//! # A specialized Logger for [`pt`](../libpt/index.html)
//!
//! This crate is part of [`pt`](../libpt/index.html), but can also be used as a standalone
//! module.
//!
//! For the library version, only the basic [`tracing`] is used, so that it is possible for
//! the end user to use the [`tracing`] frontend they desire.
//!
//! I did however decide to create a [`Logger`] struct. This struct is mainly intended to be used
//! with the python module of [`pt`](../libpt/index.html), but is still just as usable in other contexts.
//!
//! ## Technologies used for logging:
//! - [`tracing`]: base logging crate
//! - [`tracing_appender`]: Used to log to files
//! - [`tracing_subscriber`]: Used to do actual logging, formatting, to stdout

//// ATTRIBUTES ////////////////////////////////////////////////////////////////////////////////////

//// IMPORTS ///////////////////////////////////////////////////////////////////////////////////////
use std::{
    fmt,
    ops::Deref,
    path::PathBuf,
    sync::atomic::{AtomicBool, Ordering},
};

pub mod error;
use error::*;

pub use tracing::{debug, error, info, trace, warn, Level};
use tracing_appender::{
    self,
    non_blocking::{NonBlocking, WorkerGuard},
};
use tracing_subscriber::{
    fmt::{
        format::FmtSpan,
        time::{self, FormatTime},
    },
    prelude::*,
};

use anyhow::{bail, Result};

//// CONSTANTS /////////////////////////////////////////////////////////////////////////////////////
/// The log level used when none is specified
pub const DEFAULT_LOG_LEVEL: Level = Level::INFO;
/// The path where logs are stored when no path is given.
///
/// Currently, this is `/dev/null`, meaning they will be written to the void = discarded.
pub const DEFAULT_LOG_DIR: &'static str = "/dev/null";

//// STATICS ///////////////////////////////////////////////////////////////////////////////////////
static INITIALIZED: AtomicBool = AtomicBool::new(false);

//// STRUCTS ///////////////////////////////////////////////////////////////////////////////////////
/// ## Logger for [`pt`](../libpt/index.html)
///
/// This struct exists mainly for the python module, so that we can use the same logger with both
/// python and rust.
pub struct Logger;

//// IMPLEMENTATION ////////////////////////////////////////////////////////////////////////////////
/// ## Main implementation
impl Logger {
    /// ## create a `Logger`
    ///
    /// Creates a new uninitialized [`Logger`] object.
    pub fn new() -> Self {
        let l = Logger {};
        l
    }
    /// ## initializes the logger
    ///
    /// Will enable the logger to be used.
    ///
    /// Assumes some defaults, use [`init_customized`](Self::init_customized) for more control
    pub fn init(log_dir: Option<PathBuf>, max_level: Option<Level>) -> Result<()> {
        Self::init_customized(
            log_dir.is_some(),
            log_dir.unwrap_or(PathBuf::from(DEFAULT_LOG_DIR)),
            true,
            false,
            true,
            false,
            max_level.unwrap_or(DEFAULT_LOG_LEVEL),
            false,
            false,
            false,
            false,
            true,
            false,
        )
    }

    /// ## initializes the logger
    ///
    /// Will enable the logger to be used. This is a version that shows less information,
    /// useful in cases with only one sender to the logging framework.
    ///
    /// Assumes some defaults, use [`init_customized`](Self::init_customized) for more control
    pub fn init_mini(max_level: Option<Level>) -> Result<()> {
        Self::init_customized(
            false,
            PathBuf::from(DEFAULT_LOG_DIR),
            true,
            false,
            true,
            false,
            max_level.unwrap_or(DEFAULT_LOG_LEVEL),
            false,
            false,
            false,
            false,
            false,
            false,
        )
    }

    /// ## initializes the logger
    ///
    /// Will enable the logger to be used.
    pub fn init_customized(
        log_to_file: bool,
        log_dir: PathBuf,
        ansi: bool,
        display_filename: bool,
        display_level: bool,
        display_target: bool,
        max_level: Level,
        display_thread_ids: bool,
        display_thread_names: bool,
        display_line_number: bool,
        pretty: bool,
        show_time: bool,
        uptime: bool, // uptime instead of system time
    ) -> Result<()> {
        // only init if no init has been performed yet
        if INITIALIZED.load(Ordering::Relaxed) {
            warn!("trying to reinitialize the logger, ignoring");
            bail!(Error::Usage(format!("logging is already initialized")));
        }
        let subscriber = tracing_subscriber::fmt::Subscriber::builder()
            .with_level(display_level)
            .with_max_level(max_level)
            .with_ansi(ansi)
            .with_target(display_target)
            .with_file(display_filename)
            .with_thread_ids(display_thread_ids)
            .with_line_number(display_line_number)
            .with_thread_names(display_thread_names)
            .with_span_events(FmtSpan::FULL);
        // I know this is hacky, but I couldn't get it any other way. I couldn't even find a
        // project that could do it any other way. You can't apply one after another, because the
        // type is changed every time. When using Box<dyn Whatever>, some methods complain about
        // not being in trait bounds.
        // TODO: somehow find a better solution for this
        match (log_to_file, show_time, pretty, uptime) {
            (true, true, true, true) => {
                let subscriber = subscriber
                    .with_writer(new_file_appender(log_dir))
                    .with_timer(time::uptime())
                    .pretty()
                    .finish();
                tracing::subscriber::set_global_default(subscriber)?;
            }
            (true, true, true, false) => {
                let subscriber = subscriber
                    .with_writer(new_file_appender(log_dir))
                    .pretty()
                    .finish();
                tracing::subscriber::set_global_default(subscriber)?;
            }
            (true, false, true, _) => {
                let subscriber = subscriber
                    .with_writer(new_file_appender(log_dir))
                    .without_time()
                    .pretty()
                    .finish();
                tracing::subscriber::set_global_default(subscriber)?;
            }
            (true, true, false, true) => {
                let subscriber = subscriber
                    .with_writer(new_file_appender(log_dir))
                    .with_timer(time::uptime())
                    .finish();
                tracing::subscriber::set_global_default(subscriber)?;
            }
            (true, true, false, false) => {
                let subscriber = subscriber.with_writer(new_file_appender(log_dir)).finish();
                tracing::subscriber::set_global_default(subscriber)?;
            }
            (true, false, false, _) => {
                let file_appender = tracing_appender::rolling::daily(log_dir.clone(), "log");
                let (file_writer, _guard) = tracing_appender::non_blocking(file_appender);
                let subscriber = subscriber.with_writer(file_writer).without_time().finish();
                tracing::subscriber::set_global_default(subscriber)?;
            }
            (false, true, true, true) => {
                let subscriber = subscriber.pretty().with_timer(time::uptime()).finish();
                tracing::subscriber::set_global_default(subscriber)?;
            }
            (false, true, true, false) => {
                let subscriber = subscriber.pretty().with_timer(time::uptime()).finish();
                tracing::subscriber::set_global_default(subscriber)?;
            }
            (false, false, true, _) => {
                let subscriber = subscriber.without_time().pretty().finish();
                tracing::subscriber::set_global_default(subscriber)?;
            }
            (false, true, false, true) => {
                let subscriber = subscriber.with_timer(time::uptime()).finish();
                tracing::subscriber::set_global_default(subscriber)?;
            }
            (false, true, false, false) => {
                let subscriber = subscriber.finish();
                tracing::subscriber::set_global_default(subscriber)?;
            }
            (false, false, false, _) => {
                let subscriber = subscriber.without_time().finish();
                tracing::subscriber::set_global_default(subscriber)?;
            }
        }
        INITIALIZED.store(true, Ordering::Relaxed);
        Ok(())
    }

    /// ## logging at [`Level::ERROR`]
    pub fn error<T>(&self, printable: T)
    where
        T: fmt::Display,
    {
        error!("{}", printable)
    }
    /// ## logging at [`Level::WARN`]
    pub fn warn<T>(&self, printable: T)
    where
        T: fmt::Display,
    {
        warn!("{}", printable)
    }
    /// ## logging at [`Level::INFO`]
    pub fn info<T>(&self, printable: T)
    where
        T: fmt::Display,
    {
        info!("{}", printable)
    }
    /// ## logging at [`Level::DEBUG`]
    pub fn debug<T>(&self, printable: T)
    where
        T: fmt::Display,
    {
        debug!("{}", printable)
    }
    /// ## logging at [`Level::TRACE`]
    pub fn trace<T>(&self, printable: T)
    where
        T: fmt::Display,
    {
        trace!("{}", printable)
    }
}

////////////////////////////////////////////////////////////////////////////////////////////////////
impl fmt::Debug for Logger {
    /// ## DEBUG representation for [`Logger`]
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(
            f,
            "Logger: {{initialized: {}}} ",
            INITIALIZED.load(Ordering::Relaxed)
        )
    }
}

//// PUBLIC FUNCTIONS //////////////////////////////////////////////////////////////////////////////

//// PRIVATE FUNCTIONS /////////////////////////////////////////////////////////////////////////////
fn new_file_appender(log_dir: PathBuf) -> NonBlocking {
    let file_appender = tracing_appender::rolling::daily(log_dir.clone(), "log");
    return tracing_appender::non_blocking(file_appender).0;
}