// SPDX-FileCopyrightText: 2020 Serokell <https://serokell.io/>
// SPDX-FileCopyrightText: 2020 Andreas Fuchs <asf@boinkor.net>
//
// SPDX-License-Identifier: MPL-2.0

use signal_hook::{consts::signal::SIGHUP, iterator::Signals};

use clap::Clap;

use tokio::fs;
use tokio::process::Command;
use tokio::sync::mpsc;
use tokio::time::timeout;

use std::time::Duration;

use std::path::Path;

use notify::{RecommendedWatcher, RecursiveMode, Watcher};

use thiserror::Error;

#[macro_use]
extern crate log;

#[macro_use]
extern crate serde_derive;

#[macro_use]
mod utils;

/// Remote activation utility for deploy-rs
#[derive(Clap, Debug)]
#[clap(version = "1.0", author = "Serokell <https://serokell.io/>")]
struct Opts {
    /// Print debug logs to output
    #[clap(short, long)]
    debug_logs: bool,
    /// Directory to print logs to
    #[clap(long)]
    log_dir: Option<String>,

    /// Path for any temporary files that may be needed during activation
    #[clap(long)]
    temp_path: String,

    #[clap(subcommand)]
    subcmd: SubCommand,
}

#[derive(Clap, Debug)]
enum SubCommand {
    Activate(ActivateOpts),
    Wait(WaitOpts),
}

/// Activate a profile
#[derive(Clap, Debug)]
struct ActivateOpts {
    /// The closure to activate
    closure: String,
    /// The profile path to install into
    profile_path: String,

    /// Maximum time to wait for confirmation after activation
    #[clap(long)]
    confirm_timeout: u16,

    /// Wait for confirmation after deployment and rollback if not confirmed
    #[clap(long)]
    magic_rollback: bool,

    /// Auto rollback if failure
    #[clap(long)]
    auto_rollback: bool,
}

/// Activate a profile
#[derive(Clap, Debug)]
struct WaitOpts {
    /// The closure to wait for
    closure: String,
}

#[derive(Error, Debug)]
pub enum DeactivateError {
    #[error("Failed to execute the rollback command: {0}")]
    RollbackError(std::io::Error),
    #[error("The rollback resulted in a bad exit code: {0:?}")]
    RollbackExitError(Option<i32>),
    #[error("Failed to run command for listing generations: {0}")]
    ListGenError(std::io::Error),
    #[error("Command for listing generations resulted in a bad exit code: {0:?}")]
    ListGenExitError(Option<i32>),
    #[error("Error converting generation list output to utf8: {0}")]
    DecodeListGenUtf8Error(#[from] std::string::FromUtf8Error),
    #[error("Failed to run command for deleting generation: {0}")]
    DeleteGenError(std::io::Error),
    #[error("Command for deleting generations resulted in a bad exit code: {0:?}")]
    DeleteGenExitError(Option<i32>),
    #[error("Failed to run command for re-activating the last generation: {0}")]
    ReactivateError(std::io::Error),
    #[error("Command for re-activating the last generation resulted in a bad exit code: {0:?}")]
    ReactivateExitError(Option<i32>),
}

pub async fn deactivate(profile_path: &str) -> Result<(), DeactivateError> {
    warn!("De-activating due to error");

    let nix_env_rollback_exit_status = Command::new("nix-env")
        .arg("-p")
        .arg(&profile_path)
        .arg("--rollback")
        .status()
        .await
        .map_err(DeactivateError::RollbackError)?;

    match nix_env_rollback_exit_status.code() {
        Some(0) => (),
        a => return Err(DeactivateError::RollbackExitError(a)),
    };

    debug!("Listing generations");

    let nix_env_list_generations_out = Command::new("nix-env")
        .arg("-p")
        .arg(&profile_path)
        .arg("--list-generations")
        .output()
        .await
        .map_err(DeactivateError::ListGenError)?;

    match nix_env_list_generations_out.status.code() {
        Some(0) => (),
        a => return Err(DeactivateError::ListGenExitError(a)),
    };

    let generations_list = String::from_utf8(nix_env_list_generations_out.stdout)?;

    let last_generation_line = generations_list
        .lines()
        .last()
        .expect("Expected to find a generation in list");

    let last_generation_id = last_generation_line
        .split_whitespace()
        .next()
        .expect("Expected to get ID from generation entry");

    debug!("Removing generation entry {}", last_generation_line);
    warn!("Removing generation by ID {}", last_generation_id);

    let nix_env_delete_generation_exit_status = Command::new("nix-env")
        .arg("-p")
        .arg(&profile_path)
        .arg("--delete-generations")
        .arg(last_generation_id)
        .status()
        .await
        .map_err(DeactivateError::DeleteGenError)?;

    match nix_env_delete_generation_exit_status.code() {
        Some(0) => (),
        a => return Err(DeactivateError::DeleteGenExitError(a)),
    };

    info!("Attempting to re-activate the last generation");

    let re_activate_exit_status = Command::new(format!("{}/deploy-rs-activate", profile_path))
        .env("PROFILE", &profile_path)
        .current_dir(&profile_path)
        .status()
        .await
        .map_err(DeactivateError::ReactivateError)?;

    match re_activate_exit_status.code() {
        Some(0) => (),
        a => return Err(DeactivateError::ReactivateExitError(a)),
    };

    Ok(())
}

#[derive(Error, Debug)]
pub enum ActivationConfirmationError {
    #[error("Failed to create activation confirmation directory: {0}")]
    CreateConfirmDirError(std::io::Error),
    #[error("Failed to create activation confirmation file: {0}")]
    CreateConfirmFileError(std::io::Error),
    #[error("Failed to create file system watcher instance: {0}")]
    CreateWatcherError(notify::Error),
    #[error("Error forking process: {0}")]
    ForkError(i32),
    #[error("Could not watch for activation sentinel: {0}")]
    WatcherError(#[from] notify::Error),
}

#[derive(Error, Debug)]
pub enum DangerZoneError {
    #[error("Timeout elapsed for confirmation")]
    TimesUp,
    #[error("inotify stream ended without activation confirmation")]
    NoConfirmation,
    #[error("inotify encountered an error: {0}")]
    WatchError(notify::Error),
}

async fn danger_zone(
    mut events: mpsc::Receiver<Result<(), notify::Error>>,
    confirm_timeout: u16,
) -> Result<(), DangerZoneError> {
    info!("Waiting for confirmation event...");

    match timeout(Duration::from_secs(confirm_timeout as u64), events.recv()).await {
        Ok(Some(Ok(()))) => Ok(()),
        Ok(Some(Err(e))) => Err(DangerZoneError::WatchError(e)),
        Ok(None) => Err(DangerZoneError::NoConfirmation),
        Err(_) => Err(DangerZoneError::TimesUp),
    }
}

pub async fn activation_confirmation(
    profile_path: String,
    temp_path: String,
    confirm_timeout: u16,
    closure: String,
) -> Result<(), ActivationConfirmationError> {
    let lock_path = utils::make_lock_path(&temp_path, &closure);

    debug!("Ensuring parent directory exists for canary file");

    if let Some(parent) = Path::new(&lock_path).parent() {
        fs::create_dir_all(parent)
            .await
            .map_err(ActivationConfirmationError::CreateConfirmDirError)?;
    }

    debug!("Creating canary file");

    fs::File::create(&lock_path)
        .await
        .map_err(ActivationConfirmationError::CreateConfirmFileError)?;

    debug!("Creating notify watcher");

    let (deleted, done) = mpsc::channel(1);

    let mut watcher: RecommendedWatcher =
        Watcher::new_immediate(move |res: Result<notify::event::Event, notify::Error>| {
            let send_result = match res {
                Ok(e) if e.kind == notify::EventKind::Remove(notify::event::RemoveKind::File) => {
                    debug!("Got worthy removal event, sending on channel");
                    deleted.try_send(Ok(()))
                }
                Err(e) => {
                    debug!("Got error waiting for removal event, sending on channel");
                    deleted.try_send(Err(e))
                }
                Ok(_) => Ok(()), // ignore non-removal events
            };

            if let Err(e) = send_result {
                error!("Could not send file system event to watcher: {}", e);
            }
        })?;

    watcher.watch(&lock_path, RecursiveMode::NonRecursive)?;

    if let Err(err) = danger_zone(done, confirm_timeout).await {
        error!("Error waiting for confirmation event: {}", err);

        if let Err(err) = deactivate(&profile_path).await {
            error!(
                "Error de-activating due to another error waiting for confirmation, oh no...: {}",
                err
            );
        }
    }

    Ok(())
}

#[derive(Error, Debug)]
pub enum WaitError {
    #[error("Error creating watcher for activation: {0}")]
    Watcher(#[from] notify::Error),
    #[error("Error waiting for activation: {0}")]
    Waiting(#[from] DangerZoneError),
}
pub async fn wait(temp_path: String, closure: String) -> Result<(), WaitError> {
    let lock_path = utils::make_lock_path(&temp_path, &closure);

    let (created, done) = mpsc::channel(1);

    let mut watcher: RecommendedWatcher = {
        // TODO: fix wasteful clone
        let lock_path = lock_path.clone();

        Watcher::new_immediate(move |res: Result<notify::event::Event, notify::Error>| {
            let send_result = match res {
                Ok(e) if e.kind == notify::EventKind::Create(notify::event::CreateKind::File) => {
                    match &e.paths[..] {
                        [x] if x == Path::new(&lock_path) => created.try_send(Ok(())),
                        _ => Ok(()),
                    }
                }
                Err(e) => created.try_send(Err(e)),
                Ok(_) => Ok(()), // ignore non-removal events
            };

            if let Err(e) = send_result {
                error!("Could not send file system event to watcher: {}", e);
            }
        })?
    };

    watcher.watch(&temp_path, RecursiveMode::NonRecursive)?;

    // Avoid a potential race condition by checking for existence after watcher creation
    if fs::metadata(&lock_path).await.is_ok() {
        watcher.unwatch(&temp_path)?;
        return Ok(());
    }

    danger_zone(done, 60).await?;

    info!("Found canary file, done waiting!");

    Ok(())
}

#[derive(Error, Debug)]
pub enum ActivateError {
    #[error("Failed to execute the command for setting profile: {0}")]
    SetProfileError(std::io::Error),
    #[error("The command for setting profile resulted in a bad exit code: {0:?}")]
    SetProfileExitError(Option<i32>),

    #[error("Failed to execute the activation script: {0}")]
    RunActivateError(std::io::Error),
    #[error("The activation script resulted in a bad exit code: {0:?}")]
    RunActivateExitError(Option<i32>),

    #[error("There was an error de-activating after an error was encountered: {0}")]
    DeactivateError(#[from] DeactivateError),

    #[error("Failed to get activation confirmation: {0}")]
    ActivationConfirmationError(#[from] ActivationConfirmationError),
}

pub async fn activate(
    profile_path: String,
    closure: String,
    auto_rollback: bool,
    temp_path: String,
    confirm_timeout: u16,
    magic_rollback: bool,
) -> Result<(), ActivateError> {
    info!("Activating profile");

    let nix_env_set_exit_status = Command::new("nix-env")
        .arg("-p")
        .arg(&profile_path)
        .arg("--set")
        .arg(&closure)
        .status()
        .await
        .map_err(ActivateError::SetProfileError)?;

    match nix_env_set_exit_status.code() {
        Some(0) => (),
        a => {
            if auto_rollback {
                deactivate(&profile_path).await?;
            }
            return Err(ActivateError::SetProfileExitError(a));
        }
    };

    debug!("Running activation script");

    let activate_status = match Command::new(format!("{}/deploy-rs-activate", profile_path))
        .env("PROFILE", &profile_path)
        .current_dir(&profile_path)
        .status()
        .await
        .map_err(ActivateError::RunActivateError)
    {
        Ok(x) => x,
        Err(e) => {
            if auto_rollback {
                deactivate(&profile_path).await?;
            }
            return Err(e);
        }
    };

    match activate_status.code() {
        Some(0) => (),
        a => {
            if auto_rollback {
                deactivate(&profile_path).await?;
            }
            return Err(ActivateError::RunActivateExitError(a));
        }
    };

    info!("Activation succeeded!");

    if magic_rollback {
        info!("Magic rollback is enabled, setting up confirmation hook...");

        match activation_confirmation(profile_path.clone(), temp_path, confirm_timeout, closure)
            .await
        {
            Ok(()) => {}
            Err(err) => {
                deactivate(&profile_path).await?;
                return Err(ActivateError::ActivationConfirmationError(err));
            }
        };
    }

    Ok(())
}

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    // Ensure that this process stays alive after the SSH connection dies
    let mut signals = Signals::new(&[SIGHUP])?;
    std::thread::spawn(move || {
        for sig in signals.forever() {
            println!("Received NOHUP - ignoring...");
        }
    });

    let opts: Opts = Opts::parse();

    utils::init_logger(
        opts.debug_logs,
        opts.log_dir.as_deref(),
        match opts.subcmd {
            SubCommand::Activate(_) => utils::LoggerType::Activate,
            SubCommand::Wait(_) => utils::LoggerType::Wait,
        },
    )?;

    let r = match opts.subcmd {
        SubCommand::Activate(activate_opts) => activate(
            activate_opts.profile_path,
            activate_opts.closure,
            activate_opts.auto_rollback,
            opts.temp_path,
            activate_opts.confirm_timeout,
            activate_opts.magic_rollback,
        )
        .await
        .map_err(|x| Box::new(x) as Box<dyn std::error::Error>),

        SubCommand::Wait(wait_opts) => wait(opts.temp_path, wait_opts.closure)
            .await
            .map_err(|x| Box::new(x) as Box<dyn std::error::Error>),
    };

    match r {
        Ok(()) => (),
        Err(err) => good_panic!("{}", err),
    }

    Ok(())
}