random/internetiterator/src/main.rs

use std::vec::IntoIter;

use reqwest::blocking::Client;
use serde::{de::DeserializeOwned, Deserialize};

static LIB_USER_AGENT: &str = concat!(env!("CARGO_PKG_NAME"), "/", env!("CARGO_PKG_VERSION"));

/// This is the connection handler.
/// API documentation is here:
/// https://punkapi.com/documentation/v2
struct Punk {
    url: String,
    client: Client,
}

impl Punk {
    pub fn new(/* connection information here */) -> Self {
        Self {
            url: "https://api.punkapi.com/v2/beers?per_page=10".into(),
            client: Client::builder()
                .user_agent(LIB_USER_AGENT)
                .build()
                .unwrap(),
        }
    }

    /// Information about beers.
    /// (This is done like this 'cause we want a function call/method/attribute for each different
    /// information in the server; it is just that this specific server have only one data type).
    pub fn beers(&self) -> Result<BeerIter, reqwest::Error> {
        BeerIter::new(self)
    }

    pub fn get<T: DeserializeOwned>(&self, page: u16) -> Result<T, reqwest::Error> {
        let url = format!("{url}&page={page}", url=self.url, page=page);
        let data = self.client.get(&url).send()?;
        Ok(data.json::<T>()?)
    }
}

/// This is a definition of data from the API
#[derive(Deserialize)]
struct Beer {
    id: u16,
    name: String,
    tagline: String,
    // ... and let's ignore everything else 'cause that's enough.
}

/// This is the magical iterator that gets stuff from the internet
struct BeerIter<'a> {
    connection: &'a Punk,
    iter: IntoIter<Beer>,
    page: u16,
}

impl<'a> BeerIter<'a> {
    pub fn new(connection: &'a Punk) -> Result<Self, reqwest::Error> {
        let mut result = Self {
            connection,
            iter: vec![].into_iter(),
            page: 1,
        };
        result.next_page()?;
        Ok(result)
    }

    fn next_page(&mut self) -> Result<(), reqwest::Error> {
        let page = self.connection.get::<Vec<Beer>>(self.page)?;
        self.iter = page.into_iter();
        self.page += 1;
        Ok(())
    }
}

impl<'a> Iterator for BeerIter<'a> {
    type Item = Beer;

    fn next(&mut self) -> Option<Self::Item> {
        let next_item = self.iter.next();
        match next_item {
            Some(record) => Some(record),
            None => {
                self.next_page().unwrap();
                self.next()
            }
        }
    }
}

fn main() {
    let connection = Punk::new();
    let beers = connection.beers().expect("Failed to get the initial data");
    for beer in beers {
        println!("     ID: {}", beer.id);
        println!("   Name: {}", beer.name);
        println!("Tagline: {}\n", beer.tagline);
    }
    println!("Hello, world!");
}