graphql-sse/lib/use/koa.mjs

Zero-dependency, HTTP/1 safe, simple, GraphQL over Server-Sent Events Protocol server and client

import { createHandler as createRawHandler, } from '../handler.mjs';
/**
 * The ready-to-use handler for [Koa](https://expressjs.com).
 *
 * Errors thrown from the provided options or callbacks (or even due to
 * library misuse or potential bugs) will reject the handler or bubble to the
 * returned iterator. They are considered internal errors and you should take care
 * of them accordingly.
 *
 * For production environments, its recommended not to transmit the exact internal
 * error details to the client, but instead report to an error logging tool or simply
 * the console.
 *
 * ```js
 * import Koa from 'koa'; // yarn add koa
 * import mount from 'koa-mount'; // yarn add koa-mount
 * import { createHandler } from 'graphql-sse/lib/use/koa';
 * import { schema } from './my-graphql/index.mjs';
 *
 * const app = new Koa();
 * app.use(
 *   mount('/graphql/stream', async (ctx, next) => {
 *     try {
 *       await handler(ctx, next);
 *     } catch (err) {
 *       console.error(err);
 *       ctx.response.status = 500;
 *       ctx.response.message = 'Internal Server Error';
 *     }
 *   }),
 * );
 *
 * app.listen({ port: 4000 });
 * console.log('Listening to port 4000');
 * ```
 *
 * @category Server/koa
 */
export function createHandler(options) {
    const handler = createRawHandler(options);
    return async function requestListener(ctx) {
        const [body, init] = await handler({
            url: ctx.url,
            method: ctx.method,
            headers: {
                get(key) {
                    const header = ctx.headers[key];
                    return Array.isArray(header) ? header.join('\n') : header;
                },
            },
            body: () => {
                // in case koa has a body parser
                const body = ctx.request.body ||
                    ctx.req.body;
                if (body) {
                    return body;
                }
                return new Promise((resolve) => {
                    let body = '';
                    ctx.req.on('data', (chunk) => (body += chunk));
                    ctx.req.on('end', () => resolve(body));
                });
            },
            raw: ctx.req,
            context: ctx,
        });
        ctx.response.status = init.status;
        ctx.response.message = init.statusText;
        if (init.headers) {
            for (const [name, value] of Object.entries(init.headers)) {
                ctx.response.set(name, value);
            }
        }
        if (!body || typeof body === 'string') {
            ctx.body = body;
            return;
        }
        ctx.res.once('close', body.return);
        for await (const value of body) {
            const closed = await new Promise((resolve, reject) => {
                if (!ctx.res.writable) {
                    // response's close event might be late
                    resolve(true);
                }
                else {
                    ctx.res.write(value, (err) => (err ? reject(err) : resolve(false)));
                }
            });
            if (closed) {
                break;
            }
        }
        ctx.res.off('close', body.return);
        return new Promise((resolve) => ctx.res.end(resolve));
    };
}