nu-command 0.29.0

CLI for nushell
Documentation 
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use crate::prelude::*;
use nu_engine::WholeStreamCommand;
use nu_errors::ShellError;
use nu_protocol::{ReturnSuccess, Signature, SyntaxShape, UntaggedValue, Value};
use nu_source::Tagged;

use super::support::{rotate, Direction};

pub struct SubCommand;

#[derive(Deserialize)]
pub struct Arguments {
    by: Option<Tagged<u64>>,
}

#[async_trait]
impl WholeStreamCommand for SubCommand {
    fn name(&self) -> &str {
        "roll up"
    }

    fn signature(&self) -> Signature {
        Signature::build("roll up").optional("by", SyntaxShape::Int, "the number of times to roll")
    }

    fn usage(&self) -> &str {
        "Rolls the table rows"
    }

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

pub async fn roll(args: CommandArgs) -> Result<OutputStream, ShellError> {
    let name = args.call_info.name_tag.clone();
    let (args, mut input) = args.process().await?;

    let values = input.drain_vec().await;

    Ok(futures::stream::iter(
        roll_up(values, &args)
            .unwrap_or_else(|| vec![UntaggedValue::nothing().into_value(&name)])
            .into_iter()
            .map(ReturnSuccess::value),
    )
    .to_output_stream())
}

fn roll_up(values: Vec<Value>, Arguments { by: ref n }: &Arguments) -> Option<Vec<Value>> {
    rotate(values, n, Direction::Up)
}