#2 #3 Add config for customize file extension for tmp files

src/index.js

   Platform,
 } from 'react-native'
 
+
+type fetchConfig = {
+  fileCache : bool,
+  path : string,
+  appendExt : string
+};
+
 type RNFetchBlobNative = {
   fetchBlob : (
     options:fetchConfig,
     callback:(err:any, ...data:any) => void
   ) => void,
   readStream : (
-    taskId:string,
     path:string,
     encode: 'utf8' | 'ascii' | 'base64'
   ) => void,
   )
 }
 
-type fetchConfig = {
-  fileCache : bool,
-  path : string,
-};
-
 function getSystemDirs() {
   return new Promise((resolve, reject) => {
     try {
       RNFetchBlob.getEnvironmentDirs((...dirs) => {
-        console.log('##',...dirs)
         let [PictureDir, MovieDir, DocumentDir, CacheDir] = [...dirs]
         resolve({PictureDir, MovieDir, DocumentDir, CacheDir})
       })
      * @return {void}
      */
     this.flush = () => {
-      RNFetchBlob.flush(this.taskId, this.path)
+      RNFetchBlob.flush(this.path())
     }
 
     this.path = () => {
       })
 
       if(this.type === 'path') {
-        RNFetchBlob.readStream(this.taskId, this.data, encode)
+        RNFetchBlob.readStream(this.data, encode)
       }
       else {
         console.warn('RNFetchblob', 'this response data does not contains any available stream')

src/ios/RNFetchBlob/RNFetchBlob.h

 // config
 extern NSString *const CONFIG_USE_TEMP;
 extern NSString *const CONFIG_FILE_PATH;
+extern NSString *const CONFIG_FILE_EXT;
 
 // fs events
 extern NSString *const FS_EVENT_DATA;

src/ios/RNFetchBlob/RNFetchBlob.m

 #import "RCTBridge.h"
 #import "RCTEventDispatcher.h"
 
-// lib event
+// fetch configs
+NSString *const CONFIG_USE_TEMP = @"fileCache";
+NSString *const CONFIG_FILE_PATH = @"path";
+NSString *const CONFIG_FILE_EXT = @"appendExt";
+
 NSString *const MSG_EVENT = @"RNFetchBlobMessage";
 NSString *const MSG_EVENT_LOG = @"log";
 NSString *const MSG_EVENT_WARN = @"warn";
 NSString *const MSG_EVENT_ERROR = @"error";
-NSString *const CONFIG_USE_TEMP = @"fileCache";
-NSString *const CONFIG_FILE_PATH = @"path";
 NSString *const FS_EVENT_DATA = @"data";
 NSString *const FS_EVENT_END = @"end";
 NSString *const FS_EVENT_WARN = @"warn";
     return [NSSearchPathForDirectoriesInDomains(NSPicturesDirectory, NSUserDomainMask, YES) firstObject];
 }
 
-+ (NSString *) getTempPath:(NSString*)taskId {
 
++ (NSString *) getTempPath:(NSString*)taskId withExtension:(NSString *)ext {
+    
     NSString * documentDir = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) firstObject];
     NSString * filename = [NSString stringWithFormat:@"/RNFetchBlobTmp_%@", taskId];
+    if(ext != nil)
+        filename = [filename stringByAppendingString: [NSString stringWithFormat:@".%@", ext]];
     NSString * tempPath = [documentDir stringByAppendingString: filename];
     return tempPath;
 }
 }
 
 
-- (void)openWithId:(NSString *)taskId {
-    
-    NSString * tmpPath = [[self class ]getTempPath: taskId];
-    // create a file stream
-    [self openWithPath:tmpPath];
-    
-}
-
 // Write file chunk into an opened stream
 - (void)write:(NSData *) chunk toPath:(NSString *) path{
     NSUInteger left = [chunk length];
     
 }
 
-- (void)readWithTaskId:(NSString *)taskId withPath:(NSString *)path useEncoding:(NSString *)encoding {
-    self.taskId = taskId;
-    self.path = path;
-    if(path == nil)
-        [self readWithPath:[[self class]getTempPath:taskId] useEncoding:encoding];
-    else
-        [self readWithPath:path useEncoding:encoding];
-}
 
 // close file write stream
 - (void)closeOutStream {
     self.options = options;
     
     NSString * path = [self.options valueForKey:CONFIG_FILE_PATH];
+    NSString * ext = [self.options valueForKey:CONFIG_FILE_EXT];
     
     // open file stream for write
     if( path != nil) {
     }
     else if ( [self.options valueForKey:CONFIG_USE_TEMP]!= nil ) {
         self.fileStream = [[FetchBlobFS alloc]initWithCallback:self.callback];
-        [self.fileStream openWithId:taskId];
+        [self.fileStream openWithPath:[FetchBlobFS getTempPath:taskId withExtension:ext]];
     }
     
     NSURLConnection *conn = [[NSURLConnection alloc] initWithRequest:req delegate:self startImmediately:NO];
     }
     // write to tmp file
     else if( fileCache != nil) {
-        [self.fileStream write:data toPath:[FetchBlobFS getTempPath:self.taskId ]];
+        NSString * ext = [self.options valueForKey:CONFIG_FILE_EXT];
+        [self.fileStream write:data toPath:[FetchBlobFS getTempPath:self.taskId withExtension:ext]];
     }
     // cache data in memory
     else {
         data = [[NSData alloc] init];
     
     NSString * path = [self.options valueForKey:CONFIG_FILE_PATH];
+    NSString * ext = [self.options valueForKey:CONFIG_FILE_EXT];
     Boolean useCache = [self.options valueForKey:CONFIG_USE_TEMP];
     
     [self.fileStream closeInStream];
     }
     // when fileCache option is set but no path specified, save to tmp path
     else if( [self.options valueForKey:CONFIG_USE_TEMP] != nil) {
-        NSString * tmpPath = [FetchBlobFS getTempPath:taskId];
+        NSString * tmpPath = [FetchBlobFS getTempPath:taskId withExtension:ext];
         callback(@[[NSNull null], tmpPath]);
     }
     // otherwise return base64 string
     
 }
 
-RCT_EXPORT_METHOD(readStream:(NSString *)taskId withPath:(NSString *)path withEncoding:(NSString *)encoding) {
+RCT_EXPORT_METHOD(readStream:(NSString *)path withEncoding:(NSString *)encoding) {
     FetchBlobFS *fileStream = [[FetchBlobFS alloc] initWithBridgeRef:self.bridge];
-    [fileStream readWithTaskId:taskId withPath:path useEncoding:encoding];
+    [fileStream readWithPath:path useEncoding:encoding];
 }
 
-RCT_EXPORT_METHOD(flush:(NSString *)taskId withPath:(NSString *)path) {
+RCT_EXPORT_METHOD(flush:(NSString *)path) {
     NSError * error = nil;
     NSString * tmpPath = nil;
-    if(path != nil)
-        tmpPath = path;
-    else
-        tmpPath = [FetchBlobFS getTempPath:taskId];
     [[NSFileManager defaultManager] removeItemAtPath:path error:&error];
 }