From 34204cc40b7c7b272c132f003671b3ee78187b26 Mon Sep 17 00:00:00 2001
From: Jaime Pillora <dev@jpillora.com>
Date: Sat, 28 Feb 2015 17:21:18 +1100
Subject: [PATCH] initial, tests passing

---
 README.md       | 63 +++++++++++++++++++++++++++++++++++++++++++++++++
 backoff.go      | 38 +++++++++++++++++++++++++++++
 backoff_test.go | 33 ++++++++++++++++++++++++++
 3 files changed, 134 insertions(+)
 create mode 100644 README.md
 create mode 100644 backoff.go
 create mode 100644 backoff_test.go

diff --git a/README.md b/README.md
new file mode 100644
index 0000000..ca52f05
--- /dev/null
+++ b/README.md
@@ -0,0 +1,63 @@
+# Backoff
+
+A simple backoff algorithm in Go (Golang)
+
+# Usage
+
+Starts at `Min`, multiplied by `Factor` every call to
+`Duration()` where it is capped at `Max`. Commonly used
+in conjunction with `time.Sleep(duration)`.
+
+``` go
+
+b := &backoff.Backoff{
+	//These are the defaults
+	Min:    100 * time.Millisecond,
+	Max:    10 * time.Second,
+	Factor: 2,
+}
+
+fmt.Printf("%s\n", b.Duration())
+fmt.Printf("%s\n", b.Duration())
+fmt.Printf("%s\n", b.Duration())
+
+fmt.Printf("Reset!\n")
+b.Reset()
+
+fmt.Printf("%s\n", b.Duration())
+```
+
+```
+100ms
+200ms
+400ms
+Reset!
+100ms
+```
+
+#### Credits
+
+Ported from some JavaScript written by [@tj](https://github.com/tj)
+
+#### MIT License
+
+Copyright © 2015 Jaime Pillora &lt;dev@jpillora.com&gt;
+
+Permission is hereby granted, free of charge, to any person obtaining
+a copy of this software and associated documentation files (the
+'Software'), to deal in the Software without restriction, including
+without limitation the rights to use, copy, modify, merge, publish,
+distribute, sublicense, and/or sell copies of the Software, and to
+permit persons to whom the Software is furnished to do so, subject to
+the following conditions:
+
+The above copyright notice and this permission notice shall be
+included in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
\ No newline at end of file
diff --git a/backoff.go b/backoff.go
new file mode 100644
index 0000000..6e42d6d
--- /dev/null
+++ b/backoff.go
@@ -0,0 +1,38 @@
+package backoff
+
+import (
+	"math"
+	"time"
+)
+
+type Backoff struct {
+	attempts, Factor int
+	curr, Min, Max   time.Duration
+}
+
+func (b *Backoff) Duration() time.Duration {
+	//abit hacky though, if zero-value, apply defaults
+	if b.Min == 0 {
+		b.Min = 100 * time.Millisecond
+	}
+	if b.Max == 0 {
+		b.Max = 10 * time.Second
+	}
+	if b.Factor == 0 {
+		b.Factor = 2
+	}
+	if b.curr == 0 {
+		b.curr = b.Min
+	}
+
+	//calculate next duration in ms
+	ms := float64(b.curr) * math.Pow(float64(b.Factor), float64(b.attempts))
+	//bump attempts count
+	b.attempts++
+	//return as a time.Duration
+	return time.Duration(math.Min(ms, float64(b.Max)))
+}
+
+func (b *Backoff) Reset() {
+	b.attempts = 0
+}
diff --git a/backoff_test.go b/backoff_test.go
new file mode 100644
index 0000000..d68dd41
--- /dev/null
+++ b/backoff_test.go
@@ -0,0 +1,33 @@
+package backoff
+
+import (
+	"testing"
+	"time"
+)
+
+func Test1(t *testing.T) {
+
+	b := &Backoff{
+		Min:    100 * time.Millisecond,
+		Max:    10 * time.Second,
+		Factor: 2,
+	}
+
+	if b.Duration() != 100*time.Millisecond {
+		t.Error("Should be 100ms")
+	}
+
+	if b.Duration() != 200*time.Millisecond {
+		t.Error("Should be 200ms")
+	}
+
+	if b.Duration() != 400*time.Millisecond {
+		t.Error("Should be 400ms")
+	}
+
+	b.Reset()
+
+	if b.Duration() != 100*time.Millisecond {
+		t.Error("Should be 100ms again")
+	}
+}