Frontend/backend project structure

+ Base implementation of a differential synchronization based on Neil
  Fraser article/talk

See https://www.youtube.com/watch?v=S2Hp_1jqpY8

server/internal/config/config.go

@@ -0,0 +1,77 @@
+package config
+
+import (
+	"io"
+	"io/ioutil"
+
+	"github.com/caarlos0/env/v6"
+	"github.com/pkg/errors"
+
+	"gopkg.in/yaml.v2"
+)
+
+type Config struct {
+	HTTP HTTPConfig `yaml:"http"`
+	Data DataConfig `ymal:"data"`
+}
+
+type HTTPConfig struct {
+	Address string `yaml:"address" env:"GUESSTIMATE_HTTP_ADDRESS"`
+}
+
+type DataConfig struct {
+	Path string `yaml:"path" env:"GUESSTIMATE_DATA_PATH"`
+}
+
+// NewFromFile retrieves the configuration from the given file
+func NewFromFile(filepath string) (*Config, error) {
+	config := NewDefault()
+
+	data, err := ioutil.ReadFile(filepath)
+	if err != nil {
+		return nil, errors.Wrapf(err, "could not read file '%s'", filepath)
+	}
+
+	if err := yaml.Unmarshal(data, config); err != nil {
+		return nil, errors.Wrapf(err, "could not unmarshal configuration")
+	}
+
+	return config, nil
+}
+
+func WithEnvironment(conf *Config) error {
+	if err := env.Parse(conf); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func NewDumpDefault() *Config {
+	config := NewDefault()
+	return config
+}
+
+func NewDefault() *Config {
+	return &Config{
+		HTTP: HTTPConfig{
+			Address: ":8081",
+		},
+		Data: DataConfig{
+			Path: "guesstimate.db",
+		},
+	}
+}
+
+func Dump(config *Config, w io.Writer) error {
+	data, err := yaml.Marshal(config)
+	if err != nil {
+		return errors.Wrap(err, "could not dump config")
+	}
+
+	if _, err := w.Write(data); err != nil {
+		return err
+	}
+
+	return nil
+}

server/internal/config/provider.go

@@ -0,0 +1,9 @@
+package config
+
+import "gitlab.com/wpetit/goweb/service"
+
+func ServiceProvider(config *Config) service.Provider {
+	return func(ctn *service.Container) (interface{}, error) {
+		return config, nil
+	}
+}

server/internal/config/service.go

@@ -0,0 +1,33 @@
+package config
+
+import (
+	"github.com/pkg/errors"
+	"gitlab.com/wpetit/goweb/service"
+)
+
+const ServiceName service.Name = "config"
+
+// From retrieves the config service in the given container
+func From(container *service.Container) (*Config, error) {
+	service, err := container.Service(ServiceName)
+	if err != nil {
+		return nil, errors.Wrapf(err, "error while retrieving '%s' service", ServiceName)
+	}
+
+	srv, ok := service.(*Config)
+	if !ok {
+		return nil, errors.Errorf("retrieved service is not a valid '%s' service", ServiceName)
+	}
+
+	return srv, nil
+}
+
+// Must retrieves the config service in the given container or panic otherwise
+func Must(container *service.Container) *Config {
+	srv, err := From(container)
+	if err != nil {
+		panic(err)
+	}
+
+	return srv
+}