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/*
* Copyright 2018 Allan Wang
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
package com.pitchedapps.frost.injectors
import android.webkit.WebView
import androidx.annotation.VisibleForTesting
import com.pitchedapps.frost.prefs.Prefs
import com.pitchedapps.frost.utils.L
import com.pitchedapps.frost.web.FrostWebViewClient
import org.apache.commons.text.StringEscapeUtils
import kotlin.random.Random
class JsBuilder {
private val css = StringBuilder()
private val js = StringBuilder()
private var tag: String? = null
fun css(css: String): JsBuilder {
this.css.append(StringEscapeUtils.escapeEcmaScript(css))
return this
}
fun js(content: String): JsBuilder {
this.js.append(content)
return this
}
fun single(tag: String): JsBuilder {
this.tag = TagObfuscator.obfuscateTag(tag)
return this
}
fun build() = JsInjector(toString())
override fun toString(): String {
val tag = this.tag
val builder = StringBuilder().apply {
append("!function(){")
if (css.isNotBlank()) {
val cssMin = css.replace(Regex("\\s*\n\\s*"), "")
append("var a=document.createElement('style');")
append("a.innerHTML='$cssMin';")
if (tag != null) {
append("a.id='$tag';")
}
append("document.head.appendChild(a);")
}
if (js.isNotBlank()) {
append(js)
}
}
var content = builder.append("}()").toString()
if (tag != null) {
content = singleInjector(tag, content)
}
return content
}
private fun singleInjector(tag: String, content: String) = StringBuilder().apply {
append("if (!window.hasOwnProperty(\"$tag\")) {")
append("console.log(\"Registering $tag\");")
append("window.$tag = true;")
append(content)
append("}")
}.toString()
}
/**
* Contract for all injectors to allow it to interact properly with a webview
*/
interface InjectorContract {
fun inject(webView: WebView, prefs: Prefs)
/**
* Toggle the injector (usually through Prefs
* If false, will fallback to an empty action
*/
fun maybe(enable: Boolean): InjectorContract = if (enable) this else JsActions.EMPTY
}
/**
* Helper method to inject multiple functions simultaneously with a single callback
*/
fun WebView.jsInject(vararg injectors: InjectorContract, prefs: Prefs) {
injectors.asSequence().filter { it != JsActions.EMPTY }.forEach {
it.inject(this, prefs)
}
}
fun FrostWebViewClient.jsInject(vararg injectors: InjectorContract, prefs: Prefs) =
web.jsInject(*injectors, prefs = prefs)
/**
* Wrapper class to convert a function into an injector
*/
class JsInjector(val function: String) : InjectorContract {
override fun inject(webView: WebView, prefs: Prefs) =
webView.evaluateJavascript(function, null)
}
/**
* Helper object to obfuscate window tags for JS injection.
*/
@VisibleForTesting
internal object TagObfuscator {
fun obfuscateTag(tag: String): String {
val rnd = Random(tag.hashCode() + salt)
val obfuscated = buildString {
append(prefix)
append('_')
appendRandomChars(rnd, 16)
}
L.v { "TagObfuscator: Obfuscating tag '$tag' to '$obfuscated'" }
return obfuscated
}
private val salt: Long = System.currentTimeMillis()
private val prefix: String by lazy {
val rnd = Random(System.currentTimeMillis())
buildString { appendRandomChars(rnd, 8) }
}
private fun Appendable.appendRandomChars(random: Random, count: Int) {
for (i in 1..count) {
append('a' + random.nextInt(26))
}
}
}
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