handlebars 4.3.0

use std::error::Error;

use handlebars::{handlebars_helper, Handlebars};
use time::format_description::parse;
use time::OffsetDateTime;

// define a helper using helper
// a date format helper accept an `OffsetDateTime` as parameter
handlebars_helper!(date: |dt: OffsetDateTime| dt.format(&parse("[year]-[month]-[day]").unwrap()).unwrap());

// a helper returns number of provided parameters
handlebars_helper!(nargs: |*args| args.len());

// a helper provides format
handlebars_helper!(date2: |dt: OffsetDateTime, {fmt:str = "[year]-[month]-[day]"}|
    dt.format(&parse(fmt).unwrap()).unwrap()
);

fn main() -> Result<(), Box<dyn Error>> {
    // create the handlebars registry
    let mut handlebars = Handlebars::new();

    handlebars.register_helper("date", Box::new(date));
    handlebars.register_helper("date2", Box::new(date2));
    handlebars.register_helper("nargs", Box::new(nargs));

    let data = OffsetDateTime::now_utc();

    println!("{}", handlebars.render_template("{{date this}}", &data)?);
    println!("{}", handlebars.render_template("{{date2 this}}", &data)?);
    println!(
        "{}",
        handlebars.render_template("{{date2 this fmt=\"[day]/[month]/[year]\"}}", &data)?
    );

    println!("{}", handlebars.render_template("{{nargs 1 2 3 4}}", &())?);

    Ok(())
}