From 4d3bbc0c8894fbc1f72cb80292ba4cbb3ccaa399 Mon Sep 17 00:00:00 2001
From: Tai Groot <tai@taigrr.com>
Date: Mon, 21 Mar 2022 22:44:21 -0700
Subject: [PATCH] Adds hash_test code

---
 README.md    | 17 +++++++++++++++++
 hash.go      | 35 +++++++++++++++++++++++++++++++++++
 hash_test.go | 30 ++++++++++++++++++++++++++++++
 3 files changed, 82 insertions(+)
 create mode 100644 README.md
 create mode 100644 hash.go
 create mode 100644 hash_test.go

diff --git a/README.md b/README.md
new file mode 100644
index 0000000..c516fee
--- /dev/null
+++ b/README.md
@@ -0,0 +1,17 @@
+
+
+ - Take in arbitrary input and return a deterministic color
+ - Color chosen can be limited in several ways:
+   - only visually / noticibly distinct colors to choose from
+   - Color exclusions
+     - dynamic color exclusions (optional terminal context)
+   - colors within different terminal support classes (i.e. term-256)
+
+ - Offer to return Hex codes (6 digits or 3)
+ - Offer to return ascii escape codes
+ - If the input is text, offer to wrap the input text and return the output as a string
+
+
+1. take input as bytes
+1. md5 hash the input
+1. use modulo against the sum to choose the color to return from the subset of colors selected.
diff --git a/hash.go b/hash.go
new file mode 100644
index 0000000..4976e2d
--- /dev/null
+++ b/hash.go
@@ -0,0 +1,35 @@
+package go_colorhash
+
+import (
+	"crypto/md5"
+	"encoding/binary"
+	"io"
+)
+
+const MaxUint = ^uint(0)
+const MaxInt = int(MaxUint >> 1)
+
+func HashString(s string) int {
+	h := md5.New()
+	io.WriteString(h, s)
+	hashb := h.Sum(nil)
+	hashb = hashb[len(hashb)-8:]
+	lsb := binary.BigEndian.Uint64(hashb)
+	sint := int(lsb)
+	if sint < 0 {
+		sint = sint + MaxInt
+	}
+	return sint
+}
+func HashBytes(r io.Reader) int {
+	h := md5.New()
+	io.Copy(h, r)
+	hashb := h.Sum(nil)
+	hashb = hashb[len(hashb)-8:]
+	lsb := binary.BigEndian.Uint64(hashb)
+	sint := int(lsb)
+	if sint < 0 {
+		sint = sint + MaxInt
+	}
+	return sint
+}
diff --git a/hash_test.go b/hash_test.go
new file mode 100644
index 0000000..a454227
--- /dev/null
+++ b/hash_test.go
@@ -0,0 +1,30 @@
+package go_colorhash
+
+import (
+	"testing"
+)
+
+func TestHashBytes(t *testing.T) {
+	testBytes := []struct {
+		runAsUser bool
+	}{}
+	_ = testBytes
+}
+func TestHashString(t *testing.T) {
+	testStrings := []struct {
+		String string
+		Value  int
+		ID     string
+	}{{String: "", Value: 7602086723416769149, ID: "Empty string"},
+		{String: "123", Value: 1606385479620709231, ID: "123"},
+		{String: "it's as easy as", Value: 5377981271559288604, ID: "easy"},
+		{String: "hello colorhash", Value: 4155814819593785823, ID: "hello"}}
+	for _, tc := range testStrings {
+		t.Run(tc.ID, func(t *testing.T) {
+			hash := HashString(tc.String)
+			if hash != tc.Value {
+				t.Errorf("%s :: Hash resulted in value %d, but expected value is %d", tc.ID, hash, tc.Value)
+			}
+		})
+	}
+}