nushell/crates/nu-command/src/commands/reverse.rs

use crate::prelude::*;
use nu_engine::WholeStreamCommand;
use nu_errors::ShellError;
use nu_protocol::{ReturnSuccess, Signature, UntaggedValue};

pub struct Reverse;

#[async_trait]
impl WholeStreamCommand for Reverse {
    fn name(&self) -> &str {
        "reverse"
    }

    fn signature(&self) -> Signature {
        Signature::build("reverse")
    }

    fn usage(&self) -> &str {
        "Reverses the table."
    }

    async fn run(&self, args: CommandArgs) -> Result<OutputStream, ShellError> {
        reverse(args).await
    }

    fn examples(&self) -> Vec<Example> {
        vec![Example {
            description: "Sort list of numbers in descending file size",
            example: "echo [3 1 2 19 0] | reverse",
            result: Some(vec![
                UntaggedValue::int(0).into(),
                UntaggedValue::int(19).into(),
                UntaggedValue::int(2).into(),
                UntaggedValue::int(1).into(),
                UntaggedValue::int(3).into(),
            ]),
        }]
    }
}

async fn reverse(args: CommandArgs) -> Result<OutputStream, ShellError> {
    let args = args.evaluate_once().await?;
    let (input, _args) = args.parts();

    let input = input.collect::<Vec<_>>().await;
    Ok(futures::stream::iter(input.into_iter().rev().map(ReturnSuccess::value)).to_output_stream())
}

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

    #[test]
    fn examples_work_as_expected() -> Result<(), ShellError> {
        use crate::examples::test as test_examples;

        Ok(test_examples(Reverse {})?)
    }
}