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-rw-r--r--utils/difftree/difftree.go194
1 files changed, 194 insertions, 0 deletions
diff --git a/utils/difftree/difftree.go b/utils/difftree/difftree.go
new file mode 100644
index 0000000..76bdb84
--- /dev/null
+++ b/utils/difftree/difftree.go
@@ -0,0 +1,194 @@
+package difftree
+
+import (
+ "bytes"
+ "fmt"
+ "io"
+ "sort"
+ "strings"
+
+ "gopkg.in/src-d/go-git.v3"
+ "gopkg.in/src-d/go-git.v3/core"
+)
+
+type Action int
+
+func (a Action) String() string {
+ switch a {
+ case Insert:
+ return "Insert"
+ case Delete:
+ return "Delete"
+ case Modify:
+ return "Modify"
+ default:
+ panic(fmt.Sprintf("unsupported action: %d", a))
+ }
+}
+
+const (
+ Insert Action = iota
+ Delete
+ Modify
+)
+
+type Change struct {
+ Action
+ File *git.File
+}
+
+func (c *Change) String() string {
+ return fmt.Sprintf("<Action: %s, Path: %s, Size: %d>", c.Action, c.File.Name, c.File.Size)
+}
+
+type Changes []*Change
+
+func newEmpty() Changes {
+ return make([]*Change, 0, 0)
+}
+
+func New(a, b *git.Tree) (Changes, error) {
+ if a == b {
+ return newEmpty(), nil
+ }
+
+ if a == nil || b == nil {
+ return newWithEmpty(a, b)
+ }
+
+ return newDiffTree(a, b)
+}
+
+func (c Changes) Len() int {
+ return len(c)
+}
+
+func (c Changes) Swap(i, j int) {
+ c[i], c[j] = c[j], c[i]
+}
+
+func (c Changes) Less(i, j int) bool {
+ return strings.Compare(c[i].File.Name, c[j].File.Name) < 0
+}
+
+func (c Changes) String() string {
+ var buffer bytes.Buffer
+ buffer.WriteString("[")
+ comma := ""
+ for _, v := range c {
+ buffer.WriteString(comma)
+ buffer.WriteString(v.String())
+ comma = ", "
+ }
+ buffer.WriteString("]")
+
+ return buffer.String()
+}
+
+func newWithEmpty(a, b *git.Tree) (Changes, error) {
+ changes := newEmpty()
+
+ var action Action
+ var tree *git.Tree
+ if a == nil {
+ action = Insert
+ tree = b
+ } else {
+ action = Delete
+ tree = a
+ }
+
+ iter := tree.Files()
+ defer iter.Close()
+
+ for {
+ file, err := iter.Next()
+ if err == io.EOF {
+ break
+ } else if err != nil {
+ return nil, fmt.Errorf("cannot get next file: %s", err)
+ }
+
+ insert := &Change{
+ Action: action,
+ File: file,
+ }
+ changes = append(changes, insert)
+ }
+
+ return changes, nil
+}
+
+// FIXME: this is very inefficient, but correct.
+// The proper way to do this is to implement a diff-tree algorithm,
+// while taking advantage of the tree hashes to avoid traversing
+// subtrees when the hash is equal in both inputs.
+func newDiffTree(a, b *git.Tree) (Changes, error) {
+ result := newEmpty()
+
+ aChanges, err := newWithEmpty(a, nil)
+ if err != nil {
+ return nil, fmt.Errorf("cannot create nil-diff of source tree: %s", err)
+ }
+ sort.Sort(aChanges)
+
+ bChanges, err := newWithEmpty(nil, b)
+ if err != nil {
+ return nil, fmt.Errorf("cannot create nil-diff of destination tree: %s", err)
+ }
+ sort.Sort(bChanges)
+
+ for len(aChanges) > 0 && len(bChanges) > 0 {
+ switch comp := strings.Compare(aChanges[0].File.Name, bChanges[0].File.Name); {
+ case comp == 0: // append as "Modify" or ignore if not changed
+ modified, err := hasChange(a, b, aChanges[0].File.Name)
+ if err != nil {
+ return nil, err
+ }
+ if modified {
+ bChanges[0].Action = Modify
+ result = append(result, bChanges[0])
+ } else {
+ }
+ aChanges = aChanges[1:]
+ bChanges = bChanges[1:]
+ case comp < 0: // delete first a change
+ result = append(result, aChanges[0])
+ aChanges = aChanges[1:]
+ case comp > 0: // insert first b change
+ result = append(result, bChanges[0])
+ bChanges = bChanges[1:]
+ }
+ }
+
+ // append all remaining changes in aChanges, if any, as deletes
+ // append all remaining changes in bChanges, if any, as inserts
+ result = append(result, aChanges...)
+ result = append(result, bChanges...)
+
+ return result, nil
+}
+
+func hasChange(a, b *git.Tree, path string) (bool, error) {
+ ha, err := hash(a, path)
+ if err != nil {
+ return false, err
+ }
+
+ hb, err := hash(b, path)
+ if err != nil {
+ return false, err
+ }
+
+ return ha != hb, nil
+}
+
+func hash(tree *git.Tree, path string) (core.Hash, error) {
+ file, err := tree.File(path)
+ if err != nil {
+ var empty core.Hash
+ return empty, fmt.Errorf("cannot find file %s in tree: %s", path, err)
+ }
+
+ return file.Hash, nil
+}