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//! [`log::Log`] implementation using the libretro logging interface.
use super::*;
use env_logger::filter::{Builder as FilterBuilder, Filter};
use log::{Level, Metadata, Record};
use std::io::Write;

pub struct RetroLogger {
    callback: retro_log_callback,
    filter: Filter,
}

impl RetroLogger {
    pub fn new(callback: retro_log_callback) -> Self {
        let mut builder = FilterBuilder::new();
        let mut set_default_level = true;

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

            // We assume that the user passed a valid filter when the
            // environment variable was not empty.
            if !s.trim().is_empty() {
                set_default_level = false;
            }
        }

        // By default the env_logger filter defaults to the error level
        // if no directives have been set.
        if set_default_level {
            builder.filter(None, log::LevelFilter::Trace);
        }

        let filter = builder.build();

        Self { callback, filter }
    }

    fn get_retro_log_level(level: Level) -> retro_log_level {
        match level {
            Level::Error => retro_log_level::RETRO_LOG_ERROR,
            Level::Warn => retro_log_level::RETRO_LOG_WARN,
            Level::Info => retro_log_level::RETRO_LOG_INFO,
            Level::Debug => retro_log_level::RETRO_LOG_DEBUG,
            Level::Trace => retro_log_level::RETRO_LOG_DEBUG,
        }
    }
}

impl log::Log for RetroLogger {
    fn enabled(&self, metadata: &Metadata) -> bool {
        self.filter.enabled(metadata)
    }

    fn log(&self, record: &Record) {
        if !self.filter.matches(record) {
            return;
        }

        let target = if !record.target().is_empty() {
            record.target()
        } else {
            record.module_path().unwrap_or_default()
        };

        if let Some(cb) = self.callback.log {
            let mut args: Vec<u8> = Vec::new();

            if writeln!(args, "{}\0", record.args()).is_ok() {
                let level = Self::get_retro_log_level(record.level());
                let target = CString::new(target).unwrap();

                unsafe {
                    let args = CString::from_vec_unchecked(args);

                    // The callback works like `printf`
                    (cb)(
                        level,
                        "[%s] %s\n\0".as_ptr() as *const c_char,
                        target.as_ptr() as *const c_char,
                        args.as_ptr() as *const c_char,
                    )
                }
            }
        } else {
            let level = match record.level() {
                Level::Debug => "DEBUG",
                Level::Info => "INFO",
                Level::Warn => "WARN",
                Level::Error => "ERROR",
                Level::Trace => "TRACE",
            };

            let stderr = std::io::stderr();
            let mut stderr_lock = stderr.lock();

            let _ = writeln!(
                stderr_lock,
                "[libretro {}] [{}] {}",
                level,
                target,
                record.args()
            );
        }
    }

    fn flush(&self) {
        // Do nothing
    }
}