selene-core 0.3.0

use std::{
    any::{Any, TypeId},
    borrow::Borrow,
    collections::HashMap,
    rc::Rc,
};

use lunar_lib::trace;
use sled::{
    CompareAndSwapError, Db, IVec, Transactional, Tree,
    transaction::{ConflictableTransactionError, TransactionError, TransactionalTree},
};

use crate::{
    database::{
        DatabaseEntry, DatabaseError, DbKey, EntryId, Patchable, deserialize_from_ivec, library_db,
        serialize_to_ivec, sled_get_raw, validator::DatabaseReferenceError,
    },
    library::{
        album::{Album, AlbumId, TrackReference},
        artist::{ArtistGroup, ArtistId},
        track::TrackId,
    },
};

#[derive(Debug)]
pub struct CompareAndSwapValue<T: DatabaseEntry> {
    pub old: Option<IVec>,
    pub new: Option<T>,
}

impl<T: DatabaseEntry> CompareAndSwapValue<T> {
    #[must_use]
    pub fn new(old: Option<IVec>, new: Option<T>) -> Self {
        Self { old, new }
    }
}

#[derive(Debug)]
pub struct TreeCompareAndSwap<T: DatabaseEntry> {
    tree: Tree,
    swaps: HashMap<DbKey, CompareAndSwapValue<T>>,
}

impl<T: DatabaseEntry> TreeCompareAndSwap<T> {
    fn new(db: &Db) -> Self {
        Self {
            tree: T::tree(db),
            swaps: HashMap::new(),
        }
    }

    #[must_use]
    pub fn tree(&self) -> &Tree {
        &self.tree
    }
}

pub trait GenericCompareAndSwap: Any + std::fmt::Debug {
    fn tree(&self) -> &Tree;
    fn as_any(&self) -> &dyn Any;
    fn as_any_mut(&mut self) -> &mut dyn Any;
    fn apply(
        &self,
        tx_tree: &TransactionalTree,
    ) -> Result<(), ConflictableTransactionError<CompareAndSwapError>>;
}

impl<T: DatabaseEntry> GenericCompareAndSwap for TreeCompareAndSwap<T> {
    fn tree(&self) -> &Tree {
        &self.tree
    }

    fn as_any(&self) -> &dyn Any {
        self
    }

    fn as_any_mut(&mut self) -> &mut dyn Any {
        self
    }

    fn apply(
        &self,
        tx_tree: &TransactionalTree,
    ) -> Result<(), ConflictableTransactionError<CompareAndSwapError>> {
        for (k, v) in &self.swaps {
            let ivec = tx_tree.get(k)?;

            if ivec == v.old {
                if let Some(new) = &v.new {
                    tx_tree.insert(k, serialize_to_ivec(&new))?;
                } else {
                    tx_tree.remove(k)?;
                }
            } else {
                return Err(ConflictableTransactionError::Abort(CompareAndSwapError {
                    current: ivec,
                    proposed: v.new.as_ref().map(serialize_to_ivec),
                }));
            }
        }
        Ok(())
    }
}

#[derive(Debug)]
pub struct CompareAndSwapTransaction {
    swaps: HashMap<TypeId, Box<dyn GenericCompareAndSwap>>,
    database: Rc<Db>,
}

impl CompareAndSwapTransaction {
    #[must_use]
    pub(crate) fn new() -> Self {
        Self {
            swaps: HashMap::new(),
            database: Rc::new(library_db()),
        }
    }

    #[must_use]
    pub(crate) fn with_db(database: Rc<Db>) -> Self {
        Self {
            swaps: HashMap::new(),
            database,
        }
    }

    /// Patches `item` with the existing database entry, if any, else inserts
    ///
    /// Patching rules depend on how [`T`] implements [`Patchable<T>`]
    ///
    /// # Warning
    ///
    /// This function will create dangling references if not used correctly
    pub(crate) fn tx_patch<T: Patchable<T> + DatabaseEntry + 'static>(
        &mut self,
        item: T,
    ) -> Result<(), DatabaseError> {
        if let Some(mut old_item) = self.tx_get(item.id())? {
            let item_id = item.id();
            old_item.patch(item);
            self.tx_upsert(item_id, Some(old_item))?;
        } else {
            self.tx_upsert(item.id(), Some(item))?;
        }

        Ok(())
    }

    /// Gets the latest version of the item in the transaction context, looking it up in the database if its unmodified
    ///
    /// # Errors
    ///
    /// Errors if [`DatabaseEntry::db_get()`] errors
    pub fn tx_get<Id: EntryId>(&self, id: Id) -> Result<Option<Id::Entry>, DatabaseError> {
        if let Some(boxed) = self.swaps.get(&TypeId::of::<Id::Entry>()) {
            let cas_tree = boxed
                .as_any()
                .downcast_ref::<TreeCompareAndSwap<Id::Entry>>()
                .unwrap();
            if let Some(get) = cas_tree.swaps.get(id.as_bytes()) {
                return Ok(get.new.clone());
            }
        }

        let tree = Id::Entry::tree(&self.database);
        let raw = sled_get_raw(&tree, id.as_bytes())?;
        Ok(raw.map(deserialize_from_ivec))
    }

    pub(crate) fn tx_get_batch<I, A, Entry: DatabaseEntry>(
        &self,
        items: I,
    ) -> Result<Vec<Entry>, DatabaseError>
    where
        I: IntoIterator<Item = A>,
        A: Borrow<Entry::Id>,
    {
        items
            .into_iter()
            .map(|id| {
                self.tx_get(*id.borrow())?
                    .ok_or(DatabaseError::MissingEntry)
            })
            .collect()
    }

    pub fn tx_remove<Id: EntryId>(&mut self, key: Id) -> Result<(), DatabaseError> {
        let db = self.database.clone();
        let request = self.get_or_new_request::<Id::Entry>();

        let key = *key.as_bytes();
        if let Some(get_mut) = request.swaps.get_mut(&key) {
            get_mut.new = None;
        } else {
            let old = sled_get_raw(&Id::Entry::tree(&db), &key)?;
            request
                .swaps
                .insert(key, CompareAndSwapValue { old, new: None });
        }
        Ok(())
    }

    pub fn tx_upsert<T: DatabaseEntry>(
        &mut self,
        key: T::Id,
        mut new: Option<T>,
    ) -> Result<(), DatabaseError> {
        let db = self.database.clone();
        if let Some(new) = &mut new {
            new.pre_upsert(self)?;
        }

        let request = self.get_or_new_request::<T>();

        let key = *key.as_bytes();

        if let Some(get_mut) = request.swaps.get_mut(&key) {
            get_mut.new = new;
        } else {
            let old = sled_get_raw(&T::tree(&db), &key)?;
            request.swaps.insert(key, CompareAndSwapValue { old, new });
        }
        Ok(())
    }

    pub fn tx_insert<T: DatabaseEntry>(&mut self, item: T) -> Result<(), DatabaseError> {
        if self.tx_get(item.id())?.is_some() {
            return Err(DatabaseError::AlreadyInDatabase);
        }

        self.tx_upsert(item.id(), Some(item))?;
        Ok(())
    }

    pub fn get_or_new_request<T: DatabaseEntry>(&mut self) -> &mut TreeCompareAndSwap<T> {
        self.swaps
            .entry(TypeId::of::<T>())
            .or_insert_with(|| Box::new(TreeCompareAndSwap::<T>::new(&self.database)))
            .as_any_mut()
            .downcast_mut::<TreeCompareAndSwap<T>>()
            .unwrap()
    }

    #[must_use]
    pub fn trees(&self) -> Vec<&Tree> {
        self.swaps.values().map(|a| a.tree()).collect()
    }
}

/// Applies a [`CompareAndSwapTransaction`] atomically to the database
///
/// # Errors
///
/// This function will error if `[sled]` fails get, insert, or remove a key OR abort with a [`CompareAndSwapError`] if the current value does not match the expected value
pub fn apply_cas_tx(
    tx: CompareAndSwapTransaction,
    flush: bool,
) -> Result<(), TransactionError<CompareAndSwapError>> {
    tx.trees().transaction(|tx_trees| {
        for (tree, cas) in tx_trees.iter().zip(tx.swaps.values()) {
            cas.apply(tree)?;
            if flush {
                tree.flush();
            }
        }
        Ok(())
    })
}

/// Calls a closure that returns a [`CompareAndSwapTransaction`] and applies it atomically to the database
///
/// This function will be called again if a [`CompareAndSwapError`] occurs
///
/// # Errors
///
/// This function will error if `f()` returns an error, or if [`apply_cas_tx()`] fails with an error other than [`CompareAndSwapError`]
pub fn db_transaction<F, E>(mut f: F, db: Option<Db>, flush: bool) -> Result<(), E>
where
    F: FnMut(&mut CompareAndSwapTransaction) -> Result<(), E>,
    E: From<TransactionError<CompareAndSwapError>>,
{
    let db = db.map(Rc::new);

    loop {
        let mut cas_tx = if let Some(db) = db.clone() {
            CompareAndSwapTransaction::with_db(db)
        } else {
            CompareAndSwapTransaction::new()
        };

        f(&mut cas_tx)?;

        match apply_cas_tx(cas_tx, flush) {
            Ok(()) => return Ok(()),
            Err(TransactionError::Abort(CompareAndSwapError {
                current: _,
                proposed: _,
            })) => {
                trace!("Transaction (Not sync) ran into a CAS error and is retrying.");
            }
            Err(err) => return Err(err.into()),
        }
    }
}

// Safe two-way helpers
impl CompareAndSwapTransaction {
    /// Applies a two-way relinking operation, relinking to the track to a new (or no) album, and disconnecting the tracks old album, if any
    pub fn relink_track_to_album(
        &mut self,
        track_id: TrackId,
        album: Option<AlbumId>,
    ) -> Result<bool, DatabaseError> {
        let Some(mut track) = self.tx_get(track_id)? else {
            return Ok(false);
        };

        if track.metadata.album == album {
            return Ok(false);
        }

        let old_album_id = track.metadata.album;

        track.metadata.album = album;
        self.tx_upsert(track.id(), Some(track.clone()))?;

        if let Some(old_album_id) = old_album_id {
            let mut old_album = self.tx_get(old_album_id)?.ok_or({
                DatabaseReferenceError::TrackDanglingAlbumRef {
                    track: track_id,
                    album: old_album_id,
                }
            })?;

            old_album.tracks.retain(|t| t.id != track_id);

            self.tx_upsert(old_album.id(), Some(old_album))?;
        }

        if let Some(new_album_id) = album {
            let mut new_album = self
                .tx_get(new_album_id)?
                .ok_or(DatabaseError::MissingEntry)?;

            new_album.tracks.push(TrackReference {
                id: track_id,
                track_num: None,
                disc_num: None,
            });

            self.tx_upsert(new_album.id(), Some(new_album))?;
        }

        Ok(true)
    }

    /// Applies a two-way relinking operation, relinking artists to the album, and disconnecting references from removed artists
    pub fn album_set_and_relink_artists(
        &mut self,
        album_id: AlbumId,
        artists: &[ArtistId],
    ) -> Result<bool, DatabaseError> {
        let mut album = self.tx_get(album_id)?.ok_or(DatabaseError::MissingEntry)?;

        let old_artists: Vec<ArtistId> = album.artist_group.artist_ids().to_vec();

        album.artist_group = ArtistGroup::from_artist_ids(artists.iter().cloned());

        let removed_artists: Vec<ArtistId> = old_artists
            .into_iter()
            .filter(|old_artist| !artists.contains(old_artist))
            .collect();

        self.artists_add_album(album_id, artists)?;
        self.artists_remove_album(album_id, &removed_artists)?;

        self.tx_upsert(album_id, Some(album))?;
        Ok(true)
    }

    /// Applies a two-way relinking operation, relinking tracks to the album, and disconnecting references from removed tracks
    pub fn album_set_and_relink_tracks(
        &mut self,
        album_id: AlbumId,
        tracks: &[TrackId],
    ) -> Result<bool, DatabaseError> {
        let album = self.tx_get(album_id)?.ok_or(DatabaseError::MissingEntry)?;

        let old_tracks: Vec<TrackId> = album.tracks.iter().map(|t| t.id).collect();

        let removed_tracks: Vec<TrackId> = old_tracks
            .iter()
            .filter(|old_track| !tracks.contains(old_track))
            .cloned()
            .collect();

        self.album_set_tracks(album, tracks)?;
        self.tracks_set_album(Some(album_id), tracks)?;
        self.tracks_set_album(None, &removed_tracks)?;
        Ok(true)
    }
}

// Unsafe one-way helpers
impl CompareAndSwapTransaction {
    pub(crate) fn album_set_tracks(
        &mut self,
        mut album: Album,
        tracks: &[TrackId],
    ) -> Result<(), DatabaseError> {
        album.tracks = tracks
            .iter()
            .map(|t| {
                album
                    .tracks
                    .iter()
                    .find(|old| old.id == *t)
                    .cloned()
                    .unwrap_or(TrackReference {
                        id: *t,
                        track_num: None,
                        disc_num: None,
                    })
            })
            .collect();
        self.tx_upsert(album.id(), Some(album))?;
        Ok(())
    }

    pub(crate) fn tracks_set_album<'a>(
        &mut self,
        album_id: Option<AlbumId>,
        tracks: impl IntoIterator<Item = &'a TrackId>,
    ) -> Result<(), DatabaseError> {
        for track_id in tracks {
            let Some(mut track) = self.tx_get(*track_id)? else {
                return Err(DatabaseError::MissingEntry);
            };

            track.metadata.album = album_id;

            for artist_id in track.metadata.artists.artist_ids() {
                if let Some(album_id) = album_id {
                    let Some(mut artist) = self.tx_get(*artist_id)? else {
                        return Err(DatabaseError::MissingEntry);
                    };

                    if artist.albums.contains(&album_id) {
                        artist.tracks.retain(|t| t != track_id);
                        self.tx_upsert(*artist_id, Some(artist))?;
                    } else {
                        self.artist_add_tracks(*artist_id, &[*track_id])?;
                    }
                } else {
                    self.artist_add_tracks(*artist_id, &[*track_id])?;
                }
            }

            self.tx_upsert(*track_id, Some(track))?;
        }
        Ok(())
    }

    pub(crate) fn artists_remove_album(
        &mut self,
        album_id: AlbumId,
        artists: &[ArtistId],
    ) -> Result<(), DatabaseError> {
        for artist_id in artists {
            let Some(mut artist) = self.tx_get(*artist_id)? else {
                return Err(DatabaseError::MissingEntry);
            };

            artist.albums.retain(|a| *a != album_id);

            self.tx_upsert(*artist_id, Some(artist))?;
        }

        Ok(())
    }

    pub(crate) fn artists_add_album(
        &mut self,
        album_id: AlbumId,
        artists: &[ArtistId],
    ) -> Result<(), DatabaseError> {
        for artist_id in artists {
            let Some(mut artist) = self.tx_get(*artist_id)? else {
                return Err(DatabaseError::MissingEntry);
            };

            if !artist.albums.contains(&album_id) {
                artist.albums.push(album_id);
            }
            self.tx_upsert(*artist_id, Some(artist))?;
        }
        Ok(())
    }

    pub(crate) fn artist_add_tracks(
        &mut self,
        artist_id: ArtistId,
        tracks: &[TrackId],
    ) -> Result<(), DatabaseError> {
        let Some(mut artist) = self.tx_get(artist_id)? else {
            return Err(DatabaseError::MissingEntry);
        };

        for track_id in tracks {
            let Some(track) = self.tx_get(*track_id)? else {
                return Err(DatabaseError::MissingEntry);
            };

            if let Some(album_id) = track.metadata.album
                && artist.albums.contains(&album_id)
            {
                continue;
            }

            if !artist.tracks.contains(track_id) {
                artist.tracks.push(*track_id)
            }
        }

        self.tx_upsert(artist_id, Some(artist))?;

        Ok(())
    }
}