Refactor Package structure

This commit cleans up the package structure, to make two new top-level
packages `internal` (for internal-use packages) and `pkg` (for general
shared utility code).

internal/env/init.go

@@ -0,0 +1,62 @@
+package env
+
+import (
+	"os"
+
+	"github.com/FAU-CDI/wisski-distillery/internal/config"
+	"github.com/FAU-CDI/wisski-distillery/internal/core"
+	"github.com/tkw1536/goprogram/exit"
+)
+
+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 core.Params, flags core.Flags, req core.Requirements) (env *Distillery, err error) {
+	env = &Distillery{
+		Upstream: Upstream{
+			SQL:         "127.0.0.1:3306",
+			Triplestore: "127.0.0.1:7200",
+		},
+	}
+
+	if flags.InternalInDocker {
+		env.Upstream.SQL = "sql:3306"
+		env.Upstream.Triplestore = "triplestore:7200"
+	}
+
+	// if we don't need to load the config, there is nothing to do
+	if !req.NeedsDistillery {
+		return
+	}
+
+	// try to find the configuration file
+	cfg := flags.ConfigPath // command line flags first
+	if cfg == "" {
+		cfg = params.ConfigPath // then globally provided files
+	}
+	if cfg == "" {
+		return nil, errNoConfigFile
+	}
+
+	// open the config file!
+	f, err := os.Open(params.ConfigPath)
+	if err != nil {
+		return nil, errOpenConfig.WithMessageF(err)
+	}
+	defer f.Close()
+
+	// unmarshal the config
+	env.Config = &config.Config{
+		ConfigPath: cfg,
+	}
+	err = env.Config.Unmarshal(f)
+	return
+}