4 files changed, 79 insertions, 10 deletions

diff --git a/entity/dag/common_test.go b/entity/dag/common_test.go
index fa15cd1f..1898451d 100644
--- a/entity/dag/common_test.go
+++ b/entity/dag/common_test.go
@@ -23,10 +23,11 @@ type op1 struct {
 
 	OperationType int    `json:"type"`
 	Field1        string `json:"field_1"`
+	Files         []repository.Hash
 }
 
-func newOp1(author identity.Interface, field1 string) *op1 {
-	return &op1{author: author, OperationType: 1, Field1: field1}
+func newOp1(author identity.Interface, field1 string, files ...repository.Hash) *op1 {
+	return &op1{author: author, OperationType: 1, Field1: field1, Files: files}
 }
 
 func (o *op1) Id() entity.Id {
@@ -34,11 +35,15 @@ func (o *op1) Id() entity.Id {
 	return entity.DeriveId(data)
 }
 
+func (o *op1) Validate() error { return nil }
+
 func (o *op1) Author() identity.Interface {
 	return o.author
 }
 
-func (o *op1) Validate() error { return nil }
+func (o *op1) GetFiles() []repository.Hash {
+	return o.Files
+}
 
 type op2 struct {
 	author identity.Interface
@@ -56,12 +61,12 @@ func (o *op2) Id() entity.Id {
 	return entity.DeriveId(data)
 }
 
+func (o *op2) Validate() error { return nil }
+
 func (o *op2) Author() identity.Interface {
 	return o.author
 }
 
-func (o *op2) Validate() error { return nil }
-
 func unmarshaler(author identity.Interface, raw json.RawMessage) (Operation, error) {
 	var t struct {
 		OperationType int `json:"type"`
diff --git a/entity/dag/operation.go b/entity/dag/operation.go
index 94974a82..1bfb3d3d 100644
--- a/entity/dag/operation.go
+++ b/entity/dag/operation.go
@@ -3,6 +3,7 @@ package dag
 import (
 	"github.com/MichaelMure/git-bug/entity"
 	"github.com/MichaelMure/git-bug/identity"
+	"github.com/MichaelMure/git-bug/repository"
 )
 
 // Operation is a piece of data defining a change to reflect on the state of an Entity.
@@ -33,3 +34,11 @@ type Operation interface {
 	// Author returns the author of this operation
 	Author() identity.Interface
 }
+
+// OperationWithFiles is an extended Operation that has files dependency, stored in git.
+type OperationWithFiles interface {
+	Operation
+
+	// GetFiles return the files needed by this operation
+	GetFiles() []repository.Hash
+}
diff --git a/entity/dag/operation_pack.go b/entity/dag/operation_pack.go
index a436fd33..72063c60 100644
--- a/entity/dag/operation_pack.go
+++ b/entity/dag/operation_pack.go
@@ -15,10 +15,8 @@ import (
 	"github.com/MichaelMure/git-bug/util/lamport"
 )
 
-// TODO: extra data tree
-const extraEntryName = "extra"
-
 const opsEntryName = "ops"
+const extraEntryName = "extra"
 const versionEntryPrefix = "version-"
 const createClockEntryPrefix = "create-clock-"
 const editClockEntryPrefix = "edit-clock-"
@@ -118,6 +116,7 @@ func (opp *operationPack) Write(def Definition, repo repository.Repo, parentComm
 	// Make a Git tree referencing this blob and encoding the other values:
 	// - format version
 	// - clocks
+	// - extra data
 	tree := []repository.TreeEntry{
 		{ObjectType: repository.Blob, Hash: emptyBlobHash,
 			Name: fmt.Sprintf(versionEntryPrefix+"%d", def.FormatVersion)},
@@ -133,6 +132,17 @@ func (opp *operationPack) Write(def Definition, repo repository.Repo, parentComm
 			Name:       fmt.Sprintf(createClockEntryPrefix+"%d", opp.CreateTime),
 		})
 	}
+	if extraTree := opp.makeExtraTree(); len(extraTree) > 0 {
+		extraTreeHash, err := repo.StoreTree(extraTree)
+		if err != nil {
+			return "", err
+		}
+		tree = append(tree, repository.TreeEntry{
+			ObjectType: repository.Tree,
+			Hash:       extraTreeHash,
+			Name:       extraEntryName,
+		})
+	}
 
 	// Store the tree
 	treeHash, err := repo.StoreTree(tree)
@@ -163,6 +173,35 @@ func (opp *operationPack) Write(def Definition, repo repository.Repo, parentComm
 	return commitHash, nil
 }
 
+func (opp *operationPack) makeExtraTree() []repository.TreeEntry {
+	var tree []repository.TreeEntry
+	counter := 0
+	added := make(map[repository.Hash]interface{})
+
+	for _, ops := range opp.Operations {
+		ops, ok := ops.(OperationWithFiles)
+		if !ok {
+			continue
+		}
+
+		for _, file := range ops.GetFiles() {
+			if _, has := added[file]; !has {
+				tree = append(tree, repository.TreeEntry{
+					ObjectType: repository.Blob,
+					Hash:       file,
+					// The name is not important here, we only need to
+					// reference the blob.
+					Name: fmt.Sprintf("file%d", counter),
+				})
+				counter++
+				added[file] = struct{}{}
+			}
+		}
+	}
+
+	return tree
+}
+
 // readOperationPack read the operationPack encoded in git at the given Tree hash.
 //
 // Validity of the Lamport clocks is left for the caller to decide.
diff --git a/entity/dag/operation_pack_test.go b/entity/dag/operation_pack_test.go
index a12382af..0fe98dc7 100644
--- a/entity/dag/operation_pack_test.go
+++ b/entity/dag/operation_pack_test.go
@@ -1,6 +1,7 @@
 package dag
 
 import (
+	"math/rand"
 	"testing"
 
 	"github.com/stretchr/testify/require"
@@ -11,10 +12,16 @@ import (
 func TestOperationPackReadWrite(t *testing.T) {
 	repo, id1, _, resolver, def := makeTestContext()
 
+	blobHash1, err := repo.StoreData(randomData())
+	require.NoError(t, err)
+
+	blobHash2, err := repo.StoreData(randomData())
+	require.NoError(t, err)
+
 	opp := &operationPack{
 		Author: id1,
 		Operations: []Operation{
-			newOp1(id1, "foo"),
+			newOp1(id1, "foo", blobHash1, blobHash2),
 			newOp2(id1, "bar"),
 		},
 		CreateTime: 123,
@@ -36,7 +43,7 @@ func TestOperationPackReadWrite(t *testing.T) {
 	opp3 := &operationPack{
 		Author: id1,
 		Operations: []Operation{
-			newOp1(id1, "foo"),
+			newOp1(id1, "foo", blobHash1, blobHash2),
 			newOp2(id1, "bar"),
 		},
 		CreateTime: 123,
@@ -86,3 +93,12 @@ func TestOperationPackSignedReadWrite(t *testing.T) {
 	}
 	require.Equal(t, opp.Id(), opp3.Id())
 }
+
+func randomData() []byte {
+	var letterRunes = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"
+	b := make([]byte, 32)
+	for i := range b {
+		b[i] = letterRunes[rand.Intn(len(letterRunes))]
+	}
+	return b
+}