import express, {NextFunction, Request, RequestHandler, Response, Router} from 'express';
import {BadRequestError, HttpError, NotFoundHttpError, ServerError, ServiceUnavailableHttpError} from "./HttpError";
import {lib} from "nunjucks";
import Logger from "./Logger";
import WebSocketListener from "./WebSocketListener";
import ApplicationComponent from "./ApplicationComponent";
import Controller from "./Controller";
import MysqlConnectionManager from "./db/MysqlConnectionManager";
import Migration from "./db/Migration";
import {Type} from "./Utils";
import LogRequestsComponent from "./components/LogRequestsComponent";
import TemplateError = lib.TemplateError;

export default abstract class Application {
    private readonly version: string;
    private readonly controllers: Controller[] = [];
    private readonly webSocketListeners: { [p: string]: WebSocketListener } = {};
    private readonly components: ApplicationComponent<any>[] = [];

    private ready: boolean = false;

    protected constructor(version: string) {
        this.version = version;
    }

    protected abstract getMigrations(): Type<Migration>[];

    protected abstract async init(): Promise<void>;

    protected use(thing: Controller | WebSocketListener | ApplicationComponent<any>) {
        if (thing instanceof Controller) {
            this.controllers.push(thing);
        } else if (thing instanceof WebSocketListener) {
            const path = thing.path();
            this.webSocketListeners[path] = thing;
            Logger.info(`Added websocket listener on ${path}`);
        } else {
            thing.setApp(this);
            this.components.push(thing);
        }
    }

    public async start(): Promise<void> {
        Logger.info(`${this.constructor.name} v${this.version} - hi`);
        process.once('SIGINT', () => {
            this.stop().catch(console.error);
        });

        // Register migrations
        MysqlConnectionManager.registerMigrations(this.getMigrations());

        // Process command line
        if (await this.processCommandLine()) {
            await this.stop();
            return;
        }

        // Register all components and alike
        await this.init();

        // Init express
        const app = express();
        const router = express.Router({});
        app.use(router);

        // Error handler
        app.use((err: any, req: Request, res: Response, next: NextFunction) => {
            if (res.headersSent) {
                return next(err);
            }

            let errorID: string = LogRequestsComponent.logRequest(req, res, err, '500 Internal Error', err instanceof BadRequestError || err instanceof ServiceUnavailableHttpError);

            let httpError: HttpError;

            if (err instanceof HttpError) {
                httpError = err;
            } else if (err instanceof TemplateError && err.cause instanceof HttpError) {
                httpError = err.cause;
            } else {
                httpError = new ServerError('Internal server error.', err);
            }

            res.status(httpError.errorCode);
            res.format({
                html: () => {
                    res.render('errors/' + httpError.errorCode + '.njk', {
                        error_code: httpError.errorCode,
                        error_message: httpError.message,
                        error_instructions: httpError.instructions,
                        error_id: errorID,
                    });
                },
                json: () => {
                    res.json({
                        status: 'error',
                        code: httpError.errorCode,
                        message: httpError.message,
                        instructions: httpError.instructions,
                        error_id: errorID,
                    });
                },
                default: () => {
                    res.type('txt').send(`${httpError.errorCode} - ${httpError.message}\n\n${httpError.instructions}\n\nError ID: ${errorID}`);
                }
            });
        });

        // Start all components
        for (const component of this.components) {
            await component.start(app, router);
        }

        // Routes
        this.routes(router);

        this.ready = true;
    }

    protected async processCommandLine(): Promise<boolean> {
        const args = process.argv;
        for (let i = 2; i < args.length; i++) {
            switch (args[i]) {
                case '--verbose':
                    Logger.verbose();
                    break;
                case '--full-http-requests':
                    LogRequestsComponent.logFullHttpRequests();
                    break;
                case 'migration':
                    await MysqlConnectionManager.migrationCommand(args.slice(i + 1));
                    return true;
                default:
                    Logger.warn('Unrecognized argument', args[i]);
                    return true;
            }
        }
        return false;
    }

    async stop(): Promise<void> {
        Logger.info('Stopping application...');

        for (const component of this.components) {
            await component.stop();
        }

        Logger.info(`${this.constructor.name} v${this.version} - bye`);
    }

    private routes(rootRouter: Router) {
        for (const controller of this.controllers) {
            if (controller.hasGlobalHandlers()) {
                controller.setupGlobalHandlers(rootRouter);

                Logger.info(`Registered global middlewares for controller ${controller.constructor.name}`);
            }
        }

        for (const controller of this.controllers) {
            const router = express.Router();
            controller.setupRoutes(router);
            rootRouter.use(controller.getRoutesPrefix(), router);

            Logger.info(`> Registered routes for controller ${controller.constructor.name}`);
        }

        rootRouter.use((req: Request) => {
            throw new NotFoundHttpError('page', req.originalUrl);
        });
    }

    public getWebSocketListeners(): { [p: string]: WebSocketListener } {
        return this.webSocketListeners;
    }

    public isReady(): boolean {
        return this.ready;
    }

    public getVersion(): string {
        return this.version;
    }
}