package middleware

import (
	"net/http"

	"git.codelab.vc/pkg/httpx/internal/requestid"
)

// RequestID returns a middleware that propagates the request ID from the
// request context to the outgoing X-Request-Id header. This pairs with
// the server.RequestID middleware: the server stores the ID in the context,
// and the client middleware forwards it to downstream services.
func RequestID() Middleware {
	return func(next http.RoundTripper) http.RoundTripper {
		return RoundTripperFunc(func(req *http.Request) (*http.Response, error) {
			if id := requestid.FromContext(req.Context()); id != "" {
				req = req.Clone(req.Context())
				req.Header.Set("X-Request-Id", id)
			}
			return next.RoundTrip(req)
		})
	}
}