Add estimated time remaining to progress indicator

Estimates the time remaining for each download and displays it in the
progress bar. Waits for 10 seconds before showing the progress bar to
allow the download rate to stabilize, which prevents the estimated time
remaining from jumping all over the place at the start of the download
(a.k.a the "Windows copy dialog experience"). If your download takes
less than 10 seconds, you don't really need to see an ETA anyway.

This commit also refactors the Downloads class, splitting out the
download-specific functionality into a new Download class, providing
better encapsulation. As a result, I was able to simplify the call to
`update_download` because it was no longer necessary to pass the
`total_bytes` (which don't change after the download has begun).

Tested on Mac OS 10.9.

onionshare/helpers.py

@@ -19,6 +19,8 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 """
 import os, inspect, hashlib, base64, hmac, platform, zipfile, tempfile
 from itertools import izip
+import math
+import time
 
 # hack to make unicode filenames work (#141)
 import sys
@@ -112,6 +114,44 @@ def human_readable_filesize(b):
     return '{0:.1f} {1:s}'.format(round(b, 1), units[u])
 
 
+def format_seconds(seconds):
+    """Return a human-readable string of the format 1d2h3m4s"""
+    seconds_in_a_minute = 60
+    seconds_in_an_hour = seconds_in_a_minute * 60
+    seconds_in_a_day = seconds_in_an_hour * 24
+
+    days = math.floor(seconds / seconds_in_a_day)
+
+    hour_seconds = seconds % seconds_in_a_day
+    hours = math.floor(hour_seconds / seconds_in_an_hour)
+
+    minute_seconds = hour_seconds % seconds_in_an_hour
+    minutes = math.floor(minute_seconds / seconds_in_a_minute)
+
+    remaining_seconds = minute_seconds % seconds_in_a_minute
+    seconds = math.ceil(remaining_seconds)
+
+    human_readable = []
+    if days > 0:
+        human_readable.append("{}d".format(int(days)))
+    if hours > 0:
+        human_readable.append("{}h".format(int(hours)))
+    if minutes > 0:
+        human_readable.append("{}m".format(int(minutes)))
+    if seconds > 0:
+        human_readable.append("{}s".format(int(seconds)))
+    return ''.join(human_readable)
+
+
+def estimated_time_remaining(bytes_downloaded, total_bytes, started):
+    now = time.time()
+    time_elapsed = now - started  # in seconds
+    download_rate = bytes_downloaded / time_elapsed
+    remaining_bytes = total_bytes - bytes_downloaded
+    eta = remaining_bytes / download_rate
+    return format_seconds(eta)
+
+
 def is_root():
     """
     Returns if user is root.

onionshare_gui/downloads.py

@@ -17,12 +17,67 @@ GNU General Public License for more details.
 You should have received a copy of the GNU General Public License
 along with this program.  If not, see <http://www.gnu.org/licenses/>.
 """
+import time
+
 from PyQt4 import QtCore, QtGui
 
 import common
 from onionshare import strings, helpers
 
 
+class Download(object):
+
+    def __init__(self, download_id, total_bytes):
+        self.download_id = download_id
+        self.started = time.time()
+        self.total_bytes = total_bytes
+        self.downloaded_bytes = 0
+
+        # make a new progress bar
+        self.progress_bar = QtGui.QProgressBar()
+        self.progress_bar.setTextVisible(True)
+        self.progress_bar.setAlignment(QtCore.Qt.AlignHCenter)
+        self.progress_bar.setMinimum(0)
+        self.progress_bar.setMaximum(total_bytes)
+        self.progress_bar.setValue(0)
+        self.progress_bar.setStyleSheet(
+            "QProgressBar::chunk { background-color: #05B8CC; }")
+        self.progress_bar.total_bytes = total_bytes
+
+        # start at 0
+        self.update(0)
+
+    def update(self, downloaded_bytes):
+        self.downloaded_bytes = downloaded_bytes
+
+        self.progress_bar.setValue(downloaded_bytes)
+        if downloaded_bytes == self.progress_bar.total_bytes:
+            pb_fmt = "%p%"
+        else:
+            elapsed = time.time() - self.started
+            if elapsed < 10:
+                # Wait a couple of seconds for the download rate to stabilize.
+                # This prevents an "Windows copy dialog"-esque experience at
+                # the beginning of the download.
+                pb_fmt = "{0:s}, %p% (Computing ETA)".format(
+                    helpers.human_readable_filesize(downloaded_bytes))
+            else:
+                pb_fmt = "{0:s}, ETA: {1:s}, %p%".format(
+                    helpers.human_readable_filesize(downloaded_bytes),
+                    self.estimated_time_remaining)
+
+        self.progress_bar.setFormat(pb_fmt)
+
+    def cancel(self):
+        self.progress_bar.setFormat(strings._('gui_canceled'))
+
+    @property
+    def estimated_time_remaining(self):
+        return helpers.estimated_time_remaining(self.downloaded_bytes,
+                                                self.total_bytes,
+                                                self.started)
+
+
 class Downloads(QtGui.QVBoxLayout):
     """
     The downloads chunk of the GUI. This lists all of the active download
@@ -31,7 +86,7 @@ class Downloads(QtGui.QVBoxLayout):
     def __init__(self):
         super(Downloads, self).__init__()
 
-        self.progress_bars = {}
+        self.downloads = {}
 
         # downloads label
         self.downloads_label = QtGui.QLabel(strings._('gui_downloads', True))
@@ -46,40 +101,19 @@ class Downloads(QtGui.QVBoxLayout):
         """
         self.downloads_label.show()
 
-        # make a new progress bar
-        pb = QtGui.QProgressBar()
-        pb.setTextVisible(True)
-        pb.setAlignment(QtCore.Qt.AlignHCenter)
-        pb.setMinimum(0)
-        pb.setMaximum(total_bytes)
-        pb.setValue(0)
-        pb.setStyleSheet("QProgressBar::chunk { background-color: #05B8CC; }")
-        pb.total_bytes = total_bytes
-
         # add it to the list
-        self.progress_bars[download_id] = pb
-        self.addWidget(pb)
+        download = Download(download_id, total_bytes)
+        self.downloads[download_id] = download
+        self.addWidget(download.progress_bar)
 
-        # start at 0
-        self.update_download(download_id, total_bytes, 0)
-
-    def update_download(self, download_id, total_bytes, downloaded_bytes):
+    def update_download(self, download_id, downloaded_bytes):
         """
         Update the progress of a download progress bar.
         """
-        if download_id not in self.progress_bars:
-            self.add_download(download_id, total_bytes)
-
-        pb = self.progress_bars[download_id]
-        pb.setValue(downloaded_bytes)
-        if downloaded_bytes == pb.total_bytes:
-            pb.setFormat("%p%")
-        else:
-            pb.setFormat("{0:s}, %p%".format(helpers.human_readable_filesize(downloaded_bytes)))
+        self.downloads[download_id].update(downloaded_bytes)
 
     def cancel_download(self, download_id):
         """
         Update a download progress bar to show that it has been canceled.
         """
-        pb = self.progress_bars[download_id]
-        pb.setFormat(strings._('gui_canceled'))
+        self.downloads[download_id].cancel()

onionshare_gui/onionshare_gui.py

@@ -218,7 +218,7 @@ class OnionShareGui(QtGui.QWidget):
                 self.downloads.add_download(event["data"]["id"], web.zip_filesize)
 
             elif event["type"] == web.REQUEST_PROGRESS:
-                self.downloads.update_download(event["data"]["id"], web.zip_filesize, event["data"]["bytes"])
+                self.downloads.update_download(event["data"]["id"], event["data"]["bytes"])
 
                 # is the download complete?
                 if event["data"]["bytes"] == web.zip_filesize: