import config from "config";
import nunjucks, {Environment} from "nunjucks";

import ViewEngine from "./ViewEngine.js";

export default class NunjucksViewEngine extends ViewEngine {
    private readonly environment: Environment;

    public constructor(targetDir: string, ...additionalViewPaths: string[]) {
        super(targetDir, 'views', 'njk', false, ...additionalViewPaths);

        const opts = {
            autoescape: true,
            noCache: !config.get('view.cache'),
            throwOnUndefined: true,
        };
        this.environment = new nunjucks.Environment([
            ...this.assetPaths.map(path => new nunjucks.FileSystemLoader(path, opts)),
        ], opts);
    }

    public async preCompile(): Promise<void> {
        // Nunjucks doesn't need preCompilation or compilation
    }

    public async render(file: string, locals: Record<string, unknown>): Promise<string> {
        return await new Promise<string>((resolve, reject) => {
            this.environment.render(file, locals, (err, res) => {
                if (err) return reject(err);
                else if (res === null) reject('Null response from nunjucks environment.render()');
                else return resolve(res);
            });
        });
    }
}