// file: crates/common/game-realtime-websocket-lib/src/config.rs
// version: 1

const DEFAULT_CLOSE_TIMEOUT: std::time::Duration = std::time::Duration::from_secs(2);
const DEFAULT_CONNECT_TIMEOUT: std::time::Duration = std::time::Duration::from_secs(10);
const DEFAULT_MAX_FRAME_SIZE: usize = 1024 * 1024;
const DEFAULT_MAX_MESSAGE_SIZE: usize = 1024 * 1024;
const DEFAULT_MAX_WRITE_BUFFER_SIZE: usize = 2 * 1024 * 1024;
const DEFAULT_SEND_TIMEOUT: std::time::Duration = std::time::Duration::from_secs(5);
const DEFAULT_WRITE_BUFFER_SIZE: usize = 64 * 1024;

/// Product-facing limits and operation deadlines for one WebSocket connection.
#[derive(Clone, Copy, Debug, Eq, PartialEq)]
pub struct WebSocketConfig {
    max_message_size: usize,
    max_frame_size: usize,
    write_buffer_size: usize,
    max_write_buffer_size: usize,
    connect_timeout: std::time::Duration,
    send_timeout: std::time::Duration,
    close_timeout: std::time::Duration,
}

impl Default for WebSocketConfig {
    fn default() -> Self {
        return Self {
            max_message_size: DEFAULT_MAX_MESSAGE_SIZE,
            max_frame_size: DEFAULT_MAX_FRAME_SIZE,
            write_buffer_size: DEFAULT_WRITE_BUFFER_SIZE,
            max_write_buffer_size: DEFAULT_MAX_WRITE_BUFFER_SIZE,
            connect_timeout: DEFAULT_CONNECT_TIMEOUT,
            send_timeout: DEFAULT_SEND_TIMEOUT,
            close_timeout: DEFAULT_CLOSE_TIMEOUT,
        };
    }
}

impl WebSocketConfig {
    /// Returns a copy with a different maximum binary message size.
    #[must_use]
    pub fn with_max_message_size(mut self, value: usize) -> Self {
        self.max_message_size = value;
        return self;
    }

    /// Returns a copy with a different maximum WebSocket frame payload size.
    #[must_use]
    pub fn with_max_frame_size(mut self, value: usize) -> Self {
        self.max_frame_size = value;
        return self;
    }

    /// Returns a copy with a different Tungstenite write-buffer target.
    #[must_use]
    pub fn with_write_buffer_size(mut self, value: usize) -> Self {
        self.write_buffer_size = value;
        return self;
    }

    /// Returns a copy with a different hard maximum for the Tungstenite write buffer.
    #[must_use]
    pub fn with_max_write_buffer_size(mut self, value: usize) -> Self {
        self.max_write_buffer_size = value;
        return self;
    }

    /// Returns a copy with a different connection or handshake deadline.
    #[must_use]
    pub fn with_connect_timeout(mut self, value: std::time::Duration) -> Self {
        self.connect_timeout = value;
        return self;
    }

    /// Returns a copy with a different deadline for one send operation.
    #[must_use]
    pub fn with_send_timeout(mut self, value: std::time::Duration) -> Self {
        self.send_timeout = value;
        return self;
    }

    /// Returns a copy with a different deadline for a clean local close operation.
    #[must_use]
    pub fn with_close_timeout(mut self, value: std::time::Duration) -> Self {
        self.close_timeout = value;
        return self;
    }

    /// Returns the configured maximum binary message size.
    #[must_use]
    pub fn max_message_size(&self) -> usize {
        return self.max_message_size;
    }

    /// Returns the configured maximum WebSocket frame payload size.
    #[must_use]
    pub fn max_frame_size(&self) -> usize {
        return self.max_frame_size;
    }

    /// Returns the configured Tungstenite write-buffer target.
    #[must_use]
    pub fn write_buffer_size(&self) -> usize {
        return self.write_buffer_size;
    }

    /// Returns the configured hard maximum for the Tungstenite write buffer.
    #[must_use]
    pub fn max_write_buffer_size(&self) -> usize {
        return self.max_write_buffer_size;
    }

    /// Returns the configured connection or handshake deadline.
    #[must_use]
    pub fn connect_timeout(&self) -> std::time::Duration {
        return self.connect_timeout;
    }

    /// Returns the configured deadline for one send operation.
    #[must_use]
    pub fn send_timeout(&self) -> std::time::Duration {
        return self.send_timeout;
    }

    /// Returns the configured deadline for a clean local close operation.
    #[must_use]
    pub fn close_timeout(&self) -> std::time::Duration {
        return self.close_timeout;
    }

    /// Validates all invariants required before creating a WebSocket endpoint or connection.
    pub fn validate(&self) -> Result<(), game_realtime_transport_lib::TransportError> {
        if self.max_message_size == 0 {
            return Err(invalid_configuration("max_message_size must be greater than zero"));
        }
        if self.max_frame_size == 0 {
            return Err(invalid_configuration("max_frame_size must be greater than zero"));
        }
        if self.max_frame_size > self.max_message_size {
            return Err(invalid_configuration("max_frame_size must not exceed max_message_size"));
        }
        let minimum_max_write_buffer_size = match self.write_buffer_size.checked_add(self.max_message_size) {
            Some(value) => value,
            None => return Err(invalid_configuration("write_buffer_size + max_message_size overflows usize")),
        };
        if self.max_write_buffer_size < minimum_max_write_buffer_size {
            return Err(invalid_configuration("max_write_buffer_size must fit write_buffer_size plus one maximum-sized message"));
        }
        if self.connect_timeout.is_zero() {
            return Err(invalid_configuration("connect_timeout must be greater than zero"));
        }
        if self.send_timeout.is_zero() {
            return Err(invalid_configuration("send_timeout must be greater than zero"));
        }
        if self.close_timeout.is_zero() {
            return Err(invalid_configuration("close_timeout must be greater than zero"));
        }
        return Ok(());
    }
}

fn invalid_configuration(detail: &str) -> game_realtime_transport_lib::TransportError {
    return game_realtime_transport_lib::TransportError::new(game_realtime_transport_lib::TransportErrorKind::InvalidConfiguration, detail);
}

#[cfg(test)]
#[path = "../unit_tests/config.rs"]
mod tests;