// Copyright 2017 gf Author(https://github.com/gogf/gf). All Rights Reserved.
//
// This Source Code Form is subject to the terms of the MIT License.
// If a copy of the MIT was not distributed with this file,
// You can obtain one at https://github.com/gogf/gf.

// Package gfile provides easy-to-use operations for file system.
package gfile

import (
	"bytes"
	"errors"
	"github.com/gogf/gf/text/gstr"
	"os"
	"os/exec"
	"os/user"
	"path/filepath"
	"runtime"
	"strings"
	"time"

	"github.com/gogf/gf/container/gtype"
	"github.com/gogf/gf/util/gconv"
)

const (
	// Separator for file system.
	Separator = string(filepath.Separator)
)

var (
	// Default perm for file opening.
	DefaultPerm = os.FileMode(0666)

	// The absolute file path for main package.
	// It can be only checked and set once.
	mainPkgPath = gtype.NewString()

	// selfPath is the current running binary path.
	// As it is most commonly used, it is so defined as an internal package variable.
	selfPath = ""

	// Temporary directory of system.
	tempDir = "/tmp"
)

func init() {
	// Initialize internal package variable: tempDir.
	if !Exists(tempDir) {
		tempDir = os.TempDir()
	}
	// Initialize internal package variable: selfPath.
	selfPath, _ := exec.LookPath(os.Args[0])
	if selfPath != "" {
		selfPath, _ = filepath.Abs(selfPath)
	}
	if selfPath == "" {
		selfPath, _ = filepath.Abs(os.Args[0])
	}
}

// Mkdir creates directories recursively with given <path>.
// The parameter <path> is suggested to be absolute path.
func Mkdir(path string) error {
	err := os.MkdirAll(path, os.ModePerm)
	if err != nil {
		return err
	}
	return nil
}

// Create creates file with given <path> recursively.
// The parameter <path> is suggested to be absolute path.
func Create(path string) (*os.File, error) {
	dir := Dir(path)
	if !Exists(dir) {
		if err := Mkdir(dir); err != nil {
			return nil, err
		}
	}
	return os.Create(path)
}

// Open opens file/directory READONLY.
func Open(path string) (*os.File, error) {
	return os.Open(path)
}

// OpenFile opens file/directory with custom <flag> and <perm>.
// The parameter <flag> is like: O_RDONLY, O_RDWR, O_RDWR|O_CREATE|O_TRUNC, etc.
func OpenFile(path string, flag int, perm os.FileMode) (*os.File, error) {
	return os.OpenFile(path, flag, perm)
}

// OpenWithFlag opens file/directory with default perm and custom <flag>.
// The default <perm> is 0666.
// The parameter <flag> is like: O_RDONLY, O_RDWR, O_RDWR|O_CREATE|O_TRUNC, etc.
func OpenWithFlag(path string, flag int) (*os.File, error) {
	f, err := os.OpenFile(path, flag, DefaultPerm)
	if err != nil {
		return nil, err
	}
	return f, nil
}

// OpenWithFlagPerm opens file/directory with custom <flag> and <perm>.
// The parameter <flag> is like: O_RDONLY, O_RDWR, O_RDWR|O_CREATE|O_TRUNC, etc.
// The parameter <perm> is like: 0600, 0666, 0777, etc.
func OpenWithFlagPerm(path string, flag int, perm os.FileMode) (*os.File, error) {
	f, err := os.OpenFile(path, flag, perm)
	if err != nil {
		return nil, err
	}
	return f, nil
}

// Join joins string array paths with file separator of current system.
func Join(paths ...string) string {
	var s string
	for _, path := range paths {
		if s != "" {
			s += Separator
		}
		s += gstr.TrimRight(path, Separator)
	}
	return s
}

// Exists checks whether given <path> exist.
func Exists(path string) bool {
	if stat, err := os.Stat(path); stat != nil && !os.IsNotExist(err) {
		return true
	}
	return false
}

// IsDir checks whether given <path> a directory.
func IsDir(path string) bool {
	s, err := os.Stat(path)
	if err != nil {
		return false
	}
	return s.IsDir()
}

// Pwd returns absolute path of current working directory.
func Pwd() string {
	path, _ := os.Getwd()
	return path
}

// Chdir changes the current working directory to the named directory.
// If there is an error, it will be of type *PathError.
func Chdir(dir string) error {
	return os.Chdir(dir)
}

// IsFile checks whether given <path> a file, which means it's not a directory.
func IsFile(path string) bool {
	s, err := os.Stat(path)
	if err != nil {
		return false
	}
	return !s.IsDir()
}

// Alias of Stat.
// See Stat.
func Info(path string) (os.FileInfo, error) {
	return Stat(path)
}

// Stat returns a FileInfo describing the named file.
// If there is an error, it will be of type *PathError.
func Stat(path string) (os.FileInfo, error) {
	return os.Stat(path)
}

// Move renames (moves) <src> to <dst> path.
func Move(src string, dst string) error {
	return os.Rename(src, dst)
}

// Alias of Move.
// See Move.
func Rename(src string, dst string) error {
	return Move(src, dst)
}

// DirNames returns sub-file names of given directory <path>.
// Note that the returned names are NOT absolute paths.
func DirNames(path string) ([]string, error) {
	f, err := os.Open(path)
	if err != nil {
		return nil, err
	}
	list, err := f.Readdirnames(-1)
	f.Close()
	if err != nil {
		return nil, err
	}
	return list, nil
}

// Glob returns the names of all files matching pattern or nil
// if there is no matching file. The syntax of patterns is the same
// as in Match. The pattern may describe hierarchical names such as
// /usr/*/bin/ed (assuming the Separator is '/').
//
// Glob ignores file system errors such as I/O errors reading directories.
// The only possible returned error is ErrBadPattern, when pattern
// is malformed.
func Glob(pattern string, onlyNames ...bool) ([]string, error) {
	if list, err := filepath.Glob(pattern); err == nil {
		if len(onlyNames) > 0 && onlyNames[0] && len(list) > 0 {
			array := make([]string, len(list))
			for k, v := range list {
				array[k] = Basename(v)
			}
			return array, nil
		}
		return list, nil
	} else {
		return nil, err
	}
}

// Remove deletes all file/directory with <path> parameter.
// If parameter <path> is directory, it deletes it recursively.
func Remove(path string) error {
	//intlog.Print(`Remove:`, path)
	return os.RemoveAll(path)
}

// IsReadable checks whether given <path> is readable.
func IsReadable(path string) bool {
	result := true
	file, err := os.OpenFile(path, os.O_RDONLY, DefaultPerm)
	if err != nil {
		result = false
	}
	file.Close()
	return result
}

// IsWritable checks whether given <path> is writable.
//
// TODO improve performance; use golang.org/x/sys to cross-plat-form
func IsWritable(path string) bool {
	result := true
	if IsDir(path) {
		// If it's a directory, create a temporary file to test whether it's writable.
		tmpFile := strings.TrimRight(path, Separator) + Separator + gconv.String(time.Now().UnixNano())
		if f, err := Create(tmpFile); err != nil || !Exists(tmpFile) {
			result = false
		} else {
			f.Close()
			Remove(tmpFile)
		}
	} else {
		// 如果是文件，那么判断文件是否可打开
		file, err := os.OpenFile(path, os.O_WRONLY, DefaultPerm)
		if err != nil {
			result = false
		}
		file.Close()
	}
	return result
}

// See os.Chmod.
func Chmod(path string, mode os.FileMode) error {
	return os.Chmod(path, mode)
}

// Abs returns an absolute representation of path.
// If the path is not absolute it will be joined with the current
// working directory to turn it into an absolute path. The absolute
// path name for a given file is not guaranteed to be unique.
// Abs calls Clean on the result.
func Abs(path string) string {
	p, _ := filepath.Abs(path)
	return p
}

// RealPath converts the given <path> to its absolute path
// and checks if the file path exists.
// If the file does not exist, return an empty string.
func RealPath(path string) string {
	p, err := filepath.Abs(path)
	if err != nil {
		return ""
	}
	if !Exists(p) {
		return ""
	}
	return p
}

// SelfPath returns absolute file path of current running process(binary).
func SelfPath() string {
	return selfPath
}

// SelfName returns file name of current running process(binary).
func SelfName() string {
	return Basename(SelfPath())
}

// SelfDir returns absolute directory path of current running process(binary).
func SelfDir() string {
	return filepath.Dir(SelfPath())
}

// Basename returns the last element of path.
// Trailing path separators are removed before extracting the last element.
// If the path is empty, Base returns ".".
// If the path consists entirely of separators, Basename returns a single separator.
func Basename(path string) string {
	return filepath.Base(path)
}

// Name returns the last element of path without extension.
func Name(path string) string {
	base := filepath.Base(path)
	if i := strings.LastIndexByte(base, '.'); i != -1 {
		return base[:i]
	}
	return base
}

// Dir returns all but the last element of path, typically the path's directory.
// After dropping the final element, Dir calls Clean on the path and trailing
// slashes are removed.
// If the path is empty, Dir returns ".".
// If the path consists entirely of separators, Dir returns a single separator.
// The returned path does not end in a separator unless it is the root directory.
func Dir(path string) string {
	return filepath.Dir(path)
}

// IsEmpty checks whether the given <path> is empty.
// If <path> is a folder, it checks if there's any file under it.
// If <path> is a file, it checks if the file size is zero.
//
// Note that it returns true if <path> does not exist.
func IsEmpty(path string) bool {
	stat, err := Stat(path)
	if err != nil {
		return true
	}
	if stat.IsDir() {
		file, err := os.Open(path)
		if err != nil {
			return true
		}
		defer file.Close()
		names, err := file.Readdirnames(-1)
		if err != nil {
			return true
		}
		return len(names) == 0
	} else {
		return stat.Size() == 0
	}
}

// Ext returns the file name extension used by path.
// The extension is the suffix beginning at the final dot
// in the final element of path; it is empty if there is
// no dot.
//
// Note: the result contains symbol '.'.
func Ext(path string) string {
	ext := filepath.Ext(path)
	if p := strings.IndexByte(ext, '?'); p != -1 {
		ext = ext[0:p]
	}
	return ext
}

// ExtName is like function Ext, which returns the file name extension used by path,
// but the result does not contains symbol '.'.
func ExtName(path string) string {
	return strings.TrimLeft(Ext(path), ".")
}

// Home returns absolute path of current user's home directory.
func Home() (string, error) {
	u, err := user.Current()
	if nil == err {
		return u.HomeDir, nil
	}
	if "windows" == runtime.GOOS {
		return homeWindows()
	}
	return homeUnix()
}

func homeUnix() (string, error) {
	if home := os.Getenv("HOME"); home != "" {
		return home, nil
	}
	var stdout bytes.Buffer
	cmd := exec.Command("sh", "-c", "eval echo ~$USER")
	cmd.Stdout = &stdout
	if err := cmd.Run(); err != nil {
		return "", err
	}

	result := strings.TrimSpace(stdout.String())
	if result == "" {
		return "", errors.New("blank output when reading home directory")
	}

	return result, nil
}

func homeWindows() (string, error) {
	drive := os.Getenv("HOMEDRIVE")
	path := os.Getenv("HOMEPATH")
	home := drive + path
	if drive == "" || path == "" {
		home = os.Getenv("USERPROFILE")
	}
	if home == "" {
		return "", errors.New("HOMEDRIVE, HOMEPATH, and USERPROFILE are blank")
	}

	return home, nil
}

// See os.TempDir().
func TempDir() string {
	return tempDir
}