/*
 * Copyright © 2023 Collabora Ltd.
 * Copyright © 2024 Valve Software
 *
 * SPDX-License-Identifier: MIT
 */

use anyhow::{anyhow, bail, Result};
use libc::pid_t;
use nix::sys::signal;
use nix::sys::signal::Signal;
use nix::unistd::Pid;
use std::ffi::OsStr;
use std::os::unix::process::ExitStatusExt;
use std::process::ExitStatus;
use tokio::process::{Child, Command};
use tracing::error;
use zbus::interface;

use crate::to_zbus_fdo_error;

const PROCESS_PREFIX: &str = "/com/steampowered/SteamOSManager1/Process";

pub struct ProcessManager {
    // The thing that manages subprocesses.
    // Keeps a handle to the zbus connection and
    // what the next process id on the bus should be
    connection: zbus::Connection,
    next_process: u32,
}

pub struct SubProcess {
    process: Child,
    paused: bool,
    exit_code: Option<i32>,
}

impl ProcessManager {
    pub fn new(conn: zbus::Connection) -> ProcessManager {
        ProcessManager {
            connection: conn,
            next_process: 0,
        }
    }

    pub async fn get_command_object_path(
        &mut self,
        executable: &str,
        args: &[impl AsRef<OsStr>],
        operation_name: &str,
    ) -> zbus::fdo::Result<zbus::zvariant::OwnedObjectPath> {
        // Run the given executable and give back an object path
        let path = format!("{}{}", PROCESS_PREFIX, self.next_process);
        self.next_process += 1;
        let pm = ProcessManager::run_long_command(executable, args)
            .await
            .inspect_err(|message| error!("Error {operation_name}: {message}"))
            .map_err(to_zbus_fdo_error)?;
        self.connection
            .object_server()
            .at(path.as_str(), pm)
            .await?;
        zbus::zvariant::OwnedObjectPath::try_from(path).map_err(to_zbus_fdo_error)
    }

    pub async fn run_long_command(
        executable: &str,
        args: &[impl AsRef<OsStr>],
    ) -> Result<SubProcess> {
        // Run the given executable with the given arguments
        // Return an id that can be used later to pause/cancel/resume as needed
        let child = Command::new(executable).args(args).spawn()?;
        Ok(SubProcess {
            process: child,
            paused: false,
            exit_code: None,
        })
    }
}

impl SubProcess {
    fn send_signal(&self, signal: nix::sys::signal::Signal) -> Result<()> {
        let pid = match self.process.id() {
            Some(id) => id,
            None => bail!("Unable to get pid from command, it likely finished running"),
        };
        let pid: pid_t = match pid.try_into() {
            Ok(pid) => pid,
            Err(message) => bail!("Unable to get pid_t from command {message}"),
        };
        signal::kill(Pid::from_raw(pid), signal)?;
        Ok(())
    }

    fn update_exit_code(&mut self, status: ExitStatus) -> Result<i32> {
        if let Some(code) = status.code() {
            self.exit_code = Some(code);
            Ok(code)
        } else if let Some(signal) = status.signal() {
            self.exit_code = Some(-signal);
            Ok(-signal)
        } else {
            bail!("Process exited without return code or signal");
        }
    }

    fn try_wait(&mut self) -> Result<Option<i32>> {
        if self.exit_code.is_none() {
            // If we don't already have an exit code, try to wait for the process
            if let Some(status) = self.process.try_wait()? {
                self.update_exit_code(status)?;
            }
        }
        Ok(self.exit_code)
    }

    async fn exit_code_internal(&mut self) -> Result<i32> {
        if let Some(code) = self.exit_code {
            // Just give the exit_code if we have it already
            Ok(code)
        } else {
            // Otherwise wait for the process
            let status = self.process.wait().await?;
            self.update_exit_code(status)
        }
    }
}

#[interface(name = "com.steampowered.SteamOSManager1.SubProcess")]
impl SubProcess {
    pub async fn pause(&mut self) -> zbus::fdo::Result<()> {
        if self.paused {
            return Err(zbus::fdo::Error::Failed("Already paused".to_string()));
        }
        // Pause the given process if possible
        // Return true on success, false otherwise
        let result = self.send_signal(Signal::SIGSTOP).map_err(to_zbus_fdo_error);
        self.paused = true;
        result
    }

    pub async fn resume(&mut self) -> zbus::fdo::Result<()> {
        // Resume the given process if possible
        if !self.paused {
            return Err(zbus::fdo::Error::Failed("Not paused".to_string()));
        }
        let result = self.send_signal(Signal::SIGCONT).map_err(to_zbus_fdo_error);
        self.paused = false;
        result
    }

    pub async fn cancel(&mut self) -> zbus::fdo::Result<()> {
        if self.try_wait().map_err(to_zbus_fdo_error)?.is_none() {
            self.send_signal(Signal::SIGTERM)
                .map_err(to_zbus_fdo_error)?;
            if self.paused {
                self.resume().await?;
            }
        }
        Ok(())
    }

    pub async fn kill(&mut self) -> zbus::fdo::Result<()> {
        match self.try_wait().map_err(to_zbus_fdo_error)? {
            Some(_) => Ok(()),
            None => self.send_signal(signal::SIGKILL).map_err(to_zbus_fdo_error),
        }
    }

    pub async fn wait(&mut self) -> zbus::fdo::Result<i32> {
        if self.paused {
            self.resume().await?;
        }

        let code = match self.exit_code_internal().await.map_err(to_zbus_fdo_error) {
            Ok(v) => v,
            Err(_) => {
                return Err(zbus::fdo::Error::Failed(
                    "Unable to get exit code".to_string(),
                ));
            }
        };
        self.exit_code = Some(code);
        Ok(code)
    }

    pub async fn exit_code(&mut self) -> zbus::fdo::Result<i32> {
        match self.try_wait() {
            Ok(Some(i)) => Ok(i),
            _ => Err(zbus::fdo::Error::Failed(
                "Unable to get exit code. The process may still be running.".to_string(),
            )),
        }
    }
}

#[cfg(not(test))]
pub async fn script_exit_code(executable: &str, args: &[impl AsRef<OsStr>]) -> Result<i32> {
    // Run given script and return the exit code
    let mut child = Command::new(executable).args(args).spawn()?;
    let status = child.wait().await?;
    status.code().ok_or(anyhow!("Killed by signal"))
}

#[cfg(test)]
pub async fn script_exit_code(executable: &str, args: &[impl AsRef<OsStr>]) -> Result<i32> {
    let test = crate::testing::current();
    let args: Vec<&OsStr> = args.iter().map(|arg| arg.as_ref()).collect();
    let cb = test.process_cb.get();
    cb(executable, args.as_ref()).map(|(res, _)| res)
}

pub async fn run_script(executable: &str, args: &[impl AsRef<OsStr>]) -> Result<()> {
    // Run given script to get exit code and return true on success.
    // Return Err on failure, but also print an error if needed
    match script_exit_code(executable, args).await {
        Ok(0) => Ok(()),
        Ok(code) => Err(anyhow!("Exited {code}")),
        Err(message) => Err(message),
    }
}

#[cfg(not(test))]
pub async fn script_output(executable: &str, args: &[impl AsRef<OsStr>]) -> Result<String> {
    // Run given command and return the output given
    let output = Command::new(executable).args(args).output();

    let output = output.await?;

    let s = std::str::from_utf8(&output.stdout)?;
    Ok(s.to_string())
}

#[cfg(test)]
pub async fn script_output(executable: &str, args: &[impl AsRef<OsStr>]) -> Result<String> {
    let test = crate::testing::current();
    let args: Vec<&OsStr> = args.iter().map(|arg| arg.as_ref()).collect();
    let cb = test.process_cb.get();
    cb(executable, args.as_ref()).map(|(_, res)| res)
}

#[cfg(test)]
mod test {
    use super::*;
    use crate::testing;
    use nix::sys::signal::Signal;

    fn ok(_: &str, _: &[&OsStr]) -> Result<(i32, String)> {
        Ok((0, String::from("ok")))
    }

    fn code(_: &str, _: &[&OsStr]) -> Result<(i32, String)> {
        Ok((1, String::from("code")))
    }

    fn exit(_: &str, _: &[&OsStr]) -> Result<(i32, String)> {
        Err(anyhow!("oops!"))
    }

    #[tokio::test]
    async fn test_process_manager() {
        let _h = testing::start();

        let mut false_process = ProcessManager::run_long_command("/bin/false", &[] as &[String; 0])
            .await
            .unwrap();
        let mut true_process = ProcessManager::run_long_command("/bin/true", &[] as &[String; 0])
            .await
            .unwrap();

        let mut pause_process = ProcessManager::run_long_command("/usr/bin/sleep", &["0.2"])
            .await
            .unwrap();
        pause_process.pause().await.expect("pause");

        assert_eq!(
            pause_process.pause().await.unwrap_err(),
            zbus::fdo::Error::Failed("Already paused".to_string())
        );

        pause_process.resume().await.expect("resume");

        assert_eq!(
            pause_process.resume().await.unwrap_err(),
            zbus::fdo::Error::Failed("Not paused".to_string())
        );

        // Sleep gives 0 exit code when done, -1 when we haven't waited for it yet
        assert_eq!(pause_process.wait().await.unwrap(), 0);

        assert_eq!(false_process.wait().await.unwrap(), 1);
        assert_eq!(true_process.wait().await.unwrap(), 0);
    }

    #[tokio::test]
    async fn test_multikill() {
        let _h = testing::start();

        let mut sleep_process = ProcessManager::run_long_command("/usr/bin/sleep", &["0.1"])
            .await
            .unwrap();
        sleep_process.kill().await.expect("kill");

        // Killing a process should be idempotent
        sleep_process.kill().await.expect("kill");

        assert_eq!(
            sleep_process.exit_code().await.unwrap(),
            -(Signal::SIGKILL as i32)
        );
    }

    #[tokio::test]
    async fn test_terminate_unpause() {
        let _h = testing::start();

        let mut pause_process = ProcessManager::run_long_command("/usr/bin/sleep", &["0.2"])
            .await
            .unwrap();
        pause_process.pause().await.expect("pause");
        assert_eq!(pause_process.try_wait().expect("try_wait"), None);

        // Canceling a process should unpause it
        pause_process.cancel().await.expect("pause");
        assert_eq!(
            pause_process.exit_code().await.unwrap(),
            -(Signal::SIGTERM as i32)
        );
    }

    #[tokio::test]
    async fn test_exit_code_early() {
        let _h = testing::start();

        let mut sleep_process = ProcessManager::run_long_command("/usr/bin/sleep", &["0.1"])
            .await
            .unwrap();
        assert_eq!(
            sleep_process.exit_code().await.unwrap_err().to_string(),
            "org.freedesktop.DBus.Error.Failed: Unable to get exit code. The process may still be running."
        );

        assert_eq!(sleep_process.wait().await.unwrap(), 0);
    }

    #[tokio::test]
    async fn test_run_script() {
        let h = testing::start();

        h.test.process_cb.set(ok);
        assert!(run_script("", &[] as &[&OsStr]).await.is_ok());

        h.test.process_cb.set(code);
        assert_eq!(
            run_script("", &[] as &[&OsStr])
                .await
                .unwrap_err()
                .to_string(),
            "Exited 1"
        );

        h.test.process_cb.set(exit);
        assert_eq!(
            run_script("", &[] as &[&OsStr])
                .await
                .unwrap_err()
                .to_string(),
            "oops!"
        );
    }
}