nushell/crates/nu-cli/src/commands/table.rs

use crate::commands::WholeStreamCommand;
use crate::format::TableView;
use crate::prelude::*;
use nu_errors::ShellError;
use nu_protocol::{Primitive, Signature, SyntaxShape, UntaggedValue, Value};
use std::time::Instant;

const STREAM_PAGE_SIZE: usize = 1000;
const STREAM_TIMEOUT_CHECK_INTERVAL: usize = 100;

pub struct Table;

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

    fn signature(&self) -> Signature {
        Signature::build("table").named(
            "start_number",
            SyntaxShape::Number,
            "row number to start viewing from",
            Some('n'),
        )
    }

    fn usage(&self) -> &str {
        "View the contents of the pipeline as a table."
    }

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

async fn table(args: CommandArgs, registry: &CommandRegistry) -> Result<OutputStream, ShellError> {
    let registry = registry.clone();
    let mut args = args.evaluate_once(&registry).await?;
    let mut finished = false;

    let host = args.host.clone();
    let mut start_number = match args.get("start_number") {
        Some(Value {
            value: UntaggedValue::Primitive(Primitive::Int(i)),
            ..
        }) => {
            if let Some(num) = i.to_usize() {
                num
            } else {
                return Err(ShellError::labeled_error(
                    "Expected a row number",
                    "expected a row number",
                    &args.args.call_info.name_tag,
                ));
            }
        }
        _ => 0,
    };

    let mut delay_slot = None;

    while !finished {
        let mut new_input: VecDeque<Value> = VecDeque::new();

        let start_time = Instant::now();
        for idx in 0..STREAM_PAGE_SIZE {
            if let Some(val) = delay_slot {
                new_input.push_back(val);
                delay_slot = None;
            } else {
                match args.input.next().await {
                    Some(a) => {
                        if !new_input.is_empty() {
                            if let Some(descs) = new_input.get(0) {
                                let descs = descs.data_descriptors();
                                let compare = a.data_descriptors();
                                if descs != compare {
                                    delay_slot = Some(a);
                                    break;
                                } else {
                                    new_input.push_back(a);
                                }
                            } else {
                                new_input.push_back(a);
                            }
                        } else {
                            new_input.push_back(a);
                        }
                    }
                    _ => {
                        finished = true;
                        break;
                    }
                }

                // Check if we've gone over our buffering threshold
                if (idx + 1) % STREAM_TIMEOUT_CHECK_INTERVAL == 0 {
                    let end_time = Instant::now();

                    // If we've been buffering over a second, go ahead and send out what we have so far
                    if (end_time - start_time).as_secs() >= 1 {
                        break;
                    }
                }
            }
        }

        let input: Vec<Value> = new_input.into();

        if !input.is_empty() {
            let mut host = host.lock();
            let view = TableView::from_list(&input, start_number);

            if let Some(view) = view {
                handle_unexpected(&mut *host, |host| crate::format::print_view(&view, host));
            }
        }

        start_number += input.len();
    }

    Ok(OutputStream::empty())
}

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

    #[test]
    fn examples_work_as_expected() {
        use crate::examples::test as test_examples;

        test_examples(Table {})
    }
}