// Copyright 2015 The Hugo Authors. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package helpers

import (
	"errors"
	"fmt"
	"io"
	"os"
	"path/filepath"
	"regexp"
	"sort"
	"strings"
	"unicode"

	"github.com/spf13/afero"
	"golang.org/x/text/transform"
	"golang.org/x/text/unicode/norm"
)

var (
	// ErrThemeUndefined is returned when a theme has not be defined by the user.
	ErrThemeUndefined = errors.New("no theme set")
)

// filepathPathBridge is a bridge for common functionality in filepath vs path
type filepathPathBridge interface {
	Base(in string) string
	Clean(in string) string
	Dir(in string) string
	Ext(in string) string
	Join(elem ...string) string
	Separator() string
}

type filepathBridge struct {
}

func (filepathBridge) Base(in string) string {
	return filepath.Base(in)
}

func (filepathBridge) Clean(in string) string {
	return filepath.Clean(in)
}

func (filepathBridge) Dir(in string) string {
	return filepath.Dir(in)
}

func (filepathBridge) Ext(in string) string {
	return filepath.Ext(in)
}

func (filepathBridge) Join(elem ...string) string {
	return filepath.Join(elem...)
}

func (filepathBridge) Separator() string {
	return FilePathSeparator
}

var fpb filepathBridge

// MakePath takes a string with any characters and replace it
// so the string could be used in a path.
// It does so by creating a Unicode-sanitized string, with the spaces replaced,
// whilst preserving the original casing of the string.
// E.g. Social Media -> Social-Media
func (p *PathSpec) MakePath(s string) string {
	return p.UnicodeSanitize(strings.Replace(strings.TrimSpace(s), " ", "-", -1))
}

// MakePathSanitized creates a Unicode-sanitized string, with the spaces replaced
func (p *PathSpec) MakePathSanitized(s string) string {
	if p.DisablePathToLower {
		return p.MakePath(s)
	}
	return strings.ToLower(p.MakePath(s))
}

// ToSlashTrimLeading is just a filepath.ToSlaas with an added / prefix trimmer.
func ToSlashTrimLeading(s string) string {
	return strings.TrimPrefix(filepath.ToSlash(s), "/")
}

// MakeTitle converts the path given to a suitable title, trimming whitespace
// and replacing hyphens with whitespace.
func MakeTitle(inpath string) string {
	return strings.Replace(strings.TrimSpace(inpath), "-", " ", -1)
}

// From https://golang.org/src/net/url/url.go
func ishex(c rune) bool {
	switch {
	case '0' <= c && c <= '9':
		return true
	case 'a' <= c && c <= 'f':
		return true
	case 'A' <= c && c <= 'F':
		return true
	}
	return false
}

// UnicodeSanitize sanitizes string to be used in Hugo URL's, allowing only
// a predefined set of special Unicode characters.
// If RemovePathAccents configuration flag is enabled, Uniccode accents
// are also removed.
func (p *PathSpec) UnicodeSanitize(s string) string {
	source := []rune(s)
	target := make([]rune, 0, len(source))

	for i, r := range source {
		if r == '%' && i+2 < len(source) && ishex(source[i+1]) && ishex(source[i+2]) {
			target = append(target, r)
		} else if unicode.IsLetter(r) || unicode.IsDigit(r) || unicode.IsMark(r) || r == '.' || r == '/' || r == '\\' || r == '_' || r == '-' || r == '#' || r == '+' || r == '~' {
			target = append(target, r)
		}
	}

	var result string

	if p.RemovePathAccents {
		// remove accents - see https://blog.golang.org/normalization
		t := transform.Chain(norm.NFD, transform.RemoveFunc(isMn), norm.NFC)
		result, _, _ = transform.String(t, string(target))
	} else {
		result = string(target)
	}

	return result
}

func isMn(r rune) bool {
	return unicode.Is(unicode.Mn, r) // Mn: nonspacing marks
}

// ReplaceExtension takes a path and an extension, strips the old extension
// and returns the path with the new extension.
func ReplaceExtension(path string, newExt string) string {
	f, _ := fileAndExt(path, fpb)
	return f + "." + newExt
}

// GetFirstThemeDir gets the root directory of the first theme, if there is one.
// If there is no theme, returns the empty string.
func (p *PathSpec) GetFirstThemeDir() string {
	if p.ThemeSet() {
		return p.AbsPathify(filepath.Join(p.ThemesDir, p.Themes()[0]))
	}
	return ""
}

// GetThemesDir gets the absolute root theme dir path.
func (p *PathSpec) GetThemesDir() string {
	if p.ThemeSet() {
		return p.AbsPathify(p.ThemesDir)
	}
	return ""
}

// GetRelativeThemeDir gets the relative root directory of the current theme, if there is one.
// If there is no theme, returns the empty string.
func (p *PathSpec) GetRelativeThemeDir() string {
	if p.ThemeSet() {
		return strings.TrimPrefix(filepath.Join(p.ThemesDir, p.Themes()[0]), FilePathSeparator)
	}
	return ""
}

func makePathRelative(inPath string, possibleDirectories ...string) (string, error) {

	for _, currentPath := range possibleDirectories {
		if strings.HasPrefix(inPath, currentPath) {
			return strings.TrimPrefix(inPath, currentPath), nil
		}
	}
	return inPath, errors.New("Can't extract relative path, unknown prefix")
}

// Should be good enough for Hugo.
var isFileRe = regexp.MustCompile(`.*\..{1,6}$`)

// GetDottedRelativePath expects a relative path starting after the content directory.
// It returns a relative path with dots ("..") navigating up the path structure.
func GetDottedRelativePath(inPath string) string {
	inPath = filepath.Clean(filepath.FromSlash(inPath))

	if inPath == "." {
		return "./"
	}

	if !isFileRe.MatchString(inPath) && !strings.HasSuffix(inPath, FilePathSeparator) {
		inPath += FilePathSeparator
	}

	if !strings.HasPrefix(inPath, FilePathSeparator) {
		inPath = FilePathSeparator + inPath
	}

	dir, _ := filepath.Split(inPath)

	sectionCount := strings.Count(dir, FilePathSeparator)

	if sectionCount == 0 || dir == FilePathSeparator {
		return "./"
	}

	var dottedPath string

	for i := 1; i < sectionCount; i++ {
		dottedPath += "../"
	}

	return dottedPath
}

// ExtNoDelimiter takes a path and returns the extension, excluding the delmiter, i.e. "md".
func ExtNoDelimiter(in string) string {
	return strings.TrimPrefix(Ext(in), ".")
}

// Ext takes a path and returns the extension, including the delmiter, i.e. ".md".
func Ext(in string) string {
	_, ext := fileAndExt(in, fpb)
	return ext
}

// PathAndExt is the same as FileAndExt, but it uses the path package.
func PathAndExt(in string) (string, string) {
	return fileAndExt(in, pb)
}

// FileAndExt takes a path and returns the file and extension separated,
// the extension including the delmiter, i.e. ".md".
func FileAndExt(in string) (string, string) {
	return fileAndExt(in, fpb)
}

// Filename takes a path, strips out the extension,
// and returns the name of the file.
func Filename(in string) (name string) {
	name, _ = fileAndExt(in, fpb)
	return
}

// FileAndExt returns the filename and any extension of a file path as
// two separate strings.
//
// If the path, in, contains a directory name ending in a slash,
// then both name and ext will be empty strings.
//
// If the path, in, is either the current directory, the parent
// directory or the root directory, or an empty string,
// then both name and ext will be empty strings.
//
// If the path, in, represents the path of a file without an extension,
// then name will be the name of the file and ext will be an empty string.
//
// If the path, in, represents a filename with an extension,
// then name will be the filename minus any extension - including the dot
// and ext will contain the extension - minus the dot.
func fileAndExt(in string, b filepathPathBridge) (name string, ext string) {
	ext = b.Ext(in)
	base := b.Base(in)

	return extractFilename(in, ext, base, b.Separator()), ext
}

func extractFilename(in, ext, base, pathSeparator string) (name string) {

	// No file name cases. These are defined as:
	// 1. any "in" path that ends in a pathSeparator
	// 2. any "base" consisting of just an pathSeparator
	// 3. any "base" consisting of just an empty string
	// 4. any "base" consisting of just the current directory i.e. "."
	// 5. any "base" consisting of just the parent directory i.e. ".."
	if (strings.LastIndex(in, pathSeparator) == len(in)-1) || base == "" || base == "." || base == ".." || base == pathSeparator {
		name = "" // there is NO filename
	} else if ext != "" { // there was an Extension
		// return the filename minus the extension (and the ".")
		name = base[:strings.LastIndex(base, ".")]
	} else {
		// no extension case so just return base, which willi
		// be the filename
		name = base
	}
	return

}

// GetRelativePath returns the relative path of a given path.
func GetRelativePath(path, base string) (final string, err error) {
	if filepath.IsAbs(path) && base == "" {
		return "", errors.New("source: missing base directory")
	}
	name := filepath.Clean(path)
	base = filepath.Clean(base)

	name, err = filepath.Rel(base, name)
	if err != nil {
		return "", err
	}

	if strings.HasSuffix(filepath.FromSlash(path), FilePathSeparator) && !strings.HasSuffix(name, FilePathSeparator) {
		name += FilePathSeparator
	}
	return name, nil
}

// PathPrep prepares the path using the uglify setting to create paths on
// either the form /section/name/index.html or /section/name.html.
func PathPrep(ugly bool, in string) string {
	if ugly {
		return Uglify(in)
	}
	return PrettifyPath(in)
}

// PrettifyPath is the same as PrettifyURLPath but for file paths.
//     /section/name.html       becomes /section/name/index.html
//     /section/name/           becomes /section/name/index.html
//     /section/name/index.html becomes /section/name/index.html
func PrettifyPath(in string) string {
	return prettifyPath(in, fpb)
}

func prettifyPath(in string, b filepathPathBridge) string {
	if filepath.Ext(in) == "" {
		// /section/name/  -> /section/name/index.html
		if len(in) < 2 {
			return b.Separator()
		}
		return b.Join(in, "index.html")
	}
	name, ext := fileAndExt(in, b)
	if name == "index" {
		// /section/name/index.html -> /section/name/index.html
		return b.Clean(in)
	}
	// /section/name.html -> /section/name/index.html
	return b.Join(b.Dir(in), name, "index"+ext)
}

// ExtractRootPaths extracts the root paths from the supplied list of paths.
// The resulting root path will not contain any file separators, but there
// may be duplicates.
// So "/content/section/" becomes "content"
func ExtractRootPaths(paths []string) []string {
	r := make([]string, len(paths))
	for i, p := range paths {
		root := filepath.ToSlash(p)
		sections := strings.Split(root, "/")
		for _, section := range sections {
			if section != "" {
				root = section
				break
			}
		}
		r[i] = root
	}
	return r

}

// FindCWD returns the current working directory from where the Hugo
// executable is run.
func FindCWD() (string, error) {
	serverFile, err := filepath.Abs(os.Args[0])

	if err != nil {
		return "", fmt.Errorf("Can't get absolute path for executable: %v", err)
	}

	path := filepath.Dir(serverFile)
	realFile, err := filepath.EvalSymlinks(serverFile)

	if err != nil {
		if _, err = os.Stat(serverFile + ".exe"); err == nil {
			realFile = filepath.Clean(serverFile + ".exe")
		}
	}

	if err == nil && realFile != serverFile {
		path = filepath.Dir(realFile)
	}

	return path, nil
}

// SymbolicWalk is like filepath.Walk, but it supports the root being a
// symbolic link. It will still not follow symbolic links deeper down in
// the file structure.
func SymbolicWalk(fs afero.Fs, root string, walker filepath.WalkFunc) error {

	// Sanity check
	if root != "" && len(root) < 4 {
		return errors.New("Path is too short")
	}

	// Handle the root first
	fileInfo, realPath, err := getRealFileInfo(fs, root)

	if err != nil {
		return walker(root, nil, err)
	}

	if !fileInfo.IsDir() {
		return fmt.Errorf("Cannot walk regular file %s", root)
	}

	if err := walker(realPath, fileInfo, err); err != nil && err != filepath.SkipDir {
		return err
	}

	// Some of Hugo's filesystems represents an ordered root folder, i.e. project first, then theme folders.
	// Make sure that order is preserved. afero.Walk will sort the directories down in the file tree,
	// but we don't care about that.
	rootContent, err := readDir(fs, root, false)

	if err != nil {
		return walker(root, nil, err)
	}

	for _, fi := range rootContent {
		if err := afero.Walk(fs, filepath.Join(root, fi.Name()), walker); err != nil {
			return err
		}
	}

	return nil

}

func readDir(fs afero.Fs, dirname string, doSort bool) ([]os.FileInfo, error) {
	f, err := fs.Open(dirname)
	if err != nil {
		return nil, err
	}
	list, err := f.Readdir(-1)
	f.Close()
	if err != nil {
		return nil, err
	}
	if doSort {
		sort.Slice(list, func(i, j int) bool { return list[i].Name() < list[j].Name() })
	}
	return list, nil
}

func getRealFileInfo(fs afero.Fs, path string) (os.FileInfo, string, error) {
	fileInfo, err := LstatIfPossible(fs, path)
	realPath := path

	if err != nil {
		return nil, "", err
	}

	if fileInfo.Mode()&os.ModeSymlink == os.ModeSymlink {
		link, err := filepath.EvalSymlinks(path)
		if err != nil {
			return nil, "", fmt.Errorf("Cannot read symbolic link '%s', error was: %s", path, err)
		}
		fileInfo, err = LstatIfPossible(fs, link)
		if err != nil {
			return nil, "", fmt.Errorf("Cannot stat '%s', error was: %s", link, err)
		}
		realPath = link
	}
	return fileInfo, realPath, nil
}

// GetRealPath returns the real file path for the given path, whether it is a
// symlink or not.
func GetRealPath(fs afero.Fs, path string) (string, error) {
	_, realPath, err := getRealFileInfo(fs, path)

	if err != nil {
		return "", err
	}

	return realPath, nil
}

// LstatIfPossible can be used to call Lstat if possible, else Stat.
func LstatIfPossible(fs afero.Fs, path string) (os.FileInfo, error) {
	if lstater, ok := fs.(afero.Lstater); ok {
		fi, _, err := lstater.LstatIfPossible(path)
		return fi, err
	}

	return fs.Stat(path)
}

// SafeWriteToDisk is the same as WriteToDisk
// but it also checks to see if file/directory already exists.
func SafeWriteToDisk(inpath string, r io.Reader, fs afero.Fs) (err error) {
	return afero.SafeWriteReader(fs, inpath, r)
}

// WriteToDisk writes content to disk.
func WriteToDisk(inpath string, r io.Reader, fs afero.Fs) (err error) {
	return afero.WriteReader(fs, inpath, r)
}

// GetTempDir returns a temporary directory with the given sub path.
func GetTempDir(subPath string, fs afero.Fs) string {
	return afero.GetTempDir(fs, subPath)
}

// DirExists checks if a path exists and is a directory.
func DirExists(path string, fs afero.Fs) (bool, error) {
	return afero.DirExists(fs, path)
}

// IsDir checks if a given path is a directory.
func IsDir(path string, fs afero.Fs) (bool, error) {
	return afero.IsDir(fs, path)
}

// IsEmpty checks if a given path is empty.
func IsEmpty(path string, fs afero.Fs) (bool, error) {
	return afero.IsEmpty(fs, path)
}

// FileContains checks if a file contains a specified string.
func FileContains(filename string, subslice []byte, fs afero.Fs) (bool, error) {
	return afero.FileContainsBytes(fs, filename, subslice)
}

// FileContainsAny checks if a file contains any of the specified strings.
func FileContainsAny(filename string, subslices [][]byte, fs afero.Fs) (bool, error) {
	return afero.FileContainsAnyBytes(fs, filename, subslices)
}

// Exists checks if a file or directory exists.
func Exists(path string, fs afero.Fs) (bool, error) {
	return afero.Exists(fs, path)
}
