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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/>.

    //! `JournalDB` interface and implementation.

    use common::*;
    use kvdb::Database;

    /// Export the journaldb module.
    pub mod traits;
    mod archivedb;
    mod earlymergedb;
    mod overlayrecentdb;
    mod refcounteddb;

    /// Export the `JournalDB` trait.
    pub use self::traits::JournalDB;

    /// A journal database algorithm.
    #[derive(Debug, PartialEq, Clone, Copy)]
    pub enum Algorithm {
    	/// Keep all keys forever.
    	Archive,

    	/// Ancient and recent history maintained separately; recent history lasts for particular
    	/// number of blocks.
    	///
    	/// Inserts go into backing database, journal retains knowledge of whether backing DB key is
    	/// ancient or recent. Non-canon inserts get explicitly reverted and removed from backing DB.
    	EarlyMerge,

    	/// Ancient and recent history maintained separately; recent history lasts for particular
    	/// number of blocks.
    	///
    	/// Inserts go into memory overlay, which is tried for key fetches. Memory overlay gets
    	/// flushed in backing only at end of recent history.
    	OverlayRecent,

    	/// Ancient and recent history maintained separately; recent history lasts for particular
    	/// number of blocks.
    	///
    	/// References are counted in disk-backed DB.
    	RefCounted,
    }

    impl Default for Algorithm {
    	fn default() -> Algorithm { Algorithm::OverlayRecent }
    }

    impl FromStr for Algorithm {
    	type Err = String;

    	fn from_str(s: &str) -> Result<Self, Self::Err> {
    		match s {
    			"archive" => Ok(Algorithm::Archive),
    			"light" => Ok(Algorithm::EarlyMerge),
    			"fast" => Ok(Algorithm::OverlayRecent),
    			"basic" => Ok(Algorithm::RefCounted),
    			e => Err(format!("Invalid algorithm: {}", e)),
    		}
    	}
    }

    impl Algorithm {
    	/// Returns static str describing journal database algorithm.
    	pub fn as_str(&self) -> &'static str {
    		match *self {
    			Algorithm::Archive => "archive",
    			Algorithm::EarlyMerge => "light",
    			Algorithm::OverlayRecent => "fast",
    			Algorithm::RefCounted => "basic",
    		}
    	}

    	/// Returns static str describing journal database algorithm.
    	pub fn as_internal_name_str(&self) -> &'static str {
    		match *self {
    			Algorithm::Archive => "archive",
    			Algorithm::EarlyMerge => "earlymerge",
    			Algorithm::OverlayRecent => "overlayrecent",
    			Algorithm::RefCounted => "refcounted",
    		}
    	}

    	/// Returns true if pruning strategy is stable
    	pub fn is_stable(&self) -> bool {
    		match *self {
    			Algorithm::Archive | Algorithm::OverlayRecent => true,
    			_ => false,
    		}
    	}

    	/// Returns all algorithm types.
    	pub fn all_types() -> Vec<Algorithm> {
    		vec![Algorithm::Archive, Algorithm::EarlyMerge, Algorithm::OverlayRecent, Algorithm::RefCounted]
    	}
    }

    impl fmt::Display for Algorithm {
    	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
    		write!(f, "{}", self.as_str())
    	}
    }

    /// Create a new `JournalDB` trait object.
    pub fn new(backing: Arc<Database>, algorithm: Algorithm, col: Option<u32>) -> Box<JournalDB> {
    	match algorithm {
    		Algorithm::Archive => Box::new(archivedb::ArchiveDB::new(backing, col)),
    		Algorithm::EarlyMerge => Box::new(earlymergedb::EarlyMergeDB::new(backing, col)),
    		Algorithm::OverlayRecent => Box::new(overlayrecentdb::OverlayRecentDB::new(backing, col)),
    		Algorithm::RefCounted => Box::new(refcounteddb::RefCountedDB::new(backing, col)),
    	}
    }

    // all keys must be at least 12 bytes
    const DB_PREFIX_LEN : usize = 12;
    const LATEST_ERA_KEY : [u8; DB_PREFIX_LEN] = [ b'l', b'a', b's', b't', 0, 0, 0, 0, 0, 0, 0, 0 ];

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

    	#[test]
    	fn test_journal_algorithm_parsing() {
    		assert_eq!(Algorithm::Archive, "archive".parse().unwrap());
    		assert_eq!(Algorithm::EarlyMerge, "light".parse().unwrap());
    		assert_eq!(Algorithm::OverlayRecent, "fast".parse().unwrap());
    		assert_eq!(Algorithm::RefCounted, "basic".parse().unwrap());
    	}

    	#[test]
    	fn test_journal_algorithm_printing() {
    		assert_eq!(Algorithm::Archive.to_string(), "archive".to_owned());
    		assert_eq!(Algorithm::EarlyMerge.to_string(), "light".to_owned());
    		assert_eq!(Algorithm::OverlayRecent.to_string(), "fast".to_owned());
    		assert_eq!(Algorithm::RefCounted.to_string(), "basic".to_owned());
    	}

    	#[test]
    	fn test_journal_algorithm_is_stable() {
    		assert!(Algorithm::Archive.is_stable());
    		assert!(Algorithm::OverlayRecent.is_stable());
    		assert!(!Algorithm::EarlyMerge.is_stable());
    		assert!(!Algorithm::RefCounted.is_stable());
    	}

    	#[test]
    	fn test_journal_algorithm_default() {
    		assert_eq!(Algorithm::default(), Algorithm::OverlayRecent);
    	}

    	#[test]
    	fn test_journal_algorithm_all_types() {
    		// compiling should fail if some cases are not covered
    		let mut archive = 0;
    		let mut earlymerge = 0;
    		let mut overlayrecent = 0;
    		let mut refcounted = 0;

    		for a in &Algorithm::all_types() {
    			match *a {
    				Algorithm::Archive => archive += 1,
    				Algorithm::EarlyMerge => earlymerge += 1,
    				Algorithm::OverlayRecent => overlayrecent += 1,
    				Algorithm::RefCounted => refcounted += 1,
    			}
    		}

    		assert_eq!(archive, 1);
    		assert_eq!(earlymerge, 1);
    		assert_eq!(overlayrecent, 1);
    		assert_eq!(refcounted, 1);
    	}
    }

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