handle a situation when some webservers does not respect range header at first place

downloader/core/src/main/kotlin/ir/amirab/downloader/downloaditem/DownloadJob.kt

@@ -356,9 +356,14 @@ class DownloadJob(
     }
 
     private fun onPartHaveToManyError(throwable: Throwable) {
+        var paused = false
         if (throwable is DownloadValidationException) {
-            scope.launch {
-                pause(throwable)
+            if (throwable.isCritical()){
+                //stop the whole job! as we have big problem here
+                paused = true
+                scope.launch {
+                    pause(throwable)
+                }
             }
         }
         val allHaveError = partDownloaderList.values
@@ -366,11 +371,11 @@ class DownloadJob(
             .all {
                 it.injured()
             }
-        if (allHaveError) {
+        if (allHaveError && !paused) {
 //            println("all have error!")
             scope.launch {
 //                println("request pause send")
-                pause(TooManyErrorException())
+                pause(TooManyErrorException(throwable))
             }
         }
     }

downloader/core/src/main/kotlin/ir/amirab/downloader/exception/DownloadValidationException.kt

@@ -1,3 +1,5 @@
 package ir.amirab.downloader.exception
 
-abstract class DownloadValidationException(msg:String):Exception(msg)
+abstract class DownloadValidationException(msg:String):Exception(msg){
+    abstract fun isCritical():Boolean
+}

downloader/core/src/main/kotlin/ir/amirab/downloader/exception/FileChangedException.kt

@@ -2,16 +2,20 @@ package ir.amirab.downloader.exception
 
 
 sealed class FileChangedException(msg:String, ):DownloadValidationException(msg){
+    override fun isCritical(): Boolean{
+        // download must stop immediately
+        return true
+    }
     class LengthChangedException(
         val lastContentLength: Long,
         val newContentLength: Long
-    ) : DownloadValidationException(
+    ) : FileChangedException(
         "File size changed since last download! last time was $lastContentLength now it's $newContentLength"
     )
     class ETagChangedException(
         val oldETag: String,
         val newETag: String
-    ) : DownloadValidationException(
+    ) : FileChangedException(
         "File content changed since last download! last time was $oldETag now it's $newETag"
     )
 }

downloader/core/src/main/kotlin/ir/amirab/downloader/exception/NoSpaceInStorageException.kt

@@ -5,4 +5,9 @@ class NoSpaceInStorageException(
     val required: Long
 ) : DownloadValidationException(
     "No space available required=$required , available=$available"
-)
+) {
+    override fun isCritical(): Boolean {
+        // there is no space in users file system so we should stop
+        return true
+    }
+}

downloader/core/src/main/kotlin/ir/amirab/downloader/exception/ServerPartIsNotTheSameAsWeExpectException.kt

@@ -1,4 +1,21 @@
 package ir.amirab.downloader.exception
 
-//it should not happened unless web server is not respect our header
-class ServerPartIsNotTheSameAsWeExpectException(msg: String) : DownloadValidationException(msg)
+//it should not happen unless web server is not respect our header
+class ServerPartIsNotTheSameAsWeExpectException(
+    start:Long,
+    end:Long?,
+    expectedLength:Long?,
+    actualLength:Long?,
+) : DownloadValidationException (
+    "Response Length not match.expecting '${expectedLength}',but we got '$actualLength',requested range is range is ${start}-${end}"
+//            + "\n request headers ${conn.responseInfo.requestHeaders}"
+//            + "\n response headers ${conn.responseInfo.responseHeaders}"
+){
+    override fun isCritical(): Boolean {
+        // some webservers somehow does not return the expected size at the first place
+        // but after some try... they do!!!
+        // because of them, I have to make this error non-critical
+        // I have to investigate why!
+        return false
+    }
+}

downloader/core/src/main/kotlin/ir/amirab/downloader/exception/TooManyErrorException.kt

@@ -1,5 +1,8 @@
 package ir.amirab.downloader.exception
 
-class TooManyErrorException : Exception(
-    "Download is stopped because all parts exceeds max retries"
+class TooManyErrorException(
+    lastException: Throwable,
+) : Exception(
+    "Download is stopped because all parts exceeds max retries",
+    lastException,
 )

downloader/core/src/main/kotlin/ir/amirab/downloader/part/PartDownloader.kt

@@ -121,14 +121,12 @@ class PartDownloader(
                     } catch (e: Exception) {
                         tries++
                         onCanceled(e)
-                        if (!canRetry(e)) {
-                            if (e is DownloadValidationException) {
-                                iCantRetryAnymore(e)
-                            }
-                            break
-                        } else {
-                            continue
+                        when(canRetry(e)){
+                            CanRetryResult.Yes -> continue
+                            CanRetryResult.No -> {}
+                            CanRetryResult.NoAndStopDownloadJob -> iCantRetryAnymore(e)
                         }
+                        break
                     }
                     //download progress started, but maybe we have errors
                     //wait for a finish/error event...
@@ -138,16 +136,13 @@ class PartDownloader(
                     }
                     when (status) {
                         is PartDownloadStatus.Canceled -> {
-
-                            if (!canRetry(status.e)) {
-                                if (status.e is DownloadValidationException) {
-                                    iCantRetryAnymore(status.e)
-                                }
-                                break
-                            } else {
-                                tries++
-                                continue
+                            tries++
+                            when(canRetry(status.e)){
+                                CanRetryResult.Yes -> continue
+                                CanRetryResult.No -> {}
+                                CanRetryResult.NoAndStopDownloadJob -> iCantRetryAnymore(status.e)
                             }
+                            break
                         }
 
                         PartDownloadStatus.Completed -> break
@@ -169,15 +164,26 @@ class PartDownloader(
         }
     }
 
-    private fun canRetry(e: Throwable): Boolean {
+    private sealed interface CanRetryResult{
+        data object Yes:CanRetryResult
+        data object No:CanRetryResult
+        data object NoAndStopDownloadJob:CanRetryResult
+    }
+
+    private fun canRetry(e: Throwable): CanRetryResult {
         return when {
             ExceptionUtils.isNormalCancellation(e) -> {
-                false
+                CanRetryResult.No
+            }
+            e is DownloadValidationException -> if (e.isCritical()){
+                //download validation occurs, and also it is critical,
+                //so we can't proceed any further
+                CanRetryResult.NoAndStopDownloadJob
+            }else{
+                CanRetryResult.Yes
             }
-
-            e is DownloadValidationException -> false
             else -> {
-                true
+                CanRetryResult.Yes
             }
         }
     }
@@ -225,9 +231,10 @@ class PartDownloader(
         if (contentLength != partCopy.remainingLength) {
             conn.closeable.close()
             throw ServerPartIsNotTheSameAsWeExpectException(
-                "part remaining length: ${part.remainingLength} and response length: ${conn.contentLength} not match"
-                        + "\n request headers ${conn.responseInfo.requestHeaders}"
-                        + "\n response headers ${conn.responseInfo.responseHeaders}"
+                start = partCopy.current,
+                end = partCopy.to,
+                expectedLength = partCopy.remainingLength,
+                actualLength = contentLength
             )
         }
         thread = thread {