use clap::Parser;
use rand::distr::{Alphanumeric, SampleString};
use rustls_pki_types::ServerName;
use std::error::Error;
use std::fs::OpenOptions;
use std::io::Write;
use std::path::Path;
use std::sync::Arc;
use std::time::{SystemTime, UNIX_EPOCH};
use tokio::io::{AsyncReadExt, AsyncWriteExt};
use tokio::net::TcpListener;
use tokio::net::TcpStream;
use tokio_rustls::TlsConnector;
use tokio_rustls::rustls::{ClientConfig, RootCertStore};

/// Simple program that proxify requests and save responses
#[derive(Parser, Debug)]
#[command(version, about, long_about = None)]
struct Args {
    /// The address the server will listen to
    #[arg(short, long, default_value = "0.0.0.0:8000")]
    listen_address: String,

    /// Upstream address this server will connect to
    #[arg(short, long, default_value = "communiquons.org")]
    upstream_dns: String,

    /// Upstream address this server will connect to
    #[arg(short('I'), long, default_value = "10.0.1.10:443")]
    upstream_ip: String,

    /// The path on the server this server will save requests and responses
    #[arg(short, long, default_value = "storage")]
    storage_path: String,
}

/// Get the current time since epoch
pub fn time() -> u64 {
    SystemTime::now()
        .duration_since(UNIX_EPOCH)
        .unwrap()
        .as_secs()
}

pub fn rand_str(len: usize) -> String {
    Alphanumeric.sample_string(&mut rand::rng(), len)
}

#[tokio::main]
async fn main() -> Result<(), Box<dyn Error>> {
    env_logger::init_from_env(env_logger::Env::new().default_filter_or("info"));

    let args = Args::parse();

    log::info!("Will start to listen on {}", args.listen_address);
    let listener = TcpListener::bind(&args.listen_address).await?;

    std::fs::create_dir_all(Path::new(args.storage_path.as_str())).unwrap();

    loop {
        // Asynchronously wait for an inbound socket.
        let (mut client_socket, _) = listener.accept().await?;

        tokio::spawn(async move {
            let args = Args::parse();

            let base_file_name = format!(
                "{}-{}-{}",
                client_socket.peer_addr().unwrap().ip(),
                time(),
                rand_str(10)
            );

            let mut req_file = OpenOptions::new()
                .create(true)
                .write(true)
                .open(Path::new(&args.storage_path).join(format!("{base_file_name}-req")))
                .expect("Failed to create req file");
            let mut res_file = OpenOptions::new()
                .create(true)
                .write(true)
                .open(Path::new(&args.storage_path).join(format!("{base_file_name}-res")))
                .expect("Failed to create req file");

            let mut root_cert_store = RootCertStore::empty();
            root_cert_store.extend(webpki_roots::TLS_SERVER_ROOTS.iter().cloned());
            let config = ClientConfig::builder()
                .with_root_certificates(root_cert_store)
                .with_no_client_auth();
            let connector = TlsConnector::from(Arc::new(config));
            let dnsname = ServerName::try_from(args.upstream_dns.to_string()).unwrap();

            let stream = TcpStream::connect(args.upstream_ip)
                .await
                .expect("Failed to connect to upstream");
            let mut upstream = connector
                .connect(dnsname, stream)
                .await
                .expect("Failed to establish TLS connection");

            let (mut client_read, mut client_write) = client_socket.split();

            let mut buf_client = [0u8; 1024];
            let mut buf_server = [0u8; 1024];

            let mut modified_headers = false;

            loop {
                tokio::select! {
                    count = client_read.read(&mut buf_client) => {
                        let  count = match count{  Ok(count) => count, Err(e) => {
                            log::error!("Failed to read data from client, closing connection! {e}");
                            return;
                        }};
                        log::info!("Got a new client read {count}");

                        if count == 0 {
                            log::warn!("infinite loop");
                            return;
                        }

                        // We need to modify some headers (if not done already) to adapt the request to the server
                        let  buff = if !modified_headers {
                            modified_headers = true;
                            manipulate_headers(&buf_client[..count], &args.upstream_dns)
                        }
                        else {
                            buf_client[..count].to_vec()
                        };

                        upstream.write_all(&buff).await.expect("Failed to write to upstream");
                        req_file.write_all(&buff).expect("Failed to write to req");
                    }

                    count = upstream.read(&mut buf_server) => {
                        let count = match count{  Ok(count) => count,Err(e) => {
                            log::error!("Failed to read from upstream! {e}");
                            return;
                        }};
                        log::info!("Got a new upstream read {count}");
                        client_write.write_all(&buf_server[..count]).await.expect("Failed to write to client");
                        res_file.write_all(&buf_server[..count]).expect("Failed to write to res");
                    }
                }
            }
        });
    }
}

fn manipulate_headers(buff: &[u8], host: &str) -> Vec<u8> {
    // return buff.to_vec();

    let mut out = Vec::with_capacity(buff.len());

    let mut i = 0;
    while i < buff.len() {
        if buff[i] != b'\n' || i + 1 == buff.len() || !buff[i + 1..].starts_with(b"Host:") {
            out.push(buff[i]);
            i += 1;
            continue;
        }

        i += 1;
        out.push(b'\n');

        out.append(&mut format!("Host: {host}").as_bytes().to_vec());

        while buff[i] != b'\r' && buff[i] != b'\n' {
            i += 1;
        }
    }

    out
}

#[cfg(test)]
mod test {
    use crate::Args;

    #[test]
    fn verify_cli() {
        use clap::CommandFactory;
        Args::command().debug_assert()
    }
}