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)
}

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)/v/[0-9a-zA-Z]+/file\.html$")?;
    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 host = &re.captures(url).unwrap()[1];

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

    // Try to extract the link using the latest extractor
    let link = extract_dl_link_2022_08_16(&host, &body).await;

    // Try the previous extractors as fallback if it didn't work
    let link = match link {
        Err(_) => extract_dl_link_2022_07_24(&host, &body).await,
        ok => ok,
    };
    let link = match link {
        Err(_) => extract_dl_link_2022_07_17(&host, &body).await,
        ok => ok,
    };
    let link = match link {
        Err(_) => extract_dl_link_2022_03_07(&host, &body).await,
        ok => ok,
    };

    link
}

/*
Updated: 16.08.2022
Link generation code:
- `a` and `b` are random
- `omg` is always `f`
- the number used in the middle part `XXX%b` seems to be always the same as `a`

```
var a = 634851;
var b = 958673;
document.getElementById('dlbutton').omg = "f";
if (document.getElementById('dlbutton').omg != 'f') {
    a = Math.ceil(a/3);
} else {
    a = Math.floor(a/3);
}
document.getElementById('dlbutton').href = "/d/gue47sk7/"+(a + 634851%b)+"/some-file-name.part1.rar";
```
 */
pub async fn extract_dl_link_2022_08_16(host: &str, body: &str) -> Result<String> {
    let re_a = Regex::new(r#"var a = (\d+);"#)?;
    let re_b = Regex::new(r#"var b = (\d+);"#)?;

    let re_link = Regex::new(
        r#"document\.getElementById\('dlbutton'\)\.href = "(/d/.+/)"\+\(a \+ (\d+)%b\)\+"(.+)";"#,
    )?;

    if !body.contains(
        r#"document.getElementById('dlbutton').omg = "f";
    if (document.getElementById('dlbutton').omg != 'f') {
       a = Math.ceil(a/3);
    } else {
       a = Math.floor(a/3);
    }"#,
    ) {
        return Err(Error::new(ErrorKind::Other, "omg part of the link-gen not found").into());
    }

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

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

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

    let a: i64 = cap_a[1].parse()?;
    let b: i64 = cap_b[1].parse()?;

    let url_start = &cap_link[1];
    let n1: i64 = cap_link[2].parse()?;
    let url_end = &cap_link[3];

    let middle = (a / 3) + n1 % b;

    let dl_url = format!("{}{}{}{}", &host, url_start, middle, url_end);

    Ok(dl_url)
}

/*
Updated: 24.07.2022
Link generation code:

```
<span id="omg" class="2" style="display:none;"></span>
<script type="text/javascript">
    var a = function() {return 1};
    var b = function() {return a() + 1};
    var c = function() {return b() + 1};
    var d = document.getElementById('omg').getAttribute('class');
    if (true) { d = d*2;}
    document.getElementById('dlbutton').href = "/d/gue47sk7/"+(34556%1000 + a() + b() + c() + d + 5/5)+"/some-file-name.part1.rar";
```
 */
pub async fn extract_dl_link_2022_07_24(host: &str, body: &str) -> Result<String> {
    let re_link = Regex::new(
        r#"document\.getElementById\('dlbutton'\)\.href = "(/d/.+/)"\+\((\d+)%1000 \+ a\(\) \+ b\(\) \+ c\(\) \+ d \+ 5/5\)\+"(.+)";"#,
    )?;

    if !body.contains(r#"<span id="omg" class="2" style="display:none;"></span>"#) {
        return Err(Error::new(ErrorKind::Other, "span part of the link-gen not found").into());
    }

    if !body.contains(
        r#"var a = function() {return 1};
    var b = function() {return a() + 1};
    var c = function() {return b() + 1};
    var d = document.getElementById('omg').getAttribute('class');
    if (true) { d = d*2;}"#,
    ) {
        return Err(Error::new(ErrorKind::Other, "script part of the link-gen not found").into());
    }

    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 n1: u64 = cap_link[2].parse()?;
    let url_end = &cap_link[3];

    let middle = n1 % 1000 + 11;

    let dl_url = format!("{}{}{}{}", &host, url_start, middle, url_end);

    Ok(dl_url)
}

/*
Updated: 17.07.2022
Link generation code:
- `var a = $1`
- $1 is the only variable that actually changes
- effectively: `var b = "asdasd".substr(0, 3).length` seems to be fixed
- evaluates to: `var b = 3`
- `document.getElementById('dlbutton').href = "/d/0Ky7p1C6/"+(Math.pow(a, 3)+b)+"/some-file-name.part1.rar"`
- evaluates to: `href = "/d/0Ky7p1C6/"+(Math.pow(a, 3)+3)+"/some-file-name.part1.rar"`

```
var a = 114;
document.getElementById('dlbutton').omg = "asdasd".substr(0, 3);
var b = document.getElementById('dlbutton').omg.length;
document.getElementById('dlbutton').href = "/d/0Ky7p1C6/"+(Math.pow(a, 3)+b)+"/some-file-name.part1.rar";
```
 */
pub async fn extract_dl_link_2022_07_17(host: &str, body: &str) -> Result<String> {
    let re_var_a = Regex::new(r#"var a = (\d+);"#)?;

    // 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/.+/)"\+\(Math\.pow\(a, 3\)\+b\)\+"(.+)";"#,
    )?;

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

    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[2];
    let var_a: i64 = cap_var_a[1].parse()?;

    let middle = var_a.pow(3) + 3;

    let dl_url = format!("{}{}{}{}", &host, url_start, middle, url_end);

    Ok(dl_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 extract_dl_link_2022_03_07(host: &str, body: &str) -> Result<String> {
    // 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!("{}{}{}{}", &host, url_start, mixed, url_end);

    Ok(dl_url)
}