identity: wip push/pull

1 files changed, 211 insertions, 0 deletions

diff --git a/identity/identity_actions.go b/identity/identity_actions.go
new file mode 100644
index 00000000..69f77a2b
--- /dev/null
+++ b/identity/identity_actions.go
@@ -0,0 +1,211 @@
+package identity
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/MichaelMure/git-bug/repository"
+	"github.com/pkg/errors"
+)
+
+// Fetch retrieve updates from a remote
+// This does not change the local identities state
+func Fetch(repo repository.Repo, remote string) (string, error) {
+	remoteRefSpec := fmt.Sprintf(identityRemoteRefPattern, remote)
+	fetchRefSpec := fmt.Sprintf("%s:%s*", identityRefPattern, remoteRefSpec)
+
+	return repo.FetchRefs(remote, fetchRefSpec)
+}
+
+// Push update a remote with the local changes
+func Push(repo repository.Repo, remote string) (string, error) {
+	return repo.PushRefs(remote, identityRefPattern+"*")
+}
+
+// Pull will do a Fetch + MergeAll
+// This function won't give details on the underlying process. If you need more,
+// use Fetch and MergeAll separately.
+func Pull(repo repository.ClockedRepo, remote string) error {
+	_, err := Fetch(repo, remote)
+	if err != nil {
+		return err
+	}
+
+	for merge := range MergeAll(repo, remote) {
+		if merge.Err != nil {
+			return merge.Err
+		}
+		if merge.Status == MergeStatusInvalid {
+			// Not awesome: simply output the merge failure here as this function
+			// is only used in tests for now.
+			fmt.Println(merge)
+		}
+	}
+
+	return nil
+}
+
+// MergeAll will merge all the available remote identity
+// To make sure that an Identity history can't be altered, a strict fast-forward
+// only policy is applied here. As an Identity should be tied to a single user, this
+// should work in practice but it does leave a possibility that a user would edit his
+// Identity from two different repo concurrently and push the changes in a non-centralized
+// network of repositories. In this case, it would result some of the repo accepting one
+// version, some other accepting another, preventing the network in general to converge
+// to the same result. This would create a sort of partition of the network, and manual
+// cleaning would be required.
+//
+// An alternative approach would be to have a determinist rebase:
+// - any commits present in both local and remote version would be kept, never changed.
+// - newer commits would be merged in a linear chain of commits, ordered based on the
+//   Lamport time
+//
+// However, this approach leave the possibility, in the case of a compromised crypto keys,
+// of forging a new version with a bogus Lamport time to be inserted before a legit version,
+// invalidating the correct version and hijacking the Identity. There would only be a short
+// period of time where this would be possible (before the network converge) but I'm not
+// confident enough to implement that. I choose the strict fast-forward only approach,
+// despite it's potential problem with two different version as mentioned above.
+func MergeAll(repo repository.ClockedRepo, remote string) <-chan MergeResult {
+	out := make(chan MergeResult)
+
+	go func() {
+		defer close(out)
+
+		remoteRefSpec := fmt.Sprintf(identityRemoteRefPattern, remote)
+		remoteRefs, err := repo.ListRefs(remoteRefSpec)
+
+		if err != nil {
+			out <- MergeResult{Err: err}
+			return
+		}
+
+		for _, remoteRef := range remoteRefs {
+			refSplitted := strings.Split(remoteRef, "/")
+			id := refSplitted[len(refSplitted)-1]
+
+			remoteIdentity, err := ReadLocal(repo, remoteRef)
+			remoteBug, err := readBug(repo, remoteRef)
+
+			if err != nil {
+				out <- newMergeInvalidStatus(id, errors.Wrap(err, "remote bug is not readable").Error())
+				continue
+			}
+
+			// Check for error in remote data
+			if err := remoteBug.Validate(); err != nil {
+				out <- newMergeInvalidStatus(id, errors.Wrap(err, "remote bug is invalid").Error())
+				continue
+			}
+
+			localRef := bugsRefPattern + remoteBug.Id()
+			localExist, err := repo.RefExist(localRef)
+
+			if err != nil {
+				out <- newMergeError(err, id)
+				continue
+			}
+
+			// the bug is not local yet, simply create the reference
+			if !localExist {
+				err := repo.CopyRef(remoteRef, localRef)
+
+				if err != nil {
+					out <- newMergeError(err, id)
+					return
+				}
+
+				out <- newMergeStatus(MergeStatusNew, id, remoteBug)
+				continue
+			}
+
+			localBug, err := readBug(repo, localRef)
+
+			if err != nil {
+				out <- newMergeError(errors.Wrap(err, "local bug is not readable"), id)
+				return
+			}
+
+			updated, err := localBug.Merge(repo, remoteBug)
+
+			if err != nil {
+				out <- newMergeInvalidStatus(id, errors.Wrap(err, "merge failed").Error())
+				return
+			}
+
+			if updated {
+				out <- newMergeStatus(MergeStatusUpdated, id, localBug)
+			} else {
+				out <- newMergeStatus(MergeStatusNothing, id, localBug)
+			}
+		}
+	}()
+
+	return out
+}
+
+// MergeStatus represent the result of a merge operation of a bug
+type MergeStatus int
+
+const (
+	_ MergeStatus = iota
+	MergeStatusNew
+	MergeStatusInvalid
+	MergeStatusUpdated
+	MergeStatusNothing
+)
+
+// Todo: share a generalized MergeResult with the bug package ?
+type MergeResult struct {
+	// Err is set when a terminal error occur in the process
+	Err error
+
+	Id     string
+	Status MergeStatus
+
+	// Only set for invalid status
+	Reason string
+
+	// Not set for invalid status
+	Identity *Identity
+}
+
+func (mr MergeResult) String() string {
+	switch mr.Status {
+	case MergeStatusNew:
+		return "new"
+	case MergeStatusInvalid:
+		return fmt.Sprintf("invalid data: %s", mr.Reason)
+	case MergeStatusUpdated:
+		return "updated"
+	case MergeStatusNothing:
+		return "nothing to do"
+	default:
+		panic("unknown merge status")
+	}
+}
+
+func newMergeError(err error, id string) MergeResult {
+	return MergeResult{
+		Err: err,
+		Id:  id,
+	}
+}
+
+func newMergeStatus(status MergeStatus, id string, identity *Identity) MergeResult {
+	return MergeResult{
+		Id:     id,
+		Status: status,
+
+		// Identity is not set for an invalid merge result
+		Identity: identity,
+	}
+}
+
+func newMergeInvalidStatus(id string, reason string) MergeResult {
+	return MergeResult{
+		Id:     id,
+		Status: MergeStatusInvalid,
+		Reason: reason,
+	}
+}