// Copyright 2024 Google LLC
//
// Licensed under the Apache License, Version 2.0 (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.apache.org/licenses/LICENSE-2.0
//
// 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.

use crate::util::{into_raw_descriptor, ProxyConfig};
use crate::{connector::Connector, error::Error};
use libslirp_rs::libslirp::{ProxyConnect, ProxyManager};
use log::{debug, warn};
use std::net::SocketAddr;
use std::sync::Arc;
use tokio::runtime::Runtime;

/// # Manager
///
/// The `Manager` struct implements the `ProxyManager` trait from
/// `libslirp_rs`.  It is responsible for managing TCP connections
/// through an HTTP proxy using the `Connector` struct.
///
/// The `Manager` uses a `tokio::runtime::Runtime` to spawn tasks for
/// establishing proxy connections.  It takes a proxy configuration
/// string as input, which is parsed into a `ProxyConfig` to create a
/// `Connector` instance.
///
/// The `try_connect` method attempts to establish a connection to the
/// given `SocketAddr` through the proxy.  If successful, it calls the
/// `proxy_connect` function with the raw file descriptor of the
/// connected socket.
///
/// # Example
///
/// ```
/// use std::net::SocketAddr;
/// use libslirp_rs::libslirp::ProxyConnect;
///
/// struct MyProxyConnect;
///
/// impl ProxyConnect for MyProxyConnect {
///     fn proxy_connect(&self, fd: i32, sockaddr: SocketAddr) {
///         // Handle the connected socket
///     }
/// }
///
/// #[tokio::main]
/// async fn main() {
/// }
/// ```
pub struct Manager {
    runtime: Arc<Runtime>,
    connector: Connector,
}

impl Manager {
    pub fn new(proxy: &str) -> Result<Self, Error> {
        let config = ProxyConfig::from_string(&proxy)?;
        Ok(Self {
            runtime: Arc::new(Runtime::new()?),
            connector: Connector::new(config.addr, config.username, config.password),
        })
    }
}

impl ProxyManager for Manager {
    /// Attempts to establish a TCP connection to the given `sockaddr` through the proxy.
    ///
    /// This function spawns a new task in the `tokio` runtime to handle the connection process.
    /// If the connection is successful, it calls the `proxy_connect` function of the provided
    /// `ProxyConnect` object with the raw file descriptor of the connected socket.
    ///
    /// # Arguments
    ///
    /// * `sockaddr` - The target socket address to connect to.
    /// * `connect_id` - An identifier for the connection.
    /// * `connect_func` - A `ProxyConnect` object that will be called with the connected socket.
    ///
    /// # Returns
    ///
    /// `true` if the connection attempt was initiated, `false` otherwise.
    fn try_connect(
        &self,
        sockaddr: SocketAddr,
        connect_id: usize,
        connect_func: Box<dyn ProxyConnect + Send>,
    ) -> bool {
        debug!("Connecting to {sockaddr:?} with connect ID {connect_id}");
        let connector = self.connector.clone();

        self.runtime.handle().spawn(async move {
            let fd = match connector.connect(sockaddr).await {
                Ok(tcp_stream) => into_raw_descriptor(tcp_stream),
                Err(e) => {
                    warn!("Failed to connect to proxy {}. {}", sockaddr, e);
                    -1
                }
            };
            connect_func.proxy_connect(fd, sockaddr);
        });

        true
    }

    /// Removes a connection with the given `connect_id`.
    ///
    /// Currently, this function only logs a debug message.
    ///
    /// # Arguments
    ///
    /// * `connect_id` - The identifier of the connection to remove.
    fn remove(&self, connect_id: usize) {
        debug!("Remove connect ID {}", connect_id);
    }
}