feat: add WriteTo function

Writes a go-ipfs-files Node to a location in the filesystem.

filewriter.go

+package files
+
+import (
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+)
+
+// WriteTo writes the given node to the local filesystem at fpath.
+func WriteTo(nd Node, fpath string) error {
+	switch nd := nd.(type) {
+	case *Symlink:
+		return os.Symlink(nd.Target, fpath)
+	case File:
+		f, err := os.Create(fpath)
+		defer f.Close()
+		if err != nil {
+			return err
+		}
+		_, err = io.Copy(f, nd)
+		if err != nil {
+			return err
+		}
+		return nil
+	case Directory:
+		err := os.Mkdir(fpath, 0777)
+		if err != nil {
+			return err
+		}
+
+		entries := nd.Entries()
+		for entries.Next() {
+			child := filepath.Join(fpath, entries.Name())
+			if err := WriteTo(entries.Node(), child); err != nil {
+				return err
+			}
+		}
+		return entries.Err()
+	default:
+		return fmt.Errorf("file type %T at %q is not supported", nd, fpath)
+	}
+}

filewriter_test.go

+package files
+
+import (
+	"fmt"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+func TestWriteTo(t *testing.T) {
+	sf := NewMapDirectory(map[string]Node{
+		"1": NewBytesFile([]byte("Some text!\n")),
+		"2": NewBytesFile([]byte("beep")),
+		"3": NewMapDirectory(nil),
+		"4": NewBytesFile([]byte("boop")),
+		"5": NewMapDirectory(map[string]Node{
+			"a": NewBytesFile([]byte("foobar")),
+		}),
+	})
+	tmppath, err := ioutil.TempDir("", "files-test")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.RemoveAll(tmppath)
+
+	path := tmppath + "/output"
+
+	err = WriteTo(sf, path)
+	if err != nil {
+		t.Fatal(err)
+	}
+	expected := map[string]string{
+		".":   "",
+		"1":   "Some text!\n",
+		"2":   "beep",
+		"3":   "",
+		"4":   "boop",
+		"5":   "",
+		"5/a": "foobar",
+	}
+	err = filepath.Walk(path, func(cpath string, info os.FileInfo, err error) error {
+		rpath, err := filepath.Rel(path, cpath)
+		if err != nil {
+			return err
+		}
+		data, ok := expected[rpath]
+		if !ok {
+			return fmt.Errorf("expected something at %q", rpath)
+		}
+		delete(expected, rpath)
+
+		if info.IsDir() {
+			if data != "" {
+				return fmt.Errorf("expected a directory at %q", rpath)
+			}
+		} else {
+			actual, err := ioutil.ReadFile(cpath)
+			if err != nil {
+				return err
+			}
+			if string(actual) != data {
+				return fmt.Errorf("expected %q, got %q", data, string(actual))
+			}
+		}
+		return nil
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(expected) > 0 {
+		t.Fatalf("failed to find: %#v", expected)
+	}
+}