use async_std::io::prelude::*;
use async_std::{fs::File, stream};
use futures::StreamExt;
use indicatif::ProgressBar;
use url::Url;

use crate::{errors::ErrorKind, errors::PaperoniError, extractor::Extractor};

type HTMLResource = (String, String);

pub async fn fetch_html(url: &str) -> Result<HTMLResource, PaperoniError> {
    let client = surf::Client::new();
    // println!("Fetching...");

    let process_request = async {
        let mut redirect_count: u8 = 0;
        let base_url = Url::parse(&url)?;
        let mut url = base_url.clone();
        while redirect_count < 5 {
            redirect_count += 1;
            let req = surf::get(&url);
            let mut res = client.send(req).await?;
            if res.status().is_redirection() {
                if let Some(location) = res.header(surf::http::headers::LOCATION) {
                    match Url::parse(location.last().as_str()) {
                        Ok(valid_url) => url = valid_url,
                        Err(e) => match e {
                            url::ParseError::RelativeUrlWithoutBase => {
                                url = base_url.join(location.last().as_str())?
                            }
                            e => return Err(e.into()),
                        },
                    };
                }
            } else if res.status().is_success() {
                if let Some(mime) = res.content_type() {
                    if mime.essence() == "text/html" {
                        return Ok((url.to_string(), res.body_string().await?));
                    } else {
                        let msg = format!(
                            "Invalid HTTP response. Received {} instead of text/html",
                            mime.essence()
                        );

                        return Err(ErrorKind::HTTPError(msg).into());
                    }
                } else {
                    return Err(ErrorKind::HTTPError("Unknown HTTP response".to_owned()).into());
                }
            } else {
                let msg = format!("Request failed: HTTP {}", res.status());
                return Err(ErrorKind::HTTPError(msg).into());
            }
        }
        Err(ErrorKind::HTTPError("Unable to fetch HTML".to_owned()).into())
    };

    process_request.await.map_err(|mut error: PaperoniError| {
        error.set_article_source(url);
        error
    })
}

pub async fn download_images(
    extractor: &mut Extractor,
    article_origin: &Url,
    bar: &ProgressBar,
) -> Result<(), Vec<PaperoniError>> {
    if extractor.img_urls.len() > 0 {
        // println!("Downloading images...");
    }
    let img_count = extractor.img_urls.len();

    let imgs_req_iter = extractor
        .img_urls
        .iter()
        .map(|(url, _)| {
            (
                url,
                surf::Client::new().get(get_absolute_url(&url, article_origin)),
            )
        })
        .enumerate()
        .map(|(img_idx, (url, req))| async move {
            bar.set_message(format!("Downloading images [{}/{}]", img_idx + 1, img_count).as_str());
            match req.await {
                Ok(mut img_response) => {
                    // let mut img_response = req.await.expect("Unable to retrieve image");
                    let img_content: Vec<u8> = match img_response.body_bytes().await {
                        Ok(bytes) => bytes,
                        Err(e) => return Err(e.into()),
                    };
                    let img_mime = img_response
                        .content_type()
                        .map(|mime| mime.essence().to_string());
                    let img_ext = match img_response
                        .content_type()
                        .map(|mime| map_mime_subtype_to_ext(mime.subtype()).to_string())
                    {
                        Some(mime_str) => mime_str,
                        None => {
                            return Err(ErrorKind::HTTPError(
                                "Image has no Content-Type".to_owned(),
                            )
                            .into())
                        }
                    };

                    let mut img_path = std::env::temp_dir();
                    img_path.push(format!("{}.{}", hash_url(&url), &img_ext));
                    let mut img_file = match File::create(&img_path).await {
                        Ok(file) => file,
                        Err(e) => return Err(e.into()),
                    };
                    match img_file.write_all(&img_content).await {
                        Ok(_) => (),
                        Err(e) => return Err(e.into()),
                    }

                    Ok((
                        url,
                        img_path
                            .file_name()
                            .map(|os_str_name| {
                                os_str_name
                                    .to_str()
                                    .expect("Unable to get image file name")
                                    .to_string()
                            })
                            .unwrap(),
                        img_mime,
                    ))
                }
                Err(e) => Err(e.into()),
            }
        });

    // A utility closure used when update the value of an image source after downloading is successful
    let replace_existing_img_src =
        |img_item: (&String, String, Option<String>)| -> (String, Option<String>) {
            let (img_url, img_path, img_mime) = img_item;
            let img_ref = extractor
                .article()
                .select_first(&format!("img[src='{}']", img_url))
                .expect("Image node does not exist");
            let mut img_node = img_ref.attributes.borrow_mut();
            *img_node.get_mut("src").unwrap() = img_path.clone();
            // srcset is removed because readers such as Foliate then fail to display
            // the image already downloaded and stored in src
            img_node.remove("srcset");
            (img_path, img_mime)
        };

    let imgs_req_iter = stream::from_iter(imgs_req_iter)
        .buffered(10)
        .collect::<Vec<Result<_, PaperoniError>>>()
        .await;
    let mut errors = Vec::new();
    let mut replaced_imgs = Vec::new();
    for img_req_result in imgs_req_iter {
        match img_req_result {
            Ok(img_req) => replaced_imgs.push(replace_existing_img_src(img_req)),
            Err(e) => errors.push(e),
        }
    }
    extractor.img_urls = replaced_imgs;
    if errors.is_empty() {
        Ok(())
    } else {
        Err(errors)
    }
}

/// Handles getting the extension from a given MIME subtype.
fn map_mime_subtype_to_ext(subtype: &str) -> &str {
    if subtype == ("svg+xml") {
        return "svg";
    } else if subtype == "x-icon" {
        "ico"
    } else {
        subtype
    }
}

/// Utility for hashing URLs. This is used to help store files locally with unique values
fn hash_url(url: &str) -> String {
    format!("{:x}", md5::compute(url.as_bytes()))
}

fn get_absolute_url(url: &str, request_url: &Url) -> String {
    if Url::parse(url).is_ok() {
        url.to_owned()
    } else if url.starts_with("/") {
        Url::parse(&format!(
            "{}://{}",
            request_url.scheme(),
            request_url.host_str().unwrap()
        ))
        .unwrap()
        .join(url)
        .unwrap()
        .into_string()
    } else {
        request_url.join(url).unwrap().into_string()
    }
}

#[cfg(test)]
mod test {
    use super::*;
    #[test]
    fn test_map_mime_type_to_ext() {
        let mime_subtypes = vec![
            "apng", "bmp", "gif", "x-icon", "jpeg", "png", "svg+xml", "tiff", "webp",
        ];
        let exts = mime_subtypes
            .into_iter()
            .map(|mime_type| map_mime_subtype_to_ext(mime_type))
            .collect::<Vec<_>>();
        assert_eq!(
            vec!["apng", "bmp", "gif", "ico", "jpeg", "png", "svg", "tiff", "webp"],
            exts
        );
    }
}