1 files changed, 191 insertions, 0 deletions
diff --git a/objects/object_tree.go b/objects/object_tree.go
new file mode 100644
index 0000000..07c265c
--- /dev/null
+++ b/objects/object_tree.go
@@ -0,0 +1,191 @@
+package objects
+
+import (
+	"bufio"
+	"bytes"
+	"errors"
+	"fmt"
+	"sort"
+)
+
+type TreeEntryType string
+
+const (
+	TETFile    TreeEntryType = "file"
+	TETDir     TreeEntryType = "dir"
+	TETSymlink TreeEntryType = "symlink"
+)
+
+var treeEntryTypes = map[TreeEntryType]struct{}{
+	TETFile:    {},
+	TETDir:     {},
+	TETSymlink: {},
+}
+
+type TreeEntry interface {
+	Type() TreeEntryType
+	equalContent(TreeEntry) bool
+	toProperties() properties
+}
+
+func compareTreeEntries(a, b TreeEntry) bool {
+	return a.Type() == b.Type() && a.equalContent(b)
+}
+
+type TreeEntryFile ObjectId
+
+func (tef TreeEntryFile) Type() TreeEntryType {
+	return TETFile
+}
+
+func (tef TreeEntryFile) toProperties() properties {
+	return properties{"ref": ObjectId(tef).String()}
+}
+
+func (a TreeEntryFile) equalContent(_b TreeEntry) bool {
+	b, ok := _b.(TreeEntryFile)
+	return ok && ObjectId(b).Equals(ObjectId(a))
+}
+
+type TreeEntryDir ObjectId
+
+func (ted TreeEntryDir) Type() TreeEntryType {
+	return TETDir
+}
+
+func (ted TreeEntryDir) toProperties() properties {
+	return properties{"ref": ObjectId(ted).String()}
+}
+
+func (a TreeEntryDir) equalContent(_b TreeEntry) bool {
+	b, ok := _b.(TreeEntryDir)
+	return ok && ObjectId(b).Equals(ObjectId(a))
+}
+
+type TreeEntrySymlink string
+
+func (tes TreeEntrySymlink) Type() TreeEntryType {
+	return TETSymlink
+}
+
+func (tes TreeEntrySymlink) toProperties() properties {
+	return properties{"target": string(tes)}
+}
+
+func (a TreeEntrySymlink) equalContent(_b TreeEntry) bool {
+	b, ok := _b.(TreeEntrySymlink)
+	return ok && b == a
+}
+
+type Tree map[string]TreeEntry
+
+func (t Tree) Type() ObjectType {
+	return OTTree
+}
+
+func (t Tree) Payload() (out []byte) {
+	lines := []string{}
+	for name, entry := range t {
+		props := entry.toProperties()
+		props["type"] = string(entry.Type())
+		props["name"] = name
+
+		line, err := props.MarshalText()
+		if err != nil {
+			panic(err)
+		}
+
+		lines = append(lines, string(line)+"\n")
+	}
+
+	sort.Strings(lines)
+
+	for _, line := range lines {
+		out = append(out, line...)
+	}
+
+	return
+}
+
+func getObjectIdFromProps(p properties, key string) (ObjectId, error) {
+	raw, ok := p[key]
+	if !ok {
+		return ObjectId{}, fmt.Errorf("Missing key: %s", key)
+	}
+
+	oid, err := ParseObjectId(raw)
+	return oid, err
+}
+
+func (t Tree) FromPayload(payload []byte) error {
+	sc := bufio.NewScanner(bytes.NewReader(payload))
+
+	for sc.Scan() {
+		line := sc.Bytes()
+		if len(line) == 0 {
+			continue
+		}
+
+		props := make(properties)
+		if err := props.UnmarshalText(line); err != nil {
+			return nil
+		}
+
+		entry_type, ok := props["type"]
+		if !ok {
+			return errors.New("Missing property: type")
+		}
+
+		var entry TreeEntry
+		switch TreeEntryType(entry_type) {
+		case TETFile:
+			ref, err := getObjectIdFromProps(props, "ref")
+			if err != nil {
+				return err
+			}
+			entry = TreeEntryFile(ref)
+		case TETDir:
+			ref, err := getObjectIdFromProps(props, "ref")
+			if err != nil {
+				return err
+			}
+			entry = TreeEntryDir(ref)
+		case TETSymlink:
+			target, ok := props["target"]
+			if !ok {
+				return errors.New("Missing key: target")
+			}
+			entry = TreeEntrySymlink(target)
+		default:
+			// TODO: Or should we just ignore this entry? There might be more types in the future...
+			return fmt.Errorf("Unknown tree entry type: %s", entry_type)
+		}
+
+		name, ok := props["name"]
+		if !ok {
+			return errors.New("Missing property: name")
+		}
+
+		t[name] = entry
+	}
+
+	return sc.Err()
+}
+
+func (a Tree) Equals(b Tree) bool {
+	for k, va := range a {
+		vb, ok := b[k]
+		if !ok || va.Type() != vb.Type() || !va.equalContent(vb) {
+			return false
+		}
+	}
+
+	for k := range b {
+		_, ok := a[k]
+		if !ok {
+			return false
+		}
+	}
+
+	return true
+}