const fs = require('fs');
const path = require('path');

export class NodeId {


    private _nodeId: Promise<string> | null = null;

    public get nodeId() {
        if (this._nodeId) {
            return this._nodeId
        } else {
            return this.getNodeId();
        }
    }

    async getNodeId() {
        let file = path.join(__dirname, 'nodeId.txt');

        try {
            fs.accessSync(file, fs.constants.F_OK)
            // File exists
            this._nodeId = fs.readFileSync(file, 'utf8');
            //console.log("Read: " + this.nodeId);
        } catch (err) {
            // File does not exist
            this._nodeId = Promise.resolve(this.uuidv4());
            fs.writeFileSync(file, await this._nodeId);
            //console.log("Generating nodeId: " + this.nodeId);
        }
        return this._nodeId;
    }

    uuidv4() {
        return 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'.replace(/[xy]/g, function (c) {
            const r = Math.random() * 16 | 0, v = c === 'x' ? r : (r & 0x3 | 0x8);
            return v.toString(16);
        });
    }
}