From d7ef84a4040ff232662c7d00cc7e49befbd01834 Mon Sep 17 00:00:00 2001
From: Jozef Reisinger <jozef.reisinger@gmail.com>
Date: Tue, 19 Sep 2023 11:57:18 +0200
Subject: [PATCH] add promyaml kata

---
 go.mod                      |  1 +
 go.sum                      |  4 ++++
 katas.md                    |  1 +
 promyaml/promyaml.go        | 40 +++++++++++++++++++++++++++++++++++++
 promyaml/promyaml_test.go   | 32 +++++++++++++++++++++++++++++
 promyaml/testdata/prom.yaml |  9 +++++++++
 6 files changed, 87 insertions(+)
 create mode 100644 promyaml/promyaml.go
 create mode 100644 promyaml/promyaml_test.go
 create mode 100644 promyaml/testdata/prom.yaml

diff --git a/go.mod b/go.mod
index 9213828..8e71525 100644
--- a/go.mod
+++ b/go.mod
@@ -6,6 +6,7 @@ require (
 	github.com/google/go-cmp v0.5.9
 	github.com/rogpeppe/go-internal v1.11.0
 	golang.org/x/net v0.13.0
+	gopkg.in/yaml.v3 v3.0.1
 )
 
 require (
diff --git a/go.sum b/go.sum
index ab8870a..a711a6d 100644
--- a/go.sum
+++ b/go.sum
@@ -8,3 +8,7 @@ golang.org/x/sys v0.10.0 h1:SqMFp9UcQJZa+pmYuAKjd9xq1f0j5rLcDIk0mj4qAsA=
 golang.org/x/sys v0.10.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/tools v0.1.12 h1:VveCTK38A2rkS8ZqFY25HIDFscX5X9OoEhJd3quQmXU=
 golang.org/x/tools v0.1.12/go.mod h1:hNGJHUnrk76NpqgfD5Aqm5Crs+Hm0VOH/i9J2+nxYbc=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+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/katas.md b/katas.md
index f663312..97252f0 100644
--- a/katas.md
+++ b/katas.md
@@ -1,3 +1,4 @@
+* 2023-09-19: promyaml
 * 2023-09-18: kv
 * 2023-09-13: battery
 * 2023-09-11: older
diff --git a/promyaml/promyaml.go b/promyaml/promyaml.go
new file mode 100644
index 0000000..ef6466b
--- /dev/null
+++ b/promyaml/promyaml.go
@@ -0,0 +1,40 @@
+// Package promyaml shows how to get (Prometheus) configuration from YAML file.
+//
+// Level: intermediate
+// Topics: yaml, tpg-tools
+package promyaml
+
+import (
+	"os"
+	"time"
+
+	"gopkg.in/yaml.v3"
+)
+
+type Config struct {
+	Global GlobalConfig
+}
+
+type GlobalConfig struct {
+	ScrapeInterval     time.Duration     `yaml:"scrape_interval"`
+	EvaluationInterval time.Duration     `yaml:"evaluation_interval"`
+	ScrapeTimeout      time.Duration     `yaml:"scrape_timeout"`
+	ExternalLabels     map[string]string `yaml:"external_labels"`
+}
+
+func ConfigFrom(path string) (Config, error) {
+	f, err := os.Open(path)
+	if err != nil {
+		return Config{}, err
+	}
+	defer f.Close()
+	config := Config{
+		GlobalConfig{
+			ScrapeTimeout: 10 * time.Second, // default
+		},
+	}
+	if err := yaml.NewDecoder(f).Decode(&config); err != nil {
+		return Config{}, err
+	}
+	return config, err
+}
diff --git a/promyaml/promyaml_test.go b/promyaml/promyaml_test.go
new file mode 100644
index 0000000..c7f0347
--- /dev/null
+++ b/promyaml/promyaml_test.go
@@ -0,0 +1,32 @@
+package promyaml_test
+
+import (
+	"testing"
+	"time"
+
+	"github.com/jreisinger/gokatas/promyaml"
+
+	"github.com/google/go-cmp/cmp"
+)
+
+func TestConfigFrom_CorrectlyParsesYAMLData(t *testing.T) {
+	t.Parallel()
+	want := promyaml.Config{
+		Global: promyaml.GlobalConfig{
+			ScrapeInterval:     15 * time.Second,
+			EvaluationInterval: 30 * time.Second,
+			ScrapeTimeout:      10 * time.Second,
+			ExternalLabels: map[string]string{
+				"monitor": "codelab",
+				"foo":     "bar",
+			},
+		},
+	}
+	got, err := promyaml.ConfigFrom("testdata/prom.yaml")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !cmp.Equal(want, got) {
+		t.Error(cmp.Diff(want, got))
+	}
+}
diff --git a/promyaml/testdata/prom.yaml b/promyaml/testdata/prom.yaml
new file mode 100644
index 0000000..5e9ae7a
--- /dev/null
+++ b/promyaml/testdata/prom.yaml
@@ -0,0 +1,9 @@
+# my global config
+global:
+  scrape_interval: 15s
+  evaluation_interval: 30s
+  # scrape_timeout is set to the global default (10s).
+
+  external_labels:
+    monitor: codelab
+    foo: bar