// Copyright (C) 2023 Andreas Hartmann <hartan@7x.de>
// GNU General Public License v3.0+ (https://www.gnu.org/licenses/gpl-3.0.txt)
// SPDX-License-Identifier: GPL-3.0-or-later

//! # Toolbx Environment Handler.
//!
//! This module handles command-not-found errors that occur while executing inside a Toolbx
//! container. Currently, this means that commands are forwarded to the host using `flatpak-spawn`.
//! If `flatpak-spawn` isn't present, an error is thrown instead.
use super::prelude::*;

use log;
use users::{get_current_gid, get_current_uid};

use std::{io::IsTerminal, path::Path};

const TOOLBX_ENV: &str = "/run/.toolboxenv";
const CONTAINER_ENV: &str = "/run/.containerenv";
const OS_RELEASE: &str = "/etc/os-release";

#[derive(PartialEq, Eq, Debug, PartialOrd, Ord, Serialize, Deserialize)]
pub struct Toolbx {
    name: String,
}

impl fmt::Display for Toolbx {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "toolbx '{}'", self.name)
    }
}

impl Toolbx {
    /// Spawn a Toolbx container with a given name.
    ///
    /// Checks if the toolbx container exists and starts it, if necessary. If `None` is given as
    /// name, will try to determine the default toolbx name and start that instead. Returns an
    /// error if unsuccessful.
    pub fn new(name: Option<String>) -> Result<Toolbx, NewToolbxError> {
        let name = match name {
            Some(name) if !name.is_empty() => name,
            _ => match Toolbx::default_name() {
                Ok(toolbx_name) => toolbx_name,
                Err(e) => return Err(NewToolbxError::UnknownDefault(e)),
            },
        };

        // Do an optimistic start:
        // - If the container exists and isn't started, it will be started
        // - If the container exists and is started, nothing happens
        // - If the container doesn't exist, we get an error and report that
        let output = std::process::Command::new("podman")
            .args(["start", &name])
            .output()
            .map_err(|e| match e.kind() {
                std::io::ErrorKind::NotFound => NewToolbxError::NeedPodman,
                _ => NewToolbxError::IoError(e),
            })?;
        if output.status.success() {
            // All good
            Ok(Toolbx { name })
        } else {
            let stderr = String::from_utf8_lossy(&output.stderr);
            if stderr.starts_with("Error: no container with name or ID")
                && stderr.contains("found: no such container")
            {
                Err(NewToolbxError::NonExistent(name))
            } else {
                Err(NewToolbxError::Podman(output))
            }
        }
    }

    /// Get the Toolbx container currently executing CNF.
    ///
    /// Will return an error if the current execution environment isn't Toolbx.
    pub fn current() -> Result<Toolbx, CurrentToolbxError> {
        if !detect() {
            return Err(CurrentToolbxError::NotAToolbx);
        }

        let content = std::fs::read_to_string(CONTAINER_ENV).map_err(|e| {
            CurrentToolbxError::Environment {
                env_file: CONTAINER_ENV.to_string(),
                source: e,
            }
        })?;
        let name = content
            .lines()
            .find(|line| line.contains("name=\""))
            .ok_or_else(|| CurrentToolbxError::Name(CONTAINER_ENV.to_string()))?
            .trim_start_matches("name=\"")
            .trim_end_matches('"');

        Ok(Toolbx {
            name: name.to_string(),
        })
    }

    /// Get the name of the default toolbx to lookup/execute commands in.
    ///
    /// The default toolbx container name is assembled from the contents of `/etc/os-release`.
    pub fn default_name() -> Result<String, DefaultToolbxError> {
        // Construct default toolbox name by hand. Format is $ID-toolbox-$VERSION_ID, with ID
        // and VERSION_ID taken from /etc/os-release. See here:
        // https://containertoolbx.org/distros/
        log::debug!("Determining default toolbx name via {}", OS_RELEASE);

        let content =
            std::fs::read_to_string(OS_RELEASE).map_err(|e| DefaultToolbxError::UnknownOs {
                file: OS_RELEASE.to_string(),
                source: e,
            })?;
        let id = content
            .lines()
            .find(|line| line.starts_with("ID="))
            .map(|line| line.trim_start_matches("ID=").trim_matches('"'))
            .ok_or(DefaultToolbxError::Id)?;
        let version_id = content
            .lines()
            .find(|line| line.starts_with("VERSION_ID="))
            .map(|line| line.trim_start_matches("VERSION_ID=").trim_matches('"'))
            .ok_or(DefaultToolbxError::VersionId)?;

        Ok(format!("{}-toolbox-{}", id, version_id))
    }
}

impl environment::IsEnvironment for Toolbx {
    type Err = Error;

    fn exists(&self) -> bool {
        if detect() {
            true
        } else if let Environment::Host(host) = environment::current() {
            host.execute(crate::environment::cmd!("toolbox", "--version"))
                .map(|mut cmd| {
                    async_std::task::block_on(async move {
                        cmd.stdout(async_process::Stdio::null())
                            .stderr(async_process::Stdio::null())
                            .status()
                            .await
                            .map(|status| status.success())
                            .unwrap_or(false)
                    })
                })
                .unwrap_or(false)
        } else {
            false
        }
    }

    fn execute(&self, command: CommandLine) -> Result<Command, Self::Err> {
        log::debug!("Executing command '{}' in toolbx '{}'", command, self.name);

        let mut cmd: Command;
        match environment::current() {
            Environment::Distrobox(_) => {
                return Err(Error::Unimplemented(
                    "running in a toolbx from a distrobox".to_string(),
                ));
            }
            Environment::Toolbx(t) => {
                if self == &t {
                    // This is the toolbx container we are currently running in
                    // We expect toolbx containers to *always* run a unix OS, or at least something
                    // that has `sudo`.
                    if command.get_privileged() {
                        cmd = Command::new("sudo");
                        if !command.get_interactive() {
                            cmd.arg("-n");
                        }

                        cmd.arg(command.command());
                    } else {
                        cmd = Command::new(command.command());
                    }

                    cmd.args(command.args());
                } else {
                    return Err(Error::Unimplemented(
                        "running in a toolbx from another toolbx".to_string(),
                    ));
                }
            }
            Environment::Host(_) => {
                cmd = Command::new("podman");

                cmd.args(["exec", "-i"]);
                // The toolbx container by default isn't launched with the `--user` option, we must
                // take care of this ourselves.
                cmd.arg("--user");
                cmd.arg(format!("{}:{}", get_current_uid(), get_current_gid()));
                // Fix the working directory
                cmd.arg("--workdir");
                cmd.arg(std::env::current_dir().map_err(Error::UnknownCwd)?);
                // Keep some env vars
                for var in environment::read_env_vars() {
                    cmd.args(["-e", &var]);
                }

                // Only attach to the tty if we really have a tty, too
                // FIXME: Is this really the correct way to check?
                if std::io::stdout().is_terminal() && std::io::stdin().is_terminal() {
                    cmd.arg("-t");
                }

                // Can't run command in toolbx if we don't have one
                cmd.arg(&self.name);

                // This is the real command we're looking for (with arguments)
                if command.get_privileged() {
                    cmd.args(["sudo", "-S", "-E"]);
                    // NOTE: We ignore `get_interactive` here. because toolbox seems to do weird
                    // things regarding sudo. When adding the `-n` flag to request non-interactive
                    // auth, sudo will fail, requiring a pssword. However, factually running `sudo`
                    // in a toolbx container *does not* require a password under normal
                    // circumstances. Just ignoring interactivity here solves this issue (but don't
                    // ask me why).
                }

                cmd.arg(command.command()).args(command.args());

                log::debug!("Calling: {:?}", cmd);
            }
            #[cfg(test)]
            Environment::Mock(_) => unimplemented!(),
        }
        Ok(cmd)
    }
}

/// Detect if the current execution environment is a Toolbx container.
///
/// Checks for the presence of the `.toolboxenv` files.
pub fn detect() -> bool {
    Path::new(TOOLBX_ENV).exists()
}

#[derive(Debug, ThisError)]
pub enum NewToolbxError {
    #[error("working with toolbx containers requires the 'podman' executable")]
    NeedPodman,

    #[error("podman exited with non-zero code: {0:#?}")]
    Podman(std::process::Output),

    #[error("no toolbx with name {0} exists")]
    NonExistent(String),

    #[error("unknown I/O error occured")]
    IoError(#[from] std::io::Error),

    #[error("failed to determine default toolbx name")]
    UnknownDefault(#[from] DefaultToolbxError),
}

#[derive(Debug, ThisError)]
pub enum CurrentToolbxError {
    #[error("cannot read toolbx info from environment file '{env_file}'")]
    Environment {
        env_file: String,
        source: std::io::Error,
    },

    #[error("program currently isn't run from a toolbx")]
    NotAToolbx,

    #[error("failed to read toolbx name from environment file '{0}'")]
    Name(String),
}

#[derive(Debug, ThisError)]
pub enum DefaultToolbxError {
    #[error("failed to read OS information from '{file}'")]
    UnknownOs {
        file: String,
        source: std::io::Error,
    },

    #[error("cannot determine OS ID from os-release info")]
    Id,

    #[error("cannot determine OS VERSION_ID from os-release info")]
    VersionId,
}

#[derive(Debug, ThisError)]
pub enum Error {
    #[error("cannot determine current working directory")]
    UnknownCwd(#[from] std::io::Error),

    #[error("not implemented: {0}")]
    Unimplemented(String),
}