gerard2p/koaton

import * as calculate from 'etag';
import * as Stream from 'stream';
import * as fs from 'fs';

/** @ignore */
/* istanbul ignore next */
function noop () {}
/** @ignore */
const stat = function stat (path) {
    return new Promise(function (resolve, reject) {
        fs.stat(path, function (err, stats) {
            /* istanbul ignore if */
            if (err) {
                reject(err);
            }
            resolve(stats);
        });
    });
};
/**
 * Middleware for eTag generation (cached content)
 * @param {KoaContext} ctx
 * @param {KoaNext} next
 */
export default async function cached (ctx, next) {
    await next();
    const body = ctx.body;
    /* istanbul ignore if */
    if (!body || ctx.response.get('ETag') || ctx.state.nocache) return;
    const status = ctx.status / 100 | 0;
    /* istanbul ignore if */
    if (status !== 2) return;

    let etag;
    if (body instanceof Stream) {
        /* istanbul ignore if */
        if (!body.path) return;
        let stats = await stat(body.path).catch(noop);
        /* istanbul ignore if */
        if (!stats) return;
        etag = calculate(stats, configuration.static.cache.etagWeak);
    } else if ((typeof body === 'string') || Buffer.isBuffer(body)) {
        etag = calculate(body, configuration.static.cache.etagWeak);
    } else {
        etag = calculate(JSON.stringify(body), configuration.static.cache.etagWeak);
    }
    /* istanbul ignore else */
    if (etag) {
        ctx.set('ETag', etag);
    }
    if (ctx.fresh) {
        ctx.set('Cache-Control', 'public,' + ctx.response.get('Cache-Control'));
        ctx.remove('Last-Modified');
        ctx.body = null;
        ctx.status = 304;
    }
}