92 lines
2.7 KiB
Go
92 lines
2.7 KiB
Go
package rewriters
|
|
|
|
import (
|
|
_ "embed"
|
|
"fmt"
|
|
"sort"
|
|
"strings"
|
|
|
|
"golang.org/x/net/html"
|
|
"golang.org/x/net/html/atom"
|
|
)
|
|
|
|
// ScriptInjectorRewriter implements HTMLTokenRewriter
|
|
// ScriptInjectorRewriter is a struct that injects JS into the page
|
|
// It uses an HTML tokenizer to process HTML content and injects JS at a specified location
|
|
type ScriptInjectorRewriter struct {
|
|
execTime ScriptExecTime
|
|
script string
|
|
}
|
|
|
|
type ScriptExecTime int
|
|
|
|
const (
|
|
BeforeDOMContentLoaded ScriptExecTime = iota
|
|
AfterDOMContentLoaded
|
|
AfterDOMIdle
|
|
)
|
|
|
|
func (r *ScriptInjectorRewriter) ShouldModify(token *html.Token) bool {
|
|
// modify if token == <head>
|
|
return token.DataAtom == atom.Head && token.Type == html.StartTagToken
|
|
}
|
|
|
|
//go:embed after_dom_idle_script_injector.js
|
|
var afterDomIdleScriptInjector string
|
|
|
|
func (r *ScriptInjectorRewriter) ModifyToken(token *html.Token) (string, string) {
|
|
switch {
|
|
case r.execTime == BeforeDOMContentLoaded:
|
|
return "", fmt.Sprintf("\n<script>\n%s\n</script>\n", r.script)
|
|
|
|
case r.execTime == AfterDOMContentLoaded:
|
|
return "", fmt.Sprintf("\n<script>\ndocument.addEventListener('DOMContentLoaded', () => { %s });\n</script>", r.script)
|
|
|
|
case r.execTime == AfterDOMIdle:
|
|
s := strings.Replace(afterDomIdleScriptInjector, `'{{AFTER_DOM_IDLE_SCRIPT}}'`, r.script, 1)
|
|
return "", fmt.Sprintf("\n<script>\n%s\n</script>\n", s)
|
|
|
|
default:
|
|
return "", ""
|
|
}
|
|
}
|
|
|
|
// applies parameters by string replacement of the template script
|
|
func (r *ScriptInjectorRewriter) applyParams(params map[string]string) {
|
|
// Sort the keys by length in descending order
|
|
keys := make([]string, 0, len(params))
|
|
for key := range params {
|
|
keys = append(keys, key)
|
|
}
|
|
sort.Slice(keys, func(i, j int) bool {
|
|
return len(keys[i]) > len(keys[j])
|
|
})
|
|
|
|
for _, key := range keys {
|
|
r.script = strings.ReplaceAll(r.script, key, params[key])
|
|
}
|
|
}
|
|
|
|
// NewScriptInjectorRewriter implements a HtmlTokenRewriter
|
|
// and injects JS into the page for execution at a particular time
|
|
func NewScriptInjectorRewriter(script string, execTime ScriptExecTime) *ScriptInjectorRewriter {
|
|
return &ScriptInjectorRewriter{
|
|
execTime: execTime,
|
|
script: script,
|
|
}
|
|
}
|
|
|
|
// NewScriptInjectorRewriterWith implements a HtmlTokenRewriter
|
|
// and injects JS into the page for execution at a particular time
|
|
// accepting arguments into the script, which will be added via a string replace
|
|
// the params map represents the key-value pair of the params.
|
|
// the key will be string replaced with the value
|
|
func NewScriptInjectorRewriterWithParams(script string, execTime ScriptExecTime, params map[string]string) *ScriptInjectorRewriter {
|
|
rr := &ScriptInjectorRewriter{
|
|
execTime: execTime,
|
|
script: script,
|
|
}
|
|
rr.applyParams(params)
|
|
return rr
|
|
}
|