nushell/crates/nu-command/src/strings/str_/reverse.rs

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

#[derive(Clone)]
pub struct SubCommand;

impl Command for SubCommand {
    fn name(&self) -> &str {
        "str reverse"
    }

    fn signature(&self) -> Signature {
        Signature::build("str reverse")
            .input_output_types(vec![(Type::String, Type::String)])
            .vectorizes_over_list(true)
            .rest(
                "rest",
                SyntaxShape::CellPath,
                "For a data structure input, reverse strings at the given cell paths",
            )
            .category(Category::Strings)
    }

    fn usage(&self) -> &str {
        "Reverse every string in the pipeline."
    }

    fn search_terms(&self) -> Vec<&str> {
        vec!["convert", "inverse", "flip"]
    }

    fn run(
        &self,
        engine_state: &EngineState,
        stack: &mut Stack,
        call: &Call,
        input: PipelineData,
    ) -> Result<PipelineData, ShellError> {
        let cell_paths: Vec<CellPath> = call.rest(engine_state, stack, 0)?;
        let args = CellPathOnlyArgs::from(cell_paths);
        operate(action, args, input, call.head, engine_state.ctrlc.clone())
    }

    fn examples(&self) -> Vec<Example> {
        vec![
            Example {
                description: "Reverse a single string",
                example: "'Nushell' | str reverse",
                result: Some(Value::test_string("llehsuN")),
            },
            Example {
                description: "Reverse multiple strings in a list",
                example: "['Nushell' 'is' 'cool'] | str reverse",
                result: Some(Value::List {
                    vals: vec![
                        Value::test_string("llehsuN"),
                        Value::test_string("si"),
                        Value::test_string("looc"),
                    ],
                    span: Span::test_data(),
                }),
            },
        ]
    }
}

fn action(input: &Value, _arg: &CellPathOnlyArgs, head: Span) -> Value {
    match input {
        Value::String { val, .. } => Value::String {
            val: val.chars().rev().collect::<String>(),
            span: head,
        },
        Value::Error { .. } => input.clone(),
        _ => Value::Error {
            error: Box::new(ShellError::OnlySupportsThisInputType {
                exp_input_type: "string".into(),
                wrong_type: input.get_type().to_string(),
                dst_span: head,
                src_span: input.expect_span(),
            }),
        },
    }
}

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

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

        test_examples(SubCommand {})
    }
}