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

const express = require('express');

const service_loader = require('./service-loader');

module.exports = class ServConServer {

    constructor(opts){
        this._port = opts.port || 80;
        this._scanInterval = opts.scanInterval || 20000;
        this._scanTask = null;
        this._running = false;
        this._loaded = {};
        this._router = null;
        this.serviceDirectory = opts.directory || path.join(process.cwd(), 'services');
        this.app = express();
        this.app.use((req, res, next) => this._dispatch(req, res, next));
        this.server = null;
    }

    start(){
        if(!this._running){
            this._scanTask = setInterval(() => this._scanServices(), this._scanInterval);
            this._scanServices();
            this.server = this.app.listen(this._port);
            this._running = true;
        }
    }

    stop(){
        if(this._running){
            clearInterval(this._scanTask);
            this._scanTask = null;
            this.server.close();
            this._running = false;
        }
    }

    _loadService(fname, service_path){
        console.log("Load Service",fname, service_path);
        service_loader.loadService(service_path, service => {
            this._loaded[fname] = service;
        });
    }

    _scanServices(){
        console.log('scan...');
        fs.readdir(this.serviceDirectory, (err, files) => {
            if(err){
                console.log('error while scanning services', err);
            }else {
                files.forEach(file => {
                    let name = file.match(/^([a-z0-9\-\_]+)\.[0-9a-z]+$/i)[1];
                    let service_path = path.join(this.serviceDirectory, file); 
                    if(this._loaded[name]){
                        fs.stat(service_path, (err, stats) => {
                            if(err){
                                console.error(err);
                            }else if(stats.mtimeMs > this._loaded[name].modMs) {
                                this._loadService(name, service_path);
                            }
                        });
                    }else {
                        this._loadService(name, service_path);
                    }
                });
            }
        });
    }

    _logRequest(req, res){
        let time = process.hrtime();
        let msg = `[${req.method.magenta}] ${req.url.magenta} "${req.header('user-agent')}"@${req.ip}`;
        res.on('finish', () => {
            let elapsed = process.hrtime(time);
            let reqTime = Math.ceil(elapsed[0] * 1000 + elapsed[1] / 1e6) + '';
            console.debug(`${msg} [${reqTime.green}] ms`);
        });
    }

    _dispatch(req, res, next){
        this._logRequest(req, res);
        let req_url = url.parse(req.url); 
        let req_url_tokens = req_url.pathname.split('/');
        let service_name = req_url_tokens[1];
        let service = this._loaded[service_name]; 
        if(service){
            let path_tokens_splice = req_url_tokens.splice(2);
            let new_path = '/';
            path_tokens_splice.forEach(t => new_path += `${t}/`);
            req.url = `${new_path}${req_url.search || ''}`;
            service.router(req, res, next);
        }else {
            res.sendStatus(404);
        }
    }

}