import {createLogger} from "@gongt/ts-stl-library/debug/create-logger";
import {LOG_LEVEL} from "@gongt/ts-stl-library/debug/levels";
import {Readable} from "stream";
import {RequestContext} from "./base/context";
import {ExpressHandler} from "./base/handler";
import {ResponseInterface} from "./base/response-wrapper";

export type AvailableResponseType = string|Buffer|Readable;

export class DownloadHandler<ReqType> extends ExpressHandler<ReqType, AvailableResponseType, DownloadRequestContext<ReqType>> {
	protected mimeType: string = 'application/octet-stream';
	
	protected instanceContext(req, res) {
		res.header('Content-Type', this.mimeType);
		return new DownloadRequestContext<ReqType>(req, res);
	}
	
	public setMimeType(mime: string) {
		this.mimeType = mime;
	}
}

export class DownloadRequestContext<ReqType> extends RequestContext<ReqType, AvailableResponseType> {
	protected createResponseWrapper(): DownloadWrapper {
		return new DownloadWrapper(this.res);
	}
}

const debugSill = createLogger(LOG_LEVEL.SILLY, 'response');

export class DownloadWrapper extends ResponseInterface<AvailableResponseType> {
	protected responseContent: AvailableResponseType;
	
	protected asyncResolve(ret: AvailableResponseType): void {
		this.responseContent = ret;
	}
	
	protected _send() {
		const ret = this.responseContent;
		if (ret instanceof Readable) {
			debugSill('      with a stream');
			ret.pipe(this.response);
		} else if (ret instanceof Buffer || typeof ret === 'string') {
			debugSill('      with a buffer | string');
			this.response.send(ret);
		} else {
			debugSill('      empty, invalid');
			this.fatalError(new Error('empty response, or response type not known.'));
		}
	}
}