feat(internal): add uniqueid package

internal/uniqueid/unique_test.go

@@ -0,0 +1,52 @@
+package uniqueid_test
+
+import (
+	"testing"
+
+	"github.com/google/go-cmp/cmp"
+	"github.com/mrmarble/termsvg/internal/uniqueid"
+)
+
+func TestUniqueID(t *testing.T) {
+	tests := map[string]struct {
+		input  string
+		output string
+	}{
+		"Initial":    {uniqueid.New().String(), "a"},
+		"Next":       {runTimes(t, 1).String(), "b"},
+		"10 Times":   {runTimes(t, 10).String(), "k"},
+		"25 Times":   {runTimes(t, 25).String(), "z"},
+		"26 Times":   {runTimes(t, 26).String(), "aa"},
+		"27 Times":   {runTimes(t, 27).String(), "ab"},
+		"51 Times":   {runTimes(t, 51).String(), "az"},
+		"52 Times":   {runTimes(t, 52).String(), "ba"},
+		"53 Times":   {runTimes(t, 53).String(), "bb"},
+		"150 Times":  {runTimes(t, 150).String(), "eu"},
+		"1500 Times": {runTimes(t, 1500).String(), "zzes"},
+	}
+	for name, test := range tests {
+		t.Run(name, func(t *testing.T) {
+			diff(t, test.input, test.output)
+		})
+	}
+}
+
+func runTimes(t *testing.T, times int) *uniqueid.ID {
+	t.Helper()
+
+	id := uniqueid.New()
+	for i := 0; i < times; i++ {
+		id.Next()
+	}
+
+	return id
+}
+
+func diff(t *testing.T, x interface{}, y interface{}) {
+	t.Helper()
+
+	diff := cmp.Diff(x, y)
+	if diff != "" {
+		t.Fatalf(diff)
+	}
+}

internal/uniqueid/uniqueid.go

@@ -0,0 +1,31 @@
+package uniqueid
+
+type ID []rune
+
+func New() *ID {
+	var id ID = []rune{'a'}
+
+	return &id
+}
+
+func (id *ID) String() string {
+	return string(*id)
+}
+
+func (id *ID) Next() {
+	for i := len(*id) - 1; i >= 0; i-- {
+		cur := (*id)[i]
+		if cur < 'z' {
+			(*id)[i]++
+			return
+		}
+
+		if i == len(*id)-1 {
+			(*id)[i] = 'a'
+		}
+
+		if i == 0 {
+			*id = append(*id, 'a')
+		}
+	}
+}