nushell/crates/nu-cmd-dataframe/src/dataframe/eager/take.rs

use crate::dataframe::values::{Column, NuDataFrame};
use nu_engine::command_prelude::*;

use polars::prelude::DataType;

#[derive(Clone)]
pub struct TakeDF;

impl Command for TakeDF {
    fn name(&self) -> &str {
        "dfr take"
    }

    fn usage(&self) -> &str {
        "Creates new dataframe using the given indices."
    }

    fn signature(&self) -> Signature {
        Signature::build(self.name())
            .required(
                "indices",
                SyntaxShape::Any,
                "list of indices used to take data",
            )
            .input_output_type(
                Type::Custom("dataframe".into()),
                Type::Custom("dataframe".into()),
            )
            .category(Category::Custom("dataframe".into()))
    }

    fn examples(&self) -> Vec<Example> {
        vec![
            Example {
                description: "Takes selected rows from dataframe",
                example: r#"let df = ([[a b]; [4 1] [5 2] [4 3]] | dfr into-df);
    let indices = ([0 2] | dfr into-df);
    $df | dfr take $indices"#,
                result: Some(
                    NuDataFrame::try_from_columns(
                        vec![
                            Column::new(
                                "a".to_string(),
                                vec![Value::test_int(4), Value::test_int(4)],
                            ),
                            Column::new(
                                "b".to_string(),
                                vec![Value::test_int(1), Value::test_int(3)],
                            ),
                        ],
                        None,
                    )
                    .expect("simple df for test should not fail")
                    .into_value(Span::test_data()),
                ),
            },
            Example {
                description: "Takes selected rows from series",
                example: r#"let series = ([4 1 5 2 4 3] | dfr into-df);
    let indices = ([0 2] | dfr into-df);
    $series | dfr take $indices"#,
                result: Some(
                    NuDataFrame::try_from_columns(
                        vec![Column::new(
                            "0".to_string(),
                            vec![Value::test_int(4), Value::test_int(5)],
                        )],
                        None,
                    )
                    .expect("simple df for test should not fail")
                    .into_value(Span::test_data()),
                ),
            },
        ]
    }

    fn run(
        &self,
        engine_state: &EngineState,
        stack: &mut Stack,
        call: &Call,
        input: PipelineData,
    ) -> Result<PipelineData, ShellError> {
        command(engine_state, stack, call, input)
    }
}

fn command(
    engine_state: &EngineState,
    stack: &mut Stack,
    call: &Call,
    input: PipelineData,
) -> Result<PipelineData, ShellError> {
    let index_value: Value = call.req(engine_state, stack, 0)?;
    let index_span = index_value.span();
    let index = NuDataFrame::try_from_value(index_value)?.as_series(index_span)?;

    let casted = match index.dtype() {
        DataType::UInt32 | DataType::UInt64 | DataType::Int32 | DataType::Int64 => index
            .cast(&DataType::UInt32)
            .map_err(|e| ShellError::GenericError {
                error: "Error casting index list".into(),
                msg: e.to_string(),
                span: Some(index_span),
                help: None,
                inner: vec![],
            }),
        _ => Err(ShellError::GenericError {
            error: "Incorrect type".into(),
            msg: "Series with incorrect type".into(),
            span: Some(call.head),
            help: Some("Consider using a Series with type int type".into()),
            inner: vec![],
        }),
    }?;

    let indices = casted.u32().map_err(|e| ShellError::GenericError {
        error: "Error casting index list".into(),
        msg: e.to_string(),
        span: Some(index_span),
        help: None,
        inner: vec![],
    })?;

    NuDataFrame::try_from_pipeline(input, call.head).and_then(|df| {
        df.as_ref()
            .take(indices)
            .map_err(|e| ShellError::GenericError {
                error: "Error taking values".into(),
                msg: e.to_string(),
                span: Some(call.head),
                help: None,
                inner: vec![],
            })
            .map(|df| PipelineData::Value(NuDataFrame::dataframe_into_value(df, call.head), None))
    })
}

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

    #[test]
    fn test_examples() {
        test_dataframe(vec![Box::new(TakeDF {})])
    }
}