package wire

import (
	"git.smesh.lol/morly/pkg/mediaproxy"
)

// ProxyWorker is the spawn target for a media proxy domain. Receives
// ProxyRequest over its spawn channel, fetches the URL, and replies with a
// ProxyResponse. Loops until the request channel closes.
func ProxyWorker(in chan ProxyRequest, out chan ProxyResponse) {
	for {
		req, ok := <-in
		if !ok {
			return
		}
		out <- proxyFetch(req)
	}
}

// proxyFetch performs one media fetch and maps the result onto the wire form.
// A free function: its scratch arena dies at return, so a long-lived worker
// does not accumulate one fetch's working set per request.
func proxyFetch(req ProxyRequest) (resp ProxyResponse) {
	resp = ProxyResponse{ReqID: req.ReqID}
	maxBytes := int64(req.MaxBytes)
	if maxBytes <= 0 {
		maxBytes = 32 * 1024 * 1024
	}
	status, upstream, body, err := mediaproxy.Fetch(string(req.URL), maxBytes)
	if err != nil {
		resp.Status = -1
		resp.Err = []byte(err.Error())
		return resp
	}
	resp.Status = int32(status)
	if status >= 200 && status < 300 {
		ct := upstream["content-type"]
		if !proxyAllowedCT(ct) {
			resp.Status = 415
			return resp
		}
		resp.ContentType = []byte(ct)
		resp.Body = body
	}
	return resp
}

// proxyAllowedCT restricts proxied responses to image/video/octet-stream.
func proxyAllowedCT(ct string) (ok bool) {
	if len(ct) >= 6 && (ct[:6] == "image/" || ct[:6] == "video/") {
		return true
	}
	return ct == "application/octet-stream" || ct == "application/octet-stream; charset=utf-8"
}