import * as  multer from 'multer';
import * as Storage from '@google-cloud/storage';
import { Bucket, ConfigurationObject } from '@google-cloud/storage';
import * as uuid from 'uuid/v1';
import { Request } from 'express';
const storage: (options?:ConfigurationObject)=>Storage = require('@google-cloud/storage');

export default class MulterGoogleCloudStorage implements multer.StorageEngine {

	private gcobj: Storage;
	private gcsBucket: Bucket;
	private options: ConfigurationObject & { acl?: string, bucket?: string, contentType?: ContentTypeFunction };

	getFilename(req, file, cb) {
    	cb(null,`${uuid()}_${file.originalname}`);
	}
	getDestination( req, file, cb ) {
		cb( null, '' );
	}

	public getContentType: ContentTypeFunction = (req, file) => {
		return undefined;
	}

	constructor(opts?: ConfigurationObject & { filename?: any, bucket?:string, contentType?: ContentTypeFunction }) {
		 opts = opts || {};

		this.getFilename = (opts.filename || this.getFilename);
		this.getContentType = (opts.contentType || this.getContentType);

		opts.bucket = (opts.bucket || process.env.GCS_BUCKET || null);
		opts.projectId = opts.projectId || process.env.GCLOUD_PROJECT || null;
		opts.keyFilename = opts.keyFilename || process.env.GCS_KEYFILE || null;

		if (!opts.bucket) {
			throw new Error('You have to specify bucket for Google Cloud Storage to work.');
		}

		if (!opts.projectId) {
			throw new Error('You have to specify project id for Google Cloud Storage to work.');
		}

		if (!opts.keyFilename) {
			throw new Error('You have to specify credentials key file for Google Cloud Storage to work.');
		}

		this.gcobj = storage({
			projectId: opts.projectId,
			keyFilename: opts.keyFilename
		});

		this.gcsBucket = this.gcobj.bucket(opts.bucket);

		this.options = opts;
	}

	_handleFile = (req, file, cb) => {
		this.getDestination(req, file, (err, destination) => {

			if (err) {
				return cb(err);
			}

			this.getFilename(req, file, (err, filename) => {
				if (err) {
					return cb(err);
				}
				var gcFile = this.gcsBucket.file(filename);

				const streamOpts: Storage.WriteStreamOptions = {
					predefinedAcl: this.options.acl || 'private'
				};

				const contentType = this.getContentType(req, file);

				if (contentType) {
				  streamOpts.metadata = {contentType};
				}

				file.stream.pipe(
					gcFile.createWriteStream(streamOpts))
					.on('error', (err) => cb(err))
					.on('finish', (file) => cb(null, {
							path: `https://${this.options.bucket}.storage.googleapis.com/${filename}`,
							filename: filename
						})
					);
			});

		});
	}
	_removeFile =  (req, file, cb) => {
		var gcFile = this.gcsBucket.file(file.filename);
		gcFile.delete();
	};
}

export function storageEngine(opts?: ConfigurationObject & { filename?: any, bucket?:string }){

	return new MulterGoogleCloudStorage(opts);
}

export type ContentTypeFunction = (req: Request, file: Express.Multer.File) => string | undefined;