use std::fs::{create_dir_all, remove_file, symlink_metadata, File};
use std::io::prelude::*;
use std::time::{Duration, SystemTime};

use rocket::http::ContentType;
use rocket::response::Content;
use rocket::Route;

use reqwest::header::{HeaderMap, HeaderValue, ACCEPT, ACCEPT_LANGUAGE, CACHE_CONTROL, PRAGMA, USER_AGENT};
use reqwest::Client;

use regex::Regex;
use soup::prelude::*;

use crate::error::Error;
use crate::CONFIG;

pub fn routes() -> Vec<Route> {
    routes![icon]
}

const FALLBACK_ICON: &[u8; 344] = include_bytes!("../static/fallback-icon.png");

#[get("/<domain>/icon.png")]
fn icon(domain: String) -> Content<Vec<u8>> {
    let icon_type = ContentType::new("image", "x-icon");

    // Validate the domain to avoid directory traversal attacks
    if domain.contains('/') || domain.contains("..") {
        return Content(icon_type, FALLBACK_ICON.to_vec());
    }

    let icon = get_icon(&domain);

    Content(icon_type, icon)
}

fn get_icon(domain: &str) -> Vec<u8> {
    let path = format!("{}/{}.png", CONFIG.icon_cache_folder(), domain);

    if let Some(icon) = get_cached_icon(&path) {
        return icon;
    }

    if CONFIG.disable_icon_download() {
        return FALLBACK_ICON.to_vec();
    }

    // Get the icon, or fallback in case of error
    match download_icon(&domain) {
        Ok(icon) => {
            save_icon(&path, &icon);
            icon
        }
        Err(e) => {
            error!("Error downloading icon: {:?}", e);
            mark_negcache(&path);
            FALLBACK_ICON.to_vec()
        }
    }
}

fn get_cached_icon(path: &str) -> Option<Vec<u8>> {
    // Check for expiration of negatively cached copy
    if icon_is_negcached(path) {
        return Some(FALLBACK_ICON.to_vec());
    }

    // Check for expiration of successfully cached copy
    if icon_is_expired(path) {
        return None;
    }

    // Try to read the cached icon, and return it if it exists
    if let Ok(mut f) = File::open(path) {
        let mut buffer = Vec::new();

        if f.read_to_end(&mut buffer).is_ok() {
            return Some(buffer);
        }
    }

    None
}

fn file_is_expired(path: &str, ttl: u64) -> Result<bool, Error> {
    let meta = symlink_metadata(path)?;
    let modified = meta.modified()?;
    let age = SystemTime::now().duration_since(modified)?;

    Ok(ttl > 0 && ttl <= age.as_secs())
}

fn icon_is_negcached(path: &str) -> bool {
    let miss_indicator = path.to_owned() + ".miss";
    let expired = file_is_expired(&miss_indicator, CONFIG.icon_cache_negttl());

    match expired {
        // No longer negatively cached, drop the marker
        Ok(true) => {
            if let Err(e) = remove_file(&miss_indicator) {
                error!("Could not remove negative cache indicator for icon {:?}: {:?}", path, e);
            }
            false
        }
        // The marker hasn't expired yet.
        Ok(false) => true,
        // The marker is missing or inaccessible in some way.
        Err(_) => false,
    }
}

fn mark_negcache(path: &str) {
    let miss_indicator = path.to_owned() + ".miss";
    File::create(&miss_indicator).expect("Error creating negative cache marker");
}

fn icon_is_expired(path: &str) -> bool {
    let expired = file_is_expired(path, CONFIG.icon_cache_ttl());
    expired.unwrap_or(true)
}

#[derive(Debug)]
struct IconList {
    priority: u8,
    href: String,
}

/// Returns a Result with a String which holds the preferend favicon location.
/// There will always be a result with a string which will contain https://example.com/favicon.ico
/// This does not mean that that location does exists, but it is the default location.
///
/// # Argument
/// * `domain` - A string which holds the domain with extension.
///
/// # Example
/// ```
/// favicon_location1 = get_icon_url("github.com");
/// favicon_location2 = get_icon_url("gitlab.com");
/// ```
fn get_icon_url(domain: &str) -> Result<String, Error> {
    // Set some default headers for the request.
    // Use a browser like user-agent to make sure most websites will return there correct website.
    let mut headers = HeaderMap::new();
    headers.insert(USER_AGENT, HeaderValue::from_static("Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/58.0.3029.110 Safari/537.36 Edge/16.16299"));
    headers.insert(ACCEPT_LANGUAGE, HeaderValue::from_static("en-US,en;q=0.8"));
    headers.insert(CACHE_CONTROL, HeaderValue::from_static("no-cache"));
    headers.insert(PRAGMA, HeaderValue::from_static("no-cache"));
    headers.insert(ACCEPT, HeaderValue::from_static("text/html,application/xhtml+xml,application/xml; q=0.9,image/webp,image/apng,*/*;q=0.8"));

    let client = Client::builder()
        .gzip(true)
        .timeout(Duration::from_secs(5))
        .default_headers(headers)
        .build()?;

    // Default URL with secure and insecure schemes
    let ssldomain = format!("https://{}", domain);
    let httpdomain = format!("http://{}", domain);

    // Create the iconlist
    let mut iconlist: Vec<IconList> = Vec::new();

    let resp = client.get(&ssldomain).send().or_else(|_| client.get(&httpdomain).send());
    if let Ok(content) = resp {
        // Extract the URL from the respose in case redirects occured (like @ gitlab.com)
        let url = content.url().clone();

        // Add the default favicon.ico to the list with the domain the content responded from.
        iconlist.push(IconList { priority: 35, href: url.join("/favicon.ico").unwrap().into_string() });

        let soup = Soup::from_reader(content)?;
        // Search for and filter
        let favicons = soup
            .tag("link")
            .attr("rel", Regex::new(r"icon$|apple.*icon")?) // Only use icon rels
            .attr("href", Regex::new(r"(?i)\w+\.(jpg|jpeg|png|ico)(\?.*)?$")?) // Only allow specific extensions
            .find_all();

        // Loop through all the found icons and determine it's priority
        for favicon in favicons {
            let sizes = favicon.get("sizes").unwrap_or_default();
            let href = url.join(&favicon.get("href").unwrap_or_default()).unwrap().into_string();
            let priority = get_icon_priority(&href, &sizes);

            iconlist.push(IconList { priority, href })
        }
    } else {
        // Add the default favicon.ico to the list with just the given domain
        iconlist.push(IconList { priority: 35, href: format!("{}/favicon.ico", ssldomain) });
    }

    // Sort the iconlist by priority
    iconlist.sort_by_key(|x| x.priority);

    // There always is an icon in the list, so no need to check if it exists, and just return the first one
    Ok(iconlist.remove(0).href)
}

/// Returns a Integer with the priority of the type of the icon which to prefer.
/// The lower the number the better.
///
/// # Arguments
/// * `href`  - A string which holds the href value or relative path.
/// * `sizes` - The size of the icon if available as a <width>x<height> value like 32x32.
///
/// # Example
/// ```
/// priority1 = get_icon_priority("http://example.com/path/to/a/favicon.png", "32x32");
/// priority2 = get_icon_priority("https://example.com/path/to/a/favicon.ico", "");
/// ```
fn get_icon_priority(href: &str, sizes: &str) -> u8 {
    // Check if there is a dimension set
    if !sizes.is_empty() {
        let dimensions: Vec<&str> = sizes.split('x').collect();
        let width: u16 = dimensions[0].parse().unwrap();
        let height: u16 = dimensions[1].parse().unwrap();

        // Only allow square dimensions
        if width == height {
            // Change priority by given size
            if width == 32 {
                1
            } else if width == 64 {
                2
            } else if width >= 24 && width <= 128 {
                3
            } else if width == 16 {
                4
            } else {
                100
            }
        } else {
            200
        }
    } else {
        // Change priority by file extension
        if href.ends_with(".png") {
            10
        } else if href.ends_with(".jpg") || href.ends_with(".jpeg") {
            20
        } else {
            30
        }
    }
}

fn download_icon(domain: &str) -> Result<Vec<u8>, Error> {
    let url = get_icon_url(&domain)?;

    info!("Downloading icon for {} via {}...", domain, url);
    let mut res = reqwest::get(&url)?;

    res = res.error_for_status()?;

    let mut buffer: Vec<u8> = vec![];
    res.copy_to(&mut buffer)?;

    Ok(buffer)
}

fn save_icon(path: &str, icon: &[u8]) {
    create_dir_all(&CONFIG.icon_cache_folder()).expect("Error creating icon cache");

    if let Ok(mut f) = File::create(path) {
        f.write_all(icon).expect("Error writing icon file");
    };
}