//! Take a user's WebSocket JSON-RPC requests and either respond from local data or proxy the request to a backend rpc server.
//!
//! WebSockets are the preferred method of receiving requests, but not all clients have good support.

use super::authorization::{ip_is_authorized, key_is_authorized, Authorization, RequestMetadata};
use crate::errors::{Web3ProxyError, Web3ProxyResponse};
use crate::jsonrpc::JsonRpcId;
use crate::{
    app::Web3ProxyApp,
    errors::Web3ProxyResult,
    jsonrpc::{JsonRpcForwardedResponse, JsonRpcForwardedResponseEnum, JsonRpcRequest},
};
use anyhow::Context;
use axum::headers::{Origin, Referer, UserAgent};
use axum::{
    extract::ws::{Message, WebSocket, WebSocketUpgrade},
    extract::Path,
    response::{IntoResponse, Redirect},
    Extension, TypedHeader,
};
use axum_client_ip::InsecureClientIp;
use axum_macros::debug_handler;
use ethers::types::U64;
use futures::SinkExt;
use futures::{
    future::AbortHandle,
    stream::{SplitSink, SplitStream, StreamExt},
};
use handlebars::Handlebars;
use hashbrown::HashMap;
use http::{HeaderMap, StatusCode};
use serde_json::json;
use std::net::IpAddr;
use std::str::from_utf8_mut;
use std::sync::atomic::AtomicU64;
use std::sync::Arc;
use tokio::sync::{broadcast, mpsc, OwnedSemaphorePermit, RwLock as AsyncRwLock};
use tracing::{info, trace};

/// How to select backend servers for a request
#[derive(Copy, Clone, Debug, Default)]
pub enum ProxyMode {
    /// send to the "best" synced server
    #[default]
    Best,
    /// send to all synced servers and return the fastest non-error response (reverts do not count as errors here)
    Fastest(usize),
    /// send to all servers for benchmarking. return the fastest non-error response
    Versus,
    /// send all requests and responses to kafka
    /// TODO: should this be seperate from best/fastest/versus?
    Debug,
}

/// Public entrypoint for WebSocket JSON-RPC requests.
/// Queries a single server at a time
#[debug_handler]
pub async fn websocket_handler(
    Extension(app): Extension<Arc<Web3ProxyApp>>,
    InsecureClientIp(ip): InsecureClientIp,
    origin: Option<TypedHeader<Origin>>,
    ws_upgrade: Option<WebSocketUpgrade>,
) -> Web3ProxyResponse {
    _websocket_handler(ProxyMode::Best, app, &ip, origin.as_deref(), ws_upgrade).await
}

/// Public entrypoint for WebSocket JSON-RPC requests that uses all synced servers.
/// Queries all synced backends with every request! This might get expensive!
#[debug_handler]
pub async fn fastest_websocket_handler(
    Extension(app): Extension<Arc<Web3ProxyApp>>,
    InsecureClientIp(ip): InsecureClientIp,
    origin: Option<TypedHeader<Origin>>,
    ws_upgrade: Option<WebSocketUpgrade>,
) -> Web3ProxyResponse {
    // TODO: get the fastest number from the url params (default to 0/all)
    // TODO: config to disable this
    _websocket_handler(
        ProxyMode::Fastest(0),
        app,
        &ip,
        origin.as_deref(),
        ws_upgrade,
    )
    .await
}

/// Public entrypoint for WebSocket JSON-RPC requests that uses all synced servers.
/// Queries **all** backends with every request! This might get expensive!
#[debug_handler]
pub async fn versus_websocket_handler(
    Extension(app): Extension<Arc<Web3ProxyApp>>,
    InsecureClientIp(ip): InsecureClientIp,
    origin: Option<TypedHeader<Origin>>,
    ws_upgrade: Option<WebSocketUpgrade>,
) -> Web3ProxyResponse {
    // TODO: config to disable this
    _websocket_handler(ProxyMode::Versus, app, &ip, origin.as_deref(), ws_upgrade).await
}

async fn _websocket_handler(
    proxy_mode: ProxyMode,
    app: Arc<Web3ProxyApp>,
    ip: &IpAddr,
    origin: Option<&Origin>,
    ws_upgrade: Option<WebSocketUpgrade>,
) -> Web3ProxyResponse {
    let (authorization, _semaphore) = ip_is_authorized(&app, ip, origin, proxy_mode).await?;

    let authorization = Arc::new(authorization);

    match ws_upgrade {
        Some(ws) => Ok(ws
            .on_upgrade(move |socket| proxy_web3_socket(app, authorization, socket))
            .into_response()),
        None => {
            if let Some(redirect) = &app.config.redirect_public_url {
                // this is not a websocket. redirect to a friendly page
                Ok(Redirect::permanent(redirect).into_response())
            } else {
                Err(Web3ProxyError::WebsocketOnly)
            }
        }
    }
}

/// Authenticated entrypoint for WebSocket JSON-RPC requests. Web3 wallets use this.
/// Rate limit and billing based on the api key in the url.
/// Can optionally authorized based on origin, referer, or user agent.
#[debug_handler]
pub async fn websocket_handler_with_key(
    Extension(app): Extension<Arc<Web3ProxyApp>>,
    InsecureClientIp(ip): InsecureClientIp,
    Path(rpc_key): Path<String>,
    origin: Option<TypedHeader<Origin>>,
    referer: Option<TypedHeader<Referer>>,
    user_agent: Option<TypedHeader<UserAgent>>,
    ws_upgrade: Option<WebSocketUpgrade>,
) -> Web3ProxyResponse {
    _websocket_handler_with_key(
        ProxyMode::Best,
        app,
        &ip,
        rpc_key,
        origin.as_deref(),
        referer.as_deref(),
        user_agent.as_deref(),
        ws_upgrade,
    )
    .await
}

#[debug_handler]
#[allow(clippy::too_many_arguments)]
pub async fn debug_websocket_handler_with_key(
    Extension(app): Extension<Arc<Web3ProxyApp>>,
    InsecureClientIp(ip): InsecureClientIp,
    Path(rpc_key): Path<String>,
    origin: Option<TypedHeader<Origin>>,
    referer: Option<TypedHeader<Referer>>,
    user_agent: Option<TypedHeader<UserAgent>>,
    headers: HeaderMap,
    ws_upgrade: Option<WebSocketUpgrade>,
) -> Web3ProxyResponse {
    let mut response = _websocket_handler_with_key(
        ProxyMode::Debug,
        app,
        &ip,
        rpc_key,
        origin.as_deref(),
        referer.as_deref(),
        user_agent.as_deref(),
        ws_upgrade,
    )
    .await?;

    // add some headers that might be useful while debugging
    let response_headers = response.headers_mut();

    if let Some(x) = headers.get("x-amzn-trace-id").cloned() {
        response_headers.insert("x-amzn-trace-id", x);
    }

    if let Some(x) = headers.get("x-balance-id").cloned() {
        response_headers.insert("x-balance-id", x);
    }

    response_headers.insert("client-ip", ip.to_string().parse().unwrap());

    Ok(response)
}

#[debug_handler]
pub async fn fastest_websocket_handler_with_key(
    Extension(app): Extension<Arc<Web3ProxyApp>>,
    InsecureClientIp(ip): InsecureClientIp,
    Path(rpc_key): Path<String>,
    origin: Option<TypedHeader<Origin>>,
    referer: Option<TypedHeader<Referer>>,
    user_agent: Option<TypedHeader<UserAgent>>,
    ws_upgrade: Option<WebSocketUpgrade>,
) -> Web3ProxyResponse {
    // TODO: get the fastest number from the url params (default to 0/all)
    _websocket_handler_with_key(
        ProxyMode::Fastest(0),
        app,
        &ip,
        rpc_key,
        origin.as_deref(),
        referer.as_deref(),
        user_agent.as_deref(),
        ws_upgrade,
    )
    .await
}

#[debug_handler]
pub async fn versus_websocket_handler_with_key(
    Extension(app): Extension<Arc<Web3ProxyApp>>,
    InsecureClientIp(ip): InsecureClientIp,
    Path(rpc_key): Path<String>,
    origin: Option<TypedHeader<Origin>>,
    referer: Option<TypedHeader<Referer>>,
    user_agent: Option<TypedHeader<UserAgent>>,
    ws_upgrade: Option<WebSocketUpgrade>,
) -> Web3ProxyResponse {
    _websocket_handler_with_key(
        ProxyMode::Versus,
        app,
        &ip,
        rpc_key,
        origin.as_deref(),
        referer.as_deref(),
        user_agent.as_deref(),
        ws_upgrade,
    )
    .await
}

#[allow(clippy::too_many_arguments)]
async fn _websocket_handler_with_key(
    proxy_mode: ProxyMode,
    app: Arc<Web3ProxyApp>,
    ip: &IpAddr,
    rpc_key: String,
    origin: Option<&Origin>,
    referer: Option<&Referer>,
    user_agent: Option<&UserAgent>,
    ws_upgrade: Option<WebSocketUpgrade>,
) -> Web3ProxyResponse {
    let rpc_key = rpc_key.parse()?;

    let (authorization, _semaphore) =
        key_is_authorized(&app, &rpc_key, ip, origin, proxy_mode, referer, user_agent).await?;

    trace!("websocket_handler_with_key {:?}", authorization);

    let authorization = Arc::new(authorization);

    match ws_upgrade {
        Some(ws_upgrade) => {
            Ok(ws_upgrade.on_upgrade(move |socket| proxy_web3_socket(app, authorization, socket)))
        }
        None => {
            // if no websocket upgrade, this is probably a user loading the url with their browser
            match (
                &app.config.redirect_public_url,
                &app.config.redirect_rpc_key_url,
                authorization.checks.rpc_secret_key_id,
            ) {
                (None, None, _) => Err(Web3ProxyError::StatusCode(
                    StatusCode::BAD_REQUEST,
                    "this page is for rpcs".into(),
                    None,
                )),
                (Some(redirect_public_url), _, None) => {
                    Ok(Redirect::permanent(redirect_public_url).into_response())
                }
                (_, Some(redirect_rpc_key_url), Some(rpc_key_id)) => {
                    let reg = Handlebars::new();

                    let redirect_rpc_key_url = reg
                        .render_template(redirect_rpc_key_url, &json!({ "rpc_key_id": rpc_key_id }))
                        .expect("templating should always work");

                    // this is not a websocket. redirect to a page for this user
                    Ok(Redirect::permanent(&redirect_rpc_key_url).into_response())
                }
                // any other combinations get a simple error
                _ => Err(Web3ProxyError::StatusCode(
                    StatusCode::BAD_REQUEST,
                    "this page is for rpcs".into(),
                    None,
                )),
            }
        }
    }
}

async fn proxy_web3_socket(
    app: Arc<Web3ProxyApp>,
    authorization: Arc<Authorization>,
    socket: WebSocket,
) {
    // split the websocket so we can read and write concurrently
    let (ws_tx, ws_rx) = socket.split();

    // create a channel for our reader and writer can communicate. todo: benchmark different channels
    // TODO: this should be bounded. async blocking on too many messages would be fine
    let (response_sender, response_receiver) = mpsc::unbounded_channel::<Message>();

    tokio::spawn(write_web3_socket(response_receiver, ws_tx));
    tokio::spawn(read_web3_socket(app, authorization, ws_rx, response_sender));
}

/// websockets support a few more methods than http clients
async fn handle_socket_payload(
    app: Arc<Web3ProxyApp>,
    authorization: &Arc<Authorization>,
    payload: &str,
    response_sender: &mpsc::UnboundedSender<Message>,
    subscription_count: &AtomicU64,
    subscriptions: Arc<AsyncRwLock<HashMap<U64, AbortHandle>>>,
) -> Web3ProxyResult<(Message, Option<OwnedSemaphorePermit>)> {
    let (authorization, semaphore) = authorization.check_again(&app).await?;

    // TODO: handle batched requests
    let (response_id, response) = match serde_json::from_str::<JsonRpcRequest>(payload) {
        Ok(json_request) => {
            let response_id = json_request.id.clone();

            // TODO: move this to a seperate function so we can use the try operator
            let response: Web3ProxyResult<JsonRpcForwardedResponseEnum> = match &json_request.method
                [..]
            {
                "eth_subscribe" => {
                    // TODO: how can we subscribe with proxy_mode?
                    match app
                        .eth_subscribe(
                            authorization.clone(),
                            json_request,
                            subscription_count,
                            response_sender.clone(),
                        )
                        .await
                    {
                        Ok((handle, response)) => {
                            if let Some(subscription_id) = response.result.clone() {
                                let mut x = subscriptions.write().await;

                                let key: U64 = serde_json::from_str(subscription_id.get()).unwrap();

                                x.insert(key, handle);
                            }

                            Ok(response.into())
                        }
                        Err(err) => Err(err),
                    }
                }
                "eth_unsubscribe" => {
                    let request_metadata =
                        RequestMetadata::new(&app, authorization.clone(), &json_request, None)
                            .await;

                    let subscription_id: U64 =
                        if let Some(param) = json_request.params.get(0).cloned() {
                            serde_json::from_value(param)
                                .context("failed parsing [subscription_id] as a U64")?
                        } else {
                            match serde_json::from_value::<U64>(json_request.params) {
                                Ok(x) => x,
                                Err(err) => {
                                    return Err(Web3ProxyError::BadRequest(
                                        format!(
                                            "unexpected params given for eth_unsubscribe: {:?}",
                                            err
                                        )
                                        .into(),
                                    ))
                                }
                            }
                        };

                    // TODO: is this the right response?
                    let partial_response = {
                        let mut x = subscriptions.write().await;
                        match x.remove(&subscription_id) {
                            None => false,
                            Some(handle) => {
                                handle.abort();
                                true
                            }
                        }
                    };

                    let response = JsonRpcForwardedResponse::from_value(
                        json!(partial_response),
                        response_id.clone(),
                    );

                    request_metadata.add_response(&response);

                    Ok(response.into())
                }
                _ => app
                    .proxy_web3_rpc(authorization.clone(), json_request.into())
                    .await
                    .map(|(_, response, _)| response),
            };

            (response_id, response)
        }
        Err(err) => {
            let id = JsonRpcId::None.to_raw_value();
            (id, Err(err.into()))
        }
    };

    let response_str = match response {
        Ok(x) => serde_json::to_string(&x).expect("to_string should always work here"),
        Err(err) => {
            let (_, response_data) = err.as_response_parts();

            let response = JsonRpcForwardedResponse::from_response_data(response_data, response_id);

            serde_json::to_string(&response).expect("to_string should always work here")
        }
    };

    Ok((Message::Text(response_str), semaphore))
}

async fn read_web3_socket(
    app: Arc<Web3ProxyApp>,
    authorization: Arc<Authorization>,
    mut ws_rx: SplitStream<WebSocket>,
    response_sender: mpsc::UnboundedSender<Message>,
) {
    let subscriptions = Arc::new(AsyncRwLock::new(HashMap::new()));
    let subscription_count = Arc::new(AtomicU64::new(1));

    let (close_sender, mut close_receiver) = broadcast::channel(1);

    loop {
        tokio::select! {
            msg = ws_rx.next() => {
                if let Some(Ok(msg)) = msg {
                    // clone things so we can handle multiple messages in parallel
                    let close_sender = close_sender.clone();
                    let app = app.clone();
                    let authorization = authorization.clone();
                    let response_sender = response_sender.clone();
                    let subscriptions = subscriptions.clone();
                    let subscription_count = subscription_count.clone();

                    let f = async move {
                        // new message from our client. forward to a backend and then send it through response_sender
                        let (response_msg, _semaphore) = match msg {
                            Message::Text(payload) => {
                                match handle_socket_payload(
                                    app,
                                    &authorization,
                                    &payload,
                                    &response_sender,
                                    &subscription_count,
                                    subscriptions,
                                )
                                .await {
                                    Ok((m, s)) => (m, Some(s)),
                                    Err(err) => {
                                        // TODO: how can we get the id out of the payload?
                                        let m = err.into_message(None);
                                        (m, None)
                                    }
                                }
                            }
                            Message::Ping(x) => {
                                trace!("ping: {:?}", x);
                                (Message::Pong(x), None)
                            }
                            Message::Pong(x) => {
                                trace!("pong: {:?}", x);
                                return;
                            }
                            Message::Close(_) => {
                                info!("closing websocket connection");
                                // TODO: do something to close subscriptions?
                                let _ = close_sender.send(true);
                                return;
                            }
                            Message::Binary(mut payload) => {
                                let payload = from_utf8_mut(&mut payload).unwrap();

                                let (m, s) = match handle_socket_payload(
                                    app,
                                    &authorization,
                                    payload,
                                    &response_sender,
                                    &subscription_count,
                                    subscriptions,
                                )
                                .await {
                                    Ok((m, s)) => (m, Some(s)),
                                    Err(err) => {
                                        // TODO: how can we get the id out of the payload?
                                        let m = err.into_message(None);
                                        (m, None)
                                    }
                                };

                                // TODO: is this an okay way to convert from text to binary?
                                let m = if let Message::Text(m) = m {
                                    Message::Binary(m.as_bytes().to_vec())
                                } else {
                                    unimplemented!();
                                };

                                (m, s)
                            }
                        };

                        if response_sender.send(response_msg).is_err() {
                            let _ = close_sender.send(true);
                        };
                    };

                    tokio::spawn(f);
                } else {
                    break;
                }
            }
            _ = close_receiver.recv() => {
                break;
            }
        }
    }
}

async fn write_web3_socket(
    mut response_rx: mpsc::UnboundedReceiver<Message>,
    mut ws_tx: SplitSink<WebSocket, Message>,
) {
    // TODO: increment counter for open websockets

    while let Some(msg) = response_rx.recv().await {
        // a response is ready

        // we do not check rate limits here. they are checked before putting things into response_sender;

        // forward the response to through the websocket
        if let Err(err) = ws_tx.send(msg).await {
            // this is common. it happens whenever a client disconnects
            trace!("unable to write to websocket: {:?}", err);
            break;
        };
    }

    // TODO: decrement counter for open websockets
}