1 files changed, 220 insertions, 0 deletions
diff --git a/submitqueue/submitqueue.go b/submitqueue/submitqueue.go
new file mode 100644
index 000000000000..cd765acf0f10
--- /dev/null
+++ b/submitqueue/submitqueue.go
@@ -0,0 +1,220 @@
+package submitqueue
+
+import (
+	"fmt"
+
+	"github.com/tweag/gerrit-queue/gerrit"
+
+	log "github.com/sirupsen/logrus"
+)
+
+// SubmitQueueTag is the tag used to determine whether something
+// should be considered by the submit queue or not
+const SubmitQueueTag = "submit_me"
+
+// SubmitQueue contains a list of series, a gerrit connection, and some project configuration
+type SubmitQueue struct {
+	Series         []*Serie
+	gerrit         gerrit.IClient
+	ProjectName    string
+	BranchName     string
+	HEAD           string
+	SubmitQueueTag string // the tag used to submit something to the submit queue
+}
+
+// MakeSubmitQueue builds a new submit queue
+func MakeSubmitQueue(gerritClient gerrit.IClient, projectName string, branchName string, submitQueueTag string) SubmitQueue {
+	return SubmitQueue{
+		Series:         make([]*Serie, 0),
+		gerrit:         gerritClient,
+		ProjectName:    projectName,
+		BranchName:     branchName,
+		SubmitQueueTag: submitQueueTag,
+	}
+}
+
+// LoadSeries fills Series by searching and filtering changesets, and assembling them to Series.
+func (s *SubmitQueue) LoadSeries() error {
+	// Normally, we'd like to use a queryString like
+	// "status:open project:myproject branch:mybranch hashtag:submitQueueTag label:verified=+1 label:code-review=+2"
+	// to avoid filtering client-side
+	// Due to https://github.com/andygrunwald/go-gerrit/issues/71,
+	// we need to do this on the client (filterChangesets)
+	var queryString = fmt.Sprintf("status:open project:%s branch:%s", s.ProjectName, s.BranchName)
+	log.Debugf("Running query %s", queryString)
+
+	// Download changesets from gerrit
+	changesets, err := s.gerrit.SearchChangesets(queryString)
+	if err != nil {
+		return err
+	}
+	// // Filter to contain the SubmitQueueTag
+	// changesets = gerrit.FilterChangesets(changesets, func(c *gerrit.Changeset) bool {
+	// 	return c.HasTag(SubmitQueueTag)
+	// })
+	// Filter to be code reviewed and verified
+	changesets = gerrit.FilterChangesets(changesets, func(c *gerrit.Changeset) bool {
+		return c.IsCodeReviewed && c.IsVerified
+	})
+
+	// Assemble to series
+	series, err := AssembleSeries(changesets)
+	if err != nil {
+		return err
+	}
+
+	// Sort by size
+	s.Series = SortSeries(series)
+	return nil
+}
+
+// UpdateHEAD updates the HEAD field with the commit ID of the current HEAD
+func (s *SubmitQueue) UpdateHEAD() error {
+	HEAD, err := s.gerrit.GetHEAD(s.ProjectName, s.BranchName)
+	if err != nil {
+		return err
+	}
+	s.HEAD = HEAD
+	return nil
+}
+
+// TODO: clear submit queue tag if missing +1/+2?
+
+// DoSubmit submits changes that can be submitted,
+// and updates `Series` to contain the remaining ones
+// Also updates `BranchCommitID`.
+func (s *SubmitQueue) DoSubmit() error {
+	var remainingSeries []*Serie
+
+	for _, serie := range s.Series {
+		serieParentCommitIDs, err := serie.GetParentCommitIDs()
+		if err != nil {
+			return err
+		}
+		// we can only submit series with a single parent commit (otherwise they're not rebased)
+		if len(serieParentCommitIDs) != 1 {
+			return fmt.Errorf("%s has more than one parent commit", serie.String())
+		}
+		// if serie is rebased on top of current master…
+		if serieParentCommitIDs[0] == s.HEAD {
+			// submit the last changeset of the series, which submits intermediate ones too
+			_, err := s.gerrit.SubmitChangeset(serie.ChangeSets[len(serie.ChangeSets)-1])
+			if err != nil {
+				// this might fail, for various reasons:
+				//  - developers could have updated the changeset meanwhile, clearing +1/+2 bits
+				//  - master might have advanced, so this changeset isn't rebased on top of master
+				// TODO: we currently bail out entirely, but should be fine on the
+				// next loop. We might later want to improve the logic to be a bit more
+				// smarter (like log and try with the next one)
+				return err
+			}
+			// advance head to the leaf of the current serie for the next iteration
+			newHead, err := serie.GetLeafCommitID()
+			if err != nil {
+				return err
+			}
+			s.HEAD = newHead
+		} else {
+			remainingSeries = append(remainingSeries, serie)
+		}
+	}
+
+	s.Series = remainingSeries
+	return nil
+}
+
+// DoRebase rebases all remaining series on top of each other
+// they should still be ordered by series size
+// TODO: this will produce a very large series on the next run, so we might want to preserve individual series over multiple runs
+func (s *SubmitQueue) DoRebase() error {
+	newSeries := make([]*Serie, len(s.Series))
+	futureHEAD := s.HEAD
+	for _, serie := range s.Series {
+		//TODO: don't rebase everything, just pick a "good candidate"
+
+		logger := log.WithFields(log.Fields{
+			"serie": serie,
+		})
+		logger.Infof("rebasing %s on top of %s", serie, futureHEAD)
+		newSerie, err := s.RebaseSerie(serie, futureHEAD)
+		if err != nil {
+			logger.Warnf("unable to rebase serie %s", err)
+			// TODO: we want to skip on trivial rebase errors instead of bailing out.
+			// skip means adding that serie as it is to newSeries, without advancing previousLeafCommitId
+
+			// TODO: we also should talk about when to remove the submit-queue tag
+			// just because we scheduled a conflicting submit plan, doesn't mean this is not submittable.
+			// so just removing the submit-queue tag would be unfair
+			return err
+		}
+		newSeries = append(newSeries, newSerie)
+
+		// prepare for next iteration
+		futureHEAD, err = newSerie.GetLeafCommitID()
+		if err != nil {
+			// This should never happen
+			logger.Errorf("new serie shouldn't be empty: %s", newSerie)
+			return err
+		}
+
+	}
+	s.Series = newSeries
+	return nil
+}
+
+// Run starts the submit and rebase logic.
+func (s *SubmitQueue) Run() error {
+	//TODO: log decisions made and add to some ring buffer
+	var err error
+
+	commitID, err := s.gerrit.GetHEAD(s.ProjectName, s.BranchName)
+	if err != nil {
+		log.Errorf("Unable to retrieve HEAD of branch %s at project %s: %s", s.BranchName, s.ProjectName, err)
+		return err
+	}
+	s.HEAD = commitID
+
+	err = s.LoadSeries()
+	if err != nil {
+		return err
+	}
+	if len(s.Series) == 0 {
+		// Nothing to do!
+		log.Warn("Nothing to do here")
+		return nil
+	}
+	err = s.DoSubmit()
+	if err != nil {
+		return err
+	}
+	err = s.DoRebase()
+	if err != nil {
+		return err
+	}
+	return nil
+}
+
+// RebaseSerie rebases a whole serie on top of a given ref
+// TODO: only rebase a single changeset. we don't really want to join disconnected series, by rebasing them on top of each other.
+func (s *SubmitQueue) RebaseSerie(serie *Serie, ref string) (*Serie, error) {
+	newSeries := &Serie{
+		ChangeSets: make([]*gerrit.Changeset, len(serie.ChangeSets)),
+	}
+
+	rebaseOnto := ref
+	for _, changeset := range serie.ChangeSets {
+		newChangeset, err := s.gerrit.RebaseChangeset(changeset, rebaseOnto)
+
+		if err != nil {
+			// uh-oh…
+			// TODO: think about error handling
+			// TODO: remove the submit queue tag if the rebase fails (but only then, not on other errors)
+			return newSeries, err
+		}
+		newSeries.ChangeSets = append(newSeries.ChangeSets, newChangeset)
+
+		// the next changeset should be rebased on top of the current commit
+		rebaseOnto = newChangeset.CommitID
+	}
+	return newSeries, nil
+}