nautilus-network 0.56.0

// -------------------------------------------------------------------------------------------------
//  Copyright (C) 2015-2026 Nautech Systems Pty Ltd. All rights reserved.
//  https://nautechsystems.io
//
//  Licensed under the GNU Lesser General Public License Version 3.0 (the "License");
//  You may not use this file except in compliance with the License.
//  You may obtain a copy of the License at https://www.gnu.org/licenses/lgpl-3.0.en.html
//
//  Unless required by applicable law or agreed to in writing, software
//  distributed under the License is distributed on an "AS IS" BASIS,
//  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
//  See the License for the specific language governing permissions and
//  limitations under the License.
// -------------------------------------------------------------------------------------------------

//! Neutral error type for the WebSocket transport abstraction.

use std::io;

use thiserror::Error;

use super::message::CloseFrame;

/// A backend-agnostic WebSocket transport error.
///
/// Each backend translates its native error type into this enum via `From` impls
/// so the higher layers operate against a single error surface.
#[derive(Debug, Error)]
pub enum TransportError {
    /// Underlying I/O error from the socket.
    #[error("I/O error: {0}")]
    Io(#[from] io::Error),

    /// HTTP upgrade handshake failed.
    #[error("handshake failed: {0}")]
    Handshake(String),

    /// URL was invalid or unsupported.
    #[error("invalid URL: {0}")]
    InvalidUrl(String),

    /// TLS-layer failure during connect or stream operation.
    #[error("TLS error: {0}")]
    Tls(String),

    /// WebSocket protocol violation reported by the peer or detected locally.
    #[error("protocol error: {0}")]
    Protocol(String),

    /// Peer sent a close frame and the connection is closing.
    #[error("connection closed by peer")]
    ClosedByPeer(Option<CloseFrame>),

    /// Connection closed without a close frame (abnormal).
    #[error("connection closed")]
    ConnectionClosed,

    /// Connection reset by peer.
    #[error("connection reset")]
    ConnectionReset,

    /// Message exceeded the configured maximum size.
    #[error("message too large")]
    MessageTooLarge,

    /// Frame exceeded the configured maximum size.
    #[error("frame too large")]
    FrameTooLarge,

    /// UTF-8 validation failed on a text frame.
    ///
    /// Only emitted by backends that validate (e.g. `tokio-tungstenite`); the
    /// in-house HFT backend does not validate and will not produce this.
    #[error("invalid UTF-8 in text frame")]
    InvalidUtf8,

    /// Backend returned an error not covered by other variants. Carries a
    /// short description; consumers should treat as fatal.
    #[error("transport error: {0}")]
    Other(String),
}

impl TransportError {
    /// Returns `true` if the error indicates the connection is no longer usable.
    ///
    /// `InvalidUrl` is the only non-fatal variant: a bad URL is a caller-side
    /// configuration mistake that does not damage an existing connection.
    /// Everything else (including `Io` and the catch-all `Other`) implies the
    /// underlying transport cannot be reused.
    #[must_use]
    pub fn is_fatal(&self) -> bool {
        !matches!(self, Self::InvalidUrl(_))
    }

    /// Returns `true` for connection-closed style errors.
    #[must_use]
    pub fn is_closed(&self) -> bool {
        matches!(
            self,
            Self::ConnectionClosed | Self::ConnectionReset | Self::ClosedByPeer(_)
        )
    }
}

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

    use super::*;

    #[rstest]
    fn io_error_is_fatal() {
        let err = TransportError::Io(io::Error::other("boom"));
        assert!(err.is_fatal());
        assert!(!err.is_closed());
    }

    #[rstest]
    fn other_error_is_fatal() {
        let err = TransportError::Other("unexpected".into());
        assert!(err.is_fatal());
        assert!(!err.is_closed());
    }

    #[rstest]
    fn invalid_url_is_not_fatal() {
        let err = TransportError::InvalidUrl("ws://".into());
        assert!(!err.is_fatal());
        assert!(!err.is_closed());
    }

    #[rstest]
    fn closed_variants_are_closed_and_fatal() {
        let err = TransportError::ConnectionClosed;
        assert!(err.is_fatal());
        assert!(err.is_closed());

        let err = TransportError::ConnectionReset;
        assert!(err.is_fatal());
        assert!(err.is_closed());

        let err = TransportError::ClosedByPeer(Some(CloseFrame::new(1000, "bye")));
        assert!(err.is_fatal());
        assert!(err.is_closed());
    }

    #[rstest]
    fn protocol_error_is_fatal() {
        let err = TransportError::Protocol("bad opcode".into());
        assert!(err.is_fatal());
        assert!(!err.is_closed());
    }

    #[rstest]
    fn capacity_and_handshake_variants_are_fatal() {
        for err in [
            TransportError::MessageTooLarge,
            TransportError::FrameTooLarge,
            TransportError::InvalidUtf8,
            TransportError::Tls("bad".into()),
            TransportError::Handshake("bad".into()),
        ] {
            assert!(err.is_fatal(), "expected fatal: {err:?}");
            assert!(!err.is_closed(), "expected not closed: {err:?}");
        }
    }
}