// This file is part of Substrate.

// Copyright (C) Parity Technologies (UK) Ltd.
// SPDX-License-Identifier: GPL-3.0-or-later WITH Classpath-exception-2.0

// This program 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.

// This program 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 this program. If not, see <https://www.gnu.org/licenses/>.

//! Database upgrade logic.

use std::{
	fmt, fs,
	io::{self, ErrorKind, Read, Write},
	path::{Path, PathBuf},
};

use crate::{columns, utils::DatabaseType};
use codec::{Decode, Encode};
use kvdb_rocksdb::{Database, DatabaseConfig};
use sp_runtime::traits::Block as BlockT;

/// Version file name.
const VERSION_FILE_NAME: &str = "db_version";

/// Current db version.
const CURRENT_VERSION: u32 = 4;

/// Number of columns in v1.
const V1_NUM_COLUMNS: u32 = 11;
const V2_NUM_COLUMNS: u32 = 12;
const V3_NUM_COLUMNS: u32 = 12;

/// Database upgrade errors.
#[derive(Debug)]
pub enum UpgradeError {
	/// Database version cannot be read from existing db_version file.
	UnknownDatabaseVersion,
	/// Missing database version file.
	MissingDatabaseVersionFile,
	/// Database version no longer supported.
	UnsupportedVersion(u32),
	/// Database version comes from future version of the client.
	FutureDatabaseVersion(u32),
	/// Invalid justification block.
	DecodingJustificationBlock,
	/// Common io error.
	Io(io::Error),
}

pub type UpgradeResult<T> = Result<T, UpgradeError>;

impl From<io::Error> for UpgradeError {
	fn from(err: io::Error) -> Self {
		UpgradeError::Io(err)
	}
}

impl fmt::Display for UpgradeError {
	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
		match self {
			UpgradeError::UnknownDatabaseVersion => {
				write!(f, "Database version cannot be read from existing db_version file")
			},
			UpgradeError::MissingDatabaseVersionFile => write!(f, "Missing database version file"),
			UpgradeError::UnsupportedVersion(version) => {
				write!(f, "Database version no longer supported: {}", version)
			},
			UpgradeError::FutureDatabaseVersion(version) => {
				write!(f, "Database version comes from future version of the client: {}", version)
			},
			UpgradeError::DecodingJustificationBlock => {
				write!(f, "Decodoning justification block failed")
			},
			UpgradeError::Io(err) => write!(f, "Io error: {}", err),
		}
	}
}

/// Upgrade database to current version.
pub fn upgrade_db<Block: BlockT>(db_path: &Path, db_type: DatabaseType) -> UpgradeResult<()> {
	let db_version = current_version(db_path)?;
	match db_version {
		0 => return Err(UpgradeError::UnsupportedVersion(db_version)),
		1 => {
			migrate_1_to_2::<Block>(db_path, db_type)?;
			migrate_2_to_3::<Block>(db_path, db_type)?;
			migrate_3_to_4::<Block>(db_path, db_type)?;
		},
		2 => {
			migrate_2_to_3::<Block>(db_path, db_type)?;
			migrate_3_to_4::<Block>(db_path, db_type)?;
		},
		3 => {
			migrate_3_to_4::<Block>(db_path, db_type)?;
		},
		CURRENT_VERSION => (),
		_ => return Err(UpgradeError::FutureDatabaseVersion(db_version)),
	}
	update_version(db_path)?;
	Ok(())
}

/// Migration from version1 to version2:
/// 1) the number of columns has changed from 11 to 12;
/// 2) transactions column is added;
fn migrate_1_to_2<Block: BlockT>(db_path: &Path, _db_type: DatabaseType) -> UpgradeResult<()> {
	let db_cfg = DatabaseConfig::with_columns(V1_NUM_COLUMNS);
	let mut db = Database::open(&db_cfg, db_path)?;
	db.add_column().map_err(Into::into)
}

/// Migration from version2 to version3:
/// - The format of the stored Justification changed to support multiple Justifications.
fn migrate_2_to_3<Block: BlockT>(db_path: &Path, _db_type: DatabaseType) -> UpgradeResult<()> {
	let db_cfg = DatabaseConfig::with_columns(V2_NUM_COLUMNS);
	let db = Database::open(&db_cfg, db_path)?;

	// Get all the keys we need to update
	let keys: Vec<_> = db
		.iter(columns::JUSTIFICATIONS)
		.map(|r| r.map(|e| e.0))
		.collect::<Result<_, _>>()?;

	// Read and update each entry
	let mut transaction = db.transaction();
	for key in keys {
		if let Some(justification) = db.get(columns::JUSTIFICATIONS, &key)? {
			// Tag each justification with the hardcoded ID for GRANDPA to avoid the dependency on
			// the GRANDPA crate.
			// NOTE: when storing justifications the previous API would get a `Vec<u8>` and still
			// call encode on it.
			let justification = Vec::<u8>::decode(&mut &justification[..])
				.map_err(|_| UpgradeError::DecodingJustificationBlock)?;
			let justifications = sp_runtime::Justifications::from((*b"FRNK", justification));
			transaction.put_vec(columns::JUSTIFICATIONS, &key, justifications.encode());
		}
	}
	db.write(transaction)?;

	Ok(())
}

/// Migration from version3 to version4:
/// 1) the number of columns has changed from 12 to 13;
/// 2) BODY_INDEX column is added;
fn migrate_3_to_4<Block: BlockT>(db_path: &Path, _db_type: DatabaseType) -> UpgradeResult<()> {
	let db_cfg = DatabaseConfig::with_columns(V3_NUM_COLUMNS);
	let mut db = Database::open(&db_cfg, db_path)?;
	db.add_column().map_err(Into::into)
}

/// Reads current database version from the file at given path.
/// If the file does not exist returns 0.
fn current_version(path: &Path) -> UpgradeResult<u32> {
	match fs::File::open(version_file_path(path)) {
		Err(ref err) if err.kind() == ErrorKind::NotFound =>
			Err(UpgradeError::MissingDatabaseVersionFile),
		Err(_) => Err(UpgradeError::UnknownDatabaseVersion),
		Ok(mut file) => {
			let mut s = String::new();
			file.read_to_string(&mut s).map_err(|_| UpgradeError::UnknownDatabaseVersion)?;
			u32::from_str_radix(&s, 10).map_err(|_| UpgradeError::UnknownDatabaseVersion)
		},
	}
}

/// Writes current database version to the file.
/// Creates a new file if the version file does not exist yet.
pub fn update_version(path: &Path) -> io::Result<()> {
	fs::create_dir_all(path)?;
	let mut file = fs::File::create(version_file_path(path))?;
	file.write_all(format!("{}", CURRENT_VERSION).as_bytes())?;
	Ok(())
}

/// Returns the version file path.
fn version_file_path(path: &Path) -> PathBuf {
	let mut file_path = path.to_owned();
	file_path.push(VERSION_FILE_NAME);
	file_path
}

#[cfg(all(test, feature = "rocksdb"))]
mod tests {
	use super::*;
	use crate::{tests::Block, DatabaseSource};

	fn create_db(db_path: &Path, version: Option<u32>) {
		if let Some(version) = version {
			fs::create_dir_all(db_path).unwrap();
			let mut file = fs::File::create(version_file_path(db_path)).unwrap();
			file.write_all(format!("{}", version).as_bytes()).unwrap();
		}
	}

	fn open_database(db_path: &Path, db_type: DatabaseType) -> sp_blockchain::Result<()> {
		crate::utils::open_database::<Block>(
			&DatabaseSource::RocksDb { path: db_path.to_owned(), cache_size: 128 },
			db_type,
			true,
		)
		.map(|_| ())
		.map_err(|e| sp_blockchain::Error::Backend(e.to_string()))
	}

	#[test]
	fn downgrade_never_happens() {
		let db_dir = tempfile::TempDir::new().unwrap();
		create_db(db_dir.path(), Some(CURRENT_VERSION + 1));
		assert!(open_database(db_dir.path(), DatabaseType::Full).is_err());
	}

	#[test]
	fn open_empty_database_works() {
		let db_type = DatabaseType::Full;
		let db_dir = tempfile::TempDir::new().unwrap();
		let db_dir = db_dir.path().join(db_type.as_str());
		open_database(&db_dir, db_type).unwrap();
		open_database(&db_dir, db_type).unwrap();
		assert_eq!(current_version(&db_dir).unwrap(), CURRENT_VERSION);
	}

	#[test]
	fn upgrade_to_3_works() {
		let db_type = DatabaseType::Full;
		for version_from_file in &[None, Some(1), Some(2)] {
			let db_dir = tempfile::TempDir::new().unwrap();
			let db_path = db_dir.path().join(db_type.as_str());
			create_db(&db_path, *version_from_file);
			open_database(&db_path, db_type).unwrap();
			assert_eq!(current_version(&db_path).unwrap(), CURRENT_VERSION);
		}
	}

	#[test]
	fn upgrade_to_4_works() {
		let db_type = DatabaseType::Full;
		for version_from_file in &[None, Some(1), Some(2), Some(3)] {
			let db_dir = tempfile::TempDir::new().unwrap();
			let db_path = db_dir.path().join(db_type.as_str());
			create_db(&db_path, *version_from_file);
			open_database(&db_path, db_type).unwrap();
			assert_eq!(current_version(&db_path).unwrap(), CURRENT_VERSION);
		}
	}
}