sourceafButter::GzipMiddleware.fan

** (Middleware) - Automatically un-gzips HTTP response content.
** 
** Adds 'gzip' as an accepted encoding in the HTTP request header. 
** Should the response then be gzip encoded, the 'body' of the response is replaced with a decoded version. 
class GzipMiddleware : ButterMiddleware {
    
    ** Set to 'false' to disable this middleware instance. 
    Bool enabled    := true

    private static const Version webVer := Pod.find("web").version

    @NoDoc
    override ButterResponse sendRequest(Butter butter, ButterRequest req) {
        if (!enabled)
            return butter.sendRequest(req)
        
        encs := req.headers.acceptEncoding ?: QualityValues()
        if (!encs.accepts("gzip"))
            req.headers.acceptEncoding = encs.set("gzip", 1.0f)
        
        res := butter.sendRequest(req)

        res.body.buf = deGzipResponse(res)

        return res
    }
    
    internal static Buf? deGzipResponse(ButterResponse res) {
        // because v1.0.67 auto de-gzips the response, we don't have to
        if (res.headers.contentEncoding?.equalsIgnoreCase("gzip") ?: false)
            // we may still have have to un-gzip the response if web::WebUtil wasn't used to decode the stream
            // e.g. if a afBounce::BedTerminator was used.  
            // reduce the number of false positives by checking for a magic number first: http://en.wikipedia.org/wiki/Gzip
            if (res.body.buf != null && res.body.buf.size >= 10 && res.body.buf.get(0) == 0x1f && res.body.buf.get(1) == 0x8b)
                try return Zip.gzipInStream(res.body.buf.seek(0).in).readAllBuf
                catch (Err err) { /* pfft - so it wasn't a gzip, so what!? */ }
        
        // no change
        return res.body.buf
    }
}