use std::io::{Error, ErrorKind};

use anyhow::Result;
use regex::Regex;

pub fn is_zippyshare_url(url: &str) -> bool {
    Regex::new(r"^https?://(?:www\d*\.)?zippyshare\.com/v/[0-9a-zA-Z]+/file\.html$")
        .unwrap()
        .is_match(url)
}

/*
Updated: 07.03.2022
Link generation code:
- `href = $1 + ($2 % $3 + $4 % $5) + $6`
- `$1` is always `/d/XXX` where XXX is dependent on the file
- `$2`, `$3`, `$4` and `$5` are dynamic and randomly generated on each reload
- `$2` is always the same as `$4`
- `$6` is dependent on the file
- The numbers in the calculation part ($2`, `$3`, `$4` and `$5`) are hard coded

```
document.getElementById('dlbutton').href = "/d/0Ky7p1C6/" + (186549 % 51245 + 186549 % 913) + "/some-file-name.part1.rar";
```
*/
pub async fn resolve_link(url: &str) -> Result<String> {
    // Regex to check if the provided url is a zippyshare download url
    let re = Regex::new(r"(https://www\d*\.zippyshare\.com)")?;
    if !re.is_match(url) {
        return Err(Error::new(ErrorKind::Other, "URL is not a zippyshare url").into());
    }

    // Extract the hostname (with https:// prefix) for later
    let base_host = &re.captures(url).unwrap()[0];

    // Download the html body for the download page
    let body = reqwest::get(url).await?.text().await?;

    // Regex to match the javascript part of the html that generates the real download link
    let re_link = Regex::new(
        r#"document\.getElementById\('dlbutton'\)\.href = "(/d/.+/)" \+ \((\d+) % (\d+) \+ \d+ % (\d+)\) \+ "(.+)";"#,
    )?;

    let cap_link = match re_link.captures(&body) {
        Some(cap) => cap,
        None => return Err(Error::new(ErrorKind::Other, "Link not found").into()),
    };

    let url_start = &cap_link[1];
    let url_end = &cap_link[5];
    let n2: i32 = cap_link[2].parse()?;
    let n3: i32 = cap_link[3].parse()?;
    let n4 = n2;
    let n5: i32 = cap_link[4].parse()?;

    let mixed = n2 % n3 + n4 % n5;

    let dl_url = format!("{}{}{}{}", &base_host, url_start, mixed, url_end);

    Ok(dl_url)
}