nu-command 0.90.1

use itertools::Either;
use nu_engine::CallExt;
use nu_protocol::ast::{Call, RangeInclusion};
use nu_protocol::engine::{Command, EngineState, Stack};
use nu_protocol::{
    Category, Example, IntoInterruptiblePipelineData, PipelineData, PipelineIterator, Range,
    ShellError, Signature, Span, Spanned, SyntaxShape, Type, Value,
};

#[derive(Clone)]
pub struct DropNth;

impl Command for DropNth {
    fn name(&self) -> &str {
        "drop nth"
    }

    fn signature(&self) -> Signature {
        Signature::build("drop nth")
            .input_output_types(vec![(
                Type::List(Box::new(Type::Any)),
                Type::List(Box::new(Type::Any)),
            )])
            .required(
                "row number or row range",
                // FIXME: we can make this accept either Int or Range when we can compose SyntaxShapes
                SyntaxShape::Any,
                "The number of the row to drop or a range to drop consecutive rows.",
            )
            .rest("rest", SyntaxShape::Any, "The number of the row to drop.")
            .category(Category::Filters)
    }

    fn usage(&self) -> &str {
        "Drop the selected rows."
    }

    fn search_terms(&self) -> Vec<&str> {
        vec!["delete"]
    }

    fn examples(&self) -> Vec<Example> {
        vec![
            Example {
                example: "[sam,sarah,2,3,4,5] | drop nth 0 1 2",
                description: "Drop the first, second, and third row",
                result: Some(Value::list(
                    vec![Value::test_int(3), Value::test_int(4), Value::test_int(5)],
                    Span::test_data(),
                )),
            },
            Example {
                example: "[0,1,2,3,4,5] | drop nth 0 1 2",
                description: "Drop the first, second, and third row",
                result: Some(Value::list(
                    vec![Value::test_int(3), Value::test_int(4), Value::test_int(5)],
                    Span::test_data(),
                )),
            },
            Example {
                example: "[0,1,2,3,4,5] | drop nth 0 2 4",
                description: "Drop rows 0 2 4",
                result: Some(Value::list(
                    vec![Value::test_int(1), Value::test_int(3), Value::test_int(5)],
                    Span::test_data(),
                )),
            },
            Example {
                example: "[0,1,2,3,4,5] | drop nth 2 0 4",
                description: "Drop rows 2 0 4",
                result: Some(Value::list(
                    vec![Value::test_int(1), Value::test_int(3), Value::test_int(5)],
                    Span::test_data(),
                )),
            },
            Example {
                description: "Drop range rows from second to fourth",
                example: "[first second third fourth fifth] | drop nth (1..3)",
                result: Some(Value::list(
                    vec![Value::test_string("first"), Value::test_string("fifth")],
                    Span::test_data(),
                )),
            },
            Example {
                example: "[0,1,2,3,4,5] | drop nth 1..",
                description: "Drop all rows except first row",
                result: Some(Value::list(vec![Value::test_int(0)], Span::test_data())),
            },
            Example {
                example: "[0,1,2,3,4,5] | drop nth 3..",
                description: "Drop rows 3,4,5",
                result: Some(Value::list(
                    vec![Value::test_int(0), Value::test_int(1), Value::test_int(2)],
                    Span::test_data(),
                )),
            },
        ]
    }

    fn run(
        &self,
        engine_state: &EngineState,
        stack: &mut Stack,
        call: &Call,
        input: PipelineData,
    ) -> Result<PipelineData, ShellError> {
        let metadata = input.metadata();
        let number_or_range = extract_int_or_range(engine_state, stack, call)?;
        let mut lower_bound = None;
        let rows = match number_or_range {
            Either::Left(row_number) => {
                let and_rows: Vec<Spanned<i64>> = call.rest(engine_state, stack, 1)?;
                let mut rows: Vec<_> = and_rows.into_iter().map(|x| x.item as usize).collect();
                rows.push(row_number as usize);
                rows.sort_unstable();
                rows
            }
            Either::Right(row_range) => {
                let from = row_range.from.as_int()?; // as usize;
                let to = row_range.to.as_int()?; // as usize;

                // check for negative range inputs, e.g., (2..-5)
                if from.is_negative() || to.is_negative() {
                    let span: Spanned<Range> = call.req(engine_state, stack, 0)?;
                    return Err(ShellError::TypeMismatch {
                        err_message: "drop nth accepts only positive ints".to_string(),
                        span: span.span,
                    });
                }
                // check if the upper bound is smaller than the lower bound, e.g., do not accept 4..2
                if to < from {
                    let span: Spanned<Range> = call.req(engine_state, stack, 0)?;
                    return Err(ShellError::TypeMismatch {
                        err_message:
                            "The upper bound needs to be equal or larger to the lower bound"
                                .to_string(),
                        span: span.span,
                    });
                }

                // check for equality to isize::MAX because for some reason,
                // the parser returns isize::MAX when we provide a range without upper bound (e.g., 5.. )
                let mut to = to as usize;
                let from = from as usize;

                if let PipelineData::Value(Value::List { ref vals, .. }, _) = input {
                    let max = from + vals.len() - 1;
                    if to > max {
                        to = max;
                    }
                };

                if to > 0 && to as isize == isize::MAX {
                    lower_bound = Some(from);
                    vec![from]
                } else if matches!(row_range.inclusion, RangeInclusion::Inclusive) {
                    (from..=to).collect()
                } else {
                    (from..to).collect()
                }
            }
        };

        if let Some(lower_bound) = lower_bound {
            Ok(input
                .into_iter()
                .take(lower_bound)
                .collect::<Vec<_>>()
                .into_pipeline_data_with_metadata(metadata, engine_state.ctrlc.clone()))
        } else {
            Ok(DropNthIterator {
                input: input.into_iter(),
                rows,
                current: 0,
            }
            .into_pipeline_data_with_metadata(metadata, engine_state.ctrlc.clone()))
        }
    }
}

fn extract_int_or_range(
    engine_state: &EngineState,
    stack: &mut Stack,
    call: &Call,
) -> Result<Either<i64, Range>, ShellError> {
    let value = call.req::<Value>(engine_state, stack, 0)?;

    let int_opt = value.as_int().map(Either::Left).ok();
    let range_opt = value.as_range().map(|r| Either::Right(r.clone())).ok();

    int_opt
        .or(range_opt)
        .ok_or_else(|| ShellError::TypeMismatch {
            err_message: "int or range".into(),
            span: value.span(),
        })
}

struct DropNthIterator {
    input: PipelineIterator,
    rows: Vec<usize>,
    current: usize,
}

impl Iterator for DropNthIterator {
    type Item = Value;

    fn next(&mut self) -> Option<Self::Item> {
        loop {
            if let Some(row) = self.rows.first() {
                if self.current == *row {
                    self.rows.remove(0);
                    self.current += 1;
                    let _ = self.input.next();
                    continue;
                } else {
                    self.current += 1;
                    return self.input.next();
                }
            } else {
                return self.input.next();
            }
        }
    }
}

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

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

        test_examples(DropNth {})
    }
}