import nunjucks, {Environment} from "nunjucks";
import config from "config";
import {Express, NextFunction, Request, Response, Router} from "express";
import ApplicationComponent from "../ApplicationComponent";
import Controller from "../Controller";
import * as querystring from "querystring";
import * as util from "util";
import * as path from "path";
import * as fs from "fs";
import Logger from "../Logger";
import Middleware from "../Middleware";

export default class NunjucksComponent extends ApplicationComponent {
    private readonly viewsPath: string[];
    private env?: Environment;

    public constructor(viewsPath: string[] = ['views']) {
        super();
        this.viewsPath = viewsPath;
    }

    public async start(app: Express): Promise<void> {
        let coreVersion = 'unknown';
        const file = fs.existsSync(path.join(__dirname, '../../package.json')) ?
            path.join(__dirname, '../../package.json') :
            path.join(__dirname, '../package.json');

        try {
            coreVersion = JSON.parse(fs.readFileSync(file).toString()).version;
        } catch (e) {
            Logger.warn('Couldn\'t determine coreVersion.', e);
        }

        this.env = new nunjucks.Environment([
            ...this.viewsPath.map(path => new nunjucks.FileSystemLoader(path)),
            new nunjucks.FileSystemLoader(path.join(__dirname, '../../../views')),
            new nunjucks.FileSystemLoader(path.join(__dirname, '../views')),
        ], {
            autoescape: true,
            noCache: !config.get('view.cache'),
            throwOnUndefined: true,
        })
            .addGlobal('route', Controller.route)
            .addGlobal('app_version', this.getApp().getVersion())
            .addGlobal('core_version', coreVersion)
            .addGlobal('querystring', querystring)
            .addGlobal('app', config.get('app'))

            .addFilter('dump', (val) => {
                return util.inspect(val);
            })
            .addFilter('hex', (v: number) => {
                return v.toString(16);
            });
        this.env.express(app);
        app.set('view engine', 'njk');
    }

    public async init(_router: Router): Promise<void> {
        this.use(NunjucksMiddleware);
    }

    public getEnv(): Environment | undefined {
        return this.env;
    }
}

export class NunjucksMiddleware extends Middleware {
    private env?: Environment;

    protected async handle(req: Request, res: Response, next: NextFunction): Promise<void> {
        this.env = this.app.as(NunjucksComponent).getEnv();
        res.locals.url = req.url;
        res.locals.params = req.params;
        res.locals.query = req.query;
        res.locals.body = req.body;

        next();
    }

    public getEnvironment(): Environment {
        if (!this.env) throw new Error('Environment not initialized.');
        return this.env;
    }
}