Project Euler から解いていない問題を取ってくる.rs

use anyhow::Result;
use reqwest::ClientBuilder;
use scraper::{Html, Selector};
use serde::Deserialize;
use std::collections::{HashMap, HashSet};

#[tokio::main]
async fn main() -> Result<()> {
    let client = ClientBuilder::new().gzip(true).build()?;
    let cookie = "...";

    let table_selector = Selector::parse("#problems_table").unwrap();
    let a_selector = Selector::parse("a").unwrap();
    let difficulty_selector = Selector::parse("span.tooltiptext_narrow").unwrap();

    let mut problems = vec![];

    for i in 1..3 {
        let url = format!(r"https://projecteuler.net/archives;page={}", i);
        let html = client
            .get(url)
            .header("Cookie", cookie)
            .send()
            .await?
            .text()
            .await?;
        let document = Html::parse_document(&html);
        let table = document.select(&table_selector).next().unwrap();
        for row in table.select(&Selector::parse("tr").unwrap()) {
            let links = row.select(&a_selector).collect::<Vec<_>>();
            if links.len() != 2 {
                continue;
            }

            let id = links[0]
                .value()
                .attr("href")
                .unwrap()
                .replace("problem=", "")
                .parse::<u32>()?;

            let difficulty = row
                .select(&difficulty_selector)
                .next()
                .unwrap()
                .text()
                .next()
                .unwrap()
                .replace("Difficulty rating: ", "")
                .replace("%", "")
                .parse::<u32>()?;
            problems.push((id, difficulty));
        }
    }

    print_table(&problems, 20);

    Ok(())
}

fn print_table(problems: &[(u32, u32)], size: usize) {
    for _ in 0..size {
        print!("|");
    }
    println!("|");

    for _ in 0..size {
        print!("|:-----");
    }
    println!("|");

    for chunk in problems.chunks(size) {
        for problem in chunk {
            print!(
                "|[{} {}%](https://projecteuler.net/problem={})",
                problem.0, problem.1, problem.0
            );
        }

        let last = size - chunk.len();
        for _ in 0..last {
            print!("|");
        }
        println!("|");
    }
}