feat: RwLock for opening files in DomFileEditor

src/main/kotlin/app/revanced/patcher/data/impl/ResourceData.kt

@@ -30,10 +30,12 @@ class ResourceData(private val resourceCacheDirectory: File) : Data, Iterable<Fi
 }
 
 /**
- * DomFileEditor is a wrapper for a file that can be edited as a dom document.
+ * Wrapper for a file that can be edited as a dom document.
+ * Note: This constructor does not check for locks to the file when writing. Use the secondary constructor.
  *
  * @param inputStream the input stream to read the xml file from.
- * @param outputStream the output stream to write the xml file to. If null, the file will not be written.
+ * @param outputStream the output stream to write the xml file to. If null, the file will be read only.
+ *
  */
 class DomFileEditor internal constructor(
     private val inputStream: InputStream,
@@ -41,6 +43,7 @@ class DomFileEditor internal constructor(
 ) : Closeable {
     // path to the xml file to unlock the resource when closing the editor
     private var filePath: String? = null
+    private var closed: Boolean = false
 
     /**
      * The document of the xml file
@@ -48,37 +51,53 @@ class DomFileEditor internal constructor(
     val file: Document = DocumentBuilderFactory.newInstance().newDocumentBuilder().parse(inputStream)
         .also(Document::normalize)
 
+
     // lazily open an output stream
     // this is required because when constructing a DomFileEditor the output stream is created along with the input stream, which is not allowed
     // the workaround is to lazily create the output stream. This way it would be used after the input stream is closed, which happens in the constructor
     constructor(file: File) : this(file.inputStream(), lazy { file.outputStream() }) {
+        // increase the lock
+        locks.merge(file.path, 1, Integer::sum)
         filePath = file.path
-
-        // prevent sharing mutability of the same file between multiple instances of DomFileEditor
-        if (locks.contains(filePath))
-            throw IllegalStateException("Can not create a DomFileEditor for that file because it is already locked by another instance of DomFileEditor.")
-        locks.add(filePath!!)
     }
 
+    /**
+     * Closes the editor. Write backs and decreases the lock count.
+     * Note: Will not write back to the file if the file is still locked.
+     */
     override fun close() {
+        if (closed) return
+
         inputStream.close()
 
         // if the output stream is not null, do not close it
         outputStream?.let {
-            val result = StreamResult(it.value)
+            // prevent writing to same file, if it is being locked
-            TransformerFactory.newInstance().newTransformer().transform(DOMSource(file), result)
+            // isLocked will be false if the editor was created through a stream
+            val isLocked = filePath?.let { path ->
+                val isLocked = locks[path]!! > 1
+                // decrease the lock count if the editor was opened for a file
+                locks.merge(path, -1, Integer::sum)
+                isLocked
+            } ?: false
 
-            it.value.close()
+            // if unlocked, write back to the file
+            if (!isLocked) {
+                it.value.use { stream ->
+                    val result = StreamResult(stream)
+                    TransformerFactory.newInstance().newTransformer().transform(DOMSource(file), result)
+                }
+
+                it.value.close()
+                return
+            }
         }
 
-        // remove the lock, if it exists
+        closed = true
-        filePath?.let {
-            locks.remove(it)
-        }
     }
 
     private companion object {
-        // list of locked file paths
+        // map of concurrent open files
-        val locks = mutableListOf<String>()
+        val locks = mutableMapOf<String, Int>()
     }
 }