lib/tagset: add tag set as bitmask

Add tag set as a bitmask, as part of refactoring lib.TagSet.

Update #755

silent linter

fix @imiric's review comments

lib/tagset/tagset.go

@@ -0,0 +1,94 @@
+package tagset
+
+import (
+	"bytes"
+	"encoding/json"
+	"strings"
+)
+
+// TagSet is a bitmask that is used to keep track
+// which system tags should be included with which metrics.
+//go:generate enumer -type=TagSet -transform=snake -output tagset_gen.go
+type TagSet uint32
+
+//nolint: golint
+const (
+	// Default system tags includes all of the system tags emitted with metrics by default.
+	Proto TagSet = 1 << iota
+	SubProto
+	Status
+	Method
+	URL
+	Name
+	Group
+	Check
+	Error
+	ErrorCode
+	TLSVersion
+
+	// System tags not enabled by default.
+	Iter
+	VU
+	OCSPStatus
+	IP
+)
+
+// Add adds a tag to tag set.
+func (ts *TagSet) Add(tag TagSet) {
+	*ts |= tag
+}
+
+// Has checks a tag included in tag set.
+func (ts *TagSet) Has(tag TagSet) bool {
+	return *ts&tag != 0
+}
+
+// FromList converts list of tags to TagSet
+func FromList(tags []string) *TagSet {
+	ts := TagSet(0)
+	for _, tag := range tags {
+		if v, err := TagSetString(tag); err == nil {
+			ts.Add(v)
+		}
+	}
+	return &ts
+}
+
+// MarshalJSON converts the TagSet to a list (JS array).
+func (ts *TagSet) MarshalJSON() ([]byte, error) {
+	var tags []string
+	for _, tag := range TagSetValues() {
+		if ts.Has(tag) {
+			tags = append(tags, tag.String())
+		}
+	}
+	return json.Marshal(tags)
+}
+
+// UnmarshalJSON converts the tag list back to expected tag set.
+func (ts *TagSet) UnmarshalJSON(data []byte) error {
+	var tags []string
+	if err := json.Unmarshal(data, &tags); err != nil {
+		return err
+	}
+	if len(tags) != 0 {
+		*ts = *FromList(tags)
+	}
+	return nil
+}
+
+// UnmarshalText converts the tag list to TagSet.
+func (ts *TagSet) UnmarshalText(data []byte) error {
+	var list = bytes.Split(data, []byte(","))
+
+	for _, key := range list {
+		key := strings.TrimSpace(string(key))
+		if key == "" {
+			continue
+		}
+		if v, err := TagSetString(key); err == nil {
+			ts.Add(v)
+		}
+	}
+	return nil
+}

lib/tagset/tagset_test.go

@@ -0,0 +1,64 @@
+package tagset
+
+import (
+	"encoding/json"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestTagSetMarshalJSON(t *testing.T) {
+	var tests = []struct {
+		tagset   TagSet
+		expected string
+	}{
+		{IP, `["ip"]`},
+		{0, `null`},
+	}
+
+	for _, tc := range tests {
+		ts := &tc.tagset
+		got, err := json.Marshal(ts)
+		require.Nil(t, err)
+		require.Equal(t, tc.expected, string(got))
+	}
+
+}
+
+func TestTagSet_UnmarshalJSON(t *testing.T) {
+	var tests = []struct {
+		tags []byte
+		sets []TagSet
+	}{
+		{[]byte(`[]`), []TagSet{}},
+		{[]byte(`["ip", "proto"]`), []TagSet{IP, Proto}},
+	}
+
+	for _, tc := range tests {
+		ts := new(TagSet)
+		require.Nil(t, json.Unmarshal(tc.tags, ts))
+		for _, tag := range tc.sets {
+			assert.True(t, ts.Has(tag))
+		}
+	}
+
+}
+
+func TestTagSetTextUnmarshal(t *testing.T) {
+	var testMatrix = map[string]TagSet{
+		"":                      0,
+		"ip":                    IP,
+		"ip,proto":              IP | Proto,
+		"   ip  ,  proto  ":     IP | Proto,
+		"   ip  ,   ,  proto  ": IP | Proto,
+		"   ip  ,,  proto  ,,":  IP | Proto,
+	}
+
+	for input, expected := range testMatrix {
+		var set = new(TagSet)
+		err := set.UnmarshalText([]byte(input))
+		require.NoError(t, err)
+		require.Equal(t, expected, *set)
+	}
+}