use crate::common::*;

pub struct Platform;

pub trait PlatformInterface {
  /// Construct a command equivelant to running the script at `path` with the
  /// shebang line `shebang`
  fn make_shebang_command(
    path: &Path,
    command: &str,
    argument: Option<&str>,
  ) -> Result<Command, brev::OutputError>;

  /// Set the execute permission on the file pointed to by `path`
  fn set_execute_permission(path: &Path) -> Result<(), io::Error>;

  /// Extract the signal from a process exit status, if it was terminated by a signal
  fn signal_from_exit_status(exit_status: process::ExitStatus) -> Option<i32>;

  /// Translate a path from a "native" path to a path the interpreter expects
  fn to_shell_path(path: &Path) -> Result<String, String>;
}

#[cfg(unix)]
impl PlatformInterface for Platform {
  fn make_shebang_command(
    path: &Path,
    _command: &str,
    _argument: Option<&str>,
  ) -> Result<Command, brev::OutputError> {
    // shebang scripts can be executed directly on unix
    Ok(Command::new(path))
  }

  fn set_execute_permission(path: &Path) -> Result<(), io::Error> {
    use std::os::unix::fs::PermissionsExt;

    // get current permissions
    let mut permissions = fs::metadata(&path)?.permissions();

    // set the execute bit
    let current_mode = permissions.mode();
    permissions.set_mode(current_mode | 0o100);

    // set the new permissions
    fs::set_permissions(&path, permissions)
  }

  fn signal_from_exit_status(exit_status: process::ExitStatus) -> Option<i32> {
    use std::os::unix::process::ExitStatusExt;
    exit_status.signal()
  }

  fn to_shell_path(path: &Path) -> Result<String, String> {
    path
      .to_str()
      .map(str::to_string)
      .ok_or_else(|| String::from("Error getting current directory: unicode decode error"))
  }
}

#[cfg(windows)]
impl PlatformInterface for Platform {
  fn make_shebang_command(
    path: &Path,
    command: &str,
    argument: Option<&str>,
  ) -> Result<Command, brev::OutputError> {
    // Translate path to the interpreter from unix style to windows style
    let mut cygpath = Command::new("cygpath");
    cygpath.arg("--windows");
    cygpath.arg(command);

    let mut cmd = Command::new(brev::output(cygpath)?);
    if let Some(argument) = argument {
      cmd.arg(argument);
    }
    cmd.arg(path);
    Ok(cmd)
  }

  fn set_execute_permission(_path: &Path) -> Result<(), io::Error> {
    // it is not necessary to set an execute permission on a script on windows,
    // so this is a nop
    Ok(())
  }

  fn signal_from_exit_status(_exit_status: process::ExitStatus) -> Option<i32> {
    // The rust standard library does not expose a way to extract a signal
    // from a windows process exit status, so just return None
    None
  }

  fn to_shell_path(path: &Path) -> Result<String, String> {
    // Translate path from windows style to unix style
    let mut cygpath = Command::new("cygpath");
    cygpath.arg("--unix");
    cygpath.arg(path);
    brev::output(cygpath).map_err(|e| format!("Error converting shell path: {}", e))
  }
}