func (s *mongoRestoreSuite) TestMongoRestoreArgsForOldVersion(c *gc.C) {
	versionNumber := version.Number{}
	versionNumber.Major = 0
	versionNumber.Minor = 0
	_, err := backups.MongoRestoreArgsForVersion(versionNumber, "/some/fake/path")
	c.Assert(err, gc.ErrorMatches, "this backup file is incompatible with the current version of juju")
}

func (s *upgradeSuite) TestUpgradeOperationsOrdered(c *gc.C) {
	var previous version.Number
	for i, utv := range (*upgrades.UpgradeOperations)() {
		vers := utv.TargetVersion()
		if i > 0 {
			c.Check(previous.Compare(vers), gc.Equals, -1)
		}
		previous = vers
	}
}

func checkUpgradeInfoSanity(st *State, machineId string, previousVersion, targetVersion version.Number) (bson.D, error) {
	if previousVersion.Compare(targetVersion) != -1 {
		return nil, errors.Errorf("cannot sanely upgrade from %s to %s", previousVersion, targetVersion)
	}
	controllerInfo, err := st.ControllerInfo()
	if err != nil {
		return nil, errors.Annotate(err, "cannot read controllers")
	}
	validIds := set.NewStrings(controllerInfo.MachineIds...)
	if !validIds.Contains(machineId) {
		return nil, errors.Errorf("machine %q is not a controller", machineId)
	}
	return assertExpectedVersions(previousVersion, targetVersion), nil
}

// Newest returns the greatest version in src, and the tools with that version.
func (src List) Newest() (version.Number, List) {
	var result List
	var best version.Number
	for _, tools := range src {
		if best.Compare(tools.Version.Number) < 0 {
			// Found new best number; reset result list.
			best = tools.Version.Number
			result = append(result[:0], tools)
		} else if tools.Version.Number == best {
			result = append(result, tools)
		}
	}
	return best, result
}

// UpdateLatestToolsVersion looks up for the latest available version of
// juju tools and updates environementDoc with it.
func (e *Environment) UpdateLatestToolsVersion(ver version.Number) error {
	v := ver.String()
	// TODO(perrito666): I need to assert here that there isn't a newer
	// version in place.
	ops := []txn.Op{{
		C:      environmentsC,
		Id:     e.doc.UUID,
		Update: bson.D{{"$set", bson.D{{"available-tools", v}}}},
	}}
	err := e.st.runTransaction(ops)
	if err != nil {
		return errors.Trace(err)
	}
	return e.Refresh()
}

func (s *mongoRestoreSuite) TestMongoRestoreArgsForVersion121(c *gc.C) {
	dir := filepath.Join(agent.DefaultPaths.DataDir, "db")
	versionNumber := version.Number{}
	versionNumber.Major = 1
	versionNumber.Minor = 21
	args, err := backups.MongoRestoreArgsForVersion(versionNumber, "/some/fake/path")
	c.Assert(err, jc.ErrorIsNil)
	c.Assert(args, gc.HasLen, 5)
	c.Assert(args[0:5], jc.DeepEquals, []string{
		"--drop",
		"--journal",
		"--dbpath",
		dir,
		"/some/fake/path",
	})
}

// PreferredStream returns the tools stream used to search for tools, based
// on the required version, whether devel mode is required, and any user specified stream.
func PreferredStream(vers *version.Number, forceDevel bool, stream string) string {
	// If the use has already nominated a specific stream, we'll use that.
	if stream != "" && stream != ReleasedStream {
		return stream
	}
	// If we're not upgrading from a known version, we use the
	// currently running version.
	if vers == nil {
		vers = &version.Current.Number
	}
	// Devel versions are alpha or beta etc as defined by the version tag.
	// The user can also force the use of devel streams via config.
	if forceDevel || vers.IsDev() {
		return DevelStream
	}
	return ReleasedStream
}

func (s *mongoRestoreSuite) TestMongoRestoreArgsForVersion(c *gc.C) {
	dir := filepath.Join(agent.DefaultDataDir, "db")
	versionNumber := version.Number{}
	versionNumber.Major = 1
	versionNumber.Minor = 21
	args, err := backups.MongoRestoreArgsForVersion(versionNumber, "/some/fake/path")
	c.Assert(err, jc.ErrorIsNil)
	c.Assert(args, gc.HasLen, 5)
	c.Assert(args[0:5], jc.DeepEquals, []string{
		"--drop",
		"--journal",
		"--dbpath",
		dir,
		"/some/fake/path",
	})

	versionNumber.Major = 1
	versionNumber.Minor = 22
	args, err = backups.MongoRestoreArgsForVersion(versionNumber, "/some/fake/path")
	c.Assert(err, jc.ErrorIsNil)
	c.Assert(args, gc.HasLen, 6)
	c.Assert(args[0:6], jc.DeepEquals, []string{
		"--drop",
		"--journal",
		"--oplogReplay",
		"--dbpath",
		dir,
		"/some/fake/path",
	})

	versionNumber.Major = 0
	versionNumber.Minor = 0
	_, err = backups.MongoRestoreArgsForVersion(versionNumber, "/some/fake/path")
	c.Assert(err, gc.ErrorMatches, "this backup file is incompatible with the current version of juju")
}

// uploadVersion returns a copy of the supplied version with a build number
// higher than any of the supplied tools that share its major, minor and patch.
func uploadVersion(vers version.Number, existing coretools.List) version.Number {
	vers.Build++
	for _, t := range existing {
		if t.Version.Major != vers.Major || t.Version.Minor != vers.Minor || t.Version.Patch != vers.Patch {
			continue
		}
		if t.Version.Build >= vers.Build {
			vers.Build = t.Version.Build + 1
		}
	}
	return vers
}

func newOpsIterator(from, to version.Number, ops []Operation) *opsIterator {
	// If from is not known, it is 1.16.
	if from == version.Zero {
		from = version.MustParse("1.16.0")
	}

	// Clear the version tag of the target release to ensure that all
	// upgrade steps for the release are run for alpha and beta
	// releases.
	// ...but only do this if the agent version has actually changed,
	// lest we trigger upgrade mode unnecessarily for non-final
	// versions.
	if from.Compare(to) != 0 {
		to.Tag = ""
	}

	return &opsIterator{
		from:    from,
		to:      to,
		allOps:  ops,
		current: -1,
	}
}

// BundleTools bundles all the current juju tools in gzipped tar
// format to the given writer.
// If forceVersion is not nil, a FORCE-VERSION file is included in
// the tools bundle so it will lie about its current version number.
func bundleTools(w io.Writer, forceVersion *version.Number) (tvers version.Binary, sha256Hash string, err error) {
	dir, err := ioutil.TempDir("", "juju-tools")
	if err != nil {
		return version.Binary{}, "", err
	}
	defer os.RemoveAll(dir)

	if err := copyExistingJujud(dir); err != nil {
		logger.Debugf("copy existing failed: %v", err)
		if err := buildJujud(dir); err != nil {
			return version.Binary{}, "", err
		}
	}

	if forceVersion != nil {
		logger.Debugf("forcing version to %s", forceVersion)
		if err := ioutil.WriteFile(filepath.Join(dir, "FORCE-VERSION"), []byte(forceVersion.String()), 0666); err != nil {
			return version.Binary{}, "", err
		}
	}
	cmd := exec.Command(filepath.Join(dir, names.Jujud), "version")
	out, err := cmd.CombinedOutput()
	if err != nil {
		return version.Binary{}, "", fmt.Errorf("cannot get version from %q: %v; %s", cmd.Args[0], err, out)
	}
	tvs := strings.TrimSpace(string(out))
	tvers, err = version.ParseBinary(tvs)
	if err != nil {
		return version.Binary{}, "", fmt.Errorf("invalid version %q printed by jujud", tvs)
	}

	sha256hash, err := archiveAndSHA256(w, dir)
	if err != nil {
		return version.Binary{}, "", err
	}
	return tvers, sha256hash, err
}

// SetBootstrapTools returns the newest tools from the given tools list,
// and updates the agent-version configuration attribute.
func SetBootstrapTools(environ environs.Environ, possibleTools coretools.List) (coretools.List, error) {
	if len(possibleTools) == 0 {
		return nil, fmt.Errorf("no bootstrap tools available")
	}
	var newVersion version.Number
	newVersion, toolsList := possibleTools.Newest()
	logger.Infof("newest version: %s", newVersion)
	cfg := environ.Config()
	if agentVersion, _ := cfg.AgentVersion(); agentVersion != newVersion {
		cfg, err := cfg.Apply(map[string]interface{}{
			"agent-version": newVersion.String(),
		})
		if err == nil {
			err = environ.SetConfig(cfg)
		}
		if err != nil {
			return nil, fmt.Errorf("failed to update environment configuration: %v", err)
		}
	}
	bootstrapVersion := newVersion
	// We should only ever bootstrap the exact same version as the client,
	// or we risk bootstrap incompatibility. We still set agent-version to
	// the newest version, so the agent will immediately upgrade itself.
	if !isCompatibleVersion(newVersion, version.Current.Number) {
		compatibleVersion, compatibleTools := findCompatibleTools(possibleTools, version.Current.Number)
		if len(compatibleTools) == 0 {
			logger.Warningf(
				"failed to find %s tools, will attempt to use %s",
				version.Current.Number, newVersion,
			)
		} else {
			bootstrapVersion, toolsList = compatibleVersion, compatibleTools
		}
	}
	logger.Infof("picked bootstrap tools version: %s", bootstrapVersion)
	return toolsList, nil
}

// SetEnvironAgentVersion changes the agent version for the
// environment to the given version, only if the environment is in a
// stable state (all agents are running the current version).
func (st *State) SetEnvironAgentVersion(newVersion version.Number) error {
	for i := 0; i < 5; i++ {
		settings, err := readSettings(st, environGlobalKey)
		if err != nil {
			return err
		}
		agentVersion, ok := settings.Get("agent-version")
		if !ok {
			return fmt.Errorf("no agent version set in the environment")
		}
		currentVersion, ok := agentVersion.(string)
		if !ok {
			return fmt.Errorf("invalid agent version format: expected string, got %v", agentVersion)
		}
		if newVersion.String() == currentVersion {
			// Nothing to do.
			return nil
		}

		if err := st.checkCanUpgrade(currentVersion, newVersion.String()); err != nil {
			return err
		}

		ops := []txn.Op{{
			C:      st.settings.Name,
			Id:     environGlobalKey,
			Assert: bson.D{{"txn-revno", settings.txnRevno}},
			Update: bson.D{{"$set", bson.D{{"agent-version", newVersion.String()}}}},
		}}
		if err := st.runTransaction(ops); err == nil {
			return nil
		} else if err != txn.ErrAborted {
			return fmt.Errorf("cannot set agent-version: %v", err)
		}
	}
	return ErrExcessiveContention
}

// SetEnvironAgentVersion changes the agent version for the
// environment to the given version, only if the environment is in a
// stable state (all agents are running the current version).
func (st *State) SetEnvironAgentVersion(newVersion version.Number) (err error) {
	buildTxn := func(attempt int) ([]txn.Op, error) {
		settings, err := readSettings(st, environGlobalKey)
		if err != nil {
			return nil, err
		}
		agentVersion, ok := settings.Get("agent-version")
		if !ok {
			return nil, fmt.Errorf("no agent version set in the environment")
		}
		currentVersion, ok := agentVersion.(string)
		if !ok {
			return nil, fmt.Errorf("invalid agent version format: expected string, got %v", agentVersion)
		}
		if newVersion.String() == currentVersion {
			// Nothing to do.
			return nil, jujutxn.ErrNoOperations
		}

		if err := st.checkCanUpgrade(currentVersion, newVersion.String()); err != nil {
			return nil, err
		}

		ops := []txn.Op{{
			C:      st.settings.Name,
			Id:     environGlobalKey,
			Assert: bson.D{{"txn-revno", settings.txnRevno}},
			Update: bson.D{{"$set", bson.D{{"agent-version", newVersion.String()}}}},
		}}
		return ops, nil
	}
	if err = st.run(buildTxn); err == jujutxn.ErrExcessiveContention {
		err = errors.Annotate(err, "cannot set agent version")
	}
	return err
}

func isPreHAVersion(v version.Number) bool {
	return v.Compare(version.MustParse("1.19.0")) < 0
}

func isCompatibleVersion(v1, v2 version.Number) bool {
	v1.Build = 0
	v2.Build = 0
	return v1.Compare(v2) == 0
}

// SetAgentVersion sets the current agent version in the state's
// environment configuration.
// This is similar to state.SetEnvironAgentVersion but it doesn't require that
// the environment have all agents at the same version already.
func SetAgentVersion(st *state.State, vers version.Number) error {
	return st.UpdateEnvironConfig(map[string]interface{}{"agent-version": vers.String()}, nil, nil)
}