pub trait Summary {
    fn summarize(&self) -> String {
        // default implementarion
        format!("(Read more from {}...)", self.summarize_author())
    }

    fn summarize_author(&self) -> String {
        String::from("Anonymous")
    }
}

pub struct NewsArticle {
    pub headline: String,
    pub location: String,
    pub author: String,
    pub content: String,
}

impl Summary for NewsArticle {
    fn summarize(&self) -> String {
        format!("{}, by {} ({})", self.headline, self.author, self.location)
    }

    // fn summarize_author(&self) -> String {
    //     format!("{}", self.author)
    // }
}

pub struct Tweet {
    pub username: String,
    pub content: String,
    pub reply: bool,
    pub retweet: bool,
}

impl Summary for Tweet {
    // fn summarize(&self) -> String {
    //     format!("{}: {}", self.username, self.content)
    // }

    fn summarize_author(&self) -> String {
        format!("@{}", self.username)
    }
}

// Traits as parameter
// pub fn notify(item: &impl Summary) {
//     println!("Breaking news! {}", item.summarize());
// }

// Trait bound syntax
pub fn notify<T: Summary>(item: &T) {
    println!("Breaking news! {}", item.summarize());
}

// statements below are equivalent
// pub fn nofity(item1: &impl Summary, item2: Summary) {}
// pub fn nofity<T: Summary>(item1: &T, item2: &T) {}

// use std::fmt::Display;
// multiple bound
// pub fn notify(item: &(impl Summary + Display)) {}
// or
// pub fn notify<T: Summary + Display>(item: &T) {}
// where clause
// pub fn notify<T>(item: &T)
//     where T: Summary + Display
// {}

// return impl Trait
fn return_summarizble() -> impl Summary {
    Tweet {
        username: String::from("horse_ebooks"),
        content: String::from("of course, as you probably already know, people"),
        reply: false,
        retweet: false,
    }
}