/
preload.go
67 lines (58 loc) · 1.97 KB
/
preload.go
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// Copyright 2019 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package htmltask
import (
"github.com/google/webpackager/processor/htmlproc/htmldoc"
"github.com/google/webpackager/resource/httplink"
"github.com/google/webpackager/resource/preload"
"golang.org/x/net/html"
"golang.org/x/net/html/atom"
)
// ExtractPreloadTags detects <link rel="preload"> in the <head> element and
// adds them to the Preloads field.
func ExtractPreloadTags() HTMLTask {
return &extractPreloadTags{}
}
type extractPreloadTags struct{}
func (*extractPreloadTags) Run(resp *htmldoc.HTMLResponse) error {
return htmldoc.Traverse(resp.Doc.Root, func(n *html.Node) error {
if n.Type != html.ElementNode || n.DataAtom != atom.Link {
return nil
}
href := resolveURLAttr(htmldoc.FindAttr(n, "href"), resp.Doc)
if href == nil {
return nil
}
link := httplink.NewLink(href, "")
if a := htmldoc.FindAttr(n, "rel"); a != nil {
link.Params.Set(httplink.ParamRel, a.Val)
}
if a := htmldoc.FindAttr(n, "as"); a != nil {
link.Params.Set(httplink.ParamAs, a.Val)
}
if a := htmldoc.FindAttr(n, "crossorigin"); a != nil {
link.Params.Set(httplink.ParamCrossOrigin, a.Val)
}
if a := htmldoc.FindAttr(n, "media"); a != nil {
link.Params.Set(httplink.ParamMedia, a.Val)
}
if a := htmldoc.FindAttr(n, "type"); a != nil {
link.Params.Set(httplink.ParamType, a.Val)
}
if link.IsPreload() {
resp.AddPreload(preload.NewPreloadForLink(link))
}
return nil
})
}