import { Pool } from 'pg';

export interface CategoryNode {
    id: number;
    name: string;
    path: string;
}

export class CategoryRepository {
    // Inject the database connection pool
    constructor(private db: Pool) { }

    /**
     * Finds all descendants of a given path (including the path itself).
     * Uses the ltree operator <@ (is-descendant-of).
     */
    async findAllDescendants(parentPath: string): Promise<CategoryNode[]> {
        const query = `
      SELECT id, name, path 
      FROM categories 
      WHERE path <@ $1::ltree
      ORDER BY path ASC;
    `;
        const result = await this.db.query(query, [parentPath]);
        return result.rows;
    }

    /**
     * Finds only the direct children of a given path.
     * Uses lquery pattern matching (parent.*) and matches the exact next depth level.
     */
    async findDirectChildren(parentPath: string): Promise<CategoryNode[]> {
        const query = `
      SELECT id, name, path 
      FROM categories 
      WHERE path ~ $1::lquery 
        AND nlevel(path) = nlevel($2::ltree) + 1;
    `;
        const values = [`${parentPath}.*`, parentPath];
        const result = await this.db.query(query, values);
        return result.rows;
    }

    /**
     * Finds all ancestors of a path (useful for breadcrumbs).
     * Uses the ltree operator @> (is-ancestor-of).
     */
    async findAncestors(childPath: string): Promise<CategoryNode[]> {
        const query = `
      SELECT id, name, path 
      FROM categories 
      WHERE path @> $1::ltree 
      ORDER BY nlevel(path) ASC;
    `;
        const result = await this.db.query(query, [childPath]);
        return result.rows;
    }
}