Add gid set

Signed-off-by: Bryan Frimin <bryan@probo.com>

pkg/gid/set.go

@@ -0,0 +1,35 @@
+// Copyright (c) 2026 Probo Inc <hello@probo.com>.
+//
+// Permission to use, copy, modify, and/or distribute this software for any
+// purpose with or without fee is hereby granted, provided that the above
+// copyright notice and this permission notice appear in all copies.
+//
+// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
+// REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
+// AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
+// INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
+// LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
+// OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+// PERFORMANCE OF THIS SOFTWARE.
+
+package gid
+
+type (
+	Set map[GID]struct{}
+)
+
+// NewSet returns the set of distinct ids.
+func NewSet(ids ...GID) Set {
+	set := make(Set, len(ids))
+	for _, id := range ids {
+		set[id] = struct{}{}
+	}
+
+	return set
+}
+
+func (s Set) Contains(id GID) bool {
+	_, ok := s[id]
+
+	return ok
+}

pkg/gid/set_test.go

@@ -0,0 +1,117 @@
+// Copyright (c) 2026 Probo Inc <hello@probo.com>.
+//
+// Permission to use, copy, modify, and/or distribute this software for any
+// purpose with or without fee is hereby granted, provided that the above
+// copyright notice and this permission notice appear in all copies.
+//
+// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
+// REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
+// AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
+// INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
+// LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
+// OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+// PERFORMANCE OF THIS SOFTWARE.
+
+package gid_test
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"go.probo.inc/probo/pkg/gid"
+)
+
+func TestNewSet(t *testing.T) {
+	t.Parallel()
+
+	tenantID := gid.NewTenantID()
+
+	t.Run(
+		"empty",
+		func(t *testing.T) {
+			t.Parallel()
+
+			assert.Len(t, gid.NewSet(), 0)
+		},
+	)
+
+	t.Run(
+		"distinct ids",
+		func(t *testing.T) {
+			t.Parallel()
+
+			a := gid.New(tenantID, 1)
+			b := gid.New(tenantID, 2)
+
+			set := gid.NewSet(a, b)
+
+			assert.Len(t, set, 2)
+			assert.True(t, set.Contains(a))
+			assert.True(t, set.Contains(b))
+		},
+	)
+
+	t.Run(
+		"deduplicates",
+		func(t *testing.T) {
+			t.Parallel()
+
+			a := gid.New(tenantID, 1)
+			b := gid.New(tenantID, 2)
+
+			set := gid.NewSet(a, a, b, a)
+
+			assert.Len(t, set, 2)
+		},
+	)
+}
+
+func TestSet_Contains(t *testing.T) {
+	t.Parallel()
+
+	tenantID := gid.NewTenantID()
+
+	t.Run(
+		"member",
+		func(t *testing.T) {
+			t.Parallel()
+
+			a := gid.New(tenantID, 1)
+
+			assert.True(t, gid.NewSet(a).Contains(a))
+		},
+	)
+
+	t.Run(
+		"non-member",
+		func(t *testing.T) {
+			t.Parallel()
+
+			a := gid.New(tenantID, 1)
+			b := gid.New(tenantID, 2)
+
+			assert.False(t, gid.NewSet(a).Contains(b))
+		},
+	)
+
+	t.Run(
+		"nil gid only member when added",
+		func(t *testing.T) {
+			t.Parallel()
+
+			a := gid.New(tenantID, 1)
+
+			assert.False(t, gid.NewSet(a).Contains(gid.Nil))
+			assert.True(t, gid.NewSet(gid.Nil).Contains(gid.Nil))
+		},
+	)
+
+	t.Run(
+		"empty set",
+		func(t *testing.T) {
+			t.Parallel()
+
+			assert.False(t, gid.NewSet().Contains(gid.New(tenantID, 1)))
+		},
+	)
+}