nu-command 0.75.0

use crate::dataframe::values::{Column, NuDataFrame, NuExpression, NuLazyFrame};

use nu_engine::CallExt;
use nu_protocol::{
    ast::Call,
    engine::{Command, EngineState, Stack},
    Category, Example, PipelineData, ShellError, Signature, Span, SyntaxShape, Type, Value,
};

#[derive(Clone)]
pub struct LazyFilter;

impl Command for LazyFilter {
    fn name(&self) -> &str {
        "filter"
    }

    fn usage(&self) -> &str {
        "Filter dataframe based in expression"
    }

    fn signature(&self) -> Signature {
        Signature::build(self.name())
            .required(
                "filter expression",
                SyntaxShape::Any,
                "Expression that define the column selection",
            )
            .input_type(Type::Custom("dataframe".into()))
            .output_type(Type::Custom("dataframe".into()))
            .category(Category::Custom("lazyframe".into()))
    }

    fn examples(&self) -> Vec<Example> {
        vec![Example {
            description: "Filter dataframe using an expression",
            example: "[[a b]; [6 2] [4 2] [2 2]] | into df | filter ((col a) >= 4)",
            result: Some(
                NuDataFrame::try_from_columns(vec![
                    Column::new(
                        "a".to_string(),
                        vec![Value::test_int(6), Value::test_int(4)],
                    ),
                    Column::new(
                        "b".to_string(),
                        vec![Value::test_int(2), Value::test_int(2)],
                    ),
                ])
                .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> {
        let value: Value = call.req(engine_state, stack, 0)?;
        let expression = NuExpression::try_from_value(value)?;

        let lazy = NuLazyFrame::try_from_pipeline(input, call.head)?;
        let lazy = NuLazyFrame::new(
            lazy.from_eager,
            lazy.into_polars().filter(expression.into_polars()),
        );

        Ok(PipelineData::Value(lazy.into_value(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(LazyFilter {})])
    }
}