package files

import (
	"context"
	"errors"
	"fmt"

	"github.com/google/uuid"
	"github.com/jackc/pgx/v5"
)

// Favoriten der Seitenleiste. Reihenfolge und Auf-/Zugeklappt-Zustand
// liegen serverseitig, damit sie auf jedem Gerät gleich sind.

// ── Favorites ─────────────────────────────────────────────────────────────────

func (s *Store) ListFavorites(ctx context.Context, userID uuid.UUID) ([]*Favorite, error) {
	// Nur Favoriten anzeigen, die noch erreichbar sind. Ein Lesezeichen auf
	// einen Ordner, den man nicht mehr öffnen darf – weil man die Gruppe
	// verlassen hat oder die Freigabe zurückgezogen wurde – bliebe sonst als
	// toter Eintrag in der Seitenleiste stehen und liefe beim Klick ins Leere.
	rows, err := s.db.Query(ctx,
		`WITH RECURSIVE shared_roots AS (
		   SELECT e.resource_folder_id AS id
		     FROM acl_entries e
		    WHERE e.resource_folder_id IS NOT NULL
		      AND (e.subject_user_id = $1
		           OR e.subject_group_id IN (SELECT group_id FROM group_members WHERE user_id = $1))
		   UNION
		   -- Nach unten aufspannen: Wer einen Ordner freigegeben bekommt, darf
		   -- auch alles darunter, und darf sich das ebenso merken.
		   SELECT fo.id FROM folders fo JOIN shared_roots sr ON fo.parent_id = sr.id
		 )
		 SELECT f.id, f.user_id, f.folder_id, f.position, f.is_expanded, f.created_at,
		        fo.name, fo.parent_id
		 FROM favorites f
		 JOIN folders fo ON fo.id = f.folder_id
		 WHERE f.user_id = $1
		   AND ( fo.owner_id = $1
		      OR fo.group_id IN (SELECT group_id FROM group_members WHERE user_id = $1)
		      OR fo.id IN (SELECT id FROM shared_roots) )
		 ORDER BY f.position`,
		userID,
	)
	if err != nil {
		return nil, fmt.Errorf("list favorites: %w", err)
	}
	defer rows.Close()
	favs := make([]*Favorite, 0)
	for rows.Next() {
		var fav Favorite
		if err := rows.Scan(
			&fav.ID, &fav.UserID, &fav.FolderID, &fav.Position, &fav.IsExpanded, &fav.CreatedAt,
			&fav.FolderName, &fav.FolderParentID,
		); err != nil {
			return nil, err
		}
		favs = append(favs, &fav)
	}
	return favs, rows.Err()
}

func (s *Store) AddFavorite(ctx context.Context, userID, folderID uuid.UUID) (*Favorite, error) {
	var fav Favorite
	err := s.db.QueryRow(ctx,
		`INSERT INTO favorites (user_id, folder_id, position)
		 VALUES ($1, $2, (SELECT COALESCE(MAX(position)+1, 0) FROM favorites WHERE user_id=$1))
		 ON CONFLICT (user_id, folder_id) DO NOTHING
		 RETURNING id, user_id, folder_id, position, is_expanded, created_at`,
		userID, folderID,
	).Scan(&fav.ID, &fav.UserID, &fav.FolderID, &fav.Position, &fav.IsExpanded, &fav.CreatedAt)
	if errors.Is(err, pgx.ErrNoRows) {
		return nil, ErrNameTaken // already a favorite
	}
	if err != nil {
		return nil, fmt.Errorf("add favorite: %w", err)
	}
	// Fetch folder name for response.
	var f Folder
	_ = s.db.QueryRow(ctx,
		`SELECT id, owner_id, group_id, parent_id, name, created_at FROM folders WHERE id=$1`, folderID,
	).Scan(&f.ID, &f.OwnerID, &f.GroupID, &f.ParentID, &f.Name, &f.CreatedAt)
	fav.FolderName = f.Name
	fav.FolderParentID = f.ParentID
	return &fav, nil
}

func (s *Store) RemoveFavorite(ctx context.Context, userID, folderID uuid.UUID) error {
	tag, err := s.db.Exec(ctx,
		`DELETE FROM favorites WHERE user_id=$1 AND folder_id=$2`, userID, folderID)
	if err != nil {
		return fmt.Errorf("remove favorite: %w", err)
	}
	if tag.RowsAffected() == 0 {
		return ErrNotFound
	}
	return nil
}

func (s *Store) SetFavoriteExpanded(ctx context.Context, userID, folderID uuid.UUID, expanded bool) error {
	tag, err := s.db.Exec(ctx,
		`UPDATE favorites SET is_expanded=$3 WHERE user_id=$1 AND folder_id=$2`,
		userID, folderID, expanded,
	)
	if err != nil {
		return fmt.Errorf("set favorite expanded: %w", err)
	}
	if tag.RowsAffected() == 0 {
		return ErrNotFound
	}
	return nil
}

func (s *Store) ReorderFavorites(ctx context.Context, userID uuid.UUID, folderIDs []uuid.UUID) error {
	tx, err := s.db.Begin(ctx)
	if err != nil {
		return err
	}
	defer tx.Rollback(ctx)
	for i, fid := range folderIDs {
		if _, err := tx.Exec(ctx,
			`UPDATE favorites SET position=$3 WHERE user_id=$1 AND folder_id=$2`,
			userID, fid, i,
		); err != nil {
			return fmt.Errorf("reorder favorites: %w", err)
		}
	}
	return tx.Commit(ctx)
}