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use chrono::prelude::*;
use env_logger::fmt::Formatter;
use log::LevelFilter;
use log::Record;
use std::io;
use std::io::prelude::*;
use std::str::FromStr;

/// Initialize logging
///
/// Precedence: LOG_LEVEL > RUST_LOG > 'verbosity' argument.
///
/// Env:
///
/// LOG_LEVEL: Used to control levels for modules. Overrides RUST_LOG
/// This is useful to debug app only when executed through other tools
/// like `cargo run`. Falls back to RUST_LOG if not provided.
///
/// LOG_UTC: 1 for UTC, 0 for local. UTC by default
///  
/// Colors
///
/// Colors are automatic and will be disabled on pipes, or when TERM=dumb
/// is passed along.
///
pub fn init() {
    init_with_verbosity(Verbosity::Info as u8);
}

pub fn init_with_verbosity(verbosity_level: u8) {
    use env_logger::*;
    use std::env;

    const LOG_LEVEL_ENV: &str = "LOG_LEVEL";
    const LOG_UTC_ENV: &str = "LOG_UTC";

    let mut env = Env::new();
    let mut has_opts = false;
    // Use default RUST_LOG env
    let env_level = env::var(DEFAULT_FILTER_ENV);
    if env_level.is_ok() {
        has_opts = true;
    }

    // Use app specific LOG_LEVEL env that overrides RUST_LOG
    let env_level = env::var(LOG_LEVEL_ENV);
    if env_level.is_ok() {
        env = env.filter(LOG_LEVEL_ENV);
        has_opts = true;
    }

    let mut builder = Builder::from_env(env);
    if !has_opts {
        // set default log level
        builder.filter_level(Verbosity::from_occurrence(verbosity_level).log_level_filter());
    }

    let ts_utc = match env::var(LOG_UTC_ENV) {
        Ok(v) => i32::from_str(&v).unwrap_or(1) > 0,
        Err(_) => false,
    };

    builder.format(get_formatter(ts_utc));
    builder.init();
}

fn get_formatter(
    ts_utc: bool,
) -> impl Fn(&mut Formatter, &Record<'_>) -> io::Result<()> + Sync + Send + 'static {
    move |buf: &mut Formatter, record: &Record<'_>| {
        use env_logger::fmt::Color;

        let l = record.level();
        let lvl_style = buf.default_level_style(l);
        let mut ts_style = buf.style();
        let ts_style = ts_style.set_color(Color::Rgb(140, 140, 140));
        let mut path_style = buf.style();
        let path_style = path_style.set_color(Color::Cyan);

        let ts = if ts_utc {
            Utc::now().to_rfc3339_opts(SecondsFormat::Millis, true)
        } else {
            Local::now().to_rfc3339_opts(SecondsFormat::Millis, false)
        };
        writeln!(
            buf,
            "{} {} [{}] {}",
            lvl_style.value(l),
            ts_style.value(ts),
            path_style.value(record.target()),
            record.args()
        )
    }
}

#[derive(Copy, Clone, Debug)]
#[repr(u8)]
pub enum Verbosity {
    Warn = 0,
    Info,
    Debug,
    Trace,
}

impl Verbosity {
    /// Convert u8 to verbosity
    /// Anything other invalid value returns Info, as that's usually the safest
    /// not over-burdening log systems, while still providing some verbosity.
    ///
    /// Note: This is log verbosity, not log control, so doesn't support levels like
    /// Off. For that LOG_LEVEL can be used.
    pub fn from_occurrence(val: u8) -> Verbosity {
        use self::Verbosity::*;
        match val {
            0 => Warn,
            1 => Info,
            2 => Debug,
            3 => Trace,
            _ => Info,
        }
    }

    pub fn from_signed_occurrence(val: i8) -> Verbosity {
        let v = if val < 0 { 0u8 } else { val as u8 };
        Verbosity::from_occurrence(v)
    }

    fn log_level_filter(self) -> LevelFilter {
        use log::LevelFilter::*;
        match self as u8 {
            0 => Warn,
            1 => Info,
            2 => Debug,
            3 => Trace,
            _ => Info,
        }
    }
}

impl From<u8> for Verbosity {
    fn from(val: u8) -> Verbosity {
        Verbosity::from_occurrence(val)
    }
}