Add rendering of the remaining time

CHANGELOG.md

@@ -7,6 +7,7 @@ We follow [Semantic Versions](https://semver.org/).
 
 - Add class `Timer` - responsible for waiting until the scheduled time
 - Add the `Timer` to the `App`
+- Add rendering of the remaining time during the countdown
 
 
 ## Version 0.1.2

slow_start_rewatch/timer.py

@@ -1,5 +1,6 @@
 # -*- coding: utf-8 -*-
 
+import math
 import time
 from datetime import datetime
 from typing import Iterator, Optional
@@ -64,6 +65,9 @@ def countdown(self) -> None:
             self.ticks(),
             label="Waiting to submit the post (press Ctrl+C to quit):",
             fill_char=click.style("#", fg="bright_magenta"),
+            item_show_func=self.time_left,
+            show_eta=False,
+            show_percent=False,
         ) as progressbar:
             for tick in progressbar:
                 current_timestamp = datetime.now().timestamp() * 1000
@@ -94,3 +98,17 @@ def ticks(self) -> Iterator[int]:
             start_timestamp,
             -self.refresh_interval,
         ))
+
+    def time_left(self, tick: Optional[int]) -> str:
+        """Render remaining time."""
+        if self.target_time is None:
+            raise AttributeError(
+                "'target_time' must be set to render remaning time.",
+            )
+
+        if tick is None:
+            return ""
+
+        current_timestamp = datetime.fromtimestamp(math.floor(tick / 1000))
+
+        return str(self.target_time - current_timestamp)

tests/test_timer.py

@@ -98,6 +98,35 @@ def test_ticks(timer_config):
     assert generated_ticks == expected_ticks
 
 
+@pytest.mark.parametrize(("tick_datetime", "expected_time_left"), [
+    (datetime(2018, 1, 6, 10, 59, 59, 100 * 1000), "1:00:01"),
+    (datetime(2018, 1, 6, 11, 59, 59, 900 * 1000), "0:00:01"),
+    (datetime(2018, 1, 6, 12), "0:00:00"),
+    (None, ""),
+],
+)
+def test_time_left(tick_datetime, expected_time_left, timer_config):
+    """Test that the remaining time is rendered correctly."""
+    timer = Timer(
+        config=timer_config,
+        target_time=datetime(2018, 1, 6, 12, 0, 0),
+    )
+
+    tick = int(tick_datetime.timestamp() * 1000) if tick_datetime else None
+
+    time_left = timer.time_left(tick)
+
+    assert time_left == expected_time_left
+
+
+def test_time_left_invalid_call(timer_config):
+    """Test calling :meth:`Timer.time_left()` without required attributes."""
+    timer = Timer(timer_config)
+
+    with pytest.raises(AttributeError):
+        timer.time_left(1000)
+
+
 @pytest.fixture()
 def timer_config():
     """Return mock Config for testing Timer."""