//go:build !windows && !wasm

package filesystem

import (
	"io"
	"os"
	"path/filepath"
	"syscall"

	"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) {
	file, err := os.Open(path)
	if err != nil {
		return nil, err
	}
	defer file.Close()

	stat, err := file.Stat()
	if err != nil {
		return nil, err
	}

	size := stat.Size()
	if size == 0 {
		return []byte{}, nil
	}

	// use mmap to save RAM
	bs, err := syscall.Mmap(int(file.Fd()), 0, int(size), syscall.PROT_READ, syscall.MAP_SHARED)
	if err == nil {
		return bs, nil
	}

	// fallback
	reader, err := NewFileReader(path)
	if err != nil {
		return nil, err
	}
	defer reader.Close()

	return buf.ReadAllToBytes(reader)
}

func ReadAsset(file string) ([]byte, error) {
	return ReadFile(platform.GetAssetLocation(file))
}

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

func CopyFile(dst string, src string) error {
	bytes, err := ReadFile(src)
	if err != nil {
		return err
	}
	f, err := os.OpenFile(dst, os.O_CREATE|os.O_WRONLY, 0o644)
	if err != nil {
		return err
	}
	defer f.Close()

	_, err = f.Write(bytes)
	return err
}