// Copyright 2025-2026 Dillution <hskimse1@gmail.com>.
//
// This file is part of DPIBreak.
//
// DPIBreak is free software: you can redistribute it and/or modify it
// under the terms of the GNU General Public License as published by the
// Free Software Foundation, either version 3 of the License, or (at your
// option) any later version.
//
// DPIBreak is distributed in the hope that it will be useful, but WITHOUT
// ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
// FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
// for more details.
//
// You should have received a copy of the GNU General Public License
// along with DPIBreak. If not, see <https://www.gnu.org/licenses/>.

use anyhow::Result;
use windivert::{
    WinDivert,
    layer::NetworkLayer,
    prelude
};
use std::sync::{LazyLock, Mutex};
use std::thread;
use crate::{opt, pkt};

fn open_handle(filter: &str, flags: prelude::WinDivertFlags) -> WinDivert<NetworkLayer> {
    use windivert::*;

    let h = match WinDivert::network(&filter, 0, flags) {
        Ok(h) => {
            crate::info!("windivert: open: {}", filter);
            h
        },
        Err(e) => {
            crate::error!("windivert: {}", e);
            crate::error!("windivert: {}", filter);
            std::process::exit(1);
        }
    };
    h
}

pub fn bootstrap() -> Result<()> {
    if opt::daemon() {
        service_main();
    }

    Ok(())
}

static SEND_HANDLE: LazyLock<Mutex<WinDivert<NetworkLayer>>> = LazyLock::new(|| {
    let flags = prelude::WinDivertFlags::new()
        .set_send_only();

    Mutex::new(open_handle("false", flags))
});

fn send_to_raw_1(pkt: &[u8]) -> Result<()> {
    use windivert::*;

    let mut p = unsafe { packet::WinDivertPacket::<NetworkLayer>::new(pkt.to_vec()) };

    p.address.set_outbound(true);
    p.address.set_ip_checksum(true); // TODO: test if this is needed
    p.address.set_tcp_checksum(false); // For badsum; anyway it is already calculated
    p.address.set_impostor(true); // to prevent inf loop

    SEND_HANDLE.lock().expect("mutex poisoned").send(&p)?;

    Ok(())
}

pub fn send_to_raw(pkt: &[u8], _dst: std::net::IpAddr) -> Result<()> {
    send_to_raw_1(pkt)
}

macro_rules! recv_loop {
    ($handle:expr, $pkt:ident => $body:expr) => {
        let mut buf = vec![0u8; 65536];
        loop {
            match $handle.recv(Some(&mut buf)) {
                Ok($pkt) => { $body }
                Err(e) => { crate::warn!("windivert: recv: {}", e); }
            }
        }
    };
}

pub fn run() -> Result<()> {
    let mut buf = Vec::<u8>::with_capacity(super::PACKET_SIZE_CAP);

    if opt::fake_autottl() {
        let handle = open_handle(
            "!outbound and tcp and tcp.SrcPort == 443 and tcp.Syn and tcp.Ack",
            prelude::WinDivertFlags::new().set_sniff()
        );
        thread::spawn(move || { recv_loop!(handle, pkt => pkt::put_hop(&pkt.data)); });
    }

    let divert = open_handle(
        concat!(
            "outbound and tcp and tcp.DstPort == 443",
            " ", "and tcp.Payload[0] == 22",
            " ", "and tcp.Payload[5] == 1 and !impostor"
        ),
        prelude::WinDivertFlags::new()
    );

    crate::splash!("{}", super::MESSAGE_AT_RUN);

    recv_loop!(divert, pkt => {
        crate::handle_packet!(
            &pkt.data,
            &mut buf,
            handled => {},
            rejected => send_to_raw_1(&pkt.data)?
        )
    });
}

fn service_run() {
    if run().is_err() {
        std::process::exit(1);
    }
    std::process::exit(0);
}

fn service_main()  {
    use windows_services::Command;

    match windows_services::Service::new()
        .can_stop()
        .run(|_, command| {
            match command {
                Command::Start => {
                    std::thread::spawn(|| service_run());
                }
                Command::Stop => {}
                _ => {}
            }
        }) {
            Ok(_) => {}
            Err(e) => {
                println!("{e}");
                std::process::exit(1);
            }
        };
}