// Copyright 2016 Doug Goldstein
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

//! A simple logger to provide symantics similar to what is expected
//! of most UNIX utilities by logging to stderr and the higher the
//! verbosity the higher the log level
//!
//! ### Examples
//!
//! ```rust
//! #[macro_use]
//! extern crate log;
//! extern crate stderrlog;
//!
//! fn main() {
//!     stderrlog::new().module(module_path!()).init().unwrap();
//!
//!     info!("starting up");
//!
//!     // ...
//! }
//! ```
//!
//! ```rust
//! extern crate docopt;
//! #[macro_use]
//! extern crate log;
//! extern crate rustc_serialize;
//! extern crate stderrlog;
//!
//! use docopt::Docopt;
//!
//! const USAGE: &'static str = "
//! Usage: program [-q] [-v...]
//! ";
//!
//! #[derive(Debug, RustcDecodable)]
//! struct Args {
//!     flag_q: bool,
//!     flag_v: usize,
//! }
//!
//! fn main() {
//!     let args: Args = Docopt::new(USAGE)
//!                             .and_then(|d| d.decode())
//!                             .unwrap_or_else(|e| e.exit());
//!
//!     stderrlog::new()
//!             .module(module_path!())
//!             .quiet(args.flag_q)
//!             .timestamp(stderrlog::Timestamp::Second)
//!             .verbosity(args.flag_v)
//!             .init()
//!             .unwrap();
//!     info!("starting up");
//!
//!     // ...
//! }

extern crate log;
extern crate time;

use log::{LogLevelFilter, LogMetadata};
use std::io::Write;

/// State of the timestampping in the logger.
#[derive(Clone, Copy, Debug)]
pub enum Timestamp {
    /// Disable timestamping of log messages
    Off,
    /// Timestamp with second granularity
    Second,
}

#[derive(Clone, Debug)]
pub struct StdErrLog {
    verbosity: LogLevelFilter,
    quiet: bool,
    timestamp: Timestamp,
    modules: Vec<String>,
}

impl log::Log for StdErrLog {
    fn enabled(&self, metadata: &LogMetadata) -> bool {
        metadata.level() <= log::max_log_level()
    }

    fn log(&self, record: &log::LogRecord) {

        // if logging isn't enabled for this level do a quick out
        if !self.enabled(record.metadata()) {
            return;
        }

        // module we are logging for
        let curr_mod = record.location().module_path();

        // create the timestamp prefix string
        let timestamp_prefix = match self.timestamp {
            Timestamp::Off => String::new(),
            Timestamp::Second => format!("{} - ", time::now().rfc3339()),
        };

        // this logger only logs the requested modules unless the
        // vector of modules is empty
        // modules will have module::file in the module_path
        if self.modules.is_empty() || self.modules.iter().any(|x| curr_mod.starts_with(x)) {
            let _ = writeln!(&mut ::std::io::stderr(),
                             "{}{} - {}",
                             timestamp_prefix,
                             record.level(),
                             record.args());
        }
    }
}

impl StdErrLog {
    pub fn new() -> StdErrLog {
        StdErrLog {
            verbosity: LogLevelFilter::Error,
            quiet: false,
            timestamp: Timestamp::Off,
            modules: vec![],
        }
    }

    /// Sets the verbosity level of messages that will be displayed
    pub fn verbosity(&mut self, verbosity: usize) -> &mut StdErrLog {
        let log_lvl = match verbosity {
            0 => LogLevelFilter::Error,
            1 => LogLevelFilter::Warn,
            2 => LogLevelFilter::Info,
            3 => LogLevelFilter::Debug,
            _ => LogLevelFilter::Trace,
        };

        self.verbosity = log_lvl;
        self
    }

    pub fn quiet(&mut self, quiet: bool) -> &mut StdErrLog {
        self.quiet = quiet;
        self
    }

    /// Enables or disables the use of timestamps in log messages
    pub fn timestamp(&mut self, timestamp: Timestamp) -> &mut StdErrLog {
        self.timestamp = timestamp;
        self
    }

    pub fn module(&mut self, module: &str) -> &mut StdErrLog {
        self.modules.push(module.to_owned());
        self
    }

    pub fn modules(&mut self, modules: Vec<String>) -> &mut StdErrLog {
        self.modules.extend(modules);
        self
    }

    pub fn init(&self) -> Result<(), log::SetLoggerError> {

        log::set_logger(|max_log_level| {
            if self.quiet {
                max_log_level.set(LogLevelFilter::Off);
            } else {
                max_log_level.set(self.verbosity);
            }

            Box::new(self.clone())
        })
    }
}

pub fn new() -> StdErrLog {
    StdErrLog::new()
}

#[cfg(test)]
mod tests {
    #[test]
    fn test_default_level() {
        extern crate log;

        super::new().module(module_path!()).init().unwrap();

        assert_eq!(log::LogLevel::Error, log::max_log_level())
    }
}