adding config stuff

go.mod

@@ -4,7 +4,13 @@ go 1.21.1
 
 require github.com/spf13/cobra v1.7.0
 
+require github.com/stretchr/testify v1.8.4
+
 require (
+	github.com/davecgh/go-spew v1.1.1 // indirect
 	github.com/inconshreveable/mousetrap v1.1.0 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
 	github.com/spf13/pflag v1.0.5 // indirect
+	github.com/stretchr/objx v0.5.0 // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
 )

go.sum

@@ -1,10 +1,25 @@
 github.com/cpuguy83/go-md2man/v2 v2.0.2/go.mod h1:tgQtvFlXSQOSOSIRvRPT7W67SCa46tRHOmNcaadrF8o=
+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/inconshreveable/mousetrap v1.1.0 h1:wN+x4NVGpMsO7ErUn/mUI3vEoE6Jt13X2s0bqwp9tc8=
 github.com/inconshreveable/mousetrap v1.1.0/go.mod h1:vpF70FUmC8bwa3OWnCshd2FqLfsEA9PFc4w1p2J65bw=
+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/russross/blackfriday/v2 v2.1.0/go.mod h1:+Rmxgy9KzJVeS9/2gXHxylqXiyQDYRxCVz55jmeOWTM=
 github.com/spf13/cobra v1.7.0 h1:hyqWnYt1ZQShIddO5kBpj3vu05/++x6tJ6dg8EC572I=
 github.com/spf13/cobra v1.7.0/go.mod h1:uLxZILRyS/50WlhOIKD7W6V5bgeIt+4sICxh6uRMrb0=
 github.com/spf13/pflag v1.0.5 h1:iy+VFUOCP1a+8yFto/drg2CJ5u0yRoB7fZw3DKv/JXA=
 github.com/spf13/pflag v1.0.5/go.mod h1:McXfInJRrz4CZXVZOBLb0bTZqETkiAhM9Iw0y3An2Bg=
+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 h1:1zr/of2m5FGMsad5YfcqgdqdWrIhu+EBEJRhR1U7z/c=
+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 v1.8.4 h1:CcVxjf3Q8PM0mHUKJCdn+eZZtm5yQwehR5yeSVQQcUk=
+github.com/stretchr/testify v1.8.4/go.mod h1:sz/lmYIOXD/1dqDmKjjqLyZ2RngseejIcXlSw2iwfAo=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+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=

internal/config/config.go

@@ -0,0 +1,59 @@
+package config
+
+import (
+	"fmt"
+	"os"
+	"reflect"
+	"strconv"
+)
+
+const prefix = "CARTESI_"
+
+type Config struct {
+	GraphQLPort int `env:"GRAPHQL_PORT" default:"8080"`
+	InspectPort int `env:"INSPECT_PORT" default:"8081"`
+}
+
+func Load() (*Config, error) {
+	config := &Config{}
+	v := reflect.Indirect(reflect.ValueOf(config))
+	t := reflect.TypeOf(*config)
+
+	for i := 0; i < t.NumField(); i++ {
+		field := t.Field(i)
+		env, ok := field.Tag.Lookup("env")
+		if !ok {
+			return nil, fmt.Errorf(`field "%s" must have an "env" tag`, field.Name)
+		}
+
+		s := os.Getenv(prefix + env)
+		if s == "" {
+			s = field.Tag.Get("default")
+			if s == "" {
+				return nil, fmt.Errorf(`empty value for %s`, env)
+			}
+		}
+		value, err := convert(s, field.Type)
+		if err != nil {
+			return nil, err
+		}
+
+		v.FieldByName(field.Name).Set(value)
+	}
+
+	return config, nil
+}
+
+func convert(s string, t reflect.Type) (reflect.Value, error) {
+	kind := t.Kind()
+	switch kind {
+	case reflect.Int:
+		n, err := strconv.Atoi(s)
+		return reflect.ValueOf(n), err
+	case reflect.String:
+		return reflect.ValueOf(s), nil
+	default:
+		err := fmt.Errorf(`string "%s" cannot be converted to type %s`, s, kind)
+		return reflect.ValueOf(nil), err
+	}
+}

internal/config/config_test.go

@@ -0,0 +1,21 @@
+package config
+
+import (
+	"os"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestConfigDefaults(t *testing.T) {
+	_, err := Load()
+	assert.Nil(t, err)
+}
+
+func TestConfigTodo(t *testing.T) {
+	if os.Setenv("CARTESI_INSPECT_PORT", "aaa") != nil {
+		assert.Fail(t, "internal")
+	}
+	_, err := Load()
+	assert.Nil(t, err)
+}