jawk 0.1.16

JSON AWK.
Documentation 
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use std::rc::Rc;

use crate::processor::Context;

use crate::{
    functions_definitions::{Arguments, Example, FunctionDefinitions},
    json_value::JsonValue,
    selection::Get,
};

pub fn get() -> FunctionDefinitions {
    FunctionDefinitions::new("head", 2, 2, |args| {
        struct Impl(Vec<Rc<dyn Get>>);
        impl Get for Impl {
            fn get(&self, value: &Context) -> Option<JsonValue> {
                if
                let (Some(JsonValue::String(str)), Some(JsonValue::Number(index))) = (
                    self.0.apply(value, 0),
                    self.0.apply(value, 1),
                )
                {
                    if let Ok(index) = TryInto::<usize>::try_into(index) {
                        if str.len() < index {
                            Some(str.into())
                        } else {
                            let head = str[..index].to_string();
                            Some(head.into())
                        }
                    } else {
                        None
                    }
                } else {
                    None
                }
            }
        }
        Rc::new(Impl(args))
    })
        .add_description_line("Extract a string header.")
        .add_description_line(
            "If the first argument is a string and the second argument is a positive integer, the returned value will be a string with the beginning of the first argument."
        )
        .add_description_line("See also [`take`](take.md).")
        .add_example(
            Example::new()
                .add_argument("\"test-123\"")
                .add_argument("4")
                .expected_output("\"test\"")
        )
        .add_example(
            Example::new()
                .add_argument("\"test-123\"")
                .add_argument("20")
                .expected_output("\"test-123\"")
        )
        .add_example(Example::new().add_argument("20").add_argument("20"))
        .add_example(Example::new().add_argument("\"20\"").add_argument("-5"))
}