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// Copyright 2015-2020 Parity Technologies (UK) Ltd.
// This file is part of OpenEthereum.

// OpenEthereum 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.

// OpenEthereum 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 OpenEthereum.  If not, see <http://www.gnu.org/licenses/>.

//! Common log helper functions

use arrayvec::ArrayVec;
use env_logger::Builder as LogBuilder;
use rlog::LevelFilter;
use std::env;

use parking_lot::{RwLock, RwLockReadGuard};

lazy_static! {
    static ref LOG_DUMMY: () = {
        let mut builder = LogBuilder::new();
        builder.filter(None, LevelFilter::Info);

        if let Ok(log) = env::var("RUST_LOG") {
            builder.parse(&log);
        }

        if !builder.try_init().is_ok() {
            println!("logger initialization failed!");
        }
    };
}

/// Intialize log with default settings
pub fn init_log() {
    *LOG_DUMMY
}

const LOG_SIZE: usize = 128;

/// Logger implementation that keeps up to `LOG_SIZE` log elements.
pub struct RotatingLogger {
    /// Defined logger levels
    levels: String,
    /// Logs array. Latest log is always at index 0
    logs: RwLock<ArrayVec<[String; LOG_SIZE]>>,
}

impl RotatingLogger {
    /// Creates new `RotatingLogger` with given levels.
    /// It does not enforce levels - it's just read only.
    pub fn new(levels: String) -> Self {
        RotatingLogger {
            levels: levels,
            logs: RwLock::new(ArrayVec::<[_; LOG_SIZE]>::new()),
        }
    }

    /// Append new log entry
    pub fn append(&self, log: String) {
        let mut logs = self.logs.write();
        if logs.is_full() {
            logs.pop();
        }
        logs.insert(0, log);
    }

    /// Return levels
    pub fn levels(&self) -> &str {
        &self.levels
    }

    /// Return logs
    pub fn logs(&self) -> RwLockReadGuard<ArrayVec<[String; LOG_SIZE]>> {
        self.logs.read()
    }
}

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

    fn logger() -> RotatingLogger {
        RotatingLogger::new("test".to_owned())
    }

    #[test]
    fn should_return_log_levels() {
        // given
        let logger = logger();

        // when
        let levels = logger.levels();

        // then
        assert_eq!(levels, "test");
    }

    #[test]
    fn should_return_latest_logs() {
        // given
        let logger = logger();

        // when
        logger.append("a".to_owned());
        logger.append("b".to_owned());

        // then
        let logs = logger.logs();
        assert_eq!(logs[0], "b".to_owned());
        assert_eq!(logs[1], "a".to_owned());
        assert_eq!(logs.len(), 2);
    }
}