use std::env;

/// Server configuration loaded from environment variables with sensible defaults.
#[derive(Debug, Clone)]
pub struct Config {
    /// Bind address (default: 0.0.0.0)
    pub host: String,
    /// Bind port (default: 8080)
    pub port: u16,
    /// Allowed CORS origins. "*" permits everything (dev mode).
    pub cors_origins: Vec<String>,
    /// Maximum concurrent sessions (default: 100)
    pub max_sessions: usize,
    /// Seconds before an idle session is reaped (default: 300)
    pub idle_timeout_secs: u64,
    /// Max display-frame buffer depth per session (default: 60 ≈ 2 s @ 30 fps)
    pub frame_buffer_size: usize,
}

impl Config {
    /// Build configuration from `BUTTERFLY_*` env vars, falling back to defaults.
    pub fn from_env() -> Self {
        Self {
            host: env::var("BUTTERFLY_HOST").unwrap_or_else(|_| "0.0.0.0".into()),
            port: env::var("BUTTERFLY_PORT")
                .ok()
                .and_then(|v| v.parse().ok())
                .unwrap_or(8080),
            cors_origins: env::var("BUTTERFLY_CORS_ORIGINS")
                .map(|v| v.split(',').map(|s| s.trim().to_string()).collect())
                .unwrap_or_else(|_| vec!["*".into()]),
            max_sessions: env::var("BUTTERFLY_MAX_SESSIONS")
                .ok()
                .and_then(|v| v.parse().ok())
                .unwrap_or(100),
            idle_timeout_secs: env::var("BUTTERFLY_IDLE_TIMEOUT")
                .ok()
                .and_then(|v| v.parse().ok())
                .unwrap_or(300),
            frame_buffer_size: env::var("BUTTERFLY_FRAME_BUFFER")
                .ok()
                .and_then(|v| v.parse().ok())
                .unwrap_or(60),
        }
    }

    /// Address string suitable for `bind()`, e.g. "0.0.0.0:8080".
    pub fn bind_addr(&self) -> String {
        format!("{}:{}", self.host, self.port)
    }
}