import loki from 'lokijs';
import indexesJson from '../../../assets/tree.json';

export interface Index {
    id: number;
    title: string;
    numOfItems: number;
    parentId: number;
}

export const INDEX_ID_ROOT = 1;
export const INDEX_ID_PUBLIC = 3;

interface IndexJson {
    id: number;
    title: string;
    num_of_items: number;
    children: IndexJson[];
}

interface LokiColEntry {
    key: number;
    index: Index;
}

const lokiDB = new loki('database');
const lokiCol: Collection<any> = lokiDB.addCollection('indexes');
let lokiColKey: number = 0;
const store = (jsonArr: IndexJson[], parentId: number) => {
    jsonArr.forEach((json: IndexJson) => {
        const entry: LokiColEntry = {
            key: ++lokiColKey,
            index: {
                id: json.id,
                title: json.title,
                numOfItems: json.num_of_items,
                parentId: parentId,
            },
        };
        lokiCol.insert(entry);
        store(json.children, json.id)
    });
}
store(indexesJson, INDEX_ID_ROOT);

class IndexUtil {

    static getUrl(id: number): string {
        return '/database/list/' + String(id);
    }

    static get(indexId: number): Index | null {
        const filter = {
            'index.id': indexId,
        }
        const res = lokiCol.findOne(filter);
        if (res === null) {
            return null;
        }
        return res.index as Index;
    }

    static getChildren(indexId: number): Index[] {
        const filter = {
            'index.parentId': indexId,
        }
        const res = lokiCol.chain().find(filter).simplesort('key').data();
        return res.map((entry: LokiColEntry) => {
            return entry.index;
        });
    }

    static countChildren(indexId: number): number {
        const filter = {
            'index.parentId': indexId,
        }
        const res = lokiCol.count(filter);
        return res;
    }

    static getParents(parentId: number): Index[] {
        let parents: Index[] = [];
        const loop = (parentId: number) => {
            if (parentId !== INDEX_ID_ROOT) {
                const parent = this.get(parentId);
                if (parent !== null) {
                    loop(parent.parentId);
                    parents.push(parent);
                }
            }
        }
        loop(parentId);
        return parents;
    }

}

export default IndexUtil;