// New returns the instance of STI builder strategy for the given config.
// If the layeredBuilder parameter is specified, then the builder provided will
// be used for the case that the base Docker image does not have 'tar' or 'bash'
// installed.
func New(req *api.Config) (*STI, error) {
	docker, err := docker.New(req.DockerConfig, req.PullAuthentication)
	if err != nil {
		return nil, err
	}
	inst := scripts.NewInstaller(req.BuilderImage, req.ScriptsURL, docker, req.PullAuthentication)

	b := &STI{
		installer:        inst,
		config:           req,
		docker:           docker,
		git:              git.New(),
		fs:               util.NewFileSystem(),
		tar:              tar.New(),
		callbackInvoker:  util.NewCallbackInvoker(),
		requiredScripts:  []string{api.Assemble, api.Run},
		optionalScripts:  []string{api.SaveArtifacts},
		externalScripts:  map[string]bool{},
		installedScripts: map[string]bool{},
		scriptsURL:       map[string]string{},
	}

	// The sources are downloaded using the GIT downloader.
	// TODO: Add more SCM in future.
	b.source = &git.Clone{b.git, b.fs}
	b.garbage = &build.DefaultCleaner{b.fs, b.docker}
	b.layered, err = layered.New(req, b)

	// Set interfaces
	b.preparer = b
	b.artifacts = b
	b.scripts = b
	b.postExecutor = b
	return b, err
}

// NewDockerBuilder creates a new instance of DockerBuilder
func NewDockerBuilder(dockerClient DockerClient, build *api.Build) *DockerBuilder {
	return &DockerBuilder{
		dockerClient: dockerClient,
		build:        build,
		git:          git.New(),
		tar:          tar.New(),
		urlTimeout:   urlCheckTimeout,
	}
}

// NewDockerBuilder creates a new instance of DockerBuilder
func NewDockerBuilder(dockerClient DockerClient, authCfg docker.AuthConfiguration, authPresent bool, build *api.Build) *DockerBuilder {
	return &DockerBuilder{
		dockerClient: dockerClient,
		authPresent:  authPresent,
		auth:         authCfg,
		build:        build,
		git:          git.New(),
		tar:          tar.New(),
		urlTimeout:   urlCheckTimeout,
	}
}

// New returns a new instance of OnBuild builder
func New(config *api.Config) (*OnBuild, error) {
	dockerHandler, err := docker.New(config.DockerConfig, config.PullAuthentication)
	if err != nil {
		return nil, err
	}
	b := &OnBuild{
		docker: dockerHandler,
		git:    git.New(),
		fs:     util.NewFileSystem(),
		tar:    tar.New(),
	}
	// Use STI Prepare() and download the 'run' script optionally.
	s, err := sti.New(config)
	s.SetScripts([]string{}, []string{api.Assemble, api.Run})

	b.source = onBuildSourceHandler{
		&git.Clone{b.git, b.fs},
		s,
	}
	b.garbage = &build.DefaultCleaner{b.fs, b.docker}
	return b, nil
}