use eyre::{format_err, Result};
use log::{error, info, warn};
use std::collections::BTreeSet as Set;
use std::os::unix::fs::symlink;
use tokio::sync::Mutex;
use tokio::{fs, process::Command};

use crate::{bootstrap::config::Config, cmd::version::version_string, dklog, input, utils};

mod bootstrap;
mod dmcrypt;
mod lvm;
mod networks;
mod sshd;

const INIT_LOG: &str = "/var/log/init.log";

// devices used by any block target (DM, LVM...)
static USED_DEVS: Mutex<Set<String>> = Mutex::const_new(Set::new());

pub async fn run() {
    if std::process::id() != 1 {
        error!("init must run as PID 1, not {}", std::process::id());
        std::process::exit(1);
    }

    unsafe {
        use std::env;
        env::set_var("PATH", "/bin:/sbin:/usr/bin:/usr/sbin");
        env::set_var("HOME", "/root");
    }

    // open input channels
    tokio::spawn(crate::input::answer_requests_from_stdin());
    tokio::spawn(crate::input::answer_requests_from_socket());

    // also log to file
    dklog::LOG.spawn(async {
        let Ok(log_file) = (tokio::fs::File::create(INIT_LOG).await)
            .inspect_err(|e| warn!("failed to open init.log: {e}"))
        else {
            return;
        };
        dklog::LOG.copy_to(log_file).await;
    });

    // welcome
    info!("Welcome to {}", version_string());

    let uname = nix::sys::utsname::uname().expect("uname should work");
    let kernel_version = uname.release().to_string_lossy();
    info!("Linux version {kernel_version}");

    // mount basic filesystems
    mount(None, "/proc", Some("proc"), None).await;
    mount(None, "/sys", Some("sysfs"), None).await;
    mount(None, "/dev", Some("devtmpfs"), None).await;
    mount(None, "/dev/pts", Some("devpts"), Some("gid=5,mode=620")).await;

    if utils::bool_param("debug") {
        log::set_max_level(log::LevelFilter::Debug);
    }

    // extract system archive
    retry_or_ignore(async || {
        if fs::try_exists("system.azstd").await? {
            info!("unpacking system.azstd");
            let zarch = fs::read("system.azstd").await?;
            let arch = zstd::Decoder::new(zarch.as_slice())?;
            extract_cpio(arch).await
        } else if fs::try_exists("system.alz4").await? {
            info!("unpacking system.alz4");
            let zarch = fs::read("system.alz4").await?;
            let arch = lz4::Decoder::new(zarch.as_slice())?;
            extract_cpio(arch).await
        } else {
            return Ok(());
        }
    })
    .await;

    // load config
    let cfg: Config = retry(async || {
        let cfg = (fs::read("config.yaml").await)
            .map_err(|e| format_err!("failed to read config: {e}"))?;
        serde_yaml::from_slice(cfg.as_slice())
            .map_err(|e| format_err!("failed to parse config: {e}"))
    })
    .await;

    info!("config loaded");
    info!("anti-phishing-code: {}", cfg.anti_phishing_code);

    // seem to occasionaly race with Child::wait
    // tokio::spawn(child_reaper());

    // mount modules
    if let Some(ref modules) = cfg.modules {
        retry_or_ignore(async || {
            info!("mounting modules");
            mount(Some(modules), "/modules", Some("squashfs"), None).await;

            fs::create_dir_all("/lib/modules").await?;
            let modules_path = &format!("/modules/lib/modules/{kernel_version}");

            if !std::fs::exists(modules_path)? {
                return Err(format_err!(
                    "invalid modules package: {modules_path} should exist"
                ));
            }

            symlink(modules_path, format!("/lib/modules/{kernel_version}"))?;
            Ok(())
        })
        .await;
    } else {
        warn!("modules NOT mounted (not configured)");
    }

    // init devices
    info!("initializing devices");
    start_daemon("udevd", &[]).await;

    exec("udevadm", &["trigger", "-c", "add", "-t", "devices"]).await;
    exec("udevadm", &["trigger", "-c", "add", "-t", "subsystems"]).await;
    exec("udevadm", &["settle"]).await;

    // resolv.conf
    if let Some(ref resolv_conf) = cfg.resolv_conf {
        retry_or_ignore(async || {
            let path = "/etc/resolv.conf";
            info!("writing /etc/resolv.conf");
            fs::write(path, resolv_conf.as_bytes()).await?;
            Ok(())
        })
        .await;
    }

    // Wireguard VPNs
    for (name, conf) in &cfg.vpns {
        retry_or_ignore(async || {
            let dir = "/etc/wireguard";
            fs::create_dir_all(dir).await?;

            let path = &format!("{dir}/{name}.conf");
            fs::write(path, conf.as_bytes()).await?;
            chmod(path, 0o600).await?;

            try_exec("wg-quick", &["up", name]).await?;
            Ok(())
        })
        .await
    }

    // SSH service
    sshd::start(&cfg).await;

    // networks
    networks::setup(&cfg).await;

    // pre-lvm dmcrypt devs
    dmcrypt::setup(&cfg.pre_lvm_crypt).await;

    // LVM
    lvm::setup(&cfg).await;

    // post-lvm dmcrypt devs
    dmcrypt::setup(&cfg.crypt).await;

    // bootstrap the system
    bootstrap::bootstrap(cfg).await;

    // finalize
    if let Err(e) = tokio::fs::copy(INIT_LOG, format!("/system{INIT_LOG}")).await {
        warn!("failed to copy {INIT_LOG} to system: {e}");
    }

    retry(async || switch_root("/system").await).await;
}

use std::path::Path;

async fn chmod(path: impl AsRef<Path>, mode: u32) -> std::io::Result<()> {
    use std::fs::Permissions;
    use std::os::unix::fs::PermissionsExt;

    let perms = Permissions::from_mode(mode);
    fs::set_permissions(path, perms).await
}

async fn extract_cpio(mut arch: impl std::io::Read) -> Result<()> {
    loop {
        let rd = cpio::NewcReader::new(&mut arch)?;
        let entry = rd.entry();
        if entry.is_trailer() {
            return Ok(());
        }

        let path = entry.name().to_string();

        if let Err(e) = extract_cpio_entry(rd, &path).await {
            return Err(format_err!("failed to extract {path}: {e}"));
        }
    }
}

async fn extract_cpio_entry<R: std::io::Read>(
    rd: cpio::NewcReader<R>,
    path: impl AsRef<Path>,
) -> Result<()> {
    use std::os::unix::fs::chown;
    use unix_mode::Type;

    let entry = rd.entry();
    let path = path.as_ref();

    if let Some(parent) = path.parent() {
        fs::create_dir_all(parent).await?;
    }

    let mode = entry.mode();
    let uid = entry.uid();
    let gid = entry.gid();

    match Type::from(mode) {
        Type::Dir => {
            fs::create_dir_all(path).await?;
        }
        Type::File => {
            let mut data = vec![];
            rd.to_writer(&mut data)?;

            fs::write(path, data).await?;
        }
        Type::Symlink => {
            let mut data = vec![];
            rd.to_writer(&mut data)?;
            let target = &Path::new(std::str::from_utf8(&data)?);

            tokio::fs::symlink(target, path).await?;
            return Ok(());
        }
        _ => {
            warn!("{path:?}: unknown file type: {:?}", Type::from(mode));
            return Ok(());
        }
    }

    chmod(path, mode).await?;
    chown(path, Some(uid), Some(gid))?;

    Ok(())
}

async fn mount(src: Option<&str>, dst: &str, fstype: Option<&str>, opts: Option<&str>) {
    if let Err(e) = fs::create_dir_all(dst).await {
        error!("failed to create dir {dst}: {e}");
    }

    match (fstype, src) {
        (Some("ext4"), Some(src)) => {
            exec("fsck", &["-p", src]).await;
        }
        _ => {}
    }

    let mut args = vec![src.unwrap_or("none"), dst];
    if let Some(fstype) = fstype {
        args.extend(&["-t", fstype]);
    }
    if let Some(opts) = opts {
        args.extend(["-o", opts]);
    }

    retry_or_ignore(async || {
        // check source, use a loopdev if needed
        if let Some(src) = src {
            if fs::metadata(src).await?.is_file() {
                // loopdev crate has annoying dependencies, just use the normal mount program
                return try_exec("mount", &args).await;
            }
        }

        let (cmd_str, _) = cmd_str("mount", &args);
        let flags = nix::mount::MsFlags::empty();

        info!("# {cmd_str}",);
        nix::mount::mount(src, dst, fstype, flags, opts)
            .map_err(|e| format_err!("mount {dst} failed: {e}"))
    })
    .await
}

async fn start_daemon(prog: &str, args: &[&str]) {
    let (cmd_str, mut cmd) = cmd_str(prog, args);
    retry_or_ignore(async || {
        info!("starting as daemon: {cmd_str}");
        cmd.spawn()?;
        Ok(())
    })
    .await;
}

async fn try_exec(prog: &str, args: &[&str]) -> Result<()> {
    let (cmd_str, mut cmd) = cmd_str(prog, args);
    info!("# {cmd_str}");

    let s = cmd.status().await?;
    if s.success() {
        Ok(())
    } else {
        Err(format_err!("command failed: {s}"))
    }
}

async fn exec(prog: &str, args: &[&str]) {
    retry_or_ignore(async || try_exec(prog, args).await).await;
}

async fn retry_or_ignore(mut action: impl AsyncFnMut() -> Result<()>) {
    loop {
        match action().await {
            Ok(_) => return,
            Err(e) => {
                error!("{e}");

                match input::read_choice(["[r]etry", "[i]gnore", "[s]hell"]).await {
                    'r' => {}
                    'i' => return,
                    's' => exec_shell().await,
                    _ => unreachable!(),
                }
            }
        }
    }
}

async fn retry<T>(mut action: impl AsyncFnMut() -> Result<T>) -> T {
    loop {
        match action().await {
            Ok(v) => return v,
            Err(e) => {
                error!("{e}");

                match input::read_choice(["[r]etry", "[s]hell"]).await {
                    'r' => {}
                    's' => exec_shell().await,
                    _ => unreachable!(),
                }
            }
        }
    }
}

async fn exec_shell() {
    let mut child = match Command::new("ash").spawn() {
        Ok(c) => c,
        Err(e) => {
            error!("failed to exec shell: {e}");
            return;
        }
    };

    let _ = child.wait().await;
}

fn cmd_str(prog: &str, args: &[&str]) -> (String, Command) {
    use std::borrow::Cow;

    let mut buf = String::new();

    buf.push_str(&shell_escape::escape(Cow::Borrowed(prog)));

    for &arg in args {
        buf.push(' ');
        buf.push_str(&shell_escape::escape(Cow::Borrowed(arg)));
    }

    let mut cmd = Command::new(prog);
    cmd.args(args);

    (buf, cmd)
}

#[allow(unused)]
async fn child_reaper() {
    use nix::sys::wait::{waitpid, WaitPidFlag};
    use nix::unistd::Pid;
    use tokio::signal::unix::{signal, SignalKind};

    let Ok(mut sigs) =
        signal(SignalKind::child()).inspect_err(|e| warn!("failed to setup SIGCHLD handler: {e}"))
    else {
        return;
    };

    loop {
        sigs.recv().await;
        let _ = waitpid(Some(Pid::from_raw(-1)), Some(WaitPidFlag::WNOHANG));
    }
}

macro_rules! cstr {
    ($s:expr) => {
        std::ffi::CString::new($s)?.as_c_str()
    };
}

async fn switch_root(root: &str) -> Result<()> {
    info!("killing all processes and switching root");
    dklog::LOG.close().await;

    use nix::sys::signal::{kill, SIGKILL};
    use nix::unistd::Pid;

    if let Err(e) = kill(Pid::from_raw(-1), SIGKILL) {
        eprintln!("failed to kill processes: {e}");
    }

    nix::unistd::execv(
        cstr!("/sbin/switch_root"),
        &[
            cstr!("switch_root"),
            cstr!("-c"),
            cstr!("/dev/console"),
            cstr!(root),
            cstr!("/sbin/init"),
        ],
    )
    .unwrap();

    unreachable!();
}