[core] Encode html entities for forward message; fix #2241

mirai-core-utils/src/commonMain/kotlin/HtmlEntity.kt

@@ -31,6 +31,23 @@ public fun String.decodeHtmlEscape(): String = replace(STR_TO_CHAR_PATTERN) { ma
     match.value
 }
 
+public fun String.encodeHtmlEscape(): String = buildString(length) {
+    this@encodeHtmlEscape.forEach { c ->
+        if (needDoHtmlEscape(c)) {
+            append("&#").append(c.code).append(';')
+        } else {
+            append(c)
+        }
+    }
+}
+
+private fun needDoHtmlEscape(c: Char): Boolean {
+    if (c.code < 32) return true // Ascii control codes
+
+    if (c in "#@!~$%^&*()<>/\\\"'") return true
+    return false
+}
+
 
 private val STR_TO_CHAR_MAPPINGS: Map<String, String> by lazy {
 //<editor-fold defaultstate="collapsed" desc="Generated Code">

mirai-core-utils/src/commonTest/kotlin/net/mamoe/mirai/utils/HtmlEscapeTest.kt

@@ -22,4 +22,16 @@ internal class HtmlEscapeTest {
             ALL.decodeHtmlEscape()
         )
     }
+
+    @Test
+    fun testEncode() {
+        val str = buildString {
+            for (i in 1 until 2048) {
+                append(i.toChar())
+            }
+        }
+        val escaped = str.encodeHtmlEscape()
+        // println(escaped)
+        assertEquals(escaped.decodeHtmlEscape(), str)
+    }
 }

mirai-core/src/commonMain/kotlin/message/data/LongMessageInternal.kt

@@ -21,6 +21,7 @@ import net.mamoe.mirai.internal.network.protocol.data.proto.MsgTransmit
 import net.mamoe.mirai.message.MessageReceipt
 import net.mamoe.mirai.message.data.*
 import net.mamoe.mirai.message.data.visitor.MessageVisitor
+import net.mamoe.mirai.utils.encodeHtmlEscape
 import net.mamoe.mirai.utils.safeCast
 
 // internal runtime value, not serializable
@@ -152,9 +153,7 @@ internal data class ForwardMessageInternal(
     }
 }
 
-private fun String.xmlEnc(): String {
-    return this.replace("&", "&")
-}
+private fun String.xmlEnc(): String = encodeHtmlEscape()
 
 internal fun RichMessage.Key.forwardMessage(
     resId: String,