Don't create a util package - move the functionality to 'internal'

internal/load.go

@@ -0,0 +1,82 @@
+package internal
+
+import (
+	"fmt"
+	"io"
+	client "net/http"
+	"net/url"
+	"os"
+	"path/filepath"
+
+	"github.com/google/cayley/config"
+	"github.com/google/cayley/db"
+	"github.com/google/cayley/graph"
+	"github.com/google/cayley/quad"
+	"github.com/google/cayley/quad/cquads"
+	"github.com/google/cayley/quad/nquads"
+)
+
+// Load loads a graph from the given path and write it to qw.  See
+// DecompressAndLoad for more information.
+func Load(qw graph.QuadWriter, cfg *config.Config, path, typ string) error {
+	return DecompressAndLoad(qw, cfg, path, typ, db.Load)
+}
+
+// DecompressAndLoad will load or fetch a graph from the given path, decompress
+// it, and then call the given load function to process the decompressed graph.
+// If no loadFn is provided, db.Load is called.
+func DecompressAndLoad(qw graph.QuadWriter, cfg *config.Config, path, typ string, loadFn func(graph.QuadWriter, *config.Config, quad.Unmarshaler) error) error {
+	var r io.Reader
+
+	if path == "" {
+		path = cfg.DatabasePath
+	}
+	if path == "" {
+		return nil
+	}
+	u, err := url.Parse(path)
+	if err != nil || u.Scheme == "file" || u.Scheme == "" {
+		// Don't alter relative URL path or non-URL path parameter.
+		if u.Scheme != "" && err == nil {
+			// Recovery heuristic for mistyping "file://path/to/file".
+			path = filepath.Join(u.Host, u.Path)
+		}
+		f, err := os.Open(path)
+		if err != nil {
+			return fmt.Errorf("could not open file %q: %v", path, err)
+		}
+		defer f.Close()
+		r = f
+	} else {
+		res, err := client.Get(path)
+		if err != nil {
+			return fmt.Errorf("could not get resource <%s>: %v", u, err)
+		}
+		defer res.Body.Close()
+		r = res.Body
+	}
+
+	r, err = Decompressor(r)
+	if err != nil {
+		if err == io.EOF {
+			return nil
+		}
+		return err
+	}
+
+	var dec quad.Unmarshaler
+	switch typ {
+	case "cquad":
+		dec = cquads.NewDecoder(r)
+	case "nquad":
+		dec = nquads.NewDecoder(r)
+	default:
+		return fmt.Errorf("unknown quad format %q", typ)
+	}
+
+	if loadFn != nil {
+		return loadFn(qw, cfg, dec)
+	}
+
+	return db.Load(qw, cfg, dec)
+}