use fastly::http::{HeaderValue, StatusCode};
use fastly::{Request, Response, Error};
use url::Url;
use std::str::from_utf8;
use percent_encoding::percent_decode;

#[fastly::main]
fn main(req: Request) -> Result<Response, Error> {
    // Extract the `url` query parameter.
    let url_param = match req.get_query_parameter("url") {
        Some(param) => param,
        None => {
            return Ok(Response::new()
                .with_status(StatusCode::BAD_REQUEST)
                .with_body_text_html("Missing `url` query parameter"));
        }
    };

    //Decode and parse the query parameter value to a url
    let decoded_bytes = percent_decode(&url_param.as_bytes()).decode_utf8().unwrap();
    let decoded_str = match from_utf8(&decoded_bytes.as_bytes()) {
        Ok(str) => str,
        Err(_) => panic!("Failed to convert decoded bytes to UTF-8 string"),
    };
    let decoded_url = match Url::parse(decoded_str) {
        Ok(url) => url,
        Err(_) => panic!("unable to parse a valid url from query string"),
    };

    // Check if the domain is valid.
    let domain = decoded_url.host().map(|h| h.to_string()).unwrap();
    if !is_valid_domain(&domain) {
        return Ok(Response::new()
            .with_status(StatusCode::FORBIDDEN)
            .with_body_text_html("Invalid domain"));
    }

    // Return a `200 OK` response with the "hello" message.
    Ok(Response::new()
        .with_status(StatusCode::OK)
        .with_header("Content-Type", HeaderValue::from_static("text/plain"))
        .with_body_text_html("hello"))
}

// List of valid domains.
fn valid_domains() -> Vec<&'static str> {
    vec!["example.com", "fastly.com"]
}

// Checks if a domain is valid.
fn is_valid_domain(domain: &str) -> bool {
    valid_domains().contains(&domain)
}