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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.

    use std::fs;

    use linked_hash_map::LinkedHashMap;
    use page::LocalPageEndpoint;
    use handlers::FetchControl;

    pub enum ContentStatus {
    	Fetching(FetchControl),
    	Ready(LocalPageEndpoint),
    }

    #[derive(Default)]
    pub struct ContentCache {
    	cache: LinkedHashMap<String, ContentStatus>,
    }

    impl ContentCache {
    	pub fn insert(&mut self, content_id: String, status: ContentStatus) -> Option<ContentStatus> {
    		self.cache.insert(content_id, status)
    	}

    	pub fn remove(&mut self, content_id: &str) -> Option<ContentStatus> {
    		self.cache.remove(content_id)
    	}

    	pub fn get(&mut self, content_id: &str) -> Option<&mut ContentStatus> {
    		self.cache.get_refresh(content_id)
    	}

    	pub fn clear_garbage(&mut self, expected_size: usize) -> Vec<(String, ContentStatus)> {
    		let len = self.cache.len();

    		if len <= expected_size {
    			return Vec::new();
    		}

    		let mut removed = Vec::with_capacity(len - expected_size);

    		while self.cache.len() > expected_size {
    			let entry = self.cache.pop_front().expect("expected_size bounded at 0, len is greater; qed");

    			match entry.1 {
    				ContentStatus::Fetching(ref fetch) => {
    					trace!(target: "dapps", "Aborting {} because of limit.", entry.0);
    					// Mark as aborted
    					fetch.abort()
    				},
    				ContentStatus::Ready(ref endpoint) => {
    					trace!(target: "dapps", "Removing {} because of limit.", entry.0);
    					// Remove path (dir or file)
    					let res = fs::remove_dir_all(&endpoint.path()).or_else(|_| fs::remove_file(&endpoint.path()));
    					if let Err(e) = res {
    						warn!(target: "dapps", "Unable to remove dapp/content from cache: {:?}", e);
    					}
    				}
    			}

    			removed.push(entry);
    		}
    		removed
    	}

    	#[cfg(test)]
    	pub fn len(&self) -> usize {
    		self.cache.len()
    	}
    }

    #[cfg(test)]
    mod tests {
    	use super::*;

    	fn only_keys(data: Vec<(String, ContentStatus)>) -> Vec<String> {
    		data.into_iter().map(|x| x.0).collect()
    	}

    	#[test]
    	fn should_remove_least_recently_used() {
    		// given
    		let mut cache = ContentCache::default();
    		cache.insert("a".into(), ContentStatus::Fetching(Default::default()));
    		cache.insert("b".into(), ContentStatus::Fetching(Default::default()));
    		cache.insert("c".into(), ContentStatus::Fetching(Default::default()));

    		// when
    		let res = cache.clear_garbage(2);

    		// then
    		assert_eq!(cache.len(), 2);
    		assert_eq!(only_keys(res), vec!["a"]);
    	}

    	#[test]
    	fn should_update_lru_if_accessed() {
    		// given
    		let mut cache = ContentCache::default();
    		cache.insert("a".into(), ContentStatus::Fetching(Default::default()));
    		cache.insert("b".into(), ContentStatus::Fetching(Default::default()));
    		cache.insert("c".into(), ContentStatus::Fetching(Default::default()));

    		// when
    		cache.get("a");
    		let res = cache.clear_garbage(2);

    		// then
    		assert_eq!(cache.len(), 2);
    		assert_eq!(only_keys(res), vec!["b"]);
    	}

    }

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