Do a large chunk of the move to go

This commit moves a huge chunk of the code to go. The TODO.md document
indicates what is left to be done.

env/distillery.go

@@ -0,0 +1,77 @@
+package env
+
+import (
+	"context"
+	"os"
+	"strings"
+
+	"github.com/FAU-CDI/wisski-distillery/internal/config"
+	"github.com/tkw1536/goprogram/exit"
+)
+
+// Distillery represents a running instance for the distillery
+type Distillery struct {
+	Config *config.Config
+}
+
+func (dis Distillery) HTTPSEnabled() bool {
+	return dis.Config.CertbotEmail != ""
+}
+
+// Returns the default virtual host
+func (dis Distillery) DefaultVirtualHost() string {
+	VIRTUAL_HOST := dis.Config.DefaultDomain
+	if len(dis.Config.SelfExtraDomains) > 0 {
+		VIRTUAL_HOST += "," + strings.Join(dis.Config.SelfExtraDomains, ",")
+	}
+	return VIRTUAL_HOST
+}
+
+func (dis Distillery) DefaultLetsencryptHost() string {
+	if !dis.HTTPSEnabled() {
+		return ""
+	}
+	return dis.DefaultVirtualHost()
+}
+
+// Context returns a new Context belonging to this distillery
+func (dis Distillery) Context() context.Context {
+	return context.Background()
+}
+
+var errNoConfigFile = exit.Error{
+	ExitCode: exit.ExitGeneralArguments,
+	Message:  "Configuration File does not exist",
+}
+
+var errOpenConfig = exit.Error{
+	ExitCode: exit.ExitGeneralArguments,
+	Message:  "error loading configuration file: %s",
+}
+
+// NewDistillery creates a new distillery object from a set of parameters and requirements
+func NewDistillery(params Params, req Requirements) (env *Distillery, err error) {
+	env = &Distillery{}
+
+	// if we don't need to load the config, there is nothing to do
+	if !req.NeedsConfig {
+		return
+	}
+
+	// if there is no no config file, return
+	cfg := params.ConfigFilePath()
+	if cfg == "" {
+		return nil, errNoConfigFile
+	}
+
+	f, err := os.Open(params.ConfigFilePath())
+	if err != nil {
+		return nil, errOpenConfig.WithMessageF(err)
+	}
+	defer f.Close()
+
+	// unmarshal the config
+	env.Config = &config.Config{}
+	err = env.Config.Unmarshal(f)
+	return
+}