article_scraper/src/images/mod.rs

use reqwest;
use log::{
    error,
    debug,
};
use libxml::parser::Parser;
use libxml::xpath::Context;
use libxml::tree::Node;
use url;
use failure::ResultExt;
use std::error::Error;
use self::error::{ImageDownloadError, ImageDownloadErrorKind};
use base64;
use std;
use image;
use super::ScraperErrorKind;

mod error;

pub struct ImageDownloader {
    client: reqwest::Client,
    max_size: (u32, u32),
}

impl ImageDownloader {

    pub fn new(max_size: (u32, u32)) -> ImageDownloader {
        ImageDownloader {
            client: reqwest::Client::new(),
            max_size: max_size,
        }
    }

    pub fn download_images_from_string(&self, html: &str) -> Result<String, ImageDownloadError> {
        let parser = Parser::default_html();
        let doc = parser.parse_string(html).map_err(|_| {
            error!("Failed to parse HTML string");
            ImageDownloadErrorKind::HtmlParse
        })?;

        let xpath_ctx = Context::new(&doc).map_err(|()| {
            error!("Failed to create xpath context for document");
            ImageDownloadErrorKind::HtmlParse
        })?;

        self.download_images_from_context(&xpath_ctx)?;

        Ok(doc.to_string(/*format:*/ false))
    }

    pub fn download_images_from_context(&self, context: &Context) -> Result<(), ImageDownloadError> {
        let xpath = "//img";
        evaluate_xpath!(context, xpath, node_vec);
        for mut node in node_vec {
            if let Some(url) = node.get_property("src") {
                let url = url::Url::parse(&url)
                    .context(ImageDownloadErrorKind::InvalidUrl)?;
                let parent_url = match self.check_image_parent(&node, &url) {
                    Ok(url) => Some(url),
                    Err(_) => None,
                };

                let (small_image, big_image) = self.save_image(&url, &parent_url)?;
                if let Err(_) = node.set_property("src", &small_image) {
                    return Err(ImageDownloadErrorKind::HtmlParse)?;
                }
                if let Some(big_image) = big_image {
                    if let Err(_) = node.set_property("big-src", &big_image) {
                        return Err(ImageDownloadErrorKind::HtmlParse)?;
                    }
                }
            }
        }

        Ok(())
    }

    fn save_image(&self, image_url: &url::Url, parent_url: &Option<url::Url>) -> Result<(String, Option<String>), ImageDownloadError> {

        let mut response = self.client.get(image_url.clone()).send().map_err(|err| {
            error!("GET {} failed - {}", image_url.as_str(), err.description());
            err
        }).context(ImageDownloadErrorKind::Http)?;

        let content_type_small = ImageDownloader::check_image_content_type(&response)?;
        let content_type_small = content_type_small.to_str()
            .context(ImageDownloadErrorKind::ContentType)?;
        let mut content_type_big : Option<String> = None;

        let mut small_image : Vec<u8> = Vec::new();
        let mut big_image : Option<Vec<u8>> = None;

        response.copy_to(&mut small_image)
            .context(ImageDownloadErrorKind::IO)?;
        
        if let Some(parent_url) = parent_url {
            let mut response_big = self.client.get(parent_url.clone()).send()
                .context(ImageDownloadErrorKind::Http)?;
            content_type_big = Some(ImageDownloader::check_image_content_type(&response)?
                .to_str()
                .context(ImageDownloadErrorKind::ContentType)?
                .to_owned());
            let mut big_buffer : Vec<u8> = Vec::new();
            response_big.copy_to(&mut big_buffer)
                .context(ImageDownloadErrorKind::IO)?;
            big_image = Some(big_buffer);
        }

        if content_type_small != "image/svg+xml" {
            let (original_image, resized_image) = Self::scale_image(&small_image, self.max_size)?;
            if let Some(resized_image) = resized_image {
                small_image = resized_image;
                if big_image.is_none() {
                    big_image = Some(original_image);
                    content_type_big = Some(content_type_small.to_owned());
                }
            }
            else {
                small_image = original_image;
            }
        }
        
        let small_image_base64 = base64::encode(&small_image);
        let big_image_base64 = match big_image {
            Some(big_image) => Some(base64::encode(&big_image)),
            None => None,
        };
        let small_image_string = format!("data:{};base64,{}", content_type_small, small_image_base64);
        let big_image_string = match big_image_base64 {
            Some(big_image_base64) => {
                let content_type_big = content_type_big.ok_or(ImageDownloadErrorKind::ParentDownload)
                    .map_err(|err| {
                        debug!("content_type_big should not be None when a big image exists");
                        err
                    })?;
                Some(format!("data:{};base64,{}", content_type_big, big_image_base64))
            },
            None => None,
        };
        Ok((small_image_string, big_image_string))
    }

    fn check_image_content_type(response: &reqwest::Response) -> Result<reqwest::header::HeaderValue, ImageDownloadError> {
    
        if response.status().is_success() {
            if let Some(content_type) = response.headers().get(reqwest::header::CONTENT_TYPE) {
                if content_type.to_str().context(ImageDownloadErrorKind::ContentType)?.contains("image") {
                    return Ok(content_type.clone())
                }
            }

            error!("{} is not an image", response.url());
            return Err(ImageDownloadErrorKind::ContentType)?
        }

        Err(ImageDownloadErrorKind::Http)?
    }

    fn scale_image(image_buffer: &[u8], max_dimensions: (u32, u32)) -> Result<(Vec<u8>, Option<Vec<u8>>), ImageDownloadError> {
        let mut original_image : Vec<u8> = Vec::new();
        let mut resized_image : Option<Vec<u8>> = None;

        let mut image = image::load_from_memory(image_buffer)
            .map_err(|err| {
                error!("Failed to open image to resize");
                err
            }).context(ImageDownloadErrorKind::ImageScale)?;
        
        image.write_to(&mut original_image, image::ImageOutputFormat::PNG)
            .map_err(|err| {
                error!("Failed to save resized image to resize");
                err
            }).context(ImageDownloadErrorKind::ImageScale)?;

        let dimensions = Self::get_image_dimensions(&image);
        if dimensions.0 > max_dimensions.0
        || dimensions.1 > max_dimensions.1 {
            image = image.resize(max_dimensions.0, max_dimensions.1, image::FilterType::Lanczos3);
            let mut resized_buf : Vec<u8> = Vec::new();
            image.write_to(&mut resized_buf, image::ImageOutputFormat::PNG)
                .map_err(|err| {
                    error!("Failed to save resized image to resize");
                    err
                }).context(ImageDownloadErrorKind::ImageScale)?;
            resized_image = Some(resized_buf);
        }

        Ok((original_image, resized_image))
    }

    fn get_image_dimensions(image: &image::DynamicImage) -> (u32, u32) {
        match image {
            image::DynamicImage::ImageLuma8(image) => (image.width(), image.height()),
            image::DynamicImage::ImageLumaA8(image) => (image.width(), image.height()),
            image::DynamicImage::ImageRgb8(image) => (image.width(), image.height()),
            image::DynamicImage::ImageRgba8(image) => (image.width(), image.height()),
            image::DynamicImage::ImageBgr8(image) => (image.width(), image.height()),
            image::DynamicImage::ImageBgra8(image) => (image.width(), image.height()),
        }
    }

    fn check_image_parent(&self, node: &Node, child_url: &url::Url) -> Result<url::Url, ImageDownloadError> {
        if let Some(parent) = node.get_parent() {
            if parent.get_name() == "a" {
                if let Some(url) = parent.get_property("href") {
                    let parent_url = url::Url::parse(&url).context(ImageDownloadErrorKind::ParentDownload)?;
                    let parent_response = self.client.head(parent_url.clone()).send().context(ImageDownloadErrorKind::ParentDownload)?;
                    let _ = ImageDownloader::check_image_content_type(&parent_response).context(ImageDownloadErrorKind::ParentDownload)?;
                    let child_response = self.client.get(child_url.clone()).send().context(ImageDownloadErrorKind::ParentDownload)?;
                    let parent_length = Self::get_content_lenght(&parent_response).context(ImageDownloadErrorKind::ParentDownload)?;
                    let child_length = Self::get_content_lenght(&child_response).context(ImageDownloadErrorKind::ParentDownload)?;

                    if parent_length > child_length {
                        return Ok(parent_url)
                    }

                    return Ok(child_url.clone())
                }
            }
        }

        debug!("Image parent element not relevant");
        Err(ImageDownloadErrorKind::ParentDownload)?
    }

    fn get_content_lenght(response: &reqwest::Response) -> Result<u64, ImageDownloadError> {
        if response.status().is_success() {
            if let Some(content_length) = response.headers().get(reqwest::header::CONTENT_LENGTH) {
                if let Ok(content_length) = content_length.to_str() {
                    if let Ok(content_length) = content_length.parse::<u64>() {
                        return Ok(content_length)
                    }
                }
            }
        }
        Err(ImageDownloadErrorKind::ContentLenght)?
    }


}