func (i *Installer) List(conf *cfg.Config) []*cfg.Dependency {
	base := "."
	vpath := i.VendorPath()

	ic := newImportCache()

	v := &VersionHandler{
		Destination: vpath,
		Use:         ic,
		Imported:    make(map[string]bool),
		Conflicts:   make(map[string]bool),
		Config:      conf,
	}

	// Update imports
	res, err := dependency.NewResolver(base)
	if err != nil {
		msg.Die("Failed to create a resolver: %s", err)
	}
	res.Config = conf
	res.VersionHandler = v

	msg.Info("Resolving imports")
	_, err = allPackages(conf.Imports, res)
	if err != nil {
		msg.Die("Failed to retrieve a list of dependencies: %s", err)
	}

	msg.Warn("devImports not resolved.")

	return conf.Imports
}

// Get fetches one or more dependencies and installs.
//
// This includes resolving dependency resolution and re-generating the lock file.
func Get(names []string, installer *repo.Installer, insecure, skipRecursive bool) {
	base := gpath.Basepath()
	EnsureGopath()
	EnsureVendorDir()
	conf := EnsureConfig()
	glidefile, err := gpath.Glide()
	if err != nil {
		msg.Die("Could not find Glide file: %s", err)
	}

	// Add the packages to the config.
	if err := addPkgsToConfig(conf, names, insecure); err != nil {
		msg.Die("Failed to get new packages: %s", err)
	}

	// Fetch the new packages. Can't resolve versions via installer.Update if
	// get is called while the vendor/ directory is empty so we checkout
	// everything.
	installer.Checkout(conf, false)

	// Prior to resolving dependencies we need to start working with a clone
	// of the conf because we'll be making real changes to it.
	confcopy := conf.Clone()

	if !skipRecursive {
		// Get all repos and update them.
		// TODO: Can we streamline this in any way? The reason that we update all
		// of the dependencies is that we need to re-negotiate versions. For example,
		// if an existing dependency has the constraint >1.0 and this new package
		// adds the constraint <2.0, then this may re-resolve the existing dependency
		// to be between 1.0 and 2.0. But changing that dependency may then result
		// in that dependency's dependencies changing... so we sorta do the whole
		// thing to be safe.
		err = installer.Update(confcopy)
		if err != nil {
			msg.Die("Could not update packages: %s", err)
		}
	}

	// Set Reference
	if err := repo.SetReference(confcopy); err != nil {
		msg.Error("Failed to set references: %s", err)
	}

	// VendoredCleanup
	if installer.UpdateVendored {
		repo.VendoredCleanup(confcopy)
	}

	// Write YAML
	if err := conf.WriteFile(glidefile); err != nil {
		msg.Die("Failed to write glide YAML file: %s", err)
	}
	if !skipRecursive {
		// Write lock
		writeLock(conf, confcopy, base)
	} else {
		msg.Warn("Skipping lockfile generation because full dependency tree is not being calculated")
	}
}

// List lists all of the dependencies of the current project.
//
// Params:
//  - dir (string): basedir
//  - deep (bool): whether to do a deep scan or a shallow scan
//  - format (string): The format to output (text, json, json-pretty)
func List(basedir string, deep bool, format string) {
	basedir, err := filepath.Abs(basedir)
	if err != nil {
		msg.Die("Could not read directory: %s", err)
	}

	r, err := dependency.NewResolver(basedir)
	if err != nil {
		msg.Die("Could not create a resolver: %s", err)
	}
	h := &dependency.DefaultMissingPackageHandler{Missing: []string{}, Gopath: []string{}, Prefix: "vendor"}
	r.Handler = h

	localPkgs, _, err := r.ResolveLocal(deep)
	if err != nil {
		msg.Die("Error listing dependencies: %s", err)
	}
	sort.Strings(localPkgs)
	installed := make([]string, len(localPkgs))
	for i, pkg := range localPkgs {
		relPkg, err := filepath.Rel(basedir, pkg)
		if err != nil {
			// msg.Warn("Failed to Rel path: %s", err)
			relPkg = pkg
		}
		installed[i] = relPkg
	}
	l := PackageList{
		Installed: installed,
		Missing:   h.Missing,
		Gopath:    h.Gopath,
	}

	outputList(l, format)
}

func outputList(l PackageList, format string) {
	switch format {
	case textFormat:
		msg.Puts("INSTALLED packages:")
		for _, pkg := range l.Installed {
			msg.Puts("\t%s", pkg)
		}

		if len(l.Missing) > 0 {
			msg.Puts("\nMISSING packages:")
			for _, pkg := range l.Missing {
				msg.Puts("\t%s", pkg)
			}
		}
		if len(l.Gopath) > 0 {
			msg.Puts("\nGOPATH packages:")
			for _, pkg := range l.Gopath {
				msg.Puts("\t%s", pkg)
			}
		}
	case jsonFormat:
		json.NewEncoder(msg.Default.Stdout).Encode(l)
	case jsonPrettyFormat:
		b, err := json.MarshalIndent(l, "", "  ")
		if err != nil {
			msg.Die("could not unmarshal package list: %s", err)
		}
		msg.Puts(string(b))
	default:
		msg.Die("invalid output format: must be one of: json|json-pretty|text")
	}
}

// Install installs a vendor directory based on an existing Glide configuration.
func Install(installer *repo.Installer, stripVendor bool) {
	cache.SystemLock()

	base := "."
	// Ensure GOPATH
	EnsureGopath()
	EnsureVendorDir()
	conf := EnsureConfig()

	// Lockfile exists
	if !gpath.HasLock(base) {
		msg.Info("Lock file (glide.lock) does not exist. Performing update.")
		Update(installer, false, stripVendor)
		return
	}
	// Load lockfile
	lock, err := cfg.ReadLockFile(filepath.Join(base, gpath.LockFile))
	if err != nil {
		msg.Die("Could not load lockfile.")
	}
	// Verify lockfile hasn't changed
	hash, err := conf.Hash()
	if err != nil {
		msg.Die("Could not load lockfile.")
	} else if hash != lock.Hash {
		fmt.Println(hash, lock.Hash)
		foo, _ := conf.Marshal()
		fmt.Println(string(foo))
		msg.Warn("Lock file may be out of date. Hash check of YAML failed. You may need to run 'update'")
	}

	// Install
	newConf, err := installer.Install(lock, conf)
	if err != nil {
		msg.Die("Failed to install: %s", err)
	}

	msg.Info("Setting references.")

	// Set reference
	if err := repo.SetReference(newConf, installer.ResolveTest); err != nil {
		msg.Die("Failed to set references: %s (Skip to cleanup)", err)
	}

	err = installer.Export(newConf)
	if err != nil {
		msg.Die("Unable to export dependencies to vendor directory: %s", err)
	}

	if stripVendor {
		msg.Info("Removing nested vendor and Godeps/_workspace directories...")
		err := gpath.StripVendor()
		if err != nil {
			msg.Err("Unable to strip vendor directories: %s", err)
		}
	}
}

func writeLock(conf, confcopy *cfg.Config, base string) {
	hash, err := conf.Hash()
	if err != nil {
		msg.Die("Failed to generate config hash. Unable to generate lock file.")
	}
	lock := cfg.NewLockfile(confcopy.Imports, hash)
	if err := lock.WriteFile(filepath.Join(base, gpath.LockFile)); err != nil {
		msg.Die("Failed to write glide lock file: %s", err)
	}
}

// EnsureVendorDir ensures that a vendor/ directory is present in the cwd.
func EnsureVendorDir() {
	fi, err := os.Stat(gpath.VendorDir)
	if err != nil {
		msg.Debug("Creating %s", gpath.VendorDir)
		if err := os.MkdirAll(gpath.VendorDir, os.ModeDir|0755); err != nil {
			msg.Die("Could not create %s: %s", gpath.VendorDir, err)
		}
	} else if !fi.IsDir() {
		msg.Die("Vendor is not a directory")
	}
}

// writeConfigToFileOrStdout is a convenience function for import utils.
func writeConfigToFileOrStdout(config *cfg.Config, dest string) {
	if dest != "" {
		if err := config.WriteFile(dest); err != nil {
			msg.Die("Failed to write %s: %s", gpath.GlideFile, err)
		}
	} else {
		o, err := config.Marshal()
		if err != nil {
			msg.Die("Error encoding config: %s", err)
		}
		msg.Default.Stdout.Write(o)
	}
}

// ImportGB imports GB dependencies into the present glide config.
func ImportGB(dest string) {
	base := "."
	config := EnsureConfig()
	if !gb.Has(base) {
		msg.Die("There is no GB manifest to import.")
	}
	deps, err := gb.Parse(base)
	if err != nil {
		msg.Die("Failed to extract GB manifest: %s", err)
	}
	appendImports(deps, config)
	writeConfigToFileOrStdout(config, dest)
}

// ImportGom imports a Gomfile.
func ImportGom(dest string) {
	base := "."
	config := EnsureConfig()
	if !gom.Has(base) {
		msg.Die("No gom data found.")
	}
	deps, err := gom.Parse(base)
	if err != nil {
		msg.Die("Failed to extract Gomfile: %s", err)
	}
	appendImports(deps, config)
	writeConfigToFileOrStdout(config, dest)
}

// EnsureGopath fails if GOPATH is not set, or if $GOPATH/src is missing.
//
// Otherwise it returns the value of GOPATH.
func EnsureGopath() string {
	gp := os.Getenv("GOPATH")
	if gp == "" {
		msg.Die("$GOPATH is not set.")
	}
	_, err := os.Stat(path.Join(gp, "src"))
	if err != nil {
		msg.Error("Could not find %s/src.\n", gp)
		msg.Info("As of Glide 0.5/Go 1.5, this is required.\n")
		msg.Die("Wihtout src, cannot continue. %s", err)
	}
	return gp
}

// Update updates all dependencies.
//
// It begins with the dependencies in the config file, but also resolves
// transitive dependencies. The returned lockfile has all of the dependencies
// listed, but the version reconciliation has not been done.
//
// In other words, all versions in the Lockfile will be empty.
func (i *Installer) Update(conf *cfg.Config) error {
	base := "."
	vpath := i.VendorPath()

	ic := newImportCache()

	m := &MissingPackageHandler{
		destination: vpath,

		cache:          i.UseCache,
		cacheGopath:    i.UseCacheGopath,
		useGopath:      i.UseGopath,
		home:           i.Home,
		force:          i.Force,
		updateVendored: i.UpdateVendored,
		Config:         conf,
		Use:            ic,
		updated:        i.Updated,
	}

	v := &VersionHandler{
		Destination: vpath,
		Use:         ic,
		Imported:    make(map[string]bool),
		Conflicts:   make(map[string]bool),
		Config:      conf,
	}

	// Update imports
	res, err := dependency.NewResolver(base)
	if err != nil {
		msg.Die("Failed to create a resolver: %s", err)
	}
	res.Config = conf
	res.Handler = m
	res.VersionHandler = v
	res.ResolveAllFiles = i.ResolveAllFiles
	msg.Info("Resolving imports")
	_, err = allPackages(conf.Imports, res)
	if err != nil {
		msg.Die("Failed to retrieve a list of dependencies: %s", err)
	}

	if len(conf.DevImports) > 0 {
		msg.Warn("dev imports not resolved.")
	}

	err = ConcurrentUpdate(conf.Imports, vpath, i, conf)

	return err
}

func (d *VersionHandler) pkgPath(pkg string) string {
	root, sub := util.NormalizeName(pkg)

	// For the parent applications source skip the cache.
	if root == d.Config.Name {
		pth := gpath.Basepath()
		return filepath.Join(pth, filepath.FromSlash(sub))
	}

	dep := d.Config.Imports.Get(root)
	if dep == nil {
		dep = d.Config.DevImports.Get(root)
	}

	if dep == nil {
		dep, _ = d.Use.Get(root)

		if dep == nil {
			dep = &cfg.Dependency{Name: root}
		}
	}

	key, err := cache.Key(dep.Remote())
	if err != nil {
		msg.Die("Error generating cache key for %s", dep.Name)
	}

	return filepath.Join(cache.Location(), "src", key, filepath.FromSlash(sub))
}

func guessImportDeps(base string, config *cfg.Config) {
	msg.Info("Attempting to import from other package managers (use --skip-import to skip)")
	deps := []*cfg.Dependency{}
	absBase, err := filepath.Abs(base)
	if err != nil {
		msg.Die("Failed to resolve location of %s: %s", base, err)
	}

	if d, ok := guessImportGodep(absBase); ok {
		msg.Info("Importing Godep configuration")
		msg.Warn("Godep uses commit id versions. Consider using Semantic Versions with Glide")
		deps = d
	} else if d, ok := guessImportGPM(absBase); ok {
		msg.Info("Importing GPM configuration")
		deps = d
	} else if d, ok := guessImportGB(absBase); ok {
		msg.Info("Importing GB configuration")
		deps = d
	}

	for _, i := range deps {
		if i.Reference == "" {
			msg.Info("--> Found imported reference to %s", i.Name)
		} else {
			msg.Info("--> Found imported reference to %s at revision %s", i.Name, i.Reference)
		}

		config.Imports = append(config.Imports, i)
	}
}

// MirrorsList displays a list of currently setup mirrors.
func MirrorsList() error {
	home := gpath.Home()

	op := filepath.Join(home, "mirrors.yaml")

	if _, err := os.Stat(op); os.IsNotExist(err) {
		msg.Info("No mirrors exist. No mirrors.yaml file not found")
		return nil
	}

	ov, err := mirrors.ReadMirrorsFile(op)
	if err != nil {
		msg.Die("Unable to read mirrors.yaml file: %s", err)
	}

	if len(ov.Repos) == 0 {
		msg.Info("No mirrors found")
		return nil
	}

	msg.Info("Mirrors...")
	for _, r := range ov.Repos {
		if r.Vcs == "" {
			msg.Info("--> %s replaced by %s", r.Original, r.Repo)
		} else {
			msg.Info("--> %s replaced by %s (%s)", r.Original, r.Repo, r.Vcs)
		}
	}

	return nil
}

// Create creates/initializes a new Glide repository.
//
// This will fail if a glide.yaml already exists.
//
// By default, this will scan the present source code directory for dependencies.
//
// If skipImport is set to true, this will not attempt to import from an existing
// GPM, Godep, or GB project if one should exist. However, it will still attempt
// to read the local source to determine required packages.
func Create(base string, skipImport, nonInteractive bool) {
	glidefile := gpath.GlideFile
	// Guard against overwrites.
	guardYAML(glidefile)

	// Guess deps
	conf := guessDeps(base, skipImport)
	// Write YAML
	msg.Info("Writing configuration file (%s)", glidefile)
	if err := conf.WriteFile(glidefile); err != nil {
		msg.Die("Could not save %s: %s", glidefile, err)
	}

	var res bool
	if !nonInteractive {
		msg.Info("Would you like Glide to help you find ways to improve your glide.yaml configuration?")
		msg.Info("If you want to revisit this step you can use the config-wizard command at any time.")
		msg.Info("Yes (Y) or No (N)?")
		res = msg.PromptUntilYorN()
		if res {
			ConfigWizard(base)
		}
	}

	if !res {
		msg.Info("You can now edit the glide.yaml file. Consider:")
		msg.Info("--> Using versions and ranges. See https://glide.sh/docs/versions/")
		msg.Info("--> Adding additional metadata. See https://glide.sh/docs/glide.yaml/")
		msg.Info("--> Running the config-wizard command to improve the versions in your configuration")
	}
}

// Info prints information about a project based on a passed in format.
func Info(format string) {
	conf := EnsureConfig()
	var buffer bytes.Buffer
	varInit := false
	for _, varfmt := range format {
		if varInit {
			switch varfmt {
			case 'n':
				buffer.WriteString(conf.Name)
			case 'd':
				buffer.WriteString(conf.Description)
			case 'h':
				buffer.WriteString(conf.Home)
			case 'l':
				buffer.WriteString(conf.License)
			default:
				msg.Die("Invalid format %s", string(varfmt))
			}
		} else {
			switch varfmt {
			case '%':
				varInit = true
				continue
			default:
				buffer.WriteString(string(varfmt))
			}
		}
		varInit = false
	}
	msg.Puts(buffer.String())
}

// Plugin attempts to find and execute a plugin based on a command.
//
// Exit code 99 means the plugin was never executed. Code 1 means the program
// exited badly.
func Plugin(command string, args []string) {

	cwd, err := os.Getwd()
	if err != nil {
		msg.ExitCode(99)
		msg.Die("Could not get working directory: %s", err)
	}

	cmd := "glide-" + command
	var fullcmd string
	if fullcmd, err = exec.LookPath(cmd); err != nil {
		fullcmd = cwd + "/" + cmd
		if _, err := os.Stat(fullcmd); err != nil {
			msg.ExitCode(99)
			msg.Die("Command %s does not exist.", cmd)
		}
	}

	// Turning os.Args first argument from `glide` to `glide-command`
	args[0] = cmd
	// Removing the first argument (command)
	removed := false
	for i, v := range args {
		if removed == false && v == command {
			args = append(args[:i], args[i+1:]...)
			removed = true
		}
	}
	pa := os.ProcAttr{
		Files: []*os.File{os.Stdin, os.Stdout, os.Stderr},
		Dir:   cwd,
	}

	msg.Debug("Delegating to plugin %s (%v)\n", fullcmd, args)

	proc, err := os.StartProcess(fullcmd, args, &pa)
	if err != nil {
		msg.Err("Failed to execute %s: %s", cmd, err)
		os.Exit(98)
	}

	if _, err := proc.Wait(); err != nil {
		msg.Err(err.Error())
		os.Exit(1)
	}
}

// EnsureConfig loads and returns a config file.
//
// Any error will cause an immediate exit, with an error printed to Stderr.
func EnsureConfig() *cfg.Config {
	yamlpath, err := gpath.Glide()
	if err != nil {
		msg.ExitCode(2)
		msg.Die("Failed to find %s file in directory tree: %s", gpath.GlideFile, err)
	}

	yml, err := ioutil.ReadFile(yamlpath)
	if err != nil {
		msg.ExitCode(2)
		msg.Die("Failed to load %s: %s", yamlpath, err)
	}
	conf, err := cfg.ConfigFromYaml(yml)
	if err != nil {
		msg.ExitCode(3)
		msg.Die("Failed to parse %s: %s", yamlpath, err)
	}

	b := filepath.Dir(yamlpath)
	buildContext, err := util.GetBuildContext()
	if err != nil {
		msg.Die("Failed to build an import context while ensuring config: %s", err)
	}
	cwd, err := os.Getwd()
	if err != nil {
		msg.Err("Unable to get the current working directory")
	} else {
		// Determining a package name requires a relative path
		b, err = filepath.Rel(b, cwd)
		if err == nil {
			name := buildContext.PackageName(b)
			if name != conf.Name {
				msg.Warn("The name listed in the config file (%s) does not match the current location (%s)", conf.Name, name)
			}
		} else {
			msg.Warn("Problem finding the config file path (%s) relative to the current directory (%s): %s", b, cwd, err)
		}
	}

	err = mirrors.Load()
	if err != nil {
		msg.Err("Unable to load mirrors: %s", err)
	}

	return conf
}

// List lists all of the dependencies of the current project.
//
// Params:
//  - dir (string): basedir
//  - deep (bool): whether to do a deep scan or a shallow scan
func List(basedir string, deep bool) {

	basedir, err := filepath.Abs(basedir)
	if err != nil {
		msg.Die("Could not read directory: %s", err)
	}

	r, err := dependency.NewResolver(basedir)
	if err != nil {
		msg.Die("Could not create a resolver: %s", err)
	}
	h := &dependency.DefaultMissingPackageHandler{Missing: []string{}, Gopath: []string{}}
	r.Handler = h

	sortable, err := r.ResolveLocal(deep)
	if err != nil {
		msg.Die("Error listing dependencies: %s", err)
	}

	msg.Info("Sorting...")
	sort.Strings(sortable)

	msg.Puts("INSTALLED packages:")
	for _, k := range sortable {
		v, err := filepath.Rel(basedir, k)
		if err != nil {
			//msg.Warn("Failed to Rel path: %s", err)
			v = k
		}
		msg.Puts("\t%s", v)
	}

	if len(h.Missing) > 0 {
		msg.Puts("\nMISSING packages:")
		for _, pkg := range h.Missing {
			msg.Puts("\t%s", pkg)
		}
	}
	if len(h.Gopath) > 0 {
		msg.Puts("\nGOPATH packages:")
		for _, pkg := range h.Gopath {
			msg.Puts("\t%s", pkg)
		}
	}
}