//! Helper traits and types to make `std::process::Command` more ergonomic

#![warn(missing_docs)]

use std::process::{Command, Output};
use tracing::debug;
use once_cell::sync::Lazy;

/// Whether to debug-log command strings before they are run
///
/// This is true if the `FLUVIO_CMD` environment variable is
/// set to `true` (case insensitive).
static SHOULD_LOG: Lazy<bool> = Lazy::new(|| {
    std::env::var("FLUVIO_CMD")
        .map(|it| it.eq_ignore_ascii_case("true"))
        .unwrap_or(false)
});

/// `Ok(Output)` when a child process successfully runs and returns exit code `0`.
///
/// All other circumstances are regarded as `Err(CommandError)`. This includes
/// when there is an error invoking a child process, if a child process is
/// terminated, or if the child process runs and returns a non-zero exit code.
pub type CommandResult = Result<Output, CommandError>;

/// An error type describing the kinds of failure a child process may have
#[derive(thiserror::Error, Debug)]
#[error("Failed to run \"{command}\"")]
pub struct CommandError {
    /// The command that was attempting to run
    pub command: String,
    /// The kind of error that the command encountered
    pub source: CommandErrorKind,
}

/// Describes the particular kinds of errors that may occur while running a command
#[derive(thiserror::Error, Debug)]
pub enum CommandErrorKind {
    /// The child process was terminated, so did not exit successfully
    #[error("Child process was terminated and has no exit code")]
    Terminated,
    /// The child process completed with a non-zero exit code
    #[error("\
Child process completed with non-zero exit code {0}
  stdout: {}
  stderr: {}",
        String::from_utf8_lossy(&.1.stdout).to_string(),
        String::from_utf8_lossy(&.1.stderr).to_string())]
    ExitError(i32, Output),
    /// There was an error invoking the command
    #[error("An error occurred while invoking child process")]
    IoError(#[from] std::io::Error),
}

/// Adds useful extension methods to the `Command` type
pub trait CommandExt {
    /// Inherit both `stdout` and `stderr` from this process.
    ///
    /// # Example
    ///
    /// ```
    /// use std::process::Command;
    /// use fluvio_command::CommandExt;
    /// let _ = Command::new("echo")
    ///     .arg("Hello world")
    ///     .inherit()
    ///     .status();
    /// ```
    fn inherit(&mut self) -> &mut Self;
    /// Return a stringified version of the Command.
    ///
    /// ```
    /// use std::process::Command;
    /// use fluvio_command::CommandExt;
    /// let mut command = Command::new("echo");
    /// command.arg("one").arg("two three");
    /// let command_string: String = command.display();
    /// assert_eq!(command_string, "echo one two three");
    /// ```
    fn display(&mut self) -> String;
    /// Returns a result signaling the outcome of executing this command.
    ///
    /// ```
    /// use std::process::{Command, Output};
    /// use fluvio_command::{CommandExt, CommandErrorKind};
    ///
    /// // On success, we get the stdout and stderr output
    /// let output: Output = Command::new("true").result().unwrap();
    ///
    /// let error = Command::new("ls")
    ///     .arg("does-not-exist")
    ///     .result()
    ///     .unwrap_err();
    /// if let CommandErrorKind::ExitError(1i32, output) = error.source {
    ///     assert_eq!(
    ///         String::from_utf8_lossy(&output.stderr).to_string(),
    ///         "ls: does-not-exist: No such file or directory\n",
    ///     );
    /// } else {
    ///     panic!("should fail with stderr output");
    /// }
    ///
    /// let error = Command::new("foobar").result().unwrap_err();
    /// assert!(matches!(error.source, CommandErrorKind::IoError(_)));
    /// assert_eq!(error.command, "foobar");
    /// ```
    fn result(&mut self) -> CommandResult;
}

impl CommandExt for Command {
    fn inherit(&mut self) -> &mut Self {
        use std::process::Stdio;
        self.stdout(Stdio::inherit()).stderr(Stdio::inherit())
    }

    fn display(&mut self) -> String {
        format!("{:?}", self).replace("\"", "")
    }

    fn result(&mut self) -> CommandResult {
        if *SHOULD_LOG {
            debug!("Executing> {}", self.display());
        }

        self.output()
            .map_err(|e| CommandError {
                command: self.display(),
                source: CommandErrorKind::IoError(e),
            })
            .and_then(|output| match output.status.code() {
                Some(0i32) => Ok(output),
                None => Err(CommandError {
                    command: self.display(),
                    source: CommandErrorKind::Terminated,
                }),
                Some(code) => Err(CommandError {
                    command: self.display(),
                    source: CommandErrorKind::ExitError(code, output),
                }),
            })
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_output_display() {
        let error = Command::new("ls")
            .arg("does-not-exist")
            .result()
            .unwrap_err();
        let error_display = format!("{}", error.source);
        assert!(error_display.starts_with("Child process completed with non-zero exit code"));
        assert!(error_display.contains("stdout:"));
        assert!(error_display.contains("stderr:"));
    }
}