// FindVcs determines the version control information given a package dir and
// lowest root dir.
func FindVcs(root, packageDir string) (info *VcsInfo, err error) {
	path := packageDir
	for i := 0; i <= looplimit; i++ {
		for _, vcs := range vcsRegistry {
			info, err = vcs.Find(path)
			if err != nil {
				return nil, err
			}
			if info != nil {
				return info, nil
			}
		}

		nextPath := filepath.Clean(filepath.Join(path, ".."))
		// Check for root.
		if nextPath == path {
			return nil, nil
		}
		if pathos.FileHasPrefix(nextPath, root) == false {
			return nil, nil
		}
		path = nextPath
	}
	panic("loop limit")
}

func (ctx *Context) modifyRemove(pkg *Package) error {
	if len(pkg.Dir) == 0 {
		return nil
	}
	// Protect non-project paths from being removed.
	if pathos.FileHasPrefix(pkg.Dir, ctx.RootDir) == false {
		return nil
	}
	if pkg.Status == StatusLocal {
		return nil
	}
	if pkg.Status == StatusProgram && pkg.inVendor == false {
		return nil
	}
	ctx.Operation = append(ctx.Operation, &Operation{
		Pkg:  pkg,
		Src:  pkg.Dir,
		Dest: "",
	})

	// Update vendor file with correct Local field.
	vp := ctx.VendorFilePackagePath(pkg.Canonical)
	if vp != nil {
		vp.Remove = true
	}
	mvSet := make(map[*Package]struct{}, 3)
	ctx.makeSet(pkg, mvSet)

	for r := range mvSet {
		dprintf("RULE: %s -> %s\n", r.Local, r.Canonical)
		ctx.RewriteRule[r.Local] = r.Canonical
	}

	return nil
}

// findImportDir finds the absolute directory. If rel is empty vendor folders
// are not looked in.
func (ctx *Context) findImportDir(relative, importPath string) (dir, gopath string, err error) {
	if importPath == "builtin" || importPath == "unsafe" || importPath == "C" {
		return filepath.Join(ctx.Goroot, importPath), ctx.Goroot, nil
	}
	if len(relative) != 0 {
		rel := relative
		for {
			look := filepath.Join(rel, "vendor", importPath)
			nextRel := filepath.Join(rel, "..")
			if rel == nextRel {
				break
			}
			rel = nextRel
			fi, err := os.Stat(look)
			if os.IsNotExist(err) {
				continue
			}
			if err != nil {
				continue
			}
			if fi.IsDir() == false {
				continue
			}
			for _, gopath = range ctx.GopathList {
				if pathos.FileHasPrefix(look, gopath) {
					hasGo, err := hasGoFileInFolder(look)
					if err != nil {
						return "", "", err
					}
					if hasGo {
						return look, gopath, nil
					}
				}
			}
		}

	}
	for _, gopath = range ctx.GopathList {
		dir := filepath.Join(gopath, importPath)
		fi, err := os.Stat(dir)
		if os.IsNotExist(err) {
			continue
		}
		if fi.IsDir() == false {
			continue
		}

		hasGo, err := hasGoFileInFolder(dir)
		if err != nil {
			return "", "", err
		}
		if hasGo {
			return dir, gopath, nil
		}
		return "", "", ErrNotInGOPATH{fmt.Sprintf("Import: %q relative: %q", importPath, relative)}
	}
	return "", "", ErrNotInGOPATH{importPath}
}

// findImportPath takes a absolute directory and returns the import path and go path.
func (ctx *Context) findImportPath(dir string) (importPath, gopath string, err error) {
	for _, gopath := range ctx.GopathList {
		if pathos.FileHasPrefix(dir, gopath) {
			importPath = pathos.FileTrimPrefix(dir, gopath)
			importPath = pathos.SlashToImportPath(importPath)
			return importPath, gopath, nil
		}
	}
	return "", "", ErrNotInGOPATH{dir}
}

// updatePackageReferences populates the referenced field in each Package.
func (ctx *Context) updatePackageReferences() {
	canonicalUnderDirLookup := make(map[string]map[string]*Package)
	findCanonicalUnderDir := func(dir, canonical string) *Package {
		if importMap, found := canonicalUnderDirLookup[dir]; found {
			if pkg, found2 := importMap[canonical]; found2 {
				return pkg
			}
		} else {
			canonicalUnderDirLookup[dir] = make(map[string]*Package)
		}
		for _, pkg := range ctx.Package {
			if !pkg.inVendor {
				continue
			}

			removeFromEnd := len(pkg.Canonical) + len(ctx.VendorDiscoverFolder) + 2
			nextLen := len(pkg.Dir) - removeFromEnd
			if nextLen < 0 {
				continue
			}
			checkDir := pkg.Dir[:nextLen]
			if !pathos.FileHasPrefix(dir, checkDir) {
				continue
			}
			if pkg.Canonical != canonical {
				continue
			}
			canonicalUnderDirLookup[dir][canonical] = pkg
			return pkg
		}
		canonicalUnderDirLookup[dir][canonical] = nil
		return nil
	}
	for _, pkg := range ctx.Package {
		pkg.referenced = make(map[string]*Package, len(pkg.referenced))
	}
	for _, pkg := range ctx.Package {
		for _, f := range pkg.Files {
			for _, imp := range f.Imports {
				if vpkg := findCanonicalUnderDir(pkg.Dir, imp); vpkg != nil {
					vpkg.referenced[pkg.Local] = pkg
					continue
				}
				if other, found := ctx.Package[imp]; found {
					other.referenced[pkg.Local] = pkg
					continue
				}
			}
		}
	}
}

func (ctx *Context) addSingleImport(pkgInDir, imp string) error {
	if _, found := ctx.Package[imp]; found {
		return nil
	}
	// Also need to check for vendor paths that won't use the local path in import path.
	for _, pkg := range ctx.Package {
		if pkg.Canonical == imp && pkg.inVendor && pathos.FileHasPrefix(pkg.Dir, pkgInDir) {
			return nil
		}
	}
	dir, gopath, err := ctx.findImportDir(pkgInDir, imp)
	if err != nil {
		if _, is := err.(ErrNotInGOPATH); is {
			ctx.setPackage("", imp, imp, "", StatusMissing)
			return nil
		}
		return err
	}
	if pathos.FileStringEquals(gopath, ctx.Goroot) {
		ctx.setPackage(dir, imp, imp, ctx.Goroot, StatusStandard)
		return nil
	}
	df, err := os.Open(dir)
	if err != nil {
		return err
	}
	info, err := df.Readdir(-1)
	df.Close()
	if err != nil {
		return err
	}
	for _, fi := range info {
		if fi.IsDir() {
			continue
		}
		switch fi.Name()[0] {
		case '.', '_':
			continue
		}
		if pathos.FileStringEquals(dir, pkgInDir) {
			continue
		}
		path := filepath.Join(dir, fi.Name())
		err = ctx.addFileImports(path, gopath)
		if err != nil {
			return err
		}
	}
	return nil
}

func readVendorFile(vendorFilePath string) (*vendorfile.File, error) {
	vf := &vendorfile.File{}
	f, err := os.Open(vendorFilePath)
	if err != nil {
		return nil, err
	}
	defer f.Close()

	err = vf.Unmarshal(f)
	if err != nil {
		return nil, err
	}
	// Determine if local field is relative to GOPATH or vendor file.
	// Change to relative to vendor file as needed.
	folder, _ := filepath.Split(vendorFilePath)
	relToFile := 0
	relToGOPATH := 0
	for _, pkg := range vf.Package {
		p := filepath.Join(folder, pathos.SlashToFilepath(pkg.Local))
		_, err := os.Stat(p)
		if os.IsNotExist(err) {
			relToGOPATH++
			continue
		}
		relToFile++
	}
	if relToFile > relToGOPATH || len(vf.Package) == 0 {
		return vf, nil
	}

	gopathList := strings.Split(os.Getenv("GOPATH"), string(os.PathListSeparator))
	gopath := ""
	for _, gp := range gopathList {
		if pathos.FileHasPrefix(folder, gp) {
			gopath = gp
			break
		}
	}
	if len(gopath) == 0 {
		return vf, nil
	}
	prefix := pathos.SlashToImportPath(pathos.FileTrimPrefix(folder, filepath.Join(gopath, "src")))
	prefix = strings.TrimPrefix(prefix, "/")
	for _, pkg := range vf.Package {
		pkg.Local = strings.TrimPrefix(pkg.Local, prefix)
	}

	return vf, nil
}

// updatePackageReferences populates the referenced field in each Package.
func (ctx *Context) updatePackageReferences() {
	findCanonicalUnderDir := func(dir, canonical string) *Package {
		for _, pkg := range ctx.Package {
			if pkg.Status != StatusVendor {
				continue
			}

			removeFromEnd := len(pkg.Canonical) + len(ctx.VendorDiscoverFolder) + 2
			checkDir := pkg.Dir[:len(pkg.Dir)-removeFromEnd]
			if !pathos.FileHasPrefix(dir, checkDir) {
				continue
			}
			if pkg.Canonical != canonical {
				continue
			}
			return pkg
		}
		return nil
	}
	for _, pkg := range ctx.Package {
		pkg.referenced = make(map[string]*Package, len(pkg.referenced))
	}
	for _, pkg := range ctx.Package {
		for _, f := range pkg.Files {
			for _, imp := range f.Imports {
				if vpkg := findCanonicalUnderDir(pkg.Dir, imp); vpkg != nil {
					vpkg.referenced[pkg.Local] = pkg
					continue
				}
				if other, found := ctx.Package[imp]; found {
					other.referenced[pkg.Local] = pkg
					continue
				}
			}
		}
	}
}

// Rewrite rewrites files to the local path.
func (ctx *Context) rewrite() error {
	if !ctx.rewriteImports {
		return nil
	}
	if ctx.dirty {
		ctx.loadPackage()
	}
	ctx.dirty = true

	fileImports := make(map[string]map[string]*File) // map[ImportPath]map[FilePath]File
	for _, pkg := range ctx.Package {
		for _, f := range pkg.Files {
			for _, imp := range f.Imports {
				fileList := fileImports[imp]
				if fileList == nil {
					fileList = make(map[string]*File, 1)
					fileImports[imp] = fileList
				}
				fileList[f.Path] = f
			}
		}
	}
	filePaths := make(map[string]*File, len(ctx.RewriteRule))
	for from := range ctx.RewriteRule {
		for _, f := range fileImports[from] {
			filePaths[f.Path] = f
		}
	}

	/*
		RULE: co2/internal/co3/pk3 -> co1/internal/co3/pk3

		i co1/internal/co2/pk2 [co2/pk2] < ["co1/pk1"]
		i co1/internal/co3/pk3 [co3/pk3] < ["co1/pk1"]
		e co2/internal/co3/pk3 [co3/pk3] < ["co1/internal/co2/pk2"]
		l co1/pk1 < []
		s strings < ["co1/internal/co3/pk3" "co2/internal/co3/pk3"]

		Rewrite the package "co1/internal/co2/pk2" because it references a package with a rewrite.from package.
	*/
	ctx.updatePackageReferences()
	for from := range ctx.RewriteRule {
		pkg := ctx.Package[from]
		if pkg == nil {
			continue
		}
		for _, ref := range pkg.referenced {
			for _, f := range ref.Files {
				dprintf("REF RW %s\n", f.Path)
				filePaths[f.Path] = f
			}
		}
	}

	defer func() {
		ctx.RewriteRule = make(map[string]string, 3)
	}()

	if len(ctx.RewriteRule) == 0 {
		return nil
	}
	goprint := &printer.Config{
		Mode:     printer.TabIndent | printer.UseSpaces,
		Tabwidth: 8,
	}
	for _, fileInfo := range filePaths {
		if pathos.FileHasPrefix(fileInfo.Path, ctx.RootDir) == false {
			continue
		}

		// Read the file into AST, modify the AST.
		fileset := token.NewFileSet()
		f, err := parser.ParseFile(fileset, fileInfo.Path, nil, parser.ParseComments)
		if err != nil {
			return err
		}

		dprintf("RW:: File: %s\n", fileInfo.Path)

		for _, impNode := range f.Imports {
			imp, err := strconv.Unquote(impNode.Path.Value)
			if err != nil {
				return err
			}
			for from, to := range ctx.RewriteRule {
				if imp != from {
					continue
				}
				impNode.Path.Value = strconv.Quote(to)
				for i, metaImport := range fileInfo.Imports {
					if from == metaImport {
						dprintf("\tImport: %s -> %s\n", from, to)
						fileInfo.Imports[i] = to
					}
				}
				break
			}
		}

//.........这里部分代码省略.........