//! Works ordering the file system objects
use super::*;
use std::{
    collections::BTreeSet,
    path::{
	PathBuf,
	Path,
    },
    fs::Metadata,
    sync::Arc,
};

#[derive(Debug, Clone, PartialEq, Eq, Hash, PartialOrd, Ord, Copy, Default)]
pub enum OrderBy
{
    #[default]
    BirthTime,
    ChangeTime,
    AccessTime,
    ModifiedTime,
}

#[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Default)]
pub struct Config
{
    pub by: OrderBy,
}

/// Information from a file
#[derive(Debug, Clone)]
pub struct FileInfo
{
    state: Arc<Config>, //TODO: XXX: This will be a *severe* slowdown... How can we have just a reference here? Thread local? `tokio::task_local!`? Global static?
    path: PathBuf,
    meta: Metadata,
}

impl FileInfo
{
    /// Returns a factory function that produces `FileInfo`s with this config.
    #[inline] 
    pub fn factory<'a, T: Into<Arc<Config>>>(config: T) -> impl Fn(PathBuf, Metadata) -> FileInfo + 'a
    where T: 'a
    {
	let v = config.into();
	move |path, meta| -> FileInfo {
	    FileInfo::new(Arc::clone(&v), path, meta)
	}
    }

    #[inline] 
    pub fn new(config: impl Into<Arc<Config>>, path: PathBuf, meta: Metadata) -> Self
    {
	Self {
	    state: config.into(),
	    path, meta
	}
    }

    #[inline] 
    pub fn path(&self) -> &Path
    {
	&self.path
    }
    
    #[inline] 
    pub fn metadata(&self) -> &Metadata
    {
	&self.meta
    }

    #[inline] 
    pub fn config(&self) -> &Config
    {
	&self.state
    }

    #[inline] 
    pub fn config_cell(&self) -> &Arc<Config>
    {
	&self.state
    }
}

impl FileInfo
{
    #[inline]
    fn get_ordered_unix_time(&self) -> i64
    {
	use std::os::unix::prelude::*;
	
	//use std::os::linux::fs::MetadataExt as _ ; // Doesn't show birth in `statx()` :/
	use std::time::SystemTime;
	match self.state.by {
	    OrderBy::AccessTime => self.meta.atime(),
	    OrderBy::ChangeTime => self.meta.ctime(),
	    OrderBy::ModifiedTime => self.meta.mtime(),
	    // XXX: Eh, why can't we just get `st_stat` from this? These `expect()`s are slow...
	    OrderBy::BirthTime => self.meta.created()
		.expect("Failed to get creation time").duration_since(SystemTime::UNIX_EPOCH)
		.expect("Invalid creation timestamp").as_secs() as i64,//.as_secs_f64().floor() as u64
	} //XXX: Should we support nsec precision?
    }
}

impl order::Orderer<FileInfo> for FileInfo
{
    #[inline(always)] 
    fn order(a: &FileInfo, b: &FileInfo) -> std::cmp::Ordering {
	match Ord::cmp(&a.get_ordered_unix_time(), &b.get_ordered_unix_time()) {
	    std::cmp::Ordering::Equal => {
		// If times are equal, compare by path to avoid all files with same timecode overwriting eachother.
		Ord::cmp(a.path(), b.path())
		//TODO: How to handle the `-R` case nested ordering... Uhh... Recursive interface for `FSTimeMap`, like `NestedFSTimeMap` or something?
	    },
	    non_eq => non_eq,
	}
    }
}

/// Maps files based on their time
#[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord, Default)]
pub struct FSTimeMap(Arc<Config>, BTreeSet<order::Ordered<FileInfo, FileInfo>>);

impl FSTimeMap
{
    #[inline] 
    pub fn new(config: impl Into<Config>) -> Self
    {
	Self(Arc::new(config.into()), BTreeSet::new())
    }

    #[inline] 
    pub fn iter(&self) -> impl Iterator<Item = &'_ FileInfo> + ExactSizeIterator + DoubleEndedIterator + std::iter::FusedIterator + '_
    {
	self.1.iter().map(|x| x.inner())
    }

    #[inline] 
    pub fn into_iter(self) -> impl Iterator<Item = FileInfo> + ExactSizeIterator + DoubleEndedIterator + std::iter::FusedIterator + 'static
    {
	self.1.into_iter().map(|x| x.into_inner())
    }

    #[inline] 
    pub fn insert(&mut self, file: FileInfo)
    {
	self.1.insert(order::Ordered::new(file));
    }

    #[inline] 
    pub fn len(&self) -> usize
    {
	self.1.len()
    }
}