pushwire-client 0.1.1

use std::collections::HashMap;

use futures_util::{SinkExt, StreamExt};
use pushwire_core::{ChannelKind, Frame, SystemOp};
use reqwest::Client as HttpClient;
use tokio::sync::mpsc;
use tokio::task::JoinHandle;
use tokio_tungstenite::tungstenite::Message as WsMessage;
use tracing::{debug, warn};
use uuid::Uuid;

use crate::session::ConnectError;

/// Transport preference for the client connection.
#[non_exhaustive]
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum TransportPreference {
    /// Try WebSocket first, fall back to SSE if unavailable.
    WsFirst,
    /// Try SSE first, fall back to WebSocket if unavailable.
    SseFirst,
    /// WebSocket only — fail if upgrade is rejected.
    WsOnly,
    /// SSE only — client→server via POST /ack endpoint.
    SseOnly,
}

/// Message sent from session to the writer task.
#[derive(Debug)]
pub(crate) enum OutboundMsg<C: ChannelKind> {
    Frame(Frame<C>),
    System(SystemOp<C>),
    Close,
}

/// Message received from transport and forwarded to session processor.
#[derive(Debug)]
pub(crate) enum InboundMsg<C: ChannelKind> {
    Frame(Frame<C>),
    System(SystemOp<C>),
    Closed,
}

/// Active transport handle. Owns background tasks for I/O.
pub(crate) enum ActiveTransport<C: ChannelKind> {
    WebSocket {
        outbound_tx: mpsc::Sender<OutboundMsg<C>>,
        reader_handle: JoinHandle<()>,
        writer_handle: JoinHandle<()>,
    },
    Sse {
        http: HttpClient,
        ack_url: String,
        client_id: Uuid,
        reader_handle: JoinHandle<()>,
    },
}

impl<C: ChannelKind> ActiveTransport<C> {
    /// Send a frame to the server (WebSocket only).
    pub(crate) async fn send_frame(
        &self,
        frame: Frame<C>,
    ) -> Result<(), crate::session::SendError> {
        match self {
            ActiveTransport::WebSocket { outbound_tx, .. } => outbound_tx
                .send(OutboundMsg::Frame(frame))
                .await
                .map_err(|_| crate::session::SendError::ChannelClosed),
            ActiveTransport::Sse { .. } => Err(crate::session::SendError::NotConnected),
        }
    }

    /// Send a system op to the server.
    pub(crate) async fn send_system(
        &self,
        op: SystemOp<C>,
    ) -> Result<(), crate::session::SendError> {
        match self {
            ActiveTransport::WebSocket { outbound_tx, .. } => outbound_tx
                .send(OutboundMsg::System(op))
                .await
                .map_err(|_| crate::session::SendError::ChannelClosed),
            ActiveTransport::Sse {
                http,
                ack_url,
                client_id,
                ..
            } => {
                // SSE mode: only ACKs are supported via POST.
                if let SystemOp::Ack { channel, cursor } = &op {
                    let body = serde_json::json!({
                        "client_id": client_id,
                        "channel": channel,
                        "cursor": cursor,
                    });
                    let _ = http.post(ack_url).json(&body).send().await;
                    Ok(())
                } else {
                    // Other system ops not supported in SSE mode.
                    warn!("system op not supported in SSE mode, dropping");
                    Ok(())
                }
            }
        }
    }

    /// Send close signal and abort tasks.
    pub(crate) async fn close(self) {
        match self {
            ActiveTransport::WebSocket {
                outbound_tx,
                reader_handle,
                writer_handle,
            } => {
                let _ = outbound_tx.send(OutboundMsg::Close).await;
                // Give writer a moment to send the close frame, then abort.
                tokio::time::sleep(std::time::Duration::from_millis(100)).await;
                reader_handle.abort();
                writer_handle.abort();
            }
            ActiveTransport::Sse { reader_handle, .. } => {
                reader_handle.abort();
            }
        }
    }
}

// ---------------------------------------------------------------------------
// WebSocket transport
// ---------------------------------------------------------------------------

/// Connect via WebSocket, perform auth, return transport + inbound channel.
pub(crate) async fn connect_ws<C: ChannelKind>(
    url: &str,
    client_id: Uuid,
    token: Option<&str>,
    capabilities: &[C],
    resume_cursors: HashMap<C, u64>,
) -> Result<(ActiveTransport<C>, mpsc::Receiver<InboundMsg<C>>), ConnectError> {
    // Convert HTTP URL to WebSocket URL.
    let ws_url = http_to_ws_url(url);
    let rps_url = format!("{ws_url}/rps");

    let (ws_stream, _response) = tokio_tungstenite::connect_async(&rps_url)
        .await
        .map_err(|e| ConnectError::Transport(format!("WebSocket connect failed: {e}")))?;

    let (mut ws_tx, mut ws_rx) = ws_stream.split();

    // --- Auth handshake ---
    let global_cursor = resume_cursors.values().copied().max();
    let auth = SystemOp::<C>::Auth {
        client_id,
        token: token.map(String::from),
        capabilities: capabilities.to_vec(),
        resume_cursor: global_cursor,
        resume_cursors: resume_cursors.clone(),
    };
    let auth_json =
        serde_json::to_string(&auth).map_err(|e| ConnectError::Transport(e.to_string()))?;
    ws_tx
        .send(WsMessage::Text(auth_json))
        .await
        .map_err(|e| ConnectError::Transport(format!("failed to send auth: {e}")))?;

    // Wait for AuthOk.
    let auth_reply = ws_rx
        .next()
        .await
        .ok_or(ConnectError::Transport(
            "connection closed before auth reply".into(),
        ))?
        .map_err(|e| ConnectError::Transport(format!("auth reply read error: {e}")))?;

    let auth_ok: SystemOp<C> = match auth_reply {
        WsMessage::Text(text) => serde_json::from_str(&text)
            .map_err(|e| ConnectError::AuthRejected(format!("invalid auth reply: {e}")))?,
        WsMessage::Close(frame) => {
            let reason = frame
                .map(|f| f.reason.to_string())
                .unwrap_or_else(|| "unknown".into());
            return Err(ConnectError::AuthRejected(reason));
        }
        other => {
            return Err(ConnectError::Transport(format!(
                "unexpected auth reply type: {other:?}"
            )));
        }
    };

    match auth_ok {
        SystemOp::AuthOk { .. } => {
            debug!(?client_id, "auth handshake complete");
        }
        SystemOp::Error { message } => return Err(ConnectError::AuthRejected(message)),
        other => {
            return Err(ConnectError::AuthRejected(format!(
                "expected AuthOk, got {other:?}"
            )));
        }
    }

    // --- Spawn reader + writer tasks ---
    let (inbound_tx, inbound_rx) = mpsc::channel::<InboundMsg<C>>(256);
    let (outbound_tx, mut outbound_rx) = mpsc::channel::<OutboundMsg<C>>(64);

    // Reader: WS → inbound channel.
    let reader_inbound_tx = inbound_tx.clone();
    let reader_handle = tokio::spawn(async move {
        while let Some(msg) = ws_rx.next().await {
            match msg {
                Ok(WsMessage::Text(text)) => {
                    // Try parsing as SystemOp first (system channel frames wrap
                    // SystemOp in the payload), then as regular Frame.
                    if let Ok(frame) = serde_json::from_str::<Frame<C>>(&text) {
                        if frame.channel.is_system() {
                            // System channel: extract the SystemOp from payload.
                            if let Ok(op) =
                                serde_json::from_value::<SystemOp<C>>(frame.payload.clone())
                            {
                                if reader_inbound_tx
                                    .send(InboundMsg::System(op))
                                    .await
                                    .is_err()
                                {
                                    break;
                                }
                            } else {
                                // Might be a regular system-channel frame.
                                if reader_inbound_tx
                                    .send(InboundMsg::Frame(frame))
                                    .await
                                    .is_err()
                                {
                                    break;
                                }
                            }
                        } else if reader_inbound_tx
                            .send(InboundMsg::Frame(frame))
                            .await
                            .is_err()
                        {
                            break;
                        }
                    } else if let Ok(op) = serde_json::from_str::<SystemOp<C>>(&text) {
                        // Server sends SystemOps directly (not wrapped in Frame)
                        // for WebSocket connections.
                        if reader_inbound_tx
                            .send(InboundMsg::System(op))
                            .await
                            .is_err()
                        {
                            break;
                        }
                    } else {
                        warn!("failed to parse inbound WS message");
                    }
                }
                Ok(WsMessage::Close(_)) => {
                    let _ = reader_inbound_tx.send(InboundMsg::Closed).await;
                    break;
                }
                Ok(WsMessage::Ping(_) | WsMessage::Pong(_)) => {
                    // tungstenite handles ping/pong at the protocol level.
                }
                Ok(_) => {}
                Err(e) => {
                    warn!(?e, "WS read error");
                    let _ = reader_inbound_tx.send(InboundMsg::Closed).await;
                    break;
                }
            }
        }
    });

    // Writer: outbound channel → WS.
    let writer_handle = tokio::spawn(async move {
        while let Some(msg) = outbound_rx.recv().await {
            let ws_msg = match msg {
                OutboundMsg::Frame(frame) => match serde_json::to_string(&frame) {
                    Ok(json) => WsMessage::Text(json),
                    Err(e) => {
                        warn!(?e, "failed to serialize outbound frame");
                        continue;
                    }
                },
                OutboundMsg::System(op) => match serde_json::to_string(&op) {
                    Ok(json) => WsMessage::Text(json),
                    Err(e) => {
                        warn!(?e, "failed to serialize outbound system op");
                        continue;
                    }
                },
                OutboundMsg::Close => {
                    let _ = ws_tx.send(WsMessage::Close(None)).await;
                    break;
                }
            };
            if ws_tx.send(ws_msg).await.is_err() {
                break;
            }
        }
    });

    let transport = ActiveTransport::WebSocket {
        outbound_tx,
        reader_handle,
        writer_handle,
    };

    Ok((transport, inbound_rx))
}

// ---------------------------------------------------------------------------
// SSE transport
// ---------------------------------------------------------------------------

/// Connect via SSE, return transport + inbound channel.
pub(crate) async fn connect_sse<C: ChannelKind>(
    url: &str,
    client_id: Uuid,
    token: Option<&str>,
    capabilities: &[C],
    resume_cursor: Option<u64>,
) -> Result<(ActiveTransport<C>, mpsc::Receiver<InboundMsg<C>>), ConnectError> {
    let http = HttpClient::new();

    let mut sse_url = format!("{url}/rps/sse?client_id={client_id}");
    if let Some(tok) = token {
        sse_url.push_str(&format!("&token={tok}"));
    }
    if !capabilities.is_empty() {
        let caps: Vec<&str> = capabilities.iter().map(|c| c.name()).collect();
        sse_url.push_str(&format!("&capabilities={}", caps.join(",")));
        sse_url.push_str(&format!("&channels={}", caps.join(",")));
    }
    if let Some(cursor) = resume_cursor {
        sse_url.push_str(&format!("&resume_cursor={cursor}"));
    }

    let response = http
        .get(&sse_url)
        .send()
        .await
        .map_err(|e| ConnectError::Transport(format!("SSE connect failed: {e}")))?;

    if !response.status().is_success() {
        return Err(ConnectError::AuthRejected(format!(
            "SSE returned {}",
            response.status()
        )));
    }

    let (inbound_tx, inbound_rx) = mpsc::channel::<InboundMsg<C>>(256);
    let ack_url = format!("{url}/rps/ack");

    // Reader: parse SSE event stream.
    let reader_handle = tokio::spawn(async move {
        let mut stream = response.bytes_stream();
        let mut buffer = String::new();
        let mut event_type = String::new();
        let mut data_lines = Vec::<String>::new();

        while let Some(chunk) = stream.next().await {
            let bytes = match chunk {
                Ok(b) => b,
                Err(e) => {
                    warn!(?e, "SSE stream error");
                    let _ = inbound_tx.send(InboundMsg::Closed).await;
                    break;
                }
            };

            buffer.push_str(&String::from_utf8_lossy(&bytes));

            // Process complete lines.
            while let Some(newline_pos) = buffer.find('\n') {
                let line = buffer[..newline_pos].trim_end_matches('\r').to_string();
                buffer = buffer[newline_pos + 1..].to_string();

                if line.is_empty() {
                    // Empty line = end of event.
                    if !data_lines.is_empty() && (event_type == "frame" || event_type.is_empty()) {
                        let data = data_lines.join("\n");
                        if let Ok(frame) = serde_json::from_str::<Frame<C>>(&data) {
                            if frame.channel.is_system() {
                                if let Ok(op) =
                                    serde_json::from_value::<SystemOp<C>>(frame.payload.clone())
                                {
                                    let _ = inbound_tx.send(InboundMsg::System(op)).await;
                                } else {
                                    let _ = inbound_tx.send(InboundMsg::Frame(frame)).await;
                                }
                            } else {
                                let _ = inbound_tx.send(InboundMsg::Frame(frame)).await;
                            }
                        }
                    }
                    event_type.clear();
                    data_lines.clear();
                } else if let Some(value) = line.strip_prefix("event:") {
                    event_type = value.trim().to_string();
                } else if let Some(value) = line.strip_prefix("data:") {
                    data_lines.push(value.trim_start().to_string());
                }
                // Ignore id:, retry:, comments (:), etc.
            }
        }
    });

    let transport = ActiveTransport::Sse {
        http: HttpClient::new(),
        ack_url,
        client_id,
        reader_handle,
    };

    Ok((transport, inbound_rx))
}

// ---------------------------------------------------------------------------
// Transport fallback
// ---------------------------------------------------------------------------

/// Connect with fallback based on preference.
pub(crate) async fn connect_with_preference<C: ChannelKind>(
    preference: TransportPreference,
    url: &str,
    client_id: Uuid,
    token: Option<&str>,
    capabilities: &[C],
    resume_cursors: HashMap<C, u64>,
) -> Result<(ActiveTransport<C>, mpsc::Receiver<InboundMsg<C>>), ConnectError> {
    let global_cursor = resume_cursors.values().copied().max();

    match preference {
        TransportPreference::WsOnly => {
            connect_ws(url, client_id, token, capabilities, resume_cursors).await
        }
        TransportPreference::SseOnly => {
            connect_sse(url, client_id, token, capabilities, global_cursor).await
        }
        TransportPreference::WsFirst => {
            match connect_ws(url, client_id, token, capabilities, resume_cursors.clone()).await {
                Ok(result) => Ok(result),
                Err(ws_err) => {
                    debug!(?ws_err, "WS failed, falling back to SSE");
                    connect_sse(url, client_id, token, capabilities, global_cursor).await
                }
            }
        }
        TransportPreference::SseFirst => {
            match connect_sse(url, client_id, token, capabilities, global_cursor).await {
                Ok(result) => Ok(result),
                Err(sse_err) => {
                    debug!(?sse_err, "SSE failed, falling back to WS");
                    connect_ws(url, client_id, token, capabilities, resume_cursors).await
                }
            }
        }
    }
}

// ---------------------------------------------------------------------------
// Utilities
// ---------------------------------------------------------------------------

fn http_to_ws_url(url: &str) -> String {
    if let Some(rest) = url.strip_prefix("http://") {
        format!("ws://{rest}")
    } else if let Some(rest) = url.strip_prefix("https://") {
        format!("wss://{rest}")
    } else if url.starts_with("ws://") || url.starts_with("wss://") {
        url.to_string()
    } else {
        format!("ws://{url}")
    }
}