// Copyright (C) 2020-2025 Michael herstine <sp1ff@pobox.com>
//
// This file is part of mpdpopm.
//
// mpdpopm 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.
//
// mpdpopm 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 mpdpopm.  If not,
// see <http://www.gnu.org/licenses/>.

//! # mppopmd
//!
//! Maintain ratings & playcounts for your mpd server.
//!
//! # Introduction
//!
//! This is a companion daemon for [mpd](https://www.musicpd.org/) that maintains play counts &
//! ratings. Similar to [mpdfav](https://github.com/vincent-petithory/mpdfav), but written in Rust
//! (which I prefer to Go), it will allow you to maintain that information in your tags, as well as
//! the sticker database, by invoking external commands to keep your tags up-to-date (something
//! along the lines of [mpdcron](https://alip.github.io/mpdcron)).

use mpdpopm::config;
use mpdpopm::config::Config;
use mpdpopm::mpdpopm;

use backtrace::Backtrace;
use clap::Parser;
use tracing::{info, level_filters::LevelFilter};
use tracing_subscriber::{EnvFilter, Layer, Registry, layer::SubscriberExt};

use std::{fmt, io, path::PathBuf, sync::MutexGuard};

////////////////////////////////////////////////////////////////////////////////////////////////////
//                                 mppopmd application Error type                                 //
////////////////////////////////////////////////////////////////////////////////////////////////////

#[non_exhaustive]
pub enum Error {
    NoConfigArg,
    NoConfig {
        config: std::path::PathBuf,
        cause: std::io::Error,
    },
    Filter {
        source: tracing_subscriber::filter::FromEnvError,
        back: Backtrace,
    },
    Fork {
        errno: errno::Errno,
        back: Backtrace,
    },
    PathContainsNull {
        back: Backtrace,
    },
    OpenLockFile {
        errno: errno::Errno,
        back: Backtrace,
    },
    LockFile {
        errno: errno::Errno,
        back: Backtrace,
    },
    WritePid {
        errno: errno::Errno,
        back: Backtrace,
    },
    Config {
        source: crate::config::Error,
        back: Backtrace,
    },
    MpdPopm {
        source: Box<mpdpopm::Error>,
        back: Backtrace,
    },
}

impl std::fmt::Display for Error {
    #[allow(unreachable_patterns)] // the _ arm is *currently* unreachable
    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
        match self {
            Error::NoConfigArg => write!(f, "No configuration file given"),
            Error::NoConfig { config, cause } => {
                write!(f, "Configuration error ({:?}): {}", config, cause)
            }
            Error::Fork { errno, back: _ } => write!(f, "When forking, got errno {}", errno),
            Error::PathContainsNull { back: _ } => write!(f, "Path contains a null character"),
            Error::OpenLockFile { errno, back: _ } => {
                write!(f, "While opening lock file, got errno {}", errno)
            }
            Error::LockFile { errno, back: _ } => {
                write!(f, "While locking the lock file, got errno {}", errno)
            }
            Error::WritePid { errno, back: _ } => {
                write!(f, "While writing pid file, got errno {}", errno)
            }
            Error::Config { source, back: _ } => write!(f, "Configuration error: {}", source),
            Error::MpdPopm { source, back: _ } => write!(f, "mpdpopm error: {}", source),
            _ => write!(f, "Unknown mppopmd error"),
        }
    }
}

impl fmt::Debug for Error {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "{}", self)
    }
}

type Result = std::result::Result<(), Error>;

pub struct MyMutexGuardWriter<'a>(MutexGuard<'a, std::fs::File>);

impl io::Write for MyMutexGuardWriter<'_> {
    #[inline]
    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
        self.0.write(buf)
    }

    #[inline]
    fn flush(&mut self) -> io::Result<()> {
        self.0.flush()
    }

    #[inline]
    fn write_vectored(&mut self, bufs: &[io::IoSlice<'_>]) -> io::Result<usize> {
        self.0.write_vectored(bufs)
    }

    #[inline]
    fn write_all(&mut self, buf: &[u8]) -> io::Result<()> {
        self.0.write_all(buf)
    }

    #[inline]
    fn write_fmt(&mut self, fmt: std::fmt::Arguments<'_>) -> io::Result<()> {
        self.0.write_fmt(fmt)
    }
}

/// mpd + POPM
///
/// `mppopmd' is a companion daemon for `mpd' that maintains playcounts & ratings,
/// as well as implementing some handy functions. It maintains ratings & playcounts in the sticker
/// database, but it allows you to keep that information in your tags, as well, by invoking external
/// commands to keep your tags up-to-date.
#[derive(Parser)]
struct Args {
    /// path to configuration file
    #[arg(short, long)]
    config: Option<PathBuf>,

    /// enable verbose logging
    #[arg(short, long)]
    verbose: bool,

    /// enable debug loggin (implies --verbose)
    #[arg(short, long)]
    debug: bool,
}

/// Entry point for `mppopmd'.
///
/// Do *not* use the #[tokio::main] attribute here! If this program is asked to daemonize (the usual
/// case), we will fork after tokio has started its thread pool, with disastrous consequences.
/// Instead, stay synchronous until we've daemonized (or figured out that we don't need to), and
/// only then fire-up the tokio runtime.
fn main() -> Result {
    use mpdpopm::vars::VERSION;

    let args = Args::parse();

    let config = if let Some(cfgpath) = &args.config {
        match std::fs::read_to_string(cfgpath) {
            Ok(text) => config::from_str(&text).map_err(|err| Error::Config {
                source: err,
                back: Backtrace::new(),
            })?,
            // The config file (defaulted or not) either didn't exist, or we were unable to read its
            // contents...
            Err(err) => {
                // Either they did _not_, in which case they probably want to know that the config
                // file they explicitly asked for does not exist, or there was some other problem,
                // in which case we're out of options, anyway. Either way:
                return Err(Error::NoConfig {
                    config: PathBuf::from(cfgpath),
                    cause: err,
                });
            }
        }
    } else {
        Config::default()
    };

    // `--verbose' & `--debug' work as follows: if `--debug' is present, log at level Trace, no
    // matter what. Else, if `--verbose' is present, log at level Debug. Else, log at level Info.
    let lf = match (args.verbose, args.debug) {
        (_, true) => LevelFilter::TRACE,
        (true, false) => LevelFilter::DEBUG,
        _ => LevelFilter::INFO,
    };

    let filter = EnvFilter::builder()
        .with_default_directive(lf.into())
        .from_env()
        .map_err(|err| Error::Filter {
            source: err,
            back: Backtrace::new(),
        })?;

    let formatter: Box<dyn Layer<Registry> + Send + Sync> = {
        Box::new(
            tracing_subscriber::fmt::Layer::default()
                .compact()
                .with_writer(io::stdout),
        )
    };

    tracing::subscriber::set_global_default(Registry::default().with(formatter).with(filter))
        .unwrap();

    info!("mppopmd {VERSION} logging at level {lf:#?}.");
    let rt = tokio::runtime::Runtime::new().unwrap();
    rt.block_on(mpdpopm(config)).map_err(|err| Error::MpdPopm {
        source: Box::new(err),
        back: Backtrace::new(),
    })
}