better header fetching

src/en/aniplay/src/eu/kanade/tachiyomi/animeextension/en/aniplay/AniPlay.kt

@@ -32,6 +32,7 @@ import java.io.IOException
 import java.text.SimpleDateFormat
 import java.util.Date
 import java.util.Locale
+import java.util.concurrent.locks.ReentrantLock
 
 @Suppress("unused")
 class AniPlay : AniListAnimeHttpSource(), ConfigurableAnimeSource {
@@ -381,14 +382,16 @@ class AniPlay : AniListAnimeHttpSource(), ConfigurableAnimeSource {
         return if (bracketCount == 0) input.substring(startIndex - 1, endIndex) else null
     }
 
+    private val headerFetchLock = ReentrantLock()
     private var lastHeaderFetch = 0L
     private fun fetchHeaders() {
+        val internalFetchHeaders = internalFetchHeaders@{
             val currentTimestamp = Date().time
             val timeout = lastHeaderFetch + (HEADERS_TIMEOUT_MINUTES * 60 * 1000)
             // check only after 15 minutes
             if (timeout > currentTimestamp) {
                 Log.i("AniPlay", "Skipping header update. $timeout > $currentTimestamp (${timeout - currentTimestamp}).")
-            return
+                return@internalFetchHeaders
             }
 
             val baseUrl = Base64.decode("aHR0cHM6Ly9qb3NlZmZzdHJha2EuZ2l0aHViLmlvL2FuaXBsYXktaGVhZGVycy8=", Base64.DEFAULT).toString(Charsets.UTF_8)
@@ -404,12 +407,20 @@ class AniPlay : AniListAnimeHttpSource(), ConfigurableAnimeSource {
                 Log.i("AniPlay", "Fetched headers($preferredDomain): $domainHeaders")
             } catch (e: Exception) {
                 Log.e("AniPlay", "Failed to fetch new headers: \"e\"")
-            return
+                return@internalFetchHeaders
             }
 
             lastHeaderFetch = Date().time
         }
 
+        headerFetchLock.lock()
+        try {
+            internalFetchHeaders()
+        } finally {
+            headerFetchLock.unlock()
+        }
+    }
+
     private fun getHeaderValue(serverHost: String, key: String): String {
         fetchHeaders()
         try {