nushell/crates/nu_plugin_polars/src/dataframe/lazy/fill_nan.rs

use crate::{
    dataframe::values::{Column, NuDataFrame, NuExpression},
    values::{cant_convert_err, CustomValueSupport, PolarsPluginObject, PolarsPluginType},
    PolarsPlugin,
};
use nu_plugin::{EngineInterface, EvaluatedCall, PluginCommand};
use nu_protocol::{
    Category, Example, LabeledError, PipelineData, ShellError, Signature, Span, SyntaxShape, Type,
    Value,
};

#[derive(Clone)]
pub struct LazyFillNA;

impl PluginCommand for LazyFillNA {
    type Plugin = PolarsPlugin;

    fn name(&self) -> &str {
        "polars fill-nan"
    }

    fn usage(&self) -> &str {
        "Replaces NaN values with the given expression."
    }

    fn signature(&self) -> Signature {
        Signature::build(self.name())
            .required(
                "fill",
                SyntaxShape::Any,
                "Expression to use to fill the NAN values",
            )
            .input_output_type(
                Type::Custom("dataframe".into()),
                Type::Custom("dataframe".into()),
            )
            .category(Category::Custom("lazyframe".into()))
    }

    fn examples(&self) -> Vec<Example> {
        vec![
            Example {
                description: "Fills the NaN values with 0",
                example: "[1 2 NaN 3 NaN] | polars into-df | polars fill-nan 0",
                result: Some(
                    NuDataFrame::try_from_columns(
                        vec![Column::new(
                            "0".to_string(),
                            vec![
                                Value::test_int(1),
                                Value::test_int(2),
                                Value::test_int(0),
                                Value::test_int(3),
                                Value::test_int(0),
                            ],
                        )],
                        None,
                    )
                    .expect("Df for test should not fail")
                    .into_value(Span::test_data()),
                ),
            },
            Example {
                description: "Fills the NaN values of a whole dataframe",
                example: "[[a b]; [0.2 1] [0.1 NaN]] | polars into-df | polars fill-nan 0",
                result: Some(
                    NuDataFrame::try_from_columns(
                        vec![
                            Column::new(
                                "a".to_string(),
                                vec![Value::test_float(0.2), Value::test_float(0.1)],
                            ),
                            Column::new(
                                "b".to_string(),
                                vec![Value::test_int(1), Value::test_int(0)],
                            ),
                        ],
                        None,
                    )
                    .expect("Df for test should not fail")
                    .into_value(Span::test_data()),
                ),
            },
        ]
    }

    fn run(
        &self,
        plugin: &Self::Plugin,
        engine: &EngineInterface,
        call: &EvaluatedCall,
        input: PipelineData,
    ) -> Result<PipelineData, LabeledError> {
        let fill: Value = call.req(0)?;
        let value = input.into_value(call.head);

        match PolarsPluginObject::try_from_value(plugin, &value)? {
            PolarsPluginObject::NuDataFrame(df) => {
                cmd_df(plugin, engine, call, df, fill, value.span())
            }
            PolarsPluginObject::NuLazyFrame(lazy) => cmd_df(
                plugin,
                engine,
                call,
                lazy.collect(value.span())?,
                fill,
                value.span(),
            ),
            PolarsPluginObject::NuExpression(expr) => {
                Ok(cmd_expr(plugin, engine, call, expr, fill)?)
            }
            _ => Err(cant_convert_err(
                &value,
                &[
                    PolarsPluginType::NuDataFrame,
                    PolarsPluginType::NuLazyFrame,
                    PolarsPluginType::NuExpression,
                ],
            )),
        }
        .map_err(LabeledError::from)
    }
}

fn cmd_df(
    plugin: &PolarsPlugin,
    engine: &EngineInterface,
    call: &EvaluatedCall,
    frame: NuDataFrame,
    fill: Value,
    val_span: Span,
) -> Result<PipelineData, ShellError> {
    let columns = frame.columns(val_span)?;
    let dataframe = columns
        .into_iter()
        .map(|column| {
            let column_name = column.name().to_string();
            let values = column
                .into_iter()
                .map(|value| {
                    let span = value.span();
                    match value {
                        Value::Float { val, .. } => {
                            if val.is_nan() {
                                fill.clone()
                            } else {
                                value
                            }
                        }
                        Value::List { vals, .. } => {
                            NuDataFrame::fill_list_nan(vals, span, fill.clone())
                        }
                        _ => value,
                    }
                })
                .collect::<Vec<Value>>();
            Column::new(column_name, values)
        })
        .collect::<Vec<Column>>();
    let df = NuDataFrame::try_from_columns(dataframe, None)?;
    df.to_pipeline_data(plugin, engine, call.head)
}

fn cmd_expr(
    plugin: &PolarsPlugin,
    engine: &EngineInterface,
    call: &EvaluatedCall,
    expr: NuExpression,
    fill: Value,
) -> Result<PipelineData, ShellError> {
    let fill = NuExpression::try_from_value(plugin, &fill)?.to_polars();
    let expr: NuExpression = expr.to_polars().fill_nan(fill).into();
    expr.to_pipeline_data(plugin, engine, call.head)
}

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

    #[test]
    fn test_examples() -> Result<(), ShellError> {
        test_polars_plugin_command(&LazyFillNA)
    }
}