pub mod migrations;
pub mod postgres;
pub mod sqlite;

use std::{path::PathBuf, sync::Arc};

use chrono::{DateTime, Utc};
use rustc_hash::FxHashMap;
use uuid::Uuid;

use crate::{
  analytics::UsageEvent,
  enrichment::ExternalMetadata,
  error::Result,
  model::{
    AuditEntry,
    Collection,
    CollectionKind,
    ContentHash,
    CustomField,
    ManagedBlob,
    ManagedStorageStats,
    MediaId,
    MediaItem,
    Pagination,
    Tag,
  },
  playlists::Playlist,
  search::{SearchRequest, SearchResults},
  social::{Comment, Rating, ShareLink},
  subtitles::Subtitle,
  transcode::{TranscodeSession, TranscodeStatus},
  users::UserId,
};

/// Statistics about the database.
#[derive(Debug, Clone, Default)]
pub struct DatabaseStats {
  pub media_count:         u64,
  pub tag_count:           u64,
  pub collection_count:    u64,
  pub audit_count:         u64,
  pub database_size_bytes: u64,
  pub backend_name:        String,
}

/// Session data for database-backed session storage.
#[derive(Debug, Clone)]
pub struct SessionData {
  pub session_token: String,
  pub user_id:       Option<String>,
  pub username:      String,
  pub role:          String,
  pub created_at:    DateTime<Utc>,
  pub expires_at:    DateTime<Utc>,
  pub last_accessed: DateTime<Utc>,
}

#[async_trait::async_trait]
pub trait StorageBackend: Send + Sync + 'static {
  // Migrations

  /// Apply all pending database migrations.
  /// Called on server startup to ensure the schema is up to date.
  async fn run_migrations(&self) -> Result<()>;

  // Root directories

  /// Register a root directory for media scanning.
  async fn add_root_dir(&self, path: PathBuf) -> Result<()>;

  /// List all registered root directories.
  async fn list_root_dirs(&self) -> Result<Vec<PathBuf>>;

  /// Remove a root directory registration.
  /// Does not delete any media items found under this directory.
  async fn remove_root_dir(&self, path: &std::path::Path) -> Result<()>;

  // Media CRUD

  /// Insert a new media item into the database.
  /// Returns `Database` error if an item with the same ID already exists.
  async fn insert_media(&self, item: &MediaItem) -> Result<()>;

  /// Retrieve a media item by its ID.
  /// Returns `NotFound` if no item exists with the given ID.
  async fn get_media(&self, id: MediaId) -> Result<MediaItem>;

  /// Return the total number of media items in the database.
  async fn count_media(&self) -> Result<u64>;

  /// Look up a media item by its content hash.
  /// Returns `None` if no item matches the hash.
  async fn get_media_by_hash(
    &self,
    hash: &ContentHash,
  ) -> Result<Option<MediaItem>>;

  /// Get a media item by its file path (used for incremental scanning).
  /// Returns `None` if no item exists at the given path.
  async fn get_media_by_path(
    &self,
    path: &std::path::Path,
  ) -> Result<Option<MediaItem>>;

  /// List media items with pagination (offset and limit).
  async fn list_media(&self, pagination: &Pagination)
  -> Result<Vec<MediaItem>>;

  /// Update an existing media item's metadata.
  /// Returns `NotFound` if the item does not exist.
  async fn update_media(&self, item: &MediaItem) -> Result<()>;

  /// Permanently delete a media item by ID.
  /// Returns `NotFound` if the item does not exist.
  async fn delete_media(&self, id: MediaId) -> Result<()>;

  /// Delete all media items from the database. Returns the number deleted.
  async fn delete_all_media(&self) -> Result<u64>;

  // Tags

  /// Create a new tag with an optional parent for hierarchical tagging.
  async fn create_tag(
    &self,
    name: &str,
    parent_id: Option<Uuid>,
  ) -> Result<Tag>;

  /// Retrieve a tag by its ID. Returns `NotFound` if it does not exist.
  async fn get_tag(&self, id: Uuid) -> Result<Tag>;

  /// List all tags in the database.
  async fn list_tags(&self) -> Result<Vec<Tag>>;

  /// Delete a tag by ID. Also removes all media-tag associations.
  async fn delete_tag(&self, id: Uuid) -> Result<()>;

  /// Associate a tag with a media item. No-op if already tagged.
  async fn tag_media(&self, media_id: MediaId, tag_id: Uuid) -> Result<()>;

  /// Remove a tag association from a media item.
  async fn untag_media(&self, media_id: MediaId, tag_id: Uuid) -> Result<()>;

  /// Get all tags associated with a media item.
  async fn get_media_tags(&self, media_id: MediaId) -> Result<Vec<Tag>>;

  /// Get all descendant tags of a parent tag (recursive).
  async fn get_tag_descendants(&self, tag_id: Uuid) -> Result<Vec<Tag>>;

  // Collections

  /// Create a new collection. Smart collections use `filter_query` for
  /// automatic membership; manual collections use explicit add/remove.
  async fn create_collection(
    &self,
    name: &str,
    kind: CollectionKind,
    description: Option<&str>,
    filter_query: Option<&str>,
  ) -> Result<Collection>;

  /// Retrieve a collection by ID. Returns `NotFound` if it does not exist.
  async fn get_collection(&self, id: Uuid) -> Result<Collection>;

  /// List all collections.
  async fn list_collections(&self) -> Result<Vec<Collection>>;

  /// Delete a collection and all its membership entries.
  async fn delete_collection(&self, id: Uuid) -> Result<()>;

  /// Add a media item to a manual collection at the given position.
  async fn add_to_collection(
    &self,
    collection_id: Uuid,
    media_id: MediaId,
    position: i32,
  ) -> Result<()>;

  /// Remove a media item from a collection.
  async fn remove_from_collection(
    &self,
    collection_id: Uuid,
    media_id: MediaId,
  ) -> Result<()>;

  /// Get all media items in a collection, ordered by position.
  async fn get_collection_members(
    &self,
    collection_id: Uuid,
  ) -> Result<Vec<MediaItem>>;

  // Search

  /// Execute a full-text search with filters, sorting, and pagination.
  /// Uses FTS5 on `SQLite` and tsvector/trigram on `PostgreSQL`.
  async fn search(&self, request: &SearchRequest) -> Result<SearchResults>;

  // Audit

  /// Record an audit log entry for an action on a media item.
  async fn record_audit(&self, entry: &AuditEntry) -> Result<()>;

  /// List audit entries, optionally filtered to a specific media item.
  async fn list_audit_entries(
    &self,
    media_id: Option<MediaId>,
    pagination: &Pagination,
  ) -> Result<Vec<AuditEntry>>;

  // Custom fields

  /// Set a custom field on a media item (upserts if the field name exists).
  async fn set_custom_field(
    &self,
    media_id: MediaId,
    name: &str,
    field: &CustomField,
  ) -> Result<()>;

  /// Get all custom fields for a media item, keyed by field name.
  async fn get_custom_fields(
    &self,
    media_id: MediaId,
  ) -> Result<FxHashMap<String, CustomField>>;

  /// Delete a custom field from a media item by name.
  async fn delete_custom_field(
    &self,
    media_id: MediaId,
    name: &str,
  ) -> Result<()>;

  // Batch operations (transactional where supported)

  /// Delete multiple media items in a single transaction.
  /// Returns the number of items actually deleted.
  async fn batch_delete_media(&self, ids: &[MediaId]) -> Result<u64>;

  /// Apply multiple tags to multiple media items.
  /// Returns the number of new associations created.
  async fn batch_tag_media(
    &self,
    media_ids: &[MediaId],
    tag_ids: &[Uuid],
  ) -> Result<u64>;

  // Integrity

  /// List all media item IDs, paths, and content hashes.
  /// Used by integrity checks to verify files still exist on disk.
  async fn list_media_paths(
    &self,
  ) -> Result<Vec<(MediaId, std::path::PathBuf, ContentHash)>>;

  /// Update metadata fields on multiple media items at once.
  /// Only non-`None` fields are applied. Returns the number updated.
  #[allow(clippy::too_many_arguments)]
  async fn batch_update_media(
    &self,
    ids: &[MediaId],
    title: Option<&str>,
    artist: Option<&str>,
    album: Option<&str>,
    genre: Option<&str>,
    year: Option<i32>,
    description: Option<&str>,
  ) -> Result<u64>;

  // Saved searches

  /// Persist a search query so it can be re-executed later.
  async fn save_search(
    &self,
    id: uuid::Uuid,
    name: &str,
    query: &str,
    sort_order: Option<&str>,
  ) -> Result<()>;

  /// List all saved searches.
  async fn list_saved_searches(&self)
  -> Result<Vec<crate::model::SavedSearch>>;

  /// Get a single saved search by ID.
  async fn get_saved_search(
    &self,
    id: uuid::Uuid,
  ) -> Result<crate::model::SavedSearch>;

  /// Delete a saved search by ID.
  async fn delete_saved_search(&self, id: uuid::Uuid) -> Result<()>;

  // Duplicates

  /// Find groups of media items with identical content hashes.
  async fn find_duplicates(&self) -> Result<Vec<Vec<MediaItem>>>;

  /// Find groups of visually similar media using perceptual hashing.
  /// `threshold` is the maximum Hamming distance to consider a match.
  async fn find_perceptual_duplicates(
    &self,
    threshold: u32,
  ) -> Result<Vec<Vec<MediaItem>>>;

  // Database management

  /// Collect aggregate database statistics (counts, size, backend name).
  async fn database_stats(&self) -> Result<DatabaseStats>;

  /// Reclaim unused disk space (VACUUM for `SQLite`, VACUUM FULL for Postgres).
  async fn vacuum(&self) -> Result<()>;

  /// Delete all data from all tables. Destructive; used in tests.
  async fn clear_all_data(&self) -> Result<()>;

  // Thumbnail helpers
  /// List all media IDs, optionally filtering to those missing thumbnails.
  async fn list_media_ids_for_thumbnails(
    &self,
    only_missing: bool,
  ) -> Result<Vec<crate::model::MediaId>>;

  // Library statistics

  /// Compute comprehensive library statistics (sizes, counts by type,
  /// top tags/collections, duplicates).
  async fn library_statistics(&self) -> Result<LibraryStatistics>;

  // User Management

  /// List all registered users.
  async fn list_users(&self) -> Result<Vec<crate::users::User>>;

  /// Get a user by ID. Returns `NotFound` if no such user exists.
  async fn get_user(
    &self,
    id: crate::users::UserId,
  ) -> Result<crate::users::User>;

  /// Look up a user by username. Returns `NotFound` if not found.
  async fn get_user_by_username(
    &self,
    username: &str,
  ) -> Result<crate::users::User>;

  /// Create a new user with the given credentials and role.
  async fn create_user(
    &self,
    username: &str,
    password_hash: &str,
    role: crate::config::UserRole,
    profile: Option<crate::users::UserProfile>,
  ) -> Result<crate::users::User>;

  /// Update a user's password, role, or profile. Only non-`None` fields
  /// are applied.
  async fn update_user(
    &self,
    id: crate::users::UserId,
    password_hash: Option<&str>,
    role: Option<crate::config::UserRole>,
    profile: Option<crate::users::UserProfile>,
  ) -> Result<crate::users::User>;

  /// Delete a user and all associated sessions.
  async fn delete_user(&self, id: crate::users::UserId) -> Result<()>;

  /// Get the library access grants for a user.
  async fn get_user_libraries(
    &self,
    user_id: crate::users::UserId,
  ) -> Result<Vec<crate::users::UserLibraryAccess>>;

  /// Grant a user access to a library root path with the given permission.
  async fn grant_library_access(
    &self,
    user_id: crate::users::UserId,
    root_path: &str,
    permission: crate::users::LibraryPermission,
  ) -> Result<()>;

  /// Revoke a user's access to a library root path.
  async fn revoke_library_access(
    &self,
    user_id: crate::users::UserId,
    root_path: &str,
  ) -> Result<()>;

  /// Check if a user has access to a specific media item based on library
  /// permissions. Returns the permission level if access is granted, or an
  /// error if denied. Admin users (role=admin) bypass library checks and have
  /// full access.
  async fn check_library_access(
    &self,
    user_id: crate::users::UserId,
    media_id: crate::model::MediaId,
  ) -> Result<crate::users::LibraryPermission> {
    // Default implementation: get the media item's path and check against
    // user's library access
    let media = self.get_media(media_id).await?;
    // Get user's library permissions
    let libraries = self.get_user_libraries(user_id).await?;

    // If user has no library restrictions, they have no access (unless they're
    // admin) This default impl requires at least one matching library
    // permission. Use Path::starts_with for component-wise matching to prevent
    // prefix collisions (e.g. /data/user1 vs /data/user1-other).
    for lib in &libraries {
      if media.path.starts_with(std::path::Path::new(&lib.root_path)) {
        return Ok(lib.permission);
      }
    }

    Err(crate::error::PinakesError::Authorization(format!(
      "user {user_id} has no access to media {media_id}"
    )))
  }

  /// Check if a user has at least read access to a media item
  async fn has_media_read_access(
    &self,
    user_id: crate::users::UserId,
    media_id: crate::model::MediaId,
  ) -> Result<bool> {
    match self.check_library_access(user_id, media_id).await {
      Ok(perm) => Ok(perm.can_read()),
      Err(_) => Ok(false),
    }
  }

  /// Check if a user has write access to a media item
  async fn has_media_write_access(
    &self,
    user_id: crate::users::UserId,
    media_id: crate::model::MediaId,
  ) -> Result<bool> {
    match self.check_library_access(user_id, media_id).await {
      Ok(perm) => Ok(perm.can_write()),
      Err(_) => Ok(false),
    }
  }

  /// Rate a media item (1-5 stars) with an optional text review.
  /// Upserts: replaces any existing rating by the same user.
  async fn rate_media(
    &self,
    user_id: UserId,
    media_id: MediaId,
    stars: u8,
    review: Option<&str>,
  ) -> Result<Rating>;

  /// Get all ratings for a media item.
  async fn get_media_ratings(&self, media_id: MediaId) -> Result<Vec<Rating>>;

  /// Get a specific user's rating for a media item, if any.
  async fn get_user_rating(
    &self,
    user_id: UserId,
    media_id: MediaId,
  ) -> Result<Option<Rating>>;

  /// Delete a rating by ID.
  async fn delete_rating(&self, id: Uuid) -> Result<()>;

  /// Add a comment on a media item, optionally as a reply to another comment.
  async fn add_comment(
    &self,
    user_id: UserId,
    media_id: MediaId,
    text: &str,
    parent_id: Option<Uuid>,
  ) -> Result<Comment>;

  /// Get all comments for a media item.
  async fn get_media_comments(&self, media_id: MediaId)
  -> Result<Vec<Comment>>;

  /// Delete a comment by ID.
  async fn delete_comment(&self, id: Uuid) -> Result<()>;

  /// Mark a media item as a favorite for a user.
  async fn add_favorite(
    &self,
    user_id: UserId,
    media_id: MediaId,
  ) -> Result<()>;

  /// Remove a media item from a user's favorites.
  async fn remove_favorite(
    &self,
    user_id: UserId,
    media_id: MediaId,
  ) -> Result<()>;

  /// Get a user's favorited media items with pagination.
  async fn get_user_favorites(
    &self,
    user_id: UserId,
    pagination: &Pagination,
  ) -> Result<Vec<MediaItem>>;

  /// Check whether a media item is in a user's favorites.
  async fn is_favorite(
    &self,
    user_id: UserId,
    media_id: MediaId,
  ) -> Result<bool>;

  /// Create a public share link for a media item with optional password
  /// and expiry.
  async fn create_share_link(
    &self,
    media_id: MediaId,
    created_by: UserId,
    token: &str,
    password_hash: Option<&str>,
    expires_at: Option<DateTime<Utc>>,
  ) -> Result<ShareLink>;

  /// Look up a share link by its token. Returns `NotFound` if invalid.
  async fn get_share_link(&self, token: &str) -> Result<ShareLink>;

  /// Increment the view counter for a share link.
  async fn increment_share_views(&self, token: &str) -> Result<()>;

  /// Delete a share link by ID.
  async fn delete_share_link(&self, id: Uuid) -> Result<()>;

  /// Create a new playlist. Smart playlists auto-populate via `filter_query`.
  async fn create_playlist(
    &self,
    owner_id: UserId,
    name: &str,
    description: Option<&str>,
    is_public: bool,
    is_smart: bool,
    filter_query: Option<&str>,
  ) -> Result<Playlist>;

  /// Get a playlist by ID. Returns `NotFound` if it does not exist.
  async fn get_playlist(&self, id: Uuid) -> Result<Playlist>;

  /// List playlists, optionally filtered to a specific owner.
  async fn list_playlists(
    &self,
    owner_id: Option<UserId>,
  ) -> Result<Vec<Playlist>>;

  /// Update a playlist's name, description, or visibility.
  /// Only non-`None` fields are applied.
  async fn update_playlist(
    &self,
    id: Uuid,
    name: Option<&str>,
    description: Option<&str>,
    is_public: Option<bool>,
  ) -> Result<Playlist>;

  /// Delete a playlist and all its item associations.
  async fn delete_playlist(&self, id: Uuid) -> Result<()>;

  /// Add a media item to a playlist at the given position.
  async fn add_to_playlist(
    &self,
    playlist_id: Uuid,
    media_id: MediaId,
    position: i32,
  ) -> Result<()>;

  /// Remove a media item from a playlist.
  async fn remove_from_playlist(
    &self,
    playlist_id: Uuid,
    media_id: MediaId,
  ) -> Result<()>;

  /// Get all media items in a playlist, ordered by position.
  async fn get_playlist_items(
    &self,
    playlist_id: Uuid,
  ) -> Result<Vec<MediaItem>>;

  /// Move a media item to a new position within a playlist.
  async fn reorder_playlist(
    &self,
    playlist_id: Uuid,
    media_id: MediaId,
    new_position: i32,
  ) -> Result<()>;

  /// Record a usage/analytics event (play, view, download, etc.).
  async fn record_usage_event(&self, event: &UsageEvent) -> Result<()>;

  /// Query usage events, optionally filtered by media item and/or user.
  async fn get_usage_events(
    &self,
    media_id: Option<MediaId>,
    user_id: Option<UserId>,
    limit: u64,
  ) -> Result<Vec<UsageEvent>>;

  /// Get the most-viewed media items with their view counts.
  async fn get_most_viewed(&self, limit: u64) -> Result<Vec<(MediaItem, u64)>>;

  /// Get media items recently viewed by a user, most recent first.
  async fn get_recently_viewed(
    &self,
    user_id: UserId,
    limit: u64,
  ) -> Result<Vec<MediaItem>>;

  /// Update playback/watch progress for a user on a media item (in seconds).
  async fn update_watch_progress(
    &self,
    user_id: UserId,
    media_id: MediaId,
    progress_secs: f64,
  ) -> Result<()>;

  /// Get the stored watch progress (in seconds) for a user/media pair.
  async fn get_watch_progress(
    &self,
    user_id: UserId,
    media_id: MediaId,
  ) -> Result<Option<f64>>;

  /// Delete usage events older than the given timestamp.
  /// Returns the number of events deleted.
  async fn cleanup_old_events(&self, before: DateTime<Utc>) -> Result<u64>;

  /// Add a subtitle track for a media item.
  async fn add_subtitle(&self, subtitle: &Subtitle) -> Result<()>;

  /// Get all subtitle tracks for a media item.
  async fn get_media_subtitles(
    &self,
    media_id: MediaId,
  ) -> Result<Vec<Subtitle>>;

  /// Delete a subtitle track by ID.
  async fn delete_subtitle(&self, id: Uuid) -> Result<()>;

  /// Adjust the timing offset (in milliseconds) for a subtitle track.
  async fn update_subtitle_offset(
    &self,
    id: Uuid,
    offset_ms: i64,
  ) -> Result<()>;

  /// Store metadata fetched from an external source (e.g., `MusicBrainz`,
  /// `TMDb`).
  async fn store_external_metadata(
    &self,
    meta: &ExternalMetadata,
  ) -> Result<()>;

  /// Get all external metadata records for a media item.
  async fn get_external_metadata(
    &self,
    media_id: MediaId,
  ) -> Result<Vec<ExternalMetadata>>;

  /// Delete an external metadata record by ID.
  async fn delete_external_metadata(&self, id: Uuid) -> Result<()>;

  /// Create a new transcoding session for a media item.
  async fn create_transcode_session(
    &self,
    session: &TranscodeSession,
  ) -> Result<()>;

  /// Get a transcoding session by ID.
  async fn get_transcode_session(&self, id: Uuid) -> Result<TranscodeSession>;

  /// List transcoding sessions, optionally filtered to a media item.
  async fn list_transcode_sessions(
    &self,
    media_id: Option<MediaId>,
  ) -> Result<Vec<TranscodeSession>>;

  /// Update the status and progress of a transcoding session.
  async fn update_transcode_status(
    &self,
    id: Uuid,
    status: TranscodeStatus,
    progress: f32,
  ) -> Result<()>;

  /// Delete transcode sessions that expired before the given timestamp.
  /// Returns the number of sessions cleaned up.
  async fn cleanup_expired_transcodes(
    &self,
    before: DateTime<Utc>,
  ) -> Result<u64>;

  /// Create a new session in the database
  async fn create_session(&self, session: &SessionData) -> Result<()>;

  /// Get a session by its token, returns None if not found or expired
  async fn get_session(
    &self,
    session_token: &str,
  ) -> Result<Option<SessionData>>;

  /// Update the `last_accessed` timestamp for a session
  async fn touch_session(&self, session_token: &str) -> Result<()>;

  /// Extend a session's expiry time.
  /// Only extends sessions that have not already expired.
  /// Returns the new expiry time, or None if the session was not found or
  /// already expired.
  async fn extend_session(
    &self,
    session_token: &str,
    new_expires_at: DateTime<Utc>,
  ) -> Result<Option<DateTime<Utc>>>;

  /// Delete a specific session
  async fn delete_session(&self, session_token: &str) -> Result<()>;

  /// Delete all sessions for a specific user
  async fn delete_user_sessions(&self, username: &str) -> Result<u64>;

  /// Delete all expired sessions (where `expires_at` < now)
  async fn delete_expired_sessions(&self) -> Result<u64>;

  /// List all active sessions (optionally filtered by username)
  async fn list_active_sessions(
    &self,
    username: Option<&str>,
  ) -> Result<Vec<SessionData>>;

  // Book Management Methods

  /// Upsert book metadata for a media item
  async fn upsert_book_metadata(
    &self,
    metadata: &crate::model::BookMetadata,
  ) -> Result<()>;

  /// Get book metadata for a media item
  async fn get_book_metadata(
    &self,
    media_id: MediaId,
  ) -> Result<Option<crate::model::BookMetadata>>;

  /// Add an author to a book
  async fn add_book_author(
    &self,
    media_id: MediaId,
    author: &crate::model::AuthorInfo,
  ) -> Result<()>;

  /// Get all authors for a book
  async fn get_book_authors(
    &self,
    media_id: MediaId,
  ) -> Result<Vec<crate::model::AuthorInfo>>;

  /// List all distinct authors with book counts
  async fn list_all_authors(
    &self,
    pagination: &Pagination,
  ) -> Result<Vec<(String, u64)>>;

  /// List all series with book counts
  async fn list_series(&self) -> Result<Vec<(String, u64)>>;

  /// Get all books in a series, ordered by `series_index`
  async fn get_series_books(&self, series_name: &str)
  -> Result<Vec<MediaItem>>;

  /// Update reading progress for a user and book
  async fn update_reading_progress(
    &self,
    user_id: uuid::Uuid,
    media_id: MediaId,
    current_page: i32,
  ) -> Result<()>;

  /// Get reading progress for a user and book
  async fn get_reading_progress(
    &self,
    user_id: uuid::Uuid,
    media_id: MediaId,
  ) -> Result<Option<crate::model::ReadingProgress>>;

  /// Get reading list for a user filtered by status
  async fn get_reading_list(
    &self,
    user_id: uuid::Uuid,
    status: Option<crate::model::ReadingStatus>,
  ) -> Result<Vec<MediaItem>>;

  /// Search books with book-specific criteria
  async fn search_books(
    &self,
    isbn: Option<&str>,
    author: Option<&str>,
    series: Option<&str>,
    publisher: Option<&str>,
    language: Option<&str>,
    pagination: &Pagination,
  ) -> Result<Vec<MediaItem>>;

  /// Insert a media item that uses managed storage
  async fn insert_managed_media(&self, item: &MediaItem) -> Result<()>;

  /// Get or create a managed blob record (for deduplication tracking)
  async fn get_or_create_blob(
    &self,
    hash: &ContentHash,
    size: u64,
    mime_type: &str,
  ) -> Result<ManagedBlob>;

  /// Get a managed blob by its content hash
  async fn get_blob(&self, hash: &ContentHash) -> Result<Option<ManagedBlob>>;

  /// Increment the reference count for a blob
  async fn increment_blob_ref(&self, hash: &ContentHash) -> Result<()>;

  /// Decrement the reference count for a blob. Returns true if blob should be
  /// deleted.
  async fn decrement_blob_ref(&self, hash: &ContentHash) -> Result<bool>;

  /// Update the `last_verified` timestamp for a blob
  async fn update_blob_verified(&self, hash: &ContentHash) -> Result<()>;

  /// List orphaned blobs (`reference_count` = 0)
  async fn list_orphaned_blobs(&self) -> Result<Vec<ManagedBlob>>;

  /// Delete a blob record
  async fn delete_blob(&self, hash: &ContentHash) -> Result<()>;

  /// Get managed storage statistics
  async fn managed_storage_stats(&self) -> Result<ManagedStorageStats>;

  /// Register a new sync device
  async fn register_device(
    &self,
    device: &crate::sync::SyncDevice,
    token_hash: &str,
  ) -> Result<crate::sync::SyncDevice>;

  /// Get a sync device by ID
  async fn get_device(
    &self,
    id: crate::sync::DeviceId,
  ) -> Result<crate::sync::SyncDevice>;

  /// Get a sync device by its token hash
  async fn get_device_by_token(
    &self,
    token_hash: &str,
  ) -> Result<Option<crate::sync::SyncDevice>>;

  /// List all devices for a user
  async fn list_user_devices(
    &self,
    user_id: UserId,
  ) -> Result<Vec<crate::sync::SyncDevice>>;

  /// Update a sync device
  async fn update_device(&self, device: &crate::sync::SyncDevice)
  -> Result<()>;

  /// Delete a sync device
  async fn delete_device(&self, id: crate::sync::DeviceId) -> Result<()>;

  /// Update the `last_seen_at` timestamp for a device
  async fn touch_device(&self, id: crate::sync::DeviceId) -> Result<()>;

  /// Record a change in the sync log
  async fn record_sync_change(
    &self,
    change: &crate::sync::SyncLogEntry,
  ) -> Result<()>;

  /// Get changes since a cursor position
  async fn get_changes_since(
    &self,
    cursor: i64,
    limit: u64,
  ) -> Result<Vec<crate::sync::SyncLogEntry>>;

  /// Get the current sync cursor (highest sequence number)
  async fn get_current_sync_cursor(&self) -> Result<i64>;

  /// Clean up old sync log entries
  async fn cleanup_old_sync_log(&self, before: DateTime<Utc>) -> Result<u64>;

  /// Get sync state for a device and path
  async fn get_device_sync_state(
    &self,
    device_id: crate::sync::DeviceId,
    path: &str,
  ) -> Result<Option<crate::sync::DeviceSyncState>>;

  /// Insert or update device sync state
  async fn upsert_device_sync_state(
    &self,
    state: &crate::sync::DeviceSyncState,
  ) -> Result<()>;

  /// List all pending sync items for a device
  async fn list_pending_sync(
    &self,
    device_id: crate::sync::DeviceId,
  ) -> Result<Vec<crate::sync::DeviceSyncState>>;

  /// Create a new upload session
  async fn create_upload_session(
    &self,
    session: &crate::sync::UploadSession,
  ) -> Result<()>;

  /// Get an upload session by ID
  async fn get_upload_session(
    &self,
    id: Uuid,
  ) -> Result<crate::sync::UploadSession>;

  /// Update an upload session
  async fn update_upload_session(
    &self,
    session: &crate::sync::UploadSession,
  ) -> Result<()>;

  /// Record a received chunk
  async fn record_chunk(
    &self,
    upload_id: Uuid,
    chunk: &crate::sync::ChunkInfo,
  ) -> Result<()>;

  /// Get all chunks for an upload
  async fn get_upload_chunks(
    &self,
    upload_id: Uuid,
  ) -> Result<Vec<crate::sync::ChunkInfo>>;

  /// Clean up expired upload sessions
  async fn cleanup_expired_uploads(&self) -> Result<u64>;

  /// Record a sync conflict
  async fn record_conflict(
    &self,
    conflict: &crate::sync::SyncConflict,
  ) -> Result<()>;

  /// Get unresolved conflicts for a device
  async fn get_unresolved_conflicts(
    &self,
    device_id: crate::sync::DeviceId,
  ) -> Result<Vec<crate::sync::SyncConflict>>;

  /// Resolve a conflict
  async fn resolve_conflict(
    &self,
    id: Uuid,
    resolution: crate::config::ConflictResolution,
  ) -> Result<()>;

  /// Create a new share
  async fn create_share(
    &self,
    share: &crate::sharing::Share,
  ) -> Result<crate::sharing::Share>;

  /// Get a share by ID
  async fn get_share(
    &self,
    id: crate::sharing::ShareId,
  ) -> Result<crate::sharing::Share>;

  /// Get a share by its public token
  async fn get_share_by_token(
    &self,
    token: &str,
  ) -> Result<crate::sharing::Share>;

  /// List shares created by a user
  async fn list_shares_by_owner(
    &self,
    owner_id: UserId,
    pagination: &Pagination,
  ) -> Result<Vec<crate::sharing::Share>>;

  /// List shares received by a user
  async fn list_shares_for_user(
    &self,
    user_id: UserId,
    pagination: &Pagination,
  ) -> Result<Vec<crate::sharing::Share>>;

  /// List all shares for a specific target
  async fn list_shares_for_target(
    &self,
    target: &crate::sharing::ShareTarget,
  ) -> Result<Vec<crate::sharing::Share>>;

  /// Update a share
  async fn update_share(
    &self,
    share: &crate::sharing::Share,
  ) -> Result<crate::sharing::Share>;

  /// Delete a share
  async fn delete_share(&self, id: crate::sharing::ShareId) -> Result<()>;

  /// Record that a share was accessed
  async fn record_share_access(
    &self,
    id: crate::sharing::ShareId,
  ) -> Result<()>;

  /// Check share access for a user and target
  async fn check_share_access(
    &self,
    user_id: Option<UserId>,
    target: &crate::sharing::ShareTarget,
  ) -> Result<Option<crate::sharing::SharePermissions>>;

  /// Get effective permissions for a media item (considering inheritance)
  async fn get_effective_share_permissions(
    &self,
    user_id: Option<UserId>,
    media_id: MediaId,
  ) -> Result<Option<crate::sharing::SharePermissions>>;

  /// Batch delete shares
  async fn batch_delete_shares(
    &self,
    ids: &[crate::sharing::ShareId],
  ) -> Result<u64>;

  /// Clean up expired shares
  async fn cleanup_expired_shares(&self) -> Result<u64>;

  /// Record share activity
  async fn record_share_activity(
    &self,
    activity: &crate::sharing::ShareActivity,
  ) -> Result<()>;

  /// Get activity for a share
  async fn get_share_activity(
    &self,
    share_id: crate::sharing::ShareId,
    pagination: &Pagination,
  ) -> Result<Vec<crate::sharing::ShareActivity>>;

  /// Create a share notification
  async fn create_share_notification(
    &self,
    notification: &crate::sharing::ShareNotification,
  ) -> Result<()>;

  /// Get unread notifications for a user
  async fn get_unread_notifications(
    &self,
    user_id: UserId,
  ) -> Result<Vec<crate::sharing::ShareNotification>>;

  /// Mark a notification as read. Scoped to `user_id` to prevent cross-user
  /// modification. Silently no-ops if the notification belongs to a different
  /// user, which avoids leaking notification existence via error responses.
  async fn mark_notification_read(
    &self,
    id: Uuid,
    user_id: UserId,
  ) -> Result<()>;

  /// Mark all notifications as read for a user
  async fn mark_all_notifications_read(&self, user_id: UserId) -> Result<()>;

  /// Rename a media item (changes `file_name` and updates path accordingly).
  /// For external storage, this actually renames the file on disk.
  /// For managed storage, this only updates the metadata.
  /// Returns the old path for sync log recording.
  async fn rename_media(&self, id: MediaId, new_name: &str) -> Result<String>;

  /// Move a media item to a new directory.
  /// For external storage, this actually moves the file on disk.
  /// For managed storage, this only updates the path in metadata.
  /// Returns the old path for sync log recording.
  async fn move_media(
    &self,
    id: MediaId,
    new_directory: &std::path::Path,
  ) -> Result<String>;

  /// Batch move multiple media items to a new directory.
  async fn batch_move_media(
    &self,
    ids: &[MediaId],
    new_directory: &std::path::Path,
  ) -> Result<Vec<(MediaId, String)>> {
    let mut results = Vec::new();
    for id in ids {
      let old_path = self.move_media(*id, new_directory).await?;
      results.push((*id, old_path));
    }
    Ok(results)
  }

  /// Soft delete a media item (set `deleted_at` timestamp).
  async fn soft_delete_media(&self, id: MediaId) -> Result<()>;

  /// Restore a soft-deleted media item.
  async fn restore_media(&self, id: MediaId) -> Result<()>;

  /// List all soft-deleted media items.
  async fn list_trash(&self, pagination: &Pagination)
  -> Result<Vec<MediaItem>>;

  /// Permanently delete all items in trash.
  async fn empty_trash(&self) -> Result<u64>;

  /// Permanently delete items in trash older than the specified date.
  async fn purge_old_trash(&self, before: DateTime<Utc>) -> Result<u64>;

  /// Count items in trash.
  async fn count_trash(&self) -> Result<u64>;

  /// Save extracted markdown links for a media item.
  /// This replaces any existing links for the source media.
  async fn save_markdown_links(
    &self,
    media_id: MediaId,
    links: &[crate::model::MarkdownLink],
  ) -> Result<()>;

  /// Get outgoing links from a media item.
  async fn get_outgoing_links(
    &self,
    media_id: MediaId,
  ) -> Result<Vec<crate::model::MarkdownLink>>;

  /// Get backlinks (incoming links) to a media item.
  async fn get_backlinks(
    &self,
    media_id: MediaId,
  ) -> Result<Vec<crate::model::BacklinkInfo>>;

  /// Clear all links for a media item.
  async fn clear_links_for_media(&self, media_id: MediaId) -> Result<()>;

  /// Get graph data for visualization.
  ///
  /// If `center_id` is provided, returns nodes within `depth` hops of that
  /// node. If `center_id` is None, returns the entire graph (limited by
  /// internal max).
  async fn get_graph_data(
    &self,
    center_id: Option<MediaId>,
    depth: u32,
  ) -> Result<crate::model::GraphData>;

  /// Resolve unresolved links by matching `target_path` against media item
  /// paths. Returns the number of links that were resolved.
  async fn resolve_links(&self) -> Result<u64>;

  /// Update the `links_extracted_at` timestamp for a media item.
  async fn mark_links_extracted(&self, media_id: MediaId) -> Result<()>;

  /// Get count of unresolved links (links where `target_media_id` is NULL).
  async fn count_unresolved_links(&self) -> Result<u64>;

  /// Create a backup of the database to the specified path.
  ///
  /// Only supported for `SQLite` (uses VACUUM INTO). `PostgreSQL`
  /// deployments should use `pg_dump` directly; this method returns
  /// `PinakesError::InvalidOperation` for unsupported backends.
  async fn backup(&self, _dest: &std::path::Path) -> Result<()> {
    Err(crate::error::PinakesError::InvalidOperation(
      "backup not supported for this storage backend; use pg_dump for \
       PostgreSQL"
        .to_string(),
    ))
  }
}

/// Comprehensive library statistics.
#[derive(Debug, Clone, Default)]
pub struct LibraryStatistics {
  pub total_media:         u64,
  pub total_size_bytes:    u64,
  pub avg_file_size_bytes: u64,
  pub media_by_type:       Vec<(String, u64)>,
  pub storage_by_type:     Vec<(String, u64)>,
  pub newest_item:         Option<String>,
  pub oldest_item:         Option<String>,
  pub top_tags:            Vec<(String, u64)>,
  pub top_collections:     Vec<(String, u64)>,
  pub total_tags:          u64,
  pub total_collections:   u64,
  pub total_duplicates:    u64,
}

pub type DynStorageBackend = Arc<dyn StorageBackend>;