//go:build darwin || (linux && !baremetal && !wasm_unknown && !nintendoswitch) || wasip1 || wasip2

// target wasi sets GOOS=linux and thus the +linux build tag,
// even though it doesn't show up in "tinygo info target -wasi"

// Portions copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package os

import (
	"io"
	"syscall"
)

const DevNull = "/dev/null"

type syscallFd = int

// fixLongPath is a noop on non-Windows platforms.
func fixLongPath(path string) string {
	return path
}

func rename(oldname, newname string) error {
	// TODO: import rest of upstream tests, handle fancy cases
	err := syscall.Rename(oldname, newname)
	if err != nil {
		return &LinkError{"rename", oldname, newname, err}
	}
	return nil
}

// file is the real representation of *File.
// The extra level of indirection ensures that no clients of os
// can overwrite this data, which could cause the finalizer
// to close the wrong file descriptor.
type file struct {
	handle  FileHandle
	name    string
	dirinfo *dirInfo // nil unless directory being read

	// pfd is set on wasip1 by (*File).PollFD to a *poll.FD that wraps
	// the underlying syscall FD. When set, Close routes through it so
	// the refcount semantics shared with net.FileListener / net.FileConn
	// are honoured. On non-wasip1 builds pfd is a literal empty struct
	// (see pollfd_other.go) and stays at zero bytes — provided it's not
	// the last field of this struct, which is why it lives here above
	// appendMode rather than at the end.
	pfd pollFD

	appendMode bool
}

func (f *file) close() (err error) {
	if f.dirinfo != nil {
		f.dirinfo.close()
		f.dirinfo = nil
	}
	if f.pfd.Exist() {
		return f.pfd.Close()
	}
	return f.handle.Close()
}

func NewFile(fd uintptr, name string) *File {
	return &File{&file{handle: unixFileHandle(fd), name: name}}
}

// Truncate changes the size of the named file.
// If the file is a symbolic link, it changes the size of the link's target.
// If there is an error, it will be of type *PathError.
func Truncate(name string, size int64) error {
	e := ignoringEINTR(func() error {
		return syscall.Truncate(name, size)
	})
	if e != nil {
		return &PathError{Op: "truncate", Path: name, Err: e}
	}
	return nil
}

func Pipe() (r *File, w *File, err error) {
	var p [2]int
	err = handleSyscallError(pipe(p[:]))
	if err != nil {
		return
	}
	r = NewFile(uintptr(p[0]), "|0")
	w = NewFile(uintptr(p[1]), "|1")
	return
}

func tempDir() string {
	dir := Getenv("TMPDIR")
	if dir == "" {
		dir = "/tmp"
	}
	return dir
}

// Link creates newname as a hard link to the oldname file.
// If there is an error, it will be of type *LinkError.
func Link(oldname, newname string) error {
	e := ignoringEINTR(func() error {
		return syscall.Link(oldname, newname)
	})

	if e != nil {
		return &LinkError{"link", oldname, newname, e}
	}
	return nil
}

// Symlink creates newname as a symbolic link to oldname.
// On Windows, a symlink to a non-existent oldname creates a file symlink;
// if oldname is later created as a directory the symlink will not work.
// If there is an error, it will be of type *LinkError.
func Symlink(oldname, newname string) error {
	e := ignoringEINTR(func() error {
		return syscall.Symlink(oldname, newname)
	})
	if e != nil {
		return &LinkError{"symlink", oldname, newname, e}
	}
	return nil
}

// Readlink returns the destination of the named symbolic link.
// If there is an error, it will be of type *PathError.
func Readlink(name string) (string, error) {
	for len := 128; ; len *= 2 {
		b := make([]byte, len)
		var (
			n int
			e error
		)
		for {
			n, e = fixCount(syscall.Readlink(name, b))
			if e != syscall.EINTR {
				break
			}
		}
		if e != nil {
			return "", &PathError{Op: "readlink", Path: name, Err: e}
		}
		if n < len {
			return string(b[0:n]), nil
		}
	}
}

// Truncate changes the size of the file.
// It does not change the I/O offset.
// If there is an error, it will be of type *PathError.
// Alternatively just use 'raw' syscall by file name
func (f *File) Truncate(size int64) (err error) {
	if f.handle == nil {
		return ErrClosed
	}

	return Truncate(f.name, size)
}

func (f *File) chmod(mode FileMode) error {
	if f.handle == nil {
		return ErrClosed
	}

	longName := fixLongPath(f.name)
	e := ignoringEINTR(func() error {
		return syscall.Chmod(longName, syscallMode(mode))
	})
	if e != nil {
		return &PathError{Op: "chmod", Path: f.name, Err: e}
	}
	return nil
}

func (f *File) chdir() error {
	if f.handle == nil {
		return ErrClosed
	}

	// TODO: use syscall.Fchdir instead
	longName := fixLongPath(f.name)
	e := ignoringEINTR(func() error {
		return syscall.Chdir(longName)
	})
	if e != nil {
		return &PathError{Op: "chdir", Path: f.name, Err: e}
	}
	return nil
}

// ReadAt reads up to len(b) bytes from the File starting at the given absolute offset.
// It returns the number of bytes read and any error encountered, possibly io.EOF.
// At end of file, Pread returns 0, io.EOF.
// TODO: move to file_anyos once ReadAt is implemented for windows
func (f unixFileHandle) ReadAt(b []byte, offset int64) (n int, err error) {
	n, err = syscall.Pread(syscallFd(f), b, offset)
	err = handleSyscallError(err)
	if n == 0 && len(b) > 0 && err == nil {
		err = io.EOF
	}
	return
}

// WriteAt writes len(b) bytes to the File starting at byte offset off.
// It returns the number of bytes written and an error, if any.
// WriteAt returns a non-nil error when n != len(b).
//
// If file was opened with the O_APPEND flag, WriteAt returns an error.
//
// TODO: move to file_anyos once WriteAt is implemented for windows.
func (f unixFileHandle) WriteAt(b []byte, offset int64) (int, error) {
	n, err := syscall.Pwrite(syscallFd(f), b, offset)
	return n, handleSyscallError(err)
}

// Seek wraps syscall.Seek.
func (f unixFileHandle) Seek(offset int64, whence int) (int64, error) {
	newoffset, err := syscall.Seek(syscallFd(f), offset, whence)
	return newoffset, handleSyscallError(err)
}

func (f unixFileHandle) Sync() error {
	err := syscall.Fsync(syscallFd(f))
	return handleSyscallError(err)
}

type unixDirent struct {
	parent string
	name   string
	typ    FileMode
	info   FileInfo
}

func (d *unixDirent) Name() string   { return d.name }
func (d *unixDirent) IsDir() bool    { return d.typ.IsDir() }
func (d *unixDirent) Type() FileMode { return d.typ }

func (d *unixDirent) Info() (FileInfo, error) {
	if d.info != nil {
		return d.info, nil
	}
	return lstat(d.parent + "/" + d.name)
}

func newUnixDirent(parent, name string, typ FileMode) (DirEntry, error) {
	ude := &unixDirent{
		parent: parent,
		name:   name,
		typ:    typ,
	}
	if typ != ^FileMode(0) && !testingForceReadDirLstat {
		return ude, nil
	}

	info, err := lstat(parent + "/" + name)
	if err != nil {
		return nil, err
	}

	ude.typ = info.Mode().Type()
	ude.info = info
	return ude, nil
}

// Since internal/poll is not available, we need to stub this out.
// Big go requires the option to add the fd to the polling system.
//
//go:linkname net_newUnixFile net.newUnixFile
func net_newUnixFile(fd int, name string) *File {
	if fd < 0 {
		panic("invalid FD")
	}

	// see src/os/file_unix.go:162 newFile for the original implementation.
	// return newFile(fd, name, kindSock, true)
	return NewFile(uintptr(fd), name)
}
