From 25fe1ec5635fd476f91b3a7f437f9807b98031c5 Mon Sep 17 00:00:00 2001
From: Adrien Mulattieri <mula.adri@gmail.com>
Date: Thu, 4 Aug 2022 20:30:07 +0200
Subject: [PATCH] feat: Random utils functions

---
 random/random.go      | 47 ++++++++++++++++++++++
 random/random_test.go | 91 +++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 138 insertions(+)
 create mode 100644 random/random.go
 create mode 100644 random/random_test.go

diff --git a/random/random.go b/random/random.go
new file mode 100644
index 00000000..b7dd847e
--- /dev/null
+++ b/random/random.go
@@ -0,0 +1,47 @@
+package random
+
+import (
+	"fmt"
+	"math/rand"
+	"strings"
+)
+
+const NumericRunes = "0123456789"
+const LowerAlphaRunes = "abcdefghijklmnopqrstuvwxyz"
+const UpperAlphaRunes = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
+const AlphaRunes = UpperAlphaRunes + LowerAlphaRunes
+
+// Return a random string made up of characters passed
+func Runes(prefix string, length int, runes ...string) string {
+	chars := strings.Join(runes, "")
+	var bytes = make([]byte, length)
+	rand.Read(bytes)
+	for i, b := range bytes {
+		bytes[i] = chars[b%byte(len(chars))]
+	}
+	return prefix + string(bytes)
+}
+
+// Return a random string of alpha characters
+func Alpha(prefix string, length int) string {
+	return Runes(prefix, length, AlphaRunes)
+}
+
+// Return a random string of alpha and numeric characters
+func String(prefix string, length int) string {
+	return Runes(prefix, length, AlphaRunes, NumericRunes)
+}
+
+// Given a list of strings, return one of the strings randomly
+func Item(items ...string) string {
+	var bytes = make([]byte, 1)
+	rand.Read(bytes)
+	return items[bytes[0]%byte(len(items))]
+}
+
+// Return a random domain name in the form "randomAlpha.net"
+func DomainName() string {
+	return fmt.Sprintf("%s.%s",
+		Alpha("", 14),
+		Item("net", "com", "org", "io", "gov"))
+}
diff --git a/random/random_test.go b/random/random_test.go
new file mode 100644
index 00000000..0c3063af
--- /dev/null
+++ b/random/random_test.go
@@ -0,0 +1,91 @@
+package random
+
+import (
+	"fmt"
+	"math/rand"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestString(t *testing.T) {
+	rand.Seed(time.Now().UnixNano())
+	for _, tc := range []struct {
+		msg            string
+		prefix         string
+		length         int
+		contains       string
+		expectedLength int
+	}{{
+		msg:            "only made of alpha and numeric characters",
+		prefix:         "",
+		length:         10,
+		contains:       AlphaRunes + NumericRunes,
+		expectedLength: 10,
+	}, {
+		msg:            "with prefix and add to length",
+		prefix:         "abc",
+		length:         5,
+		contains:       AlphaRunes + NumericRunes,
+		expectedLength: 5 + 3, // = len("abc")
+	}} {
+		t.Run(tc.msg, func(t *testing.T) {
+			res := String(tc.prefix, tc.length)
+			assert.Equal(t, tc.expectedLength, len(res))
+			assert.Contains(t, res, tc.prefix)
+			for _, ch := range res {
+				assert.Contains(t, tc.contains, fmt.Sprintf("%c", ch))
+			}
+		})
+	}
+}
+
+func TestAlpha(t *testing.T) {
+	rand.Seed(time.Now().UnixNano())
+	for _, tc := range []struct {
+		msg            string
+		prefix         string
+		length         int
+		contains       string
+		expectedLength int
+	}{{
+		msg:            "only made of alpha characters",
+		prefix:         "",
+		length:         10,
+		contains:       AlphaRunes,
+		expectedLength: 10,
+	}, {
+		msg:            "with prefix and add to length",
+		prefix:         "abc",
+		length:         5,
+		contains:       AlphaRunes,
+		expectedLength: 5 + 3, // = len("abc")
+	}} {
+		t.Run(tc.msg, func(t *testing.T) {
+			res := Alpha(tc.prefix, tc.length)
+			assert.Equal(t, tc.expectedLength, len(res))
+			assert.Contains(t, res, tc.prefix)
+			for _, ch := range res {
+				assert.Contains(t, tc.contains, fmt.Sprintf("%c", ch))
+			}
+		})
+	}
+}
+
+func TestItem(t *testing.T) {
+	rand.Seed(time.Now().UnixNano())
+	for _, tc := range []struct {
+		msg      string
+		items    []string
+		expected string
+	}{{
+		msg:   "one of the given list",
+		items: []string{"com", "net", "org"},
+	}} {
+		t.Run(tc.msg, func(t *testing.T) {
+			res := Item(tc.items...)
+			assert.Contains(t, tc.items, res)
+		})
+	}
+}