//! WebSocket endpoint for real-time message delivery.
//!
//! Protocol:
//!   1. Client connects to /v1/ws/:fingerprint
//!   2. Server sends any queued messages (from DB)
//!   3. Server pushes new messages in real-time
//!   4. Client sends messages as binary WireMessage frames
//!   5. Server routes to recipient's WS or queues in DB

use axum::{
    extract::{
        ws::{Message, WebSocket},
        Path, State, WebSocketUpgrade,
    },
    response::IntoResponse,
    routing::get,
    Router,
};
use futures_util::{SinkExt, StreamExt};

use crate::state::AppState;

pub fn routes() -> Router<AppState> {
    Router::new().route("/ws/:fingerprint", get(ws_handler))
}

fn normalize_fp(fp: &str) -> String {
    fp.chars()
        .filter(|c| c.is_ascii_hexdigit())
        .collect::<String>()
        .to_lowercase()
}

async fn ws_handler(
    ws: WebSocketUpgrade,
    State(state): State<AppState>,
    Path(fingerprint): Path<String>,
) -> impl IntoResponse {
    let fp = normalize_fp(&fingerprint);
    tracing::info!("WS upgrade request from {}", fp);
    ws.on_upgrade(move |socket| handle_socket(socket, state, fp))
}

async fn handle_socket(socket: WebSocket, state: AppState, fingerprint: String) {
    let (mut ws_tx, mut ws_rx) = socket.split();

    // Register for push delivery
    let mut push_rx = state.register_ws(&fingerprint).await;

    // Send any queued messages from DB
    let prefix = format!("queue:{}", fingerprint);
    let mut keys_to_delete = Vec::new();
    for item in state.db.messages.scan_prefix(prefix.as_bytes()) {
        if let Ok((key, value)) = item {
            if ws_tx.send(Message::Binary(value.to_vec().into())).await.is_ok() {
                keys_to_delete.push(key);
            }
        }
    }
    for key in &keys_to_delete {
        let _ = state.db.messages.remove(key);
    }
    if !keys_to_delete.is_empty() {
        tracing::info!("WS {}: flushed {} queued messages", fingerprint, keys_to_delete.len());
    }

    // Spawn task to forward push messages to WS
    let fp_clone = fingerprint.clone();
    let mut push_task = tokio::spawn(async move {
        while let Some(msg) = push_rx.recv().await {
            if ws_tx.send(Message::Binary(msg.into())).await.is_err() {
                break;
            }
        }
        ws_tx
    });

    // Handle incoming messages from client
    let state_clone = state.clone();
    let fp_clone2 = fingerprint.clone();
    let mut recv_task = tokio::spawn(async move {
        while let Some(Ok(msg)) = ws_rx.next().await {
            match msg {
                Message::Binary(data) => {
                    // Parse as a simple { to: "fp", message: bytes } JSON
                    // Or just raw WireMessage bytes with a 32-byte fingerprint prefix
                    // For simplicity: first 32 hex chars = recipient fp, rest = message
                    if data.len() > 64 {
                        let header = String::from_utf8_lossy(&data[..64]).to_string();
                        let to_fp = normalize_fp(&header);
                        let message = &data[64..];

                        // Try push to connected client first
                        if !state_clone.push_to_client(&to_fp, message).await {
                            // Queue in DB
                            let key = format!("queue:{}:{}", to_fp, uuid::Uuid::new_v4());
                            let _ = state_clone.db.messages.insert(key.as_bytes(), message);
                        }

                        tracing::debug!("WS {}: routed message to {}", fp_clone2, to_fp);
                    }
                }
                Message::Text(text) => {
                    // JSON format: {"to": "fp", "message": [bytes]}
                    if let Ok(parsed) = serde_json::from_str::<serde_json::Value>(&text) {
                        let to = parsed.get("to").and_then(|v| v.as_str()).unwrap_or("");
                        let to_fp = normalize_fp(to);
                        if let Some(msg_arr) = parsed.get("message").and_then(|v| v.as_array()) {
                            let message: Vec<u8> = msg_arr.iter()
                                .filter_map(|v| v.as_u64().map(|n| n as u8))
                                .collect();

                            if !state_clone.push_to_client(&to_fp, &message).await {
                                let key = format!("queue:{}:{}", to_fp, uuid::Uuid::new_v4());
                                let _ = state_clone.db.messages.insert(key.as_bytes(), message);
                            }

                            // Renew alias TTL
                            crate::routes::messages::renew_alias_ttl(
                                &state_clone.db.aliases, &fp_clone2,
                            );

                            tracing::debug!("WS {}: routed JSON message to {}", fp_clone2, to_fp);
                        }
                    }
                }
                Message::Close(_) => break,
                _ => {}
            }
        }
    });

    // Wait for either task to finish
    tokio::select! {
        _ = &mut push_task => {
            recv_task.abort();
        }
        _ = &mut recv_task => {
            push_task.abort();
        }
    }

    // Unregister
    // We can't easily get the sender ref here, so just clean up by fingerprint
    // In production, use a unique connection ID
    let mut conns = state.connections.lock().await;
    if let Some(senders) = conns.get_mut(&fingerprint) {
        senders.retain(|s| !s.is_closed());
        if senders.is_empty() {
            conns.remove(&fingerprint);
        }
    }
    tracing::info!("WS {} disconnected", fingerprint);
}