package fileutil

import (
	"io/ioutil"
	"os"
	"os/user"
	"path"
	"path/filepath"
	"strings"

	"github.com/pkg/errors"
	"github.com/prysmaticlabs/prysm/shared/params"
	log "github.com/sirupsen/logrus"
)

// ExpandPath given a string which may be a relative path.
// 1. replace tilde with users home dir
// 2. expands embedded environment variables
// 3. cleans the path, e.g. /a/b/../c -> /a/c
// Note, it has limitations, e.g. ~someuser/tmp will not be expanded
func ExpandPath(p string) (string, error) {
	if strings.HasPrefix(p, "~/") || strings.HasPrefix(p, "~\\") {
		if home := HomeDir(); home != "" {
			p = home + p[1:]
		}
	}
	return filepath.Abs(path.Clean(os.ExpandEnv(p)))
}

// MkdirAll takes in a path, expands it if necessary, and looks through the
// permissions of every directory along the path, ensuring we are not attempting
// to overwrite any existing permissions. Finally, creates the directory accordingly
// with standardized, Prysm project permissions. This is the static-analysis enforced
// method for creating a directory programmatically in Prysm.
func MkdirAll(dirPath string) error {
	expanded, err := ExpandPath(dirPath)
	if err != nil {
		return err
	}
	exists, err := HasDir(expanded)
	if err != nil {
		return err
	}
	if exists {
		info, err := os.Stat(expanded)
		if err != nil {
			return err
		}
		if info.Mode().Perm() != params.BeaconIoConfig().ReadWriteExecutePermissions {
			return errors.New("dir already exists without proper 0700 permissions")
		}
	}
	return os.MkdirAll(expanded, params.BeaconIoConfig().ReadWriteExecutePermissions)
}

// WriteFile is the static-analysis enforced method for writing binary data to a file
// in Prysm, enforcing a single entrypoint with standardized permissions.
func WriteFile(file string, data []byte) error {
	expanded, err := ExpandPath(file)
	if err != nil {
		return err
	}
	if FileExists(expanded) {
		info, err := os.Stat(expanded)
		if err != nil {
			return err
		}
		if info.Mode() != params.BeaconIoConfig().ReadWritePermissions {
			return errors.New("file already exists without proper 0600 permissions")
		}
	}
	return ioutil.WriteFile(expanded, data, params.BeaconIoConfig().ReadWritePermissions)
}

// HomeDir for a user.
func HomeDir() string {
	if home := os.Getenv("HOME"); home != "" {
		return home
	}
	if usr, err := user.Current(); err == nil {
		return usr.HomeDir
	}
	return ""
}

// HasDir checks if a directory indeed exists at the specified path.
func HasDir(dirPath string) (bool, error) {
	fullPath, err := ExpandPath(dirPath)
	if err != nil {
		return false, err
	}
	info, err := os.Stat(fullPath)
	if os.IsNotExist(err) {
		return false, nil
	}
	if info == nil {
		return false, err
	}
	return info.IsDir(), err
}

// FileExists returns true if a file is not a directory and exists
// at the specified path.
func FileExists(filename string) bool {
	filePath, err := ExpandPath(filename)
	if err != nil {
		return false
	}
	info, err := os.Stat(filePath)
	if err != nil {
		if !os.IsNotExist(err) {
			log.WithError(err).Info("Checking for file existence returned an error")
		}
		return false
	}
	return info != nil && !info.IsDir()
}

// ReadFileAsBytes expands a file name's absolute path and reads it as bytes from disk.
func ReadFileAsBytes(filename string) ([]byte, error) {
	filePath, err := ExpandPath(filename)
	if err != nil {
		return nil, errors.Wrap(err, "could not determine absolute path of password file")
	}
	return ioutil.ReadFile(filePath)
}

// CopyFile copy a file from source to destination path.
func CopyFile(src, dst string) error {
	input, err := ioutil.ReadFile(src)
	if err != nil {
		return err
	}

	err = ioutil.WriteFile(dst, input, params.BeaconIoConfig().ReadWritePermissions)
	if err != nil {
		err := errors.Wrapf(err, "error creating file %s", dst)
		return err
	}
	return nil
}