//! URL Previews
//!
//! This functionality is gated by 'url_preview', but not at the unit level for
//! historical and simplicity reasons. Instead the feature gates the inclusion
//! of dependencies and nulls out results through the existing interface when
//! not featured.

use std::time::SystemTime;

use conduwuit::{Err, Result, debug, err, utils::response::LimitReadExt};
use conduwuit_core::implement;
use ipaddress::IPAddress;
use serde::Serialize;
use url::Url;

use super::Service;

#[derive(Serialize, Default)]
pub struct UrlPreviewData {
	#[serde(skip_serializing_if = "Option::is_none", rename(serialize = "og:title"))]
	pub title: Option<String>,
	#[serde(skip_serializing_if = "Option::is_none", rename(serialize = "og:description"))]
	pub description: Option<String>,
	#[serde(skip_serializing_if = "Option::is_none", rename(serialize = "og:image"))]
	pub image: Option<String>,
	#[serde(skip_serializing_if = "Option::is_none", rename(serialize = "matrix:image:size"))]
	pub image_size: Option<usize>,
	#[serde(skip_serializing_if = "Option::is_none", rename(serialize = "og:image:width"))]
	pub image_width: Option<u32>,
	#[serde(skip_serializing_if = "Option::is_none", rename(serialize = "og:image:height"))]
	pub image_height: Option<u32>,
	#[serde(skip_serializing_if = "Option::is_none", rename(serialize = "og:video"))]
	pub video: Option<String>,
	#[serde(skip_serializing_if = "Option::is_none", rename(serialize = "matrix:video:size"))]
	pub video_size: Option<usize>,
	#[serde(skip_serializing_if = "Option::is_none", rename(serialize = "og:video:width"))]
	pub video_width: Option<u32>,
	#[serde(skip_serializing_if = "Option::is_none", rename(serialize = "og:video:height"))]
	pub video_height: Option<u32>,
	#[serde(skip_serializing_if = "Option::is_none", rename(serialize = "og:audio"))]
	pub audio: Option<String>,
	#[serde(skip_serializing_if = "Option::is_none", rename(serialize = "matrix:audio:size"))]
	pub audio_size: Option<usize>,
}

#[implement(Service)]
pub async fn remove_url_preview(&self, url: &str) -> Result<()> {
	// TODO: also remove the downloaded image
	self.db.remove_url_preview(url)
}

#[implement(Service)]
pub async fn clear_url_previews(&self) { self.db.clear_url_previews().await; }

#[implement(Service)]
pub async fn set_url_preview(&self, url: &str, data: &UrlPreviewData) -> Result<()> {
	let now = SystemTime::now()
		.duration_since(SystemTime::UNIX_EPOCH)
		.expect("valid system time");
	self.db.set_url_preview(url, data, now)
}

#[implement(Service)]
pub async fn get_url_preview(&self, url: &Url) -> Result<UrlPreviewData> {
	if let Ok(preview) = self.db.get_url_preview(url.as_str()).await {
		return Ok(preview);
	}

	// ensure that only one request is made per URL
	let _request_lock = self.url_preview_mutex.lock(url.as_str()).await;

	match self.db.get_url_preview(url.as_str()).await {
		| Ok(preview) => Ok(preview),
		| Err(_) => self.request_url_preview(url).await,
	}
}

#[implement(Service)]
async fn request_url_preview(&self, url: &Url) -> Result<UrlPreviewData> {
	if let Ok(ip) = IPAddress::parse(url.host_str().expect("URL previously validated")) {
		if !self.services.client.valid_cidr_range(&ip) {
			return Err!(Request(Forbidden("Requesting from this address is forbidden")));
		}
	}

	let client = &self.services.client.url_preview;
	let response = client.head(url.as_str()).send().await?;

	debug!(%url, "URL preview response headers: {:?}", response.headers());

	if let Some(remote_addr) = response.remote_addr() {
		debug!(%url, "URL preview response remote address: {:?}", remote_addr);

		if let Ok(ip) = IPAddress::parse(remote_addr.ip().to_string()) {
			if !self.services.client.valid_cidr_range(&ip) {
				return Err!(Request(Forbidden("Requesting from this address is forbidden")));
			}
		}
	}

	let Some(content_type) = response.headers().get(reqwest::header::CONTENT_TYPE) else {
		return Err!(Request(Unknown("Unknown or invalid Content-Type header")));
	};

	let content_type = content_type
		.to_str()
		.map_err(|e| err!(Request(Unknown("Unknown or invalid Content-Type header: {e}"))))?;

	let data = match content_type {
		| html if html.starts_with("text/html") => self.download_html(url.as_str()).await?,
		| img if img.starts_with("image/") => self.download_image(url.as_str(), None).await?,
		| video if video.starts_with("video/") => self.download_video(url.as_str(), None).await?,
		| audio if audio.starts_with("audio/") => self.download_audio(url.as_str(), None).await?,
		| _ => return Err!(Request(Unknown("Unsupported Content-Type"))),
	};

	self.set_url_preview(url.as_str(), &data).await?;

	Ok(data)
}

#[cfg(feature = "url_preview")]
#[implement(Service)]
pub async fn download_image(
	&self,
	url: &str,
	preview_data: Option<UrlPreviewData>,
) -> Result<UrlPreviewData> {
	use conduwuit::utils::random_string;
	use image::ImageReader;
	use ruma::Mxc;

	let mut preview_data = preview_data.unwrap_or_default();

	let image = self
		.services
		.client
		.url_preview
		.get(url)
		.send()
		.await?
		.limit_read(
			self.services
				.server
				.config
				.max_request_size
				.try_into()
				.expect("u64 should fit in usize"),
		)
		.await?;
	
	let mxc = Mxc {
		server_name: self.services.globals.server_name(),
		media_id: &random_string(super::MXC_LENGTH),
	};

	self.create(&mxc, None, None, None, &image).await?;

	preview_data.image = Some(mxc.to_string());
	if preview_data.image_height.is_none() || preview_data.image_width.is_none() {
		let cursor = std::io::Cursor::new(&image);
		let (width, height) = match ImageReader::new(cursor).with_guessed_format() {
			| Err(_) => (None, None),
			| Ok(reader) => match reader.into_dimensions() {
				| Err(_) => (None, None),
				| Ok((width, height)) => (Some(width), Some(height)),
			},
		};

		preview_data.image_width = width;
		preview_data.image_height = height;
	}

	Ok(preview_data)
}

#[cfg(feature = "url_preview")]
#[implement(Service)]
pub async fn download_video(
	&self,
	url: &str,
	preview_data: Option<UrlPreviewData>,
) -> Result<UrlPreviewData> {
	use conduwuit::utils::random_string;
	use ruma::Mxc;

	let mut preview_data = preview_data.unwrap_or_default();

	if self.services.globals.url_preview_allow_audio_video() {
		let video = self.services.client.url_preview.get(url).send().await?;
		let video = video.bytes().await?;
		let mxc = Mxc {
			server_name: self.services.globals.server_name(),
			media_id: &random_string(super::MXC_LENGTH),
		};

		self.create(&mxc, None, None, None, &video).await?;

		preview_data.video = Some(mxc.to_string());
	}

	Ok(preview_data)
}

#[cfg(feature = "url_preview")]
#[implement(Service)]
pub async fn download_audio(
	&self,
	url: &str,
	preview_data: Option<UrlPreviewData>,
) -> Result<UrlPreviewData> {
	use conduwuit::utils::random_string;
	use ruma::Mxc;

	let mut preview_data = preview_data.unwrap_or_default();

	if self.services.globals.url_preview_allow_audio_video() {
		let audio = self.services.client.url_preview.get(url).send().await?;
		let audio = audio.bytes().await?;
		let mxc = Mxc {
			server_name: self.services.globals.server_name(),
			media_id: &random_string(super::MXC_LENGTH),
		};

		self.create(&mxc, None, None, None, &audio).await?;

		preview_data.video = Some(mxc.to_string());
	}

	Ok(preview_data)
}

#[cfg(not(feature = "url_preview"))]
#[implement(Service)]
pub async fn download_image(
	&self,
	_url: &str,
	_preview_data: Option<UrlPreviewData>,
) -> Result<UrlPreviewData> {
	Err!(FeatureDisabled("url_preview"))
}

#[cfg(not(feature = "url_preview"))]
#[implement(Service)]
pub async fn download_video(
	&self,
	_url: &str,
	_preview_data: Option<UrlPreviewData>,
) -> Result<UrlPreviewData> {
	Err!(FeatureDisabled("url_preview"))
}

#[cfg(not(feature = "url_preview"))]
#[implement(Service)]
pub async fn download_audio(
	&self,
	_url: &str,
	_preview_data: Option<UrlPreviewData>,
) -> Result<UrlPreviewData> {
	Err!(FeatureDisabled("url_preview"))
}

#[cfg(feature = "url_preview")]
#[implement(Service)]
async fn download_html(&self, url: &str) -> Result<UrlPreviewData> {
	use webpage::HTML;

	let client = &self.services.client.url_preview;
	let body = client
		.get(url)
		.send()
		.await?
		.limit_read_text(
			self.services
				.server
				.config
				.max_request_size
				.try_into()
				.expect("u64 should fit in usize"),
		)
		.await?;
	let Ok(html) = HTML::from_string(body.clone(), Some(url.to_owned())) else {
		return Err!(Request(Unknown("Failed to parse HTML")));
	};

	let mut preview_data = UrlPreviewData::default();

	if let Some(obj) = html.opengraph.images.first() {
		preview_data = self.download_image(&obj.url, Some(preview_data)).await?;
	}

	if let Some(obj) = html.opengraph.videos.first() {
		preview_data = self.download_video(&obj.url, Some(preview_data)).await?;
	}

	if let Some(obj) = html.opengraph.audios.first() {
		preview_data = self.download_audio(&obj.url, Some(preview_data)).await?;
	}

	let props = html.opengraph.properties;

	/* use OpenGraph title/description, but fall back to HTML if not available */
	preview_data.title = props.get("title").cloned().or(html.title);
	preview_data.description = props.get("description").cloned().or(html.description);

	Ok(preview_data)
}

#[cfg(not(feature = "url_preview"))]
#[implement(Service)]
async fn download_html(&self, _url: &str) -> Result<UrlPreviewData> {
	Err!(FeatureDisabled("url_preview"))
}

#[implement(Service)]
pub fn url_preview_allowed(&self, url: &Url) -> bool {
	if ["http", "https"]
		.iter()
		.all(|&scheme| scheme != url.scheme().to_lowercase())
	{
		debug!("Ignoring non-HTTP/HTTPS URL to preview: {}", url);
		return false;
	}

	let host = match url.host_str() {
		| None => {
			debug!("Ignoring URL preview for a URL that does not have a host (?): {}", url);
			return false;
		},
		| Some(h) => h.to_owned(),
	};

	let allowlist_domain_contains = self
		.services
		.globals
		.url_preview_domain_contains_allowlist();
	let allowlist_domain_explicit = self
		.services
		.globals
		.url_preview_domain_explicit_allowlist();
	let denylist_domain_explicit = self.services.globals.url_preview_domain_explicit_denylist();
	let allowlist_url_contains = self.services.globals.url_preview_url_contains_allowlist();

	if allowlist_domain_contains.contains(&"*".to_owned())
		|| allowlist_domain_explicit.contains(&"*".to_owned())
		|| allowlist_url_contains.contains(&"*".to_owned())
	{
		debug!("Config key contains * which is allowing all URL previews. Allowing URL {}", url);
		return true;
	}

	if !host.is_empty() {
		if denylist_domain_explicit.contains(&host) {
			debug!(
				"Host {} is not allowed by url_preview_domain_explicit_denylist (check 1/4)",
				&host
			);
			return false;
		}

		if allowlist_domain_explicit.contains(&host) {
			debug!(
				"Host {} is allowed by url_preview_domain_explicit_allowlist (check 2/4)",
				&host
			);
			return true;
		}

		if allowlist_domain_contains
			.iter()
			.any(|domain_s| domain_s.contains(&host.clone()))
		{
			debug!(
				"Host {} is allowed by url_preview_domain_contains_allowlist (check 3/4)",
				&host
			);
			return true;
		}

		if allowlist_url_contains
			.iter()
			.any(|url_s| url.to_string().contains(url_s))
		{
			debug!("URL {} is allowed by url_preview_url_contains_allowlist (check 4/4)", &host);
			return true;
		}

		// check root domain if available and if user has root domain checks
		if self.services.globals.url_preview_check_root_domain() {
			debug!("Checking root domain");
			match host.split_once('.') {
				| None => return false,
				| Some((_, root_domain)) => {
					if denylist_domain_explicit.contains(&root_domain.to_owned()) {
						debug!(
							"Root domain {} is not allowed by \
							 url_preview_domain_explicit_denylist (check 1/3)",
							&root_domain
						);
						return true;
					}

					if allowlist_domain_explicit.contains(&root_domain.to_owned()) {
						debug!(
							"Root domain {} is allowed by url_preview_domain_explicit_allowlist \
							 (check 2/3)",
							&root_domain
						);
						return true;
					}

					if allowlist_domain_contains
						.iter()
						.any(|domain_s| domain_s.contains(&root_domain.to_owned()))
					{
						debug!(
							"Root domain {} is allowed by url_preview_domain_contains_allowlist \
							 (check 3/3)",
							&root_domain
						);
						return true;
					}
				},
			}
		}
	}

	false
}