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

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, Value};

#[derive(Clone)]
pub struct SubCommand;

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

    fn signature(&self) -> Signature {
        Signature::build("str capitalize")
            .rest(
                "rest",
                SyntaxShape::CellPath,
                "optionally capitalize text by column paths",
            )
            .category(Category::Strings)
    }

    fn usage(&self) -> &str {
        "capitalizes text"
    }

    fn run(
        &self,
        engine_state: &EngineState,
        stack: &mut Stack,
        call: &Call,
        input: PipelineData,
    ) -> Result<PipelineData, ShellError> {
        operate(engine_state, stack, call, input)
    }

    fn examples(&self) -> Vec<Example> {
        vec![
            Example {
                description: "Capitalize contents",
                example: "'good day' | str capitalize",
                result: Some(Value::String {
                    val: "Good day".to_string(),
                    span: Span::unknown(),
                }),
            },
            Example {
                description: "Capitalize contents",
                example: "'anton' | str capitalize",
                result: Some(Value::String {
                    val: "Anton".to_string(),
                    span: Span::unknown(),
                }),
            },
            Example {
                description: "Capitalize a column in a table",
                example: "[[lang, gems]; [nu_test, 100]] | str capitalize lang",
                result: Some(Value::List {
                    vals: vec![Value::Record {
                        span: Span::unknown(),
                        cols: vec!["lang".to_string(), "gems".to_string()],
                        vals: vec![
                            Value::String {
                                val: "Nu_test".to_string(),
                                span: Span::unknown(),
                            },
                            Value::test_int(100),
                        ],
                    }],
                    span: Span::unknown(),
                }),
            },
        ]
    }
}

fn operate(
    engine_state: &EngineState,
    stack: &mut Stack,
    call: &Call,
    input: PipelineData,
) -> Result<PipelineData, ShellError> {
    let head = call.head;
    let column_paths: Vec<CellPath> = call.rest(engine_state, stack, 0)?;
    input.map(
        move |v| {
            if column_paths.is_empty() {
                action(&v, head)
            } else {
                let mut ret = v;
                for path in &column_paths {
                    let r =
                        ret.update_cell_path(&path.members, Box::new(move |old| action(old, head)));
                    if let Err(error) = r {
                        return Value::Error { error };
                    }
                }
                ret
            }
        },
        engine_state.ctrlc.clone(),
    )
}

fn action(input: &Value, head: Span) -> Value {
    match input {
        Value::String { val, .. } => Value::String {
            val: uppercase_helper(val),
            span: head,
        },
        other => Value::Error {
            error: ShellError::UnsupportedInput(
                format!(
                    "Input's type is {}. This command only works with strings.",
                    other.get_type()
                ),
                Span::unknown(),
            ),
        },
    }
}

fn uppercase_helper(s: &str) -> String {
    // apparently more performant https://stackoverflow.com/questions/38406793/why-is-capitalizing-the-first-letter-of-a-string-so-convoluted-in-rust
    let mut chars = s.chars();
    match chars.next() {
        None => String::new(),
        Some(f) => f.to_uppercase().collect::<String>() + chars.as_str(),
    }
}

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

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

        test_examples(SubCommand {})
    }
}