From 07b5bec2199a86564f6f719e4c6b0c15f566b106 Mon Sep 17 00:00:00 2001
From: Ian Gulliver <github@flamingcow.io>
Date: Thu, 20 Apr 2023 05:17:28 +0000
Subject: [PATCH] Initial commit

---
 go.mod           | 16 ++++++++++++++++
 go.sum           | 33 +++++++++++++++++++++++++++++++++
 metadata.go      | 33 +++++++++++++++++++++++++++++++++
 metadata_test.go | 29 +++++++++++++++++++++++++++++
 pkg_test.go      | 11 +++++++++++
 5 files changed, 122 insertions(+)
 create mode 100644 go.mod
 create mode 100644 go.sum
 create mode 100644 metadata.go
 create mode 100644 metadata_test.go
 create mode 100644 pkg_test.go

diff --git a/go.mod b/go.mod
new file mode 100644
index 0000000..97e5ed7
--- /dev/null
+++ b/go.mod
@@ -0,0 +1,16 @@
+module github.com/gopatchy/metadata
+
+go 1.19
+
+require (
+	github.com/stretchr/testify v1.8.2
+	go.uber.org/goleak v1.2.1
+)
+
+require (
+	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/kr/pretty v0.3.0 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
+	github.com/rogpeppe/go-internal v1.8.1-0.20211023094830-115ce09fd6b4 // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
+)
diff --git a/go.sum b/go.sum
new file mode 100644
index 0000000..abdb56f
--- /dev/null
+++ b/go.sum
@@ -0,0 +1,33 @@
+github.com/creack/pty v1.1.9/go.mod h1:oKZEueFk5CKHvIhNR5MUki03XCEU+Q6VDXinZuGJ33E=
+github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/kr/pretty v0.1.0/go.mod h1:dAy3ld7l9f0ibDNOQOHHMYYIIbhfbHSm3C4ZsoJORNo=
+github.com/kr/pretty v0.3.0 h1:WgNl7dwNpEZ6jJ9k1snq4pZsg7DOEN8hP9Xw0Tsjwk0=
+github.com/kr/pretty v0.3.0/go.mod h1:640gp4NfQd8pI5XOwp5fnNeVWj67G7CFk/SaSQn7NBk=
+github.com/kr/pty v1.1.1/go.mod h1:pFQYn66WHrOpPYNljwOMqo10TkYh1fy3cYio2l3bCsQ=
+github.com/kr/text v0.1.0/go.mod h1:4Jbv+DJW3UT/LiOwJeYQe1efqtUx/iVham/4vfdArNI=
+github.com/kr/text v0.2.0 h1:5Nx0Ya0ZqY2ygV366QzturHI13Jq95ApcVaJBhpS+AY=
+github.com/kr/text v0.2.0/go.mod h1:eLer722TekiGuMkidMxC/pM04lWEeraHUUmBw8l2grE=
+github.com/pkg/diff v0.0.0-20210226163009-20ebb0f2a09e/go.mod h1:pJLUxLENpZxwdsKMEsNbx1VGcRFpLqf3715MtcvvzbA=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/rogpeppe/go-internal v1.6.1/go.mod h1:xXDCJY+GAPziupqXw64V24skbSoqbTEfhy4qGm1nDQc=
+github.com/rogpeppe/go-internal v1.8.1-0.20211023094830-115ce09fd6b4 h1:Ha8xCaq6ln1a+R91Km45Oq6lPXj2Mla6CRJYcuV2h1w=
+github.com/rogpeppe/go-internal v1.8.1-0.20211023094830-115ce09fd6b4/go.mod h1:JeRgkft04UBgHMgCIwADu4Pn6Mtm5d4nPKWu0nJ5d+o=
+github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
+github.com/stretchr/objx v0.4.0/go.mod h1:YvHI0jy2hoMjB+UWwv71VJQ9isScKT/TqJzVSSt89Yw=
+github.com/stretchr/objx v0.5.0/go.mod h1:Yh+to48EsGEfYuaHDzXPcE3xhTkx73EhmCGUpEOglKo=
+github.com/stretchr/testify v1.7.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
+github.com/stretchr/testify v1.8.0/go.mod h1:yNjHg4UonilssWZ8iaSj1OCr/vHnekPRkoO+kdMU+MU=
+github.com/stretchr/testify v1.8.2 h1:+h33VjcLVPDHtOdpUCuF+7gSuG3yGIftsP1YvFihtJ8=
+github.com/stretchr/testify v1.8.2/go.mod h1:w2LPCIKwWwSfY2zedu0+kehJoqGctiVI29o6fzry7u4=
+go.uber.org/goleak v1.2.1 h1:NBol2c7O1ZokfZ0LEU9K6Whx/KnwvepVetCUhtKja4A=
+go.uber.org/goleak v1.2.1/go.mod h1:qlT2yGI9QafXHhZZLxlSuNsMw3FFLxBr+tBRlmO1xH4=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/check.v1 v1.0.0-20180628173108-788fd7840127 h1:qIbj1fsPNlZgppZ+VLlY7N33q108Sa+fhmuc+sWQYwY=
+gopkg.in/check.v1 v1.0.0-20180628173108-788fd7840127/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/errgo.v2 v2.1.0/go.mod h1:hNsd1EY+bozCKY1Ytp96fpM3vjJbqLJn88ws8XvfDNI=
+gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
+gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
diff --git a/metadata.go b/metadata.go
new file mode 100644
index 0000000..180c6e8
--- /dev/null
+++ b/metadata.go
@@ -0,0 +1,33 @@
+package metadata
+
+import (
+	"reflect"
+)
+
+type Metadata struct {
+	ID         string `json:"id"`
+	ETag       string `json:"etag"`
+	Generation int64  `json:"generation"`
+}
+
+func HasMetadata(obj any) bool {
+	return getMetadataField(obj).IsValid()
+}
+
+func GetMetadata(obj any) *Metadata {
+	return getMetadataField(obj).Addr().Interface().(*Metadata)
+}
+
+func ClearMetadata(obj any) {
+	SetMetadata(obj, &Metadata{})
+}
+
+func SetMetadata(obj any, md *Metadata) {
+	getMetadataField(obj).Set(reflect.ValueOf(*md))
+}
+
+func getMetadataField(obj any) reflect.Value {
+	v := reflect.ValueOf(obj)
+
+	return reflect.Indirect(v).FieldByName("Metadata")
+}
diff --git a/metadata_test.go b/metadata_test.go
new file mode 100644
index 0000000..3d45461
--- /dev/null
+++ b/metadata_test.go
@@ -0,0 +1,29 @@
+package metadata_test
+
+import (
+	"testing"
+
+	"github.com/gopatchy/metadata"
+	"github.com/stretchr/testify/require"
+)
+
+type TestType struct {
+	metadata.Metadata
+	Text string
+}
+
+func TestMetadata(t *testing.T) {
+	t.Parallel()
+
+	tt := &TestType{}
+
+	// Verify promoted field
+	tt.ID = "abc123"
+
+	m := metadata.GetMetadata(tt)
+	require.NotNil(t, m)
+	require.Equal(t, "abc123", m.ID)
+
+	metadata.ClearMetadata(tt)
+	require.Empty(t, tt.ID)
+}
diff --git a/pkg_test.go b/pkg_test.go
new file mode 100644
index 0000000..176170a
--- /dev/null
+++ b/pkg_test.go
@@ -0,0 +1,11 @@
+package metadata_test
+
+import (
+	"testing"
+
+	"go.uber.org/goleak"
+)
+
+func TestMain(m *testing.M) {
+	goleak.VerifyTestMain(m)
+}