//! Traits Deep Dive, Part 1
//!
//!   - **Date:** April 28, 2018
//!   - **Subject:** Defining and using your own traits, using other crates' traits, and the orphan rule.
//!   - [**Audio**][mp3]
//!
//! [mp3]: https://www.podtrac.com/pts/redirect.mp3/cdn.newrustacean.com/file/newrustacean/e023.mp3
//!
//! <audio style="width: 100%" title="e023: Traits Deep Dive, Part 1" controls preload=metadata><source src="https://www.podtrac.com/pts/redirect.mp3/cdn.newrustacean.com/file/newrustacean/e023.mp3"></audio>
//!
//!
//! Show Notes
//! ----------
//!
//! Traits—
//!
//! - [in the Rust book][book]
//! - [in Rust by Example][rbe]
//!
//! [book]: https://doc.rust-lang.org/book/second-edition/ch10-02-traits.html
//! [rbe]: https://rustbyexample.com/trait.html
//!
//! Also of interest: *specialization*:
//!
//! - [RFC #1210][1210]
//! - recent blog posts:
//!     + ["Maximally minimal specialization: always applicable impls"][mm]
//!     + ["Sound and ergonomic specialization for Rust"][sound]
//!
//! [1210]: https://rust-lang.github.io/rfcs/1210-impl-specialization.html
//! [PR]: https://github.com/rust-lang/rfcs/pull/1210
//! [mm]: http://smallcultfollowing.com/babysteps/blog/2018/02/09/maximally-minimal-specialization-always-applicable-impls/
//! [sound]: http://aturon.github.io/2018/04/05/sound-specialization/
//!
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use regex::Regex;

#[doc = include_str!("../docs/e023-script.md")]
pub struct Script;

/// A trait, to be implemented by types like `Breakfast`.
pub trait Eatable {
    /// The stuff to do *before* you eat things. (No implementation!)
    fn prepare(&self) -> String;

    /// How to eat things. (Has a default implementation.)
    fn eat(&self) -> String {
        self.prepare();
        String::from("Open mouth, insert food!")
    }
}

/// Just another way to eat things – exists to show conflicting trait methods.
pub trait Nomable {
    fn eat(&self) -> String {
        String::from("nom nom nom!")
    }
}

/// Breakfast is eatable, so `Breakfast` is `Eatable`!
#[allow(dead_code)]
pub enum Breakfast {
    Waffles,
    Cereal,
    Pancakes,
}

impl Eatable for Breakfast {
    fn prepare(&self) -> String {
        String::from(match *self {
            Breakfast::Cereal => "Just add milk",
            Breakfast::Pancakes | Breakfast::Waffles => "Butter plus syrup for the win",
        })
    }
}

/// Moar Breakfast is even better, so `MoarBreakfast` is also `Eatable` and `Nomable`!
#[allow(dead_code)]
pub enum MoarBreakfast {
    Waffles,
    Cereal,
    Pancakes,
    FrenchToast,
    Bagels,
}

impl Nomable for MoarBreakfast {}

impl Eatable for MoarBreakfast {
    fn prepare(&self) -> String {
        String::from(match *self {
            MoarBreakfast::Waffles | MoarBreakfast::Pancakes => "Pour syrup",
            MoarBreakfast::Cereal => "Add milk",
            MoarBreakfast::FrenchToast => "Sprinkle on powdered sugar, pour syrup",
            MoarBreakfast::Bagels => "Lightly toast, and spread cream cheese",
        })
    }

    fn eat(&self) -> String {
        let preparation = self.prepare();
        let consumption = match *self {
            MoarBreakfast::Waffles | MoarBreakfast::Pancakes | MoarBreakfast::FrenchToast => {
                "shovel into mouth with fork"
            }
            MoarBreakfast::Cereal => "enjoy the crunch",
            MoarBreakfast::Bagels => "use your fingers, of course",
        };

        format!("{}, then {}", preparation, consumption)
    }
}

impl Eatable for Regex {
    fn prepare(&self) -> String {
        String::from("This is truly absurd.")
    }

    fn eat(&self) -> String {
        format!("{} But we can do it anyway!", self.prepare())
    }
}

/// Shows how you can use traits with your own and others' types.
pub fn demo_eatable() {
    let basic = Breakfast::Cereal;
    basic.eat();

    let moar = MoarBreakfast::FrenchToast;
    Nomable::eat(&moar);

    let re = Regex::new("hallo").expect("'hallo' is a valid regex");
    re.eat();
}