use nu_engine::CallExt;
use nu_protocol::ast::Call;
use nu_protocol::engine::{Command, EngineState, Stack};
use nu_protocol::{
Category, Example, IntoInterruptiblePipelineData, PipelineData, ShellError, Signature, Span,
SyntaxShape, Type, Value,
};
#[derive(Clone)]
pub struct Every;
impl Command for Every {
fn name(&self) -> &str {
"every"
}
fn signature(&self) -> Signature {
Signature::build("every")
.input_output_types(vec![(
Type::List(Box::new(Type::Any)),
Type::List(Box::new(Type::Any)),
)])
.required(
"stride",
SyntaxShape::Int,
"How many rows to skip between (and including) each row returned.",
)
.switch(
"skip",
"skip the rows that would be returned, instead of selecting them",
Some('s'),
)
.category(Category::Filters)
}
fn usage(&self) -> &str {
"Show (or skip) every n-th row, starting from the first one."
}
fn examples(&self) -> Vec<Example> {
vec![
Example {
example: "[1 2 3 4 5] | every 2",
description: "Get every second row",
result: Some(Value::list(
vec![Value::test_int(1), Value::test_int(3), Value::test_int(5)],
Span::test_data(),
)),
},
Example {
example: "[1 2 3 4 5] | every 2 --skip",
description: "Skip every second row",
result: Some(Value::list(
vec![Value::test_int(2), Value::test_int(4)],
Span::test_data(),
)),
},
]
}
fn run(
&self,
engine_state: &EngineState,
stack: &mut Stack,
call: &Call,
input: PipelineData,
) -> Result<PipelineData, ShellError> {
let stride = match call.req::<usize>(engine_state, stack, 0)? {
0 => 1,
stride => stride,
};
let skip = call.has_flag(engine_state, stack, "skip")?;
let metadata = input.metadata();
Ok(input
.into_iter()
.enumerate()
.filter_map(move |(i, value)| {
if (i % stride != 0) == skip {
Some(value)
} else {
None
}
})
.into_pipeline_data_with_metadata(metadata, engine_state.ctrlc.clone()))
}
}
#[cfg(test)]
mod test {
use super::*;
#[test]
fn test_examples() {
use crate::test_examples;
test_examples(Every {})
}
}