from_millis(connect_timeout_ms),
            max_connections,
            max_connections_per_ip,
            try_servers,
            forced_hosts,
            log_level,
            log_json,
            shutdown_drain: Duration::from_millis(shutdown_drain_ms),
            #[cfg(feature = "metrics")]
            metrics_addr,
        }
        .validate()
    }

    /// Validate the configuration and return it unchanged on success.
    ///
    /// # Errors
    ///
    /// Returns an error if any field contains an unsupported value.
    pub fn validate(self) -> Result<Self, ConfigError> {
        if self.forwarding_secret.is_empty() {
            return Err(ConfigError::MissingForwardingSecret);
        }

        if !(0..=12).contains(&self.compression_level) {
            return Err(ConfigError::InvalidCompressionLevel(self.compression_level));
        }

        if self.max_connections == 0 {
            return Err(ConfigError::InvalidConnectionLimit(
                "DEEPSLATE_MAX_CONNECTIONS",
            ));
        }

        if self.max_connections_per_ip == 0 {
            return Err(ConfigError::InvalidConnectionLimit(
                "DEEPSLATE_MAX_CONNECTIONS_PER_IP",
            ));
        }

        Ok(self)
    }
}

impl Default for Config {
    fn default() -> Self {
        Self {
            listen_addr: SocketAddr::from((Ipv4Addr::UNSPECIFIED, 25_565)),
            #[cfg(feature = "grpc")]
            grpc_addr: SocketAddr::from((Ipv4Addr::LOCALHOST, 25_577)),
            #[cfg(feature = "grpc")]
            grpc_auth_token: None,
            online_mode: true,
            forwarding_secret: Vec::new(),
            compression_threshold: 256,
            compression_level: 1,
            motd: "A Deepslate Proxy".to_string(),
            max_players: 500,
            read_timeout: Duration::from_secs(30),
            connect_timeout: Duration::from_secs(5),
            max_connections: 10_000,
            max_connections_per_ip: 3,
            try_servers: vec![],
            forced_hosts: HashMap::new(),
            log_level: "info".to_string(),
            log_json: false,
            shutdown_drain: Duration::from_secs(10),
            #[cfg(feature = "metrics")]
            metrics_addr: SocketAddr::from((Ipv4Addr::LOCALHOST, 9100)),
        }
    }
}

/// Read an environment variable or return a default.
fn env_or(key: &str, default: &str) -> String {
    std::env::var(key).unwrap_or_else(|_| default.to_string())
}

/// Read a required environment variable.
fn env_required(key: &'static str) -> Result<String, ConfigError> {
    std::env::var(key).map_err(|_| ConfigError::MissingEnv(key))
}

/// Parse a boolean environment variable (accepts true/false/1/0, case-insensitive).
fn env_bool(key: &'static str, default: bool) -> Result<bool, ConfigError> {
    std::env::var(key).map_or_else(
        |_| Ok(default),
        |val| match val.to_lowercase().as_str() {
            "true" | "1" => Ok(true),
            "false" | "0" => Ok(false),
            _ => Err(ConfigError::InvalidBool { key, value: val }),
        },
    )
}

/// Parse a forced-hosts string into a hostname-to-server-list map.
///
/// Expected format: `host1=srv1,srv2;host2=srv3,srv4`.
/// Entries are separated by `;`, and server IDs within an entry by `,`.
/// Hostnames are lowercased for case-insensitive matching.
/// Whitespace around delimiters is trimmed.
/// Empty entries (no `=`) and entries with no server IDs are silently ignored.
fn parse_forced_hosts(raw: &str) -> HashMap<String, Vec<String>> {
    let mut map = HashMap::new();
    for entry in raw.split(';') {
        let entry = entry.trim();
        if entry.is_empty() {
            continue;
        }
        let Some((host, servers_raw)) = entry.split_once('=') else {
            continue;
        };
        let host = host.trim().to_lowercase();
        if host.is_empty() {
            continue;
        }
        let servers: Vec<String> = servers_raw
            .split(',')
            .map(str::trim)
            .filter(|s| !s.is_empty())
            .map(String::from)
            .collect();
        if !servers.is_empty() {
            map.insert(host, servers);
        }
    }
    map
}

/// Load the Velocity forwarding secret.
///
/// Checks `DEEPSLATE_FORWARDING_SECRET_FILE` first — if set, the secret is
/// read from the file at that path (trailing newlines are stripped).  Otherwise
/// falls back to reading the value of `DEEPSLATE_FORWARDING_SECRET` directly.
///
/// When both variables are set, the file variant takes precedence following
/// the Docker / Kubernetes secrets convention.
fn forwarding_secret_from_env() -> Result<Vec<u8>, ConfigError> {
    if let Ok(path) = std::env::var("DEEPSLATE_FORWARDING_SECRET_FILE") {
        let path = path.trim().to_owned();
        let contents =
            std::fs::read(&path).map_err(|source| ConfigError::SecretFileRead { path, source })?;
        Ok(contents
            .strip_suffix(b"\r\n")
            .or_else(|| contents.strip_suffix(b"\n"))
            .unwrap_or(&contents)
            .to_vec())
    } else {
        env_required("DEEPSLATE_FORWARDING_SECRET").map(String::into_bytes)
    }
}

/// Load the optional gRPC authentication token.
///
/// Checks `DEEPSLATE_GRPC_AUTH_TOKEN_FILE` first — if set, the token is read
/// from the file at that path (trailing newlines are stripped). Otherwise falls
/// back to reading `DEEPSLATE_GRPC_AUTH_TOKEN` directly. Returns `None` when
/// neither variable is set.
#[cfg(feature = "grpc")]
fn grpc_auth_token_from_env() -> Result<Option<String>, ConfigError> {
    if let Ok(path) = std::env::var("DEEPSLATE_GRPC_AUTH_TOKEN_FILE") {
        let path = path.trim().to_owned();
        let contents =
            std::fs::read(&path).map_err(|source| ConfigError::SecretFileRead { path, source })?;
        let token = contents
            .strip_suffix(b"\r\n")
            .or_else(|| contents.strip_suffix(b"\n"))
            .unwrap_or(&contents);
        let token = String::from_utf8_lossy(token).into_owned();
        if token.is_empty() {
            Ok(None)
        } else {
            Ok(Some(token))
        }
    } else if let Ok(val) = std::env::var("DEEPSLATE_GRPC_AUTH_TOKEN") {
        let val = val.trim().to_owned();
        if val.is_empty() {
            Ok(None)
        } else {
            Ok(Some(val))
        }
    } else {
        Ok(None)
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    const FILE_VAR: &str = "DEEPSLATE_FORWARDING_SECRET_FILE";
    const ENV_VAR: &str = "DEEPSLATE_FORWARDING_SECRET";

    #[test]
    fn secret_from_env_var() {
        temp_env::with_vars([(ENV_VAR, Some("my-secret")), (FILE_VAR, None)], || {
            let secret = forwarding_secret_from_env().unwrap();
            assert_eq!(secret, b"my-secret");
        });
    }

    #[test]
    fn secret_from_file() {
        let dir = tempfile::tempdir().unwrap();
        let path = dir.path().join("secret");
        std::fs::write(&path, b"file-secret").unwrap();

        temp_env::with_vars(
            [
                (FILE_VAR, Some(path.to_str().unwrap())),
                (ENV_VAR, None::<&str>),
            ],
            || {
                let secret = forwarding_secret_from_env().unwrap();
                assert_eq!(secret, b"file-secret");
            },
        );
    }

    #[test]
    fn secret_file_trims_trailing_lf() {
        let dir = tempfile::tempdir().unwrap();
        let path = dir.path().join("secret");
        std::fs::write(&path, b"file-secret\n").unwrap();

        temp_env::with_vars(
            [
                (FILE_VAR, Some(path.to_str().unwrap())),
                (ENV_VAR, None::<&str>),
            ],
            || {
                let secret = forwarding_secret_from_env().unwrap();
                assert_eq!(secret, b"file-secret");
            },
        );
    }

    #[test]
    fn secret_file_trims_trailing_crlf() {
        let dir = tempfile::tempdir().unwrap();
        let path = dir.path().join("secret");
        std::fs::write(&path, b"file-secret\r\n").unwrap();

        temp_env::with_vars(
            [
                (FILE_VAR, Some(path.to_str().unwrap())),
                (ENV_VAR, None::<&str>),
            ],
            || {
                let secret = forwarding_secret_from_env().unwrap();
                assert_eq!(secret, b"file-secret");
            },
        );
    }

    #[test]
    fn secret_file_takes_precedence() {
        let dir = tempfile::tempdir().unwrap();
        let path = dir.path().join("secret");
        std::fs::write(&path, b"from-file").unwrap();

        temp_env::with_vars(
            [
                (FILE_VAR, Some(path.to_str().unwrap())),
                (ENV_VAR, Some("from-env")),
            ],
            || {
                let secret = forwarding_secret_from_env().unwrap();
                assert_eq!(secret, b"from-file");
            },
        );
    }

    #[test]
    fn secret_file_missing_returns_error() {
        temp_env::with_vars(
            [(FILE_VAR, Some("/no/such/file")), (ENV_VAR, None::<&str>)],
            || {
                let err = forwarding_secret_from_env().unwrap_err();
                assert!(
                    matches!(err, ConfigError::SecretFileRead { .. }),
                    "expected SecretFileRead, got {err:?}"
                );
            },
        );
    }

    #[test]
    fn secret_neither_set_returns_error() {
        temp_env::with_vars([(ENV_VAR, None::<&str>), (FILE_VAR, None::<&str>)], || {
            let err = forwarding_secret_from_env().unwrap_err();
            assert!(
                matches!(err, ConfigError::MissingEnv(_)),
                "expected MissingEnv, got {err:?}"
            );
        });
    }

    #[test]
    fn parse_forced_hosts_single_entry() {
        let map = parse_forced_hosts("pvp.example.com=pvp,pvp-fallback");
        assert_eq!(
            map.get("pvp.example.com").unwrap(),
            &["pvp", "pvp-fallback"]
        );
    }

    #[test]
    fn parse_forced_hosts_multiple_entries() {
        let map = parse_forced_hosts("pvp.example.com=pvp;lobby.example.com=lobby1,lobby2");
        assert_eq!(map.len(), 2);
        assert_eq!(map.get("pvp.example.com").unwrap(), &["pvp"]);
        assert_eq!(map.get("lobby.example.com").unwrap(), &["lobby1", "lobby2"]);
    }

    #[test]
    fn parse_forced_hosts_trims_whitespace() {
        let map = parse_forced_hosts(" pvp.example.com = pvp , games ; lobby.example.com = lobby ");
        assert_eq!(map.get("pvp.example.com").unwrap(), &["pvp", "games"]);
        assert_eq!(map.get("lobby.example.com").unwrap(), &["lobby"]);
    }

    #[test]
    fn parse_forced_hosts_lowercases_hostname() {
        let map = parse_forced_hosts("PVP.Example.COM=pvp");
        assert!(map.contains_key("pvp.example.com"));
        assert!(!map.contains_key("PVP.Example.COM"));
    }

    #[test]
    fn parse_forced_hosts_empty_string() {
        let map = parse_forced_hosts("");
        assert!(map.is_empty());
    }

    #[test]
    fn parse_forced_hosts_skips_malformed() {
        let map = parse_forced_hosts("no-equals;also-bad;good.host=srv");
        assert_eq!(map.len(), 1);
        assert_eq!(map.get("good.host").unwrap(), &["srv"]);
    }

    #[test]
    fn parse_forced_hosts_skips_empty_server_list() {
        let map = parse_forced_hosts("empty.host=;good.host=srv");
        assert_eq!(map.len(), 1);
        assert!(!map.contains_key("empty.host"));
    }

    #[test]
    fn validate_rejects_zero_max_connections() {
        let config = Config {
            forwarding_secret: b"secret".to_vec(),
            max_connections: 0,
            ..Config::default()
        };
        let err = config.validate().unwrap_err();
        assert!(
            matches!(err, ConfigError::InvalidConnectionLimit(_)),
            "expected InvalidConnectionLimit, got {err:?}"
        );
    }

    #[test]
    fn validate_rejects_zero_max_connections_per_ip() {
        let config = Config {
            forwarding_secret: b"secret".to_vec(),
            max_connections_per_ip: 0,
            ..Config::default()
        };
        let err = config.validate().unwrap_err();
        assert!(
            matches!(err, ConfigError::InvalidConnectionLimit(_)),
            "expected InvalidConnectionLimit, got {err:?}"
        );
    }

    #[test]
    fn validate_accepts_valid_connection_limits() {
        let config = Config {
            forwarding_secret: b"secret".to_vec(),
            max_connections: 5000,
            max_connections_per_ip: 10,
            ..Config::default()
        };
        assert!(config.validate().is_ok());
    }
}