From 56958493fe0bc8477fe8bdd9c44b30d421ea3315 Mon Sep 17 00:00:00 2001
From: Joost Jager <joost.jager@gmail.com>
Date: Mon, 9 Dec 2019 13:28:05 +0100
Subject: [PATCH] invoices/test: add test clock

---
 invoices/clock_test.go | 77 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 77 insertions(+)
 create mode 100644 invoices/clock_test.go

diff --git a/invoices/clock_test.go b/invoices/clock_test.go
new file mode 100644
index 000000000..41dd49912
--- /dev/null
+++ b/invoices/clock_test.go
@@ -0,0 +1,77 @@
+package invoices
+
+import (
+	"sync"
+	"time"
+)
+
+// testClock can be used in tests to mock time.
+type testClock struct {
+	currentTime time.Time
+	timeChanMap map[time.Time][]chan time.Time
+	timeLock    sync.Mutex
+}
+
+// newTestClock returns a new test clock.
+func newTestClock(startTime time.Time) *testClock {
+	return &testClock{
+		currentTime: startTime,
+		timeChanMap: make(map[time.Time][]chan time.Time),
+	}
+}
+
+// now returns the current (test) time.
+func (c *testClock) now() time.Time {
+	c.timeLock.Lock()
+	defer c.timeLock.Unlock()
+
+	return c.currentTime
+}
+
+// tickAfter returns a channel that will receive a tick at the specified time.
+func (c *testClock) tickAfter(duration time.Duration) <-chan time.Time {
+	c.timeLock.Lock()
+	defer c.timeLock.Unlock()
+
+	triggerTime := c.currentTime.Add(duration)
+	log.Debugf("tickAfter called: duration=%v, trigger_time=%v",
+		duration, triggerTime)
+
+	ch := make(chan time.Time, 1)
+
+	// If already expired, tick immediately.
+	if !triggerTime.After(c.currentTime) {
+		ch <- c.currentTime
+		return ch
+	}
+
+	// Otherwise store the channel until the trigger time is there.
+	chans := c.timeChanMap[triggerTime]
+	chans = append(chans, ch)
+	c.timeChanMap[triggerTime] = chans
+
+	return ch
+}
+
+// setTime sets the (test) time and triggers tick channels when they expire.
+func (c *testClock) setTime(now time.Time) {
+	c.timeLock.Lock()
+	defer c.timeLock.Unlock()
+
+	c.currentTime = now
+	remainingChans := make(map[time.Time][]chan time.Time)
+	for triggerTime, chans := range c.timeChanMap {
+		// If the trigger time is still in the future, keep this channel
+		// in the channel map for later.
+		if triggerTime.After(now) {
+			remainingChans[triggerTime] = chans
+			continue
+		}
+
+		for _, c := range chans {
+			c <- now
+		}
+	}
+
+	c.timeChanMap = remainingChans
+}