package filesystem

import (
	"errors"
	"io"
	"os"
	"path/filepath"
	"strings"

	"github.com/xtls/xray-core/common/buf"
	"github.com/xtls/xray-core/common/platform"
)

type FileReaderFunc func(path string) (io.ReadCloser, error)

var NewFileReader FileReaderFunc = func(path string) (io.ReadCloser, error) {
	return os.Open(path)
}

func ReadFile(path string) ([]byte, error) {
	reader, err := NewFileReader(path)
	if err != nil {
		return nil, err
	}
	defer reader.Close()

	return buf.ReadAllToBytes(reader)
}

func OpenAsset(file string) (io.ReadCloser, int64, error) {
	path, info, err := getAssetFileLocation(file)
	if err != nil {
		return nil, 0, err
	}
	r, err := NewFileReader(path)
	return r, info.Size(), err
}

func ResolveAsset(file string) (string, error) {
	path, _, err := getAssetFileLocation(file)
	return path, err
}

func getAssetFileLocation(file string) (string, os.FileInfo, error) {
	if !filepath.IsLocal(file) || file == "." {
		return "", nil, errors.New("asset path must stay in asset directory")
	}
	local, err := filepath.Localize(file)
	if err != nil {
		return "", nil, err
	}
	path := platform.GetAssetLocation(local)
	info, err := os.Stat(path)
	if err != nil {
		return "", nil, err
	}
	if !info.Mode().IsRegular() {
		return "", nil, errors.New("asset is not a regular file")
	}
	return path, info, nil
}

func ReadCert(file string) ([]byte, error) {
	if filepath.IsAbs(file) {
		return ReadFile(file)
	}
	return ReadFile(platform.GetCertLocation(file))
}

// ResolveLuaFile finds a local .lua script and returns its absolute path.
// Relative paths: XRAY_LOCATION_CONFDIR > XRAY_LOCATION_CONFIG > working dir > executable dir.
func ResolveLuaFile(path string) (string, error) {
	if !strings.EqualFold(filepath.Ext(path), ".lua") {
		return "", errors.New("Lua file extension must be .lua")
	}
	if filepath.IsAbs(path) {
		return path, nil
	}
	for _, dir := range []string{
		platform.GetConfDirPath(),
		platform.NewEnvFlag(platform.ConfigLocation).GetValue(func() string { return "" }),
		".",
		platform.GetExecutableDir(),
	} {
		if dir != "" {
			resolved := filepath.Join(dir, path)
			if _, err := os.Stat(resolved); err == nil {
				return filepath.Abs(resolved)
			} else if !os.IsNotExist(err) {
				return "", err
			}
		}
	}
	return "", os.ErrNotExist
}