1 files changed, 50 insertions, 27 deletions

diff --git a/bug/operation.go b/bug/operation.go
index a408e167..91b77e56 100644
--- a/bug/operation.go
+++ b/bug/operation.go
@@ -1,11 +1,13 @@
 package bug
 
 import (
-	"github.com/MichaelMure/git-bug/util/git"
-	"github.com/pkg/errors"
-
+	"crypto/sha256"
+	"encoding/json"
 	"fmt"
 	"time"
+
+	"github.com/MichaelMure/git-bug/util/git"
+	"github.com/pkg/errors"
 )
 
 // OperationType is an operation type identifier
@@ -18,22 +20,23 @@ const (
 	AddCommentOp
 	SetStatusOp
 	LabelChangeOp
+	EditCommentOp
 )
 
 // Operation define the interface to fulfill for an edit operation of a Bug
 type Operation interface {
-	// OpType return the type of operation
-	OpType() OperationType
+	// base return the OpBase of the Operation, for package internal use
+	base() *OpBase
+	// Hash return the hash of the operation, to be used for back references
+	Hash() (git.Hash, error)
 	// Time return the time when the operation was added
 	Time() time.Time
 	// GetUnixTime return the unix timestamp when the operation was added
 	GetUnixTime() int64
-	// GetAuthor return the author of the operation
-	GetAuthor() Person
 	// GetFiles return the files needed by this operation
 	GetFiles() []git.Hash
 	// Apply the operation to a Snapshot to create the final state
-	Apply(snapshot Snapshot) Snapshot
+	Apply(snapshot *Snapshot)
 	// Validate check if the operation is valid (ex: a title is a single line)
 	Validate() error
 	// SetMetadata store arbitrary metadata about the operation
@@ -42,16 +45,42 @@ type Operation interface {
 	GetMetadata(key string) (string, bool)
 }
 
+func hashRaw(data []byte) git.Hash {
+	hasher := sha256.New()
+	// Write can't fail
+	_, _ = hasher.Write(data)
+	return git.Hash(fmt.Sprintf("%x", hasher.Sum(nil)))
+}
+
+// hash compute the hash of the serialized operation
+func hashOperation(op Operation) (git.Hash, error) {
+	base := op.base()
+
+	if base.hash != "" {
+		return base.hash, nil
+	}
+
+	data, err := json.Marshal(op)
+	if err != nil {
+		return "", err
+	}
+
+	base.hash = hashRaw(data)
+
+	return base.hash, nil
+}
+
 // OpBase implement the common code for all operations
 type OpBase struct {
-	OperationType OperationType     `json:"type"`
-	Author        Person            `json:"author"`
-	UnixTime      int64             `json:"timestamp"`
+	OperationType OperationType `json:"type"`
+	Author        Person        `json:"author"`
+	UnixTime      int64         `json:"timestamp"`
+	hash          git.Hash
 	Metadata      map[string]string `json:"metadata,omitempty"`
 }
 
-// NewOpBase is the constructor for an OpBase
-func NewOpBase(opType OperationType, author Person, unixTime int64) *OpBase {
+// newOpBase is the constructor for an OpBase
+func newOpBase(opType OperationType, author Person, unixTime int64) *OpBase {
 	return &OpBase{
 		OperationType: opType,
 		Author:        author,
@@ -59,11 +88,6 @@ func NewOpBase(opType OperationType, author Person, unixTime int64) *OpBase {
 	}
 }
 
-// OpType return the type of operation
-func (op *OpBase) OpType() OperationType {
-	return op.OperationType
-}
-
 // Time return the time when the operation was added
 func (op *OpBase) Time() time.Time {
 	return time.Unix(op.UnixTime, 0)
@@ -74,27 +98,26 @@ func (op *OpBase) GetUnixTime() int64 {
 	return op.UnixTime
 }
 
-// GetAuthor return the author of the operation
-func (op *OpBase) GetAuthor() Person {
-	return op.Author
-}
-
 // GetFiles return the files needed by this operation
 func (op *OpBase) GetFiles() []git.Hash {
 	return nil
 }
 
 // Validate check the OpBase for errors
-func OpBaseValidate(op Operation, opType OperationType) error {
-	if op.OpType() != opType {
-		return fmt.Errorf("incorrect operation type (expected: %v, actual: %v)", opType, op.OpType())
+func opBaseValidate(op Operation, opType OperationType) error {
+	if op.base().OperationType != opType {
+		return fmt.Errorf("incorrect operation type (expected: %v, actual: %v)", opType, op.base().OperationType)
+	}
+
+	if _, err := op.Hash(); err != nil {
+		return errors.Wrap(err, "op is not serializable")
 	}
 
 	if op.GetUnixTime() == 0 {
 		return fmt.Errorf("time not set")
 	}
 
-	if err := op.GetAuthor().Validate(); err != nil {
+	if err := op.base().Author.Validate(); err != nil {
 		return errors.Wrap(err, "author")
 	}