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    // Copyright 2015-2017 Parity Technologies (UK) Ltd.
    // This file is part of Parity.

    // Parity is free software: you can redistribute it and/or modify
    // it under the terms of the GNU General Public License as published by
    // the Free Software Foundation, either version 3 of the License, or
    // (at your option) any later version.

    // Parity is distributed in the hope that it will be useful,
    // but WITHOUT ANY WARRANTY; without even the implied warranty of
    // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    // GNU General Public License for more details.

    // You should have received a copy of the GNU General Public License
    // along with Parity.  If not, see <http://www.gnu.org/licenses/>.

    //! Fetchable Dapps support.
    //! Manages downloaded (cached) Dapps and downloads them when necessary.
    //! Uses `URLHint` to resolve addresses into Dapps bundle file location.

    mod installers;

    use std::{fs, env};
    use std::path::PathBuf;
    use std::sync::Arc;
    use rustc_serialize::hex::FromHex;
    use fetch::{Client as FetchClient, Fetch};
    use hash_fetch::urlhint::{URLHintContract, URLHint, URLHintResult};
    use parity_reactor::Remote;

    use hyper;
    use hyper::status::StatusCode;

    use {SyncStatus, random_filename};
    use util::Mutex;
    use page::LocalPageEndpoint;
    use handlers::{ContentHandler, ContentFetcherHandler};
    use endpoint::{Endpoint, EndpointPath, Handler};
    use apps::cache::{ContentCache, ContentStatus};

    /// Limit of cached dapps/content
    const MAX_CACHED_DAPPS: usize = 20;

    pub trait Fetcher: Send + Sync + 'static {
    	fn contains(&self, content_id: &str) -> bool;

    	fn to_async_handler(&self, path: EndpointPath, control: hyper::Control) -> Box<Handler>;
    }

    pub struct ContentFetcher<F: Fetch = FetchClient, R: URLHint + Send + Sync + 'static = URLHintContract> {
    	dapps_path: PathBuf,
    	resolver: R,
    	cache: Arc<Mutex<ContentCache>>,
    	sync: Arc<SyncStatus>,
    	embeddable_on: Option<(String, u16)>,
    	remote: Remote,
    	fetch: F,
    }

    impl<R: URLHint + Send + Sync + 'static, F: Fetch> Drop for ContentFetcher<F, R> {
    	fn drop(&mut self) {
    		// Clear cache path
    		let _ = fs::remove_dir_all(&self.dapps_path);
    	}
    }

    impl<R: URLHint + Send + Sync + 'static, F: Fetch> ContentFetcher<F, R> {

    	pub fn new(resolver: R, sync_status: Arc<SyncStatus>, embeddable_on: Option<(String, u16)>, remote: Remote, fetch: F) -> Self {
    		let mut dapps_path = env::temp_dir();
    		dapps_path.push(random_filename());

    		ContentFetcher {
    			dapps_path: dapps_path,
    			resolver: resolver,
    			sync: sync_status,
    			cache: Arc::new(Mutex::new(ContentCache::default())),
    			embeddable_on: embeddable_on,
    			remote: remote,
    			fetch: fetch,
    		}
    	}

    	fn still_syncing(address: Option<(String, u16)>) -> Box<Handler> {
    		Box::new(ContentHandler::error(
    			StatusCode::ServiceUnavailable,
    			"Sync In Progress",
    			"Your node is still syncing. We cannot resolve any content before it's fully synced.",
    			Some("<a href=\"javascript:window.location.reload()\">Refresh</a>"),
    			address,
    		))
    	}

    	#[cfg(test)]
    	fn set_status(&self, content_id: &str, status: ContentStatus) {
    		self.cache.lock().insert(content_id.to_owned(), status);
    	}
    }

    impl<R: URLHint + Send + Sync + 'static, F: Fetch> Fetcher for ContentFetcher<F, R> {
    	fn contains(&self, content_id: &str) -> bool {
    		{
    			let mut cache = self.cache.lock();
    			// Check if we already have the app
    			if cache.get(content_id).is_some() {
    				return true;
    			}
    		}
    		// fallback to resolver
    		if let Ok(content_id) = content_id.from_hex() {
    			// else try to resolve the app_id
    			let has_content = self.resolver.resolve(content_id).is_some();
    			// if there is content or we are syncing return true
    			has_content || self.sync.is_major_importing()
    		} else {
    			false
    		}
    	}

    	fn to_async_handler(&self, path: EndpointPath, control: hyper::Control) -> Box<Handler> {
    		let mut cache = self.cache.lock();
    		let content_id = path.app_id.clone();

    		let (new_status, handler) = {
    			let status = cache.get(&content_id);
    			match status {
    				// Just serve the content
    				Some(&mut ContentStatus::Ready(ref endpoint)) => {
    					(None, endpoint.to_async_handler(path, control))
    				},
    				// Content is already being fetched
    				Some(&mut ContentStatus::Fetching(ref fetch_control)) if !fetch_control.is_deadline_reached() => {
    					trace!(target: "dapps", "Content fetching in progress. Waiting...");
    					(None, fetch_control.to_async_handler(path, control))
    				},
    				// We need to start fetching the content
    				_ => {
    					trace!(target: "dapps", "Content unavailable. Fetching... {:?}", content_id);
    					let content_hex = content_id.from_hex().expect("to_handler is called only when `contains` returns true.");
    					let content = self.resolver.resolve(content_hex);

    					let cache = self.cache.clone();
    					let id = content_id.clone();
    					let on_done = move |result: Option<LocalPageEndpoint>| {
    						let mut cache = cache.lock();
    						match result {
    							Some(endpoint) => cache.insert(id.clone(), ContentStatus::Ready(endpoint)),
    							// In case of error
    							None => cache.remove(&id),
    						};
    					};

    					match content {
    						// Don't serve dapps if we are still syncing (but serve content)
    						Some(URLHintResult::Dapp(_)) if self.sync.is_major_importing() => {
    							(None, Self::still_syncing(self.embeddable_on.clone()))
    						},
    						Some(URLHintResult::Dapp(dapp)) => {
    							let handler = ContentFetcherHandler::new(
    								dapp.url(),
    								path,
    								control,
    								installers::Dapp::new(
    									content_id.clone(),
    									self.dapps_path.clone(),
    									Box::new(on_done),
    									self.embeddable_on.clone(),
    								),
    								self.embeddable_on.clone(),
    								self.remote.clone(),
    								self.fetch.clone(),
    							);

    							(Some(ContentStatus::Fetching(handler.fetch_control())), Box::new(handler) as Box<Handler>)
    						},
    						Some(URLHintResult::Content(content)) => {
    							let handler = ContentFetcherHandler::new(
    								content.url,
    								path,
    								control,
    								installers::Content::new(
    									content_id.clone(),
    									content.mime,
    									self.dapps_path.clone(),
    									Box::new(on_done),
    								),
    								self.embeddable_on.clone(),
    								self.remote.clone(),
    								self.fetch.clone(),
    							);

    							(Some(ContentStatus::Fetching(handler.fetch_control())), Box::new(handler) as Box<Handler>)
    						},
    						None if self.sync.is_major_importing() => {
    							(None, Self::still_syncing(self.embeddable_on.clone()))
    						},
    						None => {
    							// This may happen when sync status changes in between
    							// `contains` and `to_handler`
    							(None, Box::new(ContentHandler::error(
    								StatusCode::NotFound,
    								"Resource Not Found",
    								"Requested resource was not found.",
    								None,
    								self.embeddable_on.clone(),
    							)) as Box<Handler>)
    						},
    					}
    				},
    			}
    		};

    		if let Some(status) = new_status {
    			cache.clear_garbage(MAX_CACHED_DAPPS);
    			cache.insert(content_id, status);
    		}

    		handler
    	}
    }

    #[cfg(test)]
    mod tests {
    	use std::env;
    	use std::sync::Arc;
    	use util::Bytes;
    	use fetch::{Fetch, Client};
    	use hash_fetch::urlhint::{URLHint, URLHintResult};
    	use parity_reactor::Remote;

    	use apps::cache::ContentStatus;
    	use endpoint::EndpointInfo;
    	use page::LocalPageEndpoint;
    	use super::{ContentFetcher, Fetcher};

    	struct FakeResolver;
    	impl URLHint for FakeResolver {
    		fn resolve(&self, _id: Bytes) -> Option<URLHintResult> {
    			None
    		}
    	}

    	#[test]
    	fn should_true_if_contains_the_app() {
    		// given
    		let path = env::temp_dir();
    		let fetcher = ContentFetcher::new(FakeResolver, Arc::new(|| false), None, Remote::new_sync(), Client::new().unwrap());
    		let handler = LocalPageEndpoint::new(path, EndpointInfo {
    			name: "fake".into(),
    			description: "".into(),
    			version: "".into(),
    			author: "".into(),
    			icon_url: "".into(),
    		}, Default::default(), None);

    		// when
    		fetcher.set_status("test", ContentStatus::Ready(handler));
    		fetcher.set_status("test2", ContentStatus::Fetching(Default::default()));

    		// then
    		assert_eq!(fetcher.contains("test"), true);
    		assert_eq!(fetcher.contains("test2"), true);
    		assert_eq!(fetcher.contains("test3"), false);
    	}
    }

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