Merge pull request #990 from forslund/feature/downloader

Add class for handling downloads

mycroft/util/download.py

@@ -0,0 +1,104 @@
+from threading import Thread
+import requests
+import os
+from os.path import exists
+
+_running_downloads = {}
+
+
+def _get_download_tmp(dest):
+    tmp_base = dest + '.part'
+    if not exists(tmp_base):
+        return tmp_base
+    else:
+        i = 1
+        while(True):
+            tmp = tmp_base + '.' + str(i)
+            if not exists(tmp):
+                return tmp
+            else:
+                i += 1
+
+
+class Downloader(Thread):
+    """
+        Downloader is a thread based downloader instance when instanciated
+        it will download the provided url to a file on disk.
+
+        When the download is complete or failed the `.done` property will
+        be set to true and the `.status` will indicate the status code.
+        200 = Success.
+
+        Args:
+            url:            Url to download
+            dest:           Path to save data to
+            complet_action: Function to run when download is complete.
+                            `func(dest)`
+    """
+    def __init__(self, url, dest, complete_action=None):
+        super(Downloader, self).__init__()
+        self.url = url
+        self.dest = dest
+        self.complete_action = complete_action
+        self.status = None
+        self.done = False
+        self._abort = False
+
+        #  Start thread
+        self.start()
+
+    def run(self):
+        """
+            Does the actual download.
+        """
+        r = requests.get(self.url, stream=True)
+        tmp = _get_download_tmp(self.dest)
+        with open(tmp, 'w') as f:
+            for chunk in r.iter_content():
+                f.write(chunk)
+                if self._abort:
+                    break
+
+        self.status = r.status_code
+        if not self._abort and self.status == 200:
+            self.finalize(tmp)
+        else:
+            self.cleanup(self, tmp)
+        self.done = True
+        arg_hash = hash(self.url + self.dest)
+
+        #  Remove from list of currently running downloads
+        if arg_hash in _running_downloads:
+            _running_downloads.pop(arg_hash)
+
+    def finalize(self, tmp):
+        """
+            Move the .part file to the final destination and perform any
+            actions that should be performed at completion.
+        """
+        os.rename(tmp, self.dest)
+        if self.complete_action:
+            self.complete_action(self.dest)
+
+    def cleanup(tmp):
+        """
+            Cleanup after download attempt
+        """
+        if exists(tmp):
+            os.remove(self.dest + '.part')
+        if self.status == 200:
+            self.status = -1
+
+    def abort(self):
+        """
+            Abort download process
+        """
+        self._abort = True
+
+
+def download(url, dest, complete_action=None):
+    global _running_downloads
+    arg_hash = hash(url + dest)
+    if arg_hash not in _running_downloads:
+        _running_downloads[arg_hash] = Downloader(url, dest, complete_action)
+    return _running_downloads[arg_hash]