// updateReviewDiffs updates the status of a differential review so that it matches the state of the repo.
//
// This consists of making sure the latest commit pushed to the review ref has a corresponding
// diff in the differential review.
func (arc Arcanist) updateReviewDiffs(repo repository.Repo, review differentialReview, headCommit string, req request.Request, comments map[string]comment.Comment) {
	if review.isClosed() {
		return
	}

	headRevision := repository.Revision(headCommit)
	mergeBase, err := repo.GetMergeBase(repository.Revision(req.TargetRef), headRevision)
	if err != nil {
		// This can happen if the target ref has been deleted while we were performing the updates.
		return
	}

	for _, hashPair := range review.Hashes {
		if len(hashPair) == 2 && hashPair[0] == commitHashType && hashPair[1] == headCommit {
			// The review already has the hash of the HEAD commit, so we have nothing to do beyond mirroring comments
			// and build status if applicable
			arc.mirrorCommentsIntoReview(repo, review, comments)
			return
		}
	}

	diff, err := arc.createDifferentialDiff(repo, mergeBase, headRevision, req, review.Diffs)
	if err != nil {
		log.Fatal(err)
	}
	if diff == nil {
		// This means that phabricator silently refused to create the diff. Just move on.
		return
	}

	updateRequest := differentialUpdateRevisionRequest{ID: review.ID, DiffID: strconv.Itoa(diff.ID)}
	var updateResponse differentialUpdateRevisionResponse
	runArcCommandOrDie("differential.updaterevision", updateRequest, &updateResponse)
	if updateResponse.Error != "" {
		log.Fatal(updateResponse.ErrorMessage)
	}
}
// EnsureRequestExists runs the "arcanist" command-line tool to create a Differential diff for the given request, if one does not already exist.
func (arc Arcanist) EnsureRequestExists(repo repository.Repo, revision repository.Revision, req request.Request, comments map[string]comment.Comment) {

	// If this revision has been previously closed shortcut all processing
	if closedRevisionsMap[revision] {
		return
	}

	mergeBase, err := repo.GetMergeBase(repository.Revision(req.TargetRef), revision)
	if err != nil {
		// There are lots of reasons that we might not be able to compute a merge base,
		// (e.g. the revision already being merged in, or being dropped and garbage collected),
		// but they all indicate that the review request is no longer valid.
		log.Printf("Ignoring review request '%v', because we could not compute a merge base", req)
		return
	}

	existingReviews := arc.listDifferentialReviewsOrDie(req.ReviewRef, revision)
	if mergeBase == revision {
		// The change has already been merged in, so we should simply close any open reviews.
		for _, review := range existingReviews {
			if !review.isClosed() {
				review.close()
			}
		}
		closedRevisionsMap[revision] = true
		return
	}

	headDetails, err := repo.GetDetails(repository.Revision(req.ReviewRef))
	if err != nil {
		// The given review ref has been deleted (or never existed), but the change wasn't merged.
		// TODO(ojarjur): We should mark the existing reviews as abandoned.
		log.Printf("Ignoring review because the review ref '%s' does not exist", req.ReviewRef)
		return
	}

	if len(existingReviews) > 0 {
		// The change is still pending, but we already have existing reviews, so we should just update those.
		for _, review := range existingReviews {
			arc.updateReviewDiffs(repo, review, headDetails.Commit, req, comments)
		}
		return
	}

	diff, err := arc.createDifferentialDiff(repo, mergeBase, revision, req, []string{})
	if err != nil {
		log.Fatal(err)
	}
	if diff == nil {
		// The revision is already merged in, ignore it.
		return
	}
	rev, err := arc.createDifferentialRevision(repo, revision, diff.ID, req)
	if err != nil {
		log.Fatal(err)
	}
	log.Printf("Created diff %v and revision %v for the review of %s", diff, rev, revision)

	// If the review already contains multiple commits by the time we mirror it, then
	// we need to ensure that at least the first and last ones are added.
	existingReviews = arc.listDifferentialReviewsOrDie(req.ReviewRef, revision)
	for _, review := range existingReviews {
		arc.updateReviewDiffs(repo, review, headDetails.Commit, req, comments)
	}
}