import fs from 'fs/promises';
import path from 'path';

export async function findMatches(query, cacheDir) {
    if (!query || !query.trim()) return [];
    const terms = query.toLowerCase().split(/\s+/).filter(t => t);

    // Load category tree
    const treePath = path.join(cacheDir, 'category_tree.json');
    let tree = [];
    try {
        const treeData = await fs.readFile(treePath, 'utf-8');
        tree = JSON.parse(treeData);
    } catch (e) {
        console.error("Failed to load category tree for search", e);
        return [];
    }

    const matchingCategoryIds = new Set();

    // Helper to check text match
    const isMatch = (text) => {
        if (!text) return false;
        const lower = text.toLowerCase();
        return terms.every(t => lower.includes(t));
    };

    // Flatten tree to linear list for easier iteration
    const queue = [...tree];
    const nodes = [];
    while (queue.length > 0) {
        const node = queue.shift();
        nodes.push(node);
        if (node.children) {
            queue.push(...node.children);
        }
    }

    // Process in chunks to avoid too many open files
    const CHUNK_SIZE = 50;
    for (let i = 0; i < nodes.length; i += CHUNK_SIZE) {
        const chunk = nodes.slice(i, i + CHUNK_SIZE);
        await Promise.all(chunk.map(async (node) => {
            let nodeMatches = false;

            // Check category name
            if (isMatch(node.cName)) {
                nodeMatches = true;
            } else {
                // Check products
                try {
                    const prodPath = path.join(cacheDir, 'products', `category_${node.kKategorie}.json`);
                    // Check if file exists before reading to avoid throwing too many errors
                    // Actually readFile throws ENOENT which is fine
                    const prodData = await fs.readFile(prodPath, 'utf-8');
                    const products = JSON.parse(prodData);

                    if (products.some(p => isMatch(p.cName))) {
                        nodeMatches = true;
                    }
                } catch (e) {
                    // Ignore missing files
                }
            }

            if (nodeMatches) {
                matchingCategoryIds.add(node.kKategorie);
            }
        }));

        if (matchingCategoryIds.size >= 20) {
            break;
        }
    }

    return Array.from(matchingCategoryIds);
}