Merge pull request #532 from MichaelMure/dag-entity

Work towards a reusable entity datastructure + commit signature

1 files changed, 260 insertions, 0 deletions

diff --git a/entity/dag/entity_actions.go b/entity/dag/entity_actions.go
new file mode 100644
index 00000000..2926e992
--- /dev/null
+++ b/entity/dag/entity_actions.go
@@ -0,0 +1,260 @@
+package dag
+
+import (
+	"fmt"
+
+	"github.com/pkg/errors"
+
+	"github.com/MichaelMure/git-bug/entity"
+	"github.com/MichaelMure/git-bug/identity"
+	"github.com/MichaelMure/git-bug/repository"
+)
+
+// ListLocalIds list all the available local Entity's Id
+func ListLocalIds(def Definition, repo repository.RepoData) ([]entity.Id, error) {
+	refs, err := repo.ListRefs(fmt.Sprintf("refs/%s/", def.Namespace))
+	if err != nil {
+		return nil, err
+	}
+	return entity.RefsToIds(refs), nil
+}
+
+// Fetch retrieve updates from a remote
+// This does not change the local entity state
+func Fetch(def Definition, repo repository.Repo, remote string) (string, error) {
+	return repo.FetchRefs(remote, def.Namespace)
+}
+
+// Push update a remote with the local changes
+func Push(def Definition, repo repository.Repo, remote string) (string, error) {
+	return repo.PushRefs(remote, def.Namespace)
+}
+
+// Pull will do a Fetch + MergeAll
+// Contrary to MergeAll, this function will return an error if a merge fail.
+func Pull(def Definition, repo repository.ClockedRepo, resolver identity.Resolver, remote string, author identity.Interface) error {
+	_, err := Fetch(def, repo, remote)
+	if err != nil {
+		return err
+	}
+
+	for merge := range MergeAll(def, repo, resolver, remote, author) {
+		if merge.Err != nil {
+			return merge.Err
+		}
+		if merge.Status == entity.MergeStatusInvalid {
+			return errors.Errorf("merge failure: %s", merge.Reason)
+		}
+	}
+
+	return nil
+}
+
+// MergeAll will merge all the available remote Entity:
+//
+// Multiple scenario exist:
+// 1. if the remote Entity doesn't exist locally, it's created
+//    --> emit entity.MergeStatusNew
+// 2. if the remote and local Entity have the same state, nothing is changed
+//    --> emit entity.MergeStatusNothing
+// 3. if the local Entity has new commits but the remote don't, nothing is changed
+//    --> emit entity.MergeStatusNothing
+// 4. if the remote has new commit, the local bug is updated to match the same history
+//    (fast-forward update)
+//    --> emit entity.MergeStatusUpdated
+// 5. if both local and remote Entity have new commits (that is, we have a concurrent edition),
+//    a merge commit with an empty operationPack is created to join both branch and form a DAG.
+//    --> emit entity.MergeStatusUpdated
+//
+// Note: an author is necessary for the case where a merge commit is created, as this commit will
+// have an author and may be signed if a signing key is available.
+func MergeAll(def Definition, repo repository.ClockedRepo, resolver identity.Resolver, remote string, author identity.Interface) <-chan entity.MergeResult {
+	out := make(chan entity.MergeResult)
+
+	go func() {
+		defer close(out)
+
+		remoteRefSpec := fmt.Sprintf("refs/remotes/%s/%s/", remote, def.Namespace)
+		remoteRefs, err := repo.ListRefs(remoteRefSpec)
+		if err != nil {
+			out <- entity.MergeResult{Err: err}
+			return
+		}
+
+		for _, remoteRef := range remoteRefs {
+			out <- merge(def, repo, resolver, remoteRef, author)
+		}
+	}()
+
+	return out
+}
+
+// merge perform a merge to make sure a local Entity is up to date.
+// See MergeAll for more details.
+func merge(def Definition, repo repository.ClockedRepo, resolver identity.Resolver, remoteRef string, author identity.Interface) entity.MergeResult {
+	id := entity.RefToId(remoteRef)
+
+	if err := id.Validate(); err != nil {
+		return entity.NewMergeInvalidStatus(id, errors.Wrap(err, "invalid ref").Error())
+	}
+
+	remoteEntity, err := read(def, repo, resolver, remoteRef)
+	if err != nil {
+		return entity.NewMergeInvalidStatus(id,
+			errors.Wrapf(err, "remote %s is not readable", def.Typename).Error())
+	}
+
+	// Check for error in remote data
+	if err := remoteEntity.Validate(); err != nil {
+		return entity.NewMergeInvalidStatus(id,
+			errors.Wrapf(err, "remote %s data is invalid", def.Typename).Error())
+	}
+
+	localRef := fmt.Sprintf("refs/%s/%s", def.Namespace, id.String())
+
+	// SCENARIO 1
+	// if the remote Entity doesn't exist locally, it's created
+
+	localExist, err := repo.RefExist(localRef)
+	if err != nil {
+		return entity.NewMergeError(err, id)
+	}
+
+	if !localExist {
+		// the bug is not local yet, simply create the reference
+		err := repo.CopyRef(remoteRef, localRef)
+		if err != nil {
+			return entity.NewMergeError(err, id)
+		}
+
+		return entity.NewMergeNewStatus(id, remoteEntity)
+	}
+
+	localCommit, err := repo.ResolveRef(localRef)
+	if err != nil {
+		return entity.NewMergeError(err, id)
+	}
+
+	remoteCommit, err := repo.ResolveRef(remoteRef)
+	if err != nil {
+		return entity.NewMergeError(err, id)
+	}
+
+	// SCENARIO 2
+	// if the remote and local Entity have the same state, nothing is changed
+
+	if localCommit == remoteCommit {
+		// nothing to merge
+		return entity.NewMergeNothingStatus(id)
+	}
+
+	// SCENARIO 3
+	// if the local Entity has new commits but the remote don't, nothing is changed
+
+	localCommits, err := repo.ListCommits(localRef)
+	if err != nil {
+		return entity.NewMergeError(err, id)
+	}
+
+	for _, hash := range localCommits {
+		if hash == remoteCommit {
+			return entity.NewMergeNothingStatus(id)
+		}
+	}
+
+	// SCENARIO 4
+	// if the remote has new commit, the local bug is updated to match the same history
+	// (fast-forward update)
+
+	remoteCommits, err := repo.ListCommits(remoteRef)
+	if err != nil {
+		return entity.NewMergeError(err, id)
+	}
+
+	// fast-forward is possible if otherRef include ref
+	fastForwardPossible := false
+	for _, hash := range remoteCommits {
+		if hash == localCommit {
+			fastForwardPossible = true
+			break
+		}
+	}
+
+	if fastForwardPossible {
+		err = repo.UpdateRef(localRef, remoteCommit)
+		if err != nil {
+			return entity.NewMergeError(err, id)
+		}
+		return entity.NewMergeUpdatedStatus(id, remoteEntity)
+	}
+
+	// SCENARIO 5
+	// if both local and remote Entity have new commits (that is, we have a concurrent edition),
+	// a merge commit with an empty operationPack is created to join both branch and form a DAG.
+
+	// fast-forward is not possible, we need to create a merge commit
+	// For simplicity when reading and to have clocks that record this change, we store
+	// an empty operationPack.
+	// First step is to collect those clocks.
+
+	localEntity, err := read(def, repo, resolver, localRef)
+	if err != nil {
+		return entity.NewMergeError(err, id)
+	}
+
+	editTime, err := repo.Increment(fmt.Sprintf(editClockPattern, def.Namespace))
+	if err != nil {
+		return entity.NewMergeError(err, id)
+	}
+
+	opp := &operationPack{
+		Author:     author,
+		Operations: nil,
+		CreateTime: 0,
+		EditTime:   editTime,
+	}
+
+	commitHash, err := opp.Write(def, repo, localCommit, remoteCommit)
+	if err != nil {
+		return entity.NewMergeError(err, id)
+	}
+
+	// finally update the ref
+	err = repo.UpdateRef(localRef, commitHash)
+	if err != nil {
+		return entity.NewMergeError(err, id)
+	}
+
+	// Note: we don't need to update localEntity state (lastCommit, operations...) as we
+	// discard it entirely anyway.
+
+	return entity.NewMergeUpdatedStatus(id, localEntity)
+}
+
+// Remove delete an Entity.
+// Remove is idempotent.
+func Remove(def Definition, repo repository.ClockedRepo, id entity.Id) error {
+	var matches []string
+
+	ref := fmt.Sprintf("refs/%s/%s", def.Namespace, id.String())
+	matches = append(matches, ref)
+
+	remotes, err := repo.GetRemotes()
+	if err != nil {
+		return err
+	}
+
+	for remote := range remotes {
+		ref = fmt.Sprintf("refs/remotes/%s/%s/%s", remote, def.Namespace, id.String())
+		matches = append(matches, ref)
+	}
+
+	for _, ref = range matches {
+		err = repo.RemoveRef(ref)
+		if err != nil {
+			return err
+		}
+	}
+
+	return nil
+}