package catalog

import (
	"context"
	"fmt"
	"slices"
	"time"

	"github.com/jackc/pgx/v5"
	"github.com/jackc/pgx/v5/pgxpool"

	"github.com/Silo-Server/silo-server/internal/models"
)

// LibraryItemRepository provides CRUD operations for the media_item_libraries
// junction table.
type LibraryItemRepository struct {
	pool *pgxpool.Pool
}

// NewLibraryItemRepository creates a new LibraryItemRepository backed by the
// given pool.
func NewLibraryItemRepository(pool *pgxpool.Pool) *LibraryItemRepository {
	return &LibraryItemRepository{pool: pool}
}

// libraryItemColumns is the list of columns returned by all SELECT queries on
// media_item_libraries.
const libraryItemColumns = `content_id, media_folder_id, first_seen_at`

// scanLibraryItem scans a single row into a *models.MediaItemLibrary.
func scanLibraryItem(row pgx.Row) (*models.MediaItemLibrary, error) {
	var lib models.MediaItemLibrary
	err := row.Scan(
		&lib.ContentID,
		&lib.MediaFolderID,
		&lib.FirstSeenAt,
	)
	if err != nil {
		return nil, fmt.Errorf("scanning media item library: %w", err)
	}
	return &lib, nil
}

// scanLibraryItems scans multiple rows into a []*models.MediaItemLibrary slice.
func scanLibraryItems(rows pgx.Rows) ([]*models.MediaItemLibrary, error) {
	var items []*models.MediaItemLibrary
	for rows.Next() {
		var lib models.MediaItemLibrary
		err := rows.Scan(
			&lib.ContentID,
			&lib.MediaFolderID,
			&lib.FirstSeenAt,
		)
		if err != nil {
			return nil, fmt.Errorf("scanning media item library row: %w", err)
		}
		items = append(items, &lib)
	}
	if err := rows.Err(); err != nil {
		return nil, fmt.Errorf("iterating media item library rows: %w", err)
	}
	return items, nil
}

// Upsert inserts a junction record linking a media item to a media folder.
// If the record already exists (same content_id and media_folder_id), the
// operation is a no-op via ON CONFLICT DO NOTHING.
func (r *LibraryItemRepository) Upsert(ctx context.Context, contentID string, folderID int, firstSeenAt time.Time) error {
	query := `
		INSERT INTO media_item_libraries (content_id, media_folder_id, first_seen_at)
		VALUES ($1, $2, $3)
		ON CONFLICT (content_id, media_folder_id) DO NOTHING`

	_, err := r.pool.Exec(ctx, query, contentID, folderID, firstSeenAt)
	if err != nil {
		return fmt.Errorf("upserting media item library: %w", err)
	}

	return nil
}

// GetByItem returns all library junction records for a given content ID.
func (r *LibraryItemRepository) GetByItem(ctx context.Context, contentID string) ([]*models.MediaItemLibrary, error) {
	query := `SELECT ` + libraryItemColumns + `
		FROM media_item_libraries
		WHERE content_id = $1
		ORDER BY media_folder_id ASC`

	rows, err := r.pool.Query(ctx, query, contentID)
	if err != nil {
		return nil, fmt.Errorf("getting library items by content: %w", err)
	}
	defer rows.Close()

	return scanLibraryItems(rows)
}

// GetByFolder returns all library junction records for a given media folder ID.
func (r *LibraryItemRepository) GetByFolder(ctx context.Context, folderID int) ([]*models.MediaItemLibrary, error) {
	query := `SELECT ` + libraryItemColumns + `
		FROM media_item_libraries
		WHERE media_folder_id = $1
		ORDER BY first_seen_at DESC`

	rows, err := r.pool.Query(ctx, query, folderID)
	if err != nil {
		return nil, fmt.Errorf("getting library items by folder: %w", err)
	}
	defer rows.Close()

	return scanLibraryItems(rows)
}

// GetItemsInFolder returns a membership map for the provided content IDs within
// a single library folder.
func (r *LibraryItemRepository) GetItemsInFolder(ctx context.Context, contentIDs []string, folderID int) (map[string]bool, error) {
	result := make(map[string]bool, len(contentIDs))
	if len(contentIDs) == 0 {
		return result, nil
	}

	rows, err := r.pool.Query(ctx,
		`SELECT req.content_id
		FROM unnest($2::text[]) AS req(content_id)
		WHERE EXISTS (
			SELECT 1
			FROM media_item_libraries mil
			WHERE mil.media_folder_id = $1
			  AND mil.content_id = req.content_id
		)
		OR EXISTS (
			SELECT 1
			FROM episode_libraries el
			WHERE el.media_folder_id = $1
			  AND el.episode_id = req.content_id
		)`,
		folderID, contentIDs,
	)
	if err != nil {
		return nil, fmt.Errorf("getting folder membership for items: %w", err)
	}
	defer rows.Close()

	for rows.Next() {
		var contentID string
		if err := rows.Scan(&contentID); err != nil {
			return nil, fmt.Errorf("scanning folder membership row: %w", err)
		}
		result[contentID] = true
	}
	if err := rows.Err(); err != nil {
		return nil, fmt.Errorf("iterating folder membership rows: %w", err)
	}

	return result, nil
}

// GetItemsInFolders returns membership for the provided content IDs across
// any of the supplied folders. Used by the user-collection sync service to
// constrain imports to a chosen subset of libraries in one query rather than
// looping GetItemsInFolder per library.
func (r *LibraryItemRepository) GetItemsInFolders(ctx context.Context, contentIDs []string, folderIDs []int) (map[string]bool, error) {
	result := make(map[string]bool, len(contentIDs))
	if len(contentIDs) == 0 || len(folderIDs) == 0 {
		return result, nil
	}

	rows, err := r.pool.Query(ctx,
		`SELECT req.content_id
		FROM unnest($2::text[]) AS req(content_id)
		WHERE EXISTS (
			SELECT 1
			FROM media_item_libraries mil
			WHERE mil.media_folder_id = ANY($1)
			  AND mil.content_id = req.content_id
		)
		OR EXISTS (
			SELECT 1
			FROM episode_libraries el
			WHERE el.media_folder_id = ANY($1)
			  AND el.episode_id = req.content_id
		)`,
		folderIDs, contentIDs,
	)
	if err != nil {
		return nil, fmt.Errorf("getting multi-folder membership for items: %w", err)
	}
	defer rows.Close()

	for rows.Next() {
		var contentID string
		if err := rows.Scan(&contentID); err != nil {
			return nil, fmt.Errorf("scanning multi-folder membership row: %w", err)
		}
		result[contentID] = true
	}
	if err := rows.Err(); err != nil {
		return nil, fmt.Errorf("iterating multi-folder membership rows: %w", err)
	}
	return result, nil
}

func (r *LibraryItemRepository) GetFolderIDsForItem(ctx context.Context, contentID string) ([]int, error) {
	rows, err := r.pool.Query(ctx, `
		SELECT media_folder_id
		FROM media_item_libraries
		WHERE content_id = $1
		ORDER BY media_folder_id ASC
	`, contentID)
	if err != nil {
		return nil, fmt.Errorf("getting folder IDs for item: %w", err)
	}
	defer rows.Close()

	var ids []int
	for rows.Next() {
		var id int
		if err := rows.Scan(&id); err != nil {
			return nil, fmt.Errorf("scanning folder ID for item: %w", err)
		}
		ids = append(ids, id)
	}
	if err := rows.Err(); err != nil {
		return nil, fmt.Errorf("iterating folder IDs for item: %w", err)
	}
	return ids, nil
}

func (r *LibraryItemRepository) CountFoldersForItem(ctx context.Context, contentID string) (int, error) {
	var count int
	if err := r.pool.QueryRow(ctx, `
		SELECT COUNT(*)
		FROM media_item_libraries
		WHERE content_id = $1
	`, contentID).Scan(&count); err != nil {
		return 0, fmt.Errorf("counting folders for item: %w", err)
	}
	return count, nil
}

func (r *LibraryItemRepository) GetDistinctMetadataLanguagesForItem(ctx context.Context, contentID string) ([]string, error) {
	rows, err := r.pool.Query(ctx, `
		SELECT DISTINCT COALESCE(NULLIF(mf.metadata_language, ''), 'en') AS language
		FROM media_item_libraries mil
		JOIN media_folders mf ON mf.id = mil.media_folder_id
		WHERE mil.content_id = $1
		ORDER BY language ASC
	`, contentID)
	if err != nil {
		return nil, fmt.Errorf("getting metadata languages for item: %w", err)
	}
	defer rows.Close()

	var languages []string
	for rows.Next() {
		var language string
		if err := rows.Scan(&language); err != nil {
			return nil, fmt.Errorf("scanning metadata language for item: %w", err)
		}
		languages = append(languages, language)
	}
	if err := rows.Err(); err != nil {
		return nil, fmt.Errorf("iterating metadata languages for item: %w", err)
	}
	return slices.Compact(languages), nil
}

// Delete removes a junction record linking a media item to a media folder.
func (r *LibraryItemRepository) Delete(ctx context.Context, contentID string, folderID int) error {
	_, err := r.pool.Exec(ctx,
		"DELETE FROM media_item_libraries WHERE content_id = $1 AND media_folder_id = $2",
		contentID, folderID,
	)
	if err != nil {
		return fmt.Errorf("deleting media item library: %w", err)
	}

	return nil
}

// ReconcileFolderMembership removes library memberships for content that no
// longer has any non-missing files in the given folder. It also deletes orphaned
// media items once they no longer belong to any library. Returns removed
// membership count, deleted item count, orphaned S3 image dirs, and any error.
func (r *LibraryItemRepository) ReconcileFolderMembership(ctx context.Context, folderID int) (int, int, []string, error) {
	tx, err := r.pool.Begin(ctx)
	if err != nil {
		return 0, 0, nil, fmt.Errorf("beginning membership reconciliation transaction: %w", err)
	}
	defer func() { _ = tx.Rollback(ctx) }()

	rows, err := tx.Query(ctx, `
		DELETE FROM media_item_libraries mil
		WHERE mil.media_folder_id = $1
		  AND NOT EXISTS (
			SELECT 1
			FROM media_files mf
			WHERE mf.media_folder_id = mil.media_folder_id
			  AND mf.content_id = mil.content_id
			  AND mf.missing_since IS NULL
		  )
		RETURNING mil.content_id
	`, folderID)
	if err != nil {
		return 0, 0, nil, fmt.Errorf("deleting stale folder memberships: %w", err)
	}
	defer rows.Close()

	removedContentIDs := make([]string, 0)
	for rows.Next() {
		var contentID string
		if err := rows.Scan(&contentID); err != nil {
			return 0, 0, nil, fmt.Errorf("scanning removed folder membership: %w", err)
		}
		removedContentIDs = append(removedContentIDs, contentID)
	}
	if err := rows.Err(); err != nil {
		return 0, 0, nil, fmt.Errorf("iterating removed folder memberships: %w", err)
	}
	rows.Close()

	deletedItems := 0
	var orphanedImageDirs []string
	if len(removedContentIDs) > 0 {
		// Find items that will become orphaned (no remaining library memberships).
		orphanIDs, err := collectOrphanIDs(ctx, tx, removedContentIDs)
		if err != nil {
			return 0, 0, nil, err
		}

		// Collect image paths before deletion.
		if len(orphanIDs) > 0 {
			orphanedImageDirs, err = collectImageDirs(ctx, tx, orphanIDs)
			if err != nil {
				return 0, 0, nil, err
			}
		}

		tag, err := tx.Exec(ctx, `
			DELETE FROM media_items mi
			WHERE mi.content_id = ANY($1)
			  AND NOT EXISTS (
				SELECT 1
				FROM media_item_libraries mil
				WHERE mil.content_id = mi.content_id
			  )
		`, removedContentIDs)
		if err != nil {
			return 0, 0, nil, fmt.Errorf("deleting orphaned media items after folder reconciliation: %w", err)
		}
		deletedItems = int(tag.RowsAffected())
	}

	if err := tx.Commit(ctx); err != nil {
		return 0, 0, nil, fmt.Errorf("committing membership reconciliation transaction: %w", err)
	}

	return len(removedContentIDs), deletedItems, orphanedImageDirs, nil
}