nginx_lua_download_proxy.conf

    location /_/ {
        set $location_prefix '/_/';
        set $target_uri '';
        set $target_host '';
        set $target_url '';

        access_by_lua_block {
            local target_uri = ngx.var.request_uri:sub(ngx.var.location_prefix:len() + 1)

            if (not target_uri:lower():match("^https?://.+")) then
                ngx.header['Content-Type'] = 'text/html'
                ngx.say('Invalid URL: ' .. target_uri)
                ngx.exit(ngx.HTTP_BAD_REQUEST)
            end

            local host, url = target_uri:match("^(.....?://[^/]+)(.*)$")
            if (url == '') then
                url = '/'
            end

            ngx.var.target_host = host
            ngx.var.target_url = url
            ngx.var.target_uri = host .. url
        }

        proxy_ssl_server_name on;
        proxy_pass $target_uri;
        proxy_connect_timeout 5s;

        header_filter_by_lua_block {
            local r = ngx.header['Location']
            if (r and r ~= '') then
                if (not r:lower():match("^https?://.+")) then
                    if (r:match("^/")) then
                        r = ngx.var.target_host .. r
                    else
                        local tu = ngx.var.target_url
                        if (not tu:match("/$")) then
                            tu = tu:sub(1, tu:find("/[^/]*$"))
                        end
                        r = ngx.var.target_host .. tu .. r
                    end
                end
                r = ngx.var.scheme .. '://' .. ngx.var.host .. ngx.var.location_prefix .. r
                ngx.header['Location'] = r
            end
        }
    }