// +build darwin nintendoswitch wasi

package syscall

import (
	"unsafe"
)

type sliceHeader struct {
	buf *byte
	len uintptr
	cap uintptr
}

func Close(fd int) (err error) {
	if libc_close(int32(fd)) < 0 {
		err = getErrno()
	}
	return
}

func Write(fd int, p []byte) (n int, err error) {
	buf, count := splitSlice(p)
	n = libc_write(int32(fd), buf, uint(count))
	if n < 0 {
		err = getErrno()
	}
	return
}

func Read(fd int, p []byte) (n int, err error) {
	buf, count := splitSlice(p)
	n = libc_read(int32(fd), buf, uint(count))
	if n < 0 {
		err = getErrno()
	}
	return
}

func Pread(fd int, p []byte, offset int64) (n int, err error) {
	buf, count := splitSlice(p)
	n = libc_pread(int32(fd), buf, uint(count), offset)
	if n < 0 {
		err = getErrno()
	}
	return
}

func Seek(fd int, offset int64, whence int) (off int64, err error) {
	return 0, ENOSYS // TODO
}

func Open(path string, flag int, mode uint32) (fd int, err error) {
	data := cstring(path)
	fd = int(libc_open(&data[0], int32(flag), mode))
	if fd < 0 {
		err = getErrno()
	}
	return
}

func Chdir(path string) (err error) {
	data := cstring(path)
	fail := int(libc_chdir(&data[0]))
	if fail < 0 {
		err = getErrno()
	}
	return
}

func Chmod(path string, mode uint32) (err error) {
	data := cstring(path)
	fail := int(libc_chmod(&data[0], mode))
	if fail < 0 {
		err = getErrno()
	}
	return
}

func Mkdir(path string, mode uint32) (err error) {
	data := cstring(path)
	fail := int(libc_mkdir(&data[0], mode))
	if fail < 0 {
		err = getErrno()
	}
	return
}

func Rmdir(path string) (err error) {
	data := cstring(path)
	fail := int(libc_rmdir(&data[0]))
	if fail < 0 {
		err = getErrno()
	}
	return
}

func Rename(from, to string) (err error) {
	fromdata := cstring(from)
	todata := cstring(to)
	fail := int(libc_rename(&fromdata[0], &todata[0]))
	if fail < 0 {
		err = getErrno()
	}
	return
}

func Unlink(path string) (err error) {
	data := cstring(path)
	fail := int(libc_unlink(&data[0]))
	if fail < 0 {
		err = getErrno()
	}
	return
}

func Kill(pid int, sig Signal) (err error) {
	return ENOSYS // TODO
}

type SysProcAttr struct{}

func Pipe2(p []int, flags int) (err error) {
	return ENOSYS // TODO
}

func Getenv(key string) (value string, found bool) {
	data := cstring(key)
	raw := libc_getenv(&data[0])
	if raw == nil {
		return "", false
	}

	ptr := uintptr(unsafe.Pointer(raw))
	for size := uintptr(0); ; size++ {
		v := *(*byte)(unsafe.Pointer(ptr))
		if v == 0 {
			src := *(*[]byte)(unsafe.Pointer(&sliceHeader{buf: raw, len: size, cap: size}))
			return string(src), true
		}
		ptr += unsafe.Sizeof(byte(0))
	}
}

func Setenv(key, val string) (err error) {
	keydata := cstring(key)
	valdata := cstring(val)
	errCode := libc_setenv(&keydata[0], &valdata[0], 1)
	if errCode != 0 {
		err = getErrno()
	}
	return
}

func Unsetenv(key string) (err error) {
	keydata := cstring(key)
	errCode := libc_unsetenv(&keydata[0])
	if errCode != 0 {
		err = getErrno()
	}
	return
}

func Clearenv() {
	for _, s := range Environ() {
		for j := 0; j < len(s); j++ {
			if s[j] == '=' {
				Unsetenv(s[0:j])
				break
			}
		}
	}
}

func Mmap(fd int, offset int64, length int, prot int, flags int) (data []byte, err error) {
	addr := libc_mmap(nil, uintptr(length), int32(prot), int32(flags), int32(fd), uintptr(offset))
	if addr == unsafe.Pointer(^uintptr(0)) {
		return nil, getErrno()
	}
	return (*[1 << 30]byte)(addr)[:length:length], nil
}

func Mprotect(b []byte, prot int) (err error) {
	errCode := libc_mprotect(unsafe.Pointer(&b[0]), uintptr(len(b)), int32(prot))
	if errCode != 0 {
		err = getErrno()
	}
	return
}

func Environ() []string {
	environ := libc_environ
	var envs []string
	for *environ != nil {
		// Convert the C string to a Go string.
		length := libc_strlen(*environ)
		var envVar string
		rawEnvVar := (*struct {
			ptr    unsafe.Pointer
			length uintptr
		})(unsafe.Pointer(&envVar))
		rawEnvVar.ptr = *environ
		rawEnvVar.length = length
		envs = append(envs, envVar)
		// This is the Go equivalent of "environ++" in C.
		environ = (*unsafe.Pointer)(unsafe.Pointer(uintptr(unsafe.Pointer(environ)) + unsafe.Sizeof(environ)))
	}
	return envs
}

// cstring converts a Go string to a C string.
func cstring(s string) []byte {
	data := make([]byte, len(s)+1)
	copy(data, s)
	// final byte should be zero from the initial allocation
	return data
}

func splitSlice(p []byte) (buf *byte, len uintptr) {
	slice := (*sliceHeader)(unsafe.Pointer(&p))
	return slice.buf, slice.len
}

//export strlen
func libc_strlen(ptr unsafe.Pointer) uintptr

// ssize_t write(int fd, const void *buf, size_t count)
//export write
func libc_write(fd int32, buf *byte, count uint) int

// char *getenv(const char *name);
//export getenv
func libc_getenv(name *byte) *byte

// int setenv(const char *name, const char *val, int replace);
//export setenv
func libc_setenv(name *byte, val *byte, replace int32) int32

// int unsetenv(const char *name);
//export unsetenv
func libc_unsetenv(name *byte) int32

// ssize_t read(int fd, void *buf, size_t count);
//export read
func libc_read(fd int32, buf *byte, count uint) int

// ssize_t pread(int fd, void *buf, size_t count, off_t offset);
//export pread
func libc_pread(fd int32, buf *byte, count uint, offset int64) int

// int open(const char *pathname, int flags, mode_t mode);
//export open
func libc_open(pathname *byte, flags int32, mode uint32) int32

// int close(int fd)
//export close
func libc_close(fd int32) int32

// void *mmap(void *addr, size_t length, int prot, int flags, int fd, off_t offset);
//export mmap
func libc_mmap(addr unsafe.Pointer, length uintptr, prot, flags, fd int32, offset uintptr) unsafe.Pointer

// int mprotect(void *addr, size_t len, int prot);
//export mprotect
func libc_mprotect(addr unsafe.Pointer, len uintptr, prot int32) int32

// int chdir(const char *pathname, mode_t mode);
//export chdir
func libc_chdir(pathname *byte) int32

// int chmod(const char *pathname, mode_t mode);
//export chmod
func libc_chmod(pathname *byte, mode uint32) int32

// int mkdir(const char *pathname, mode_t mode);
//export mkdir
func libc_mkdir(pathname *byte, mode uint32) int32

// int rmdir(const char *pathname);
//export rmdir
func libc_rmdir(pathname *byte) int32

// int rename(const char *from, *to);
//export rename
func libc_rename(from, too *byte) int32

// int unlink(const char *pathname);
//export unlink
func libc_unlink(pathname *byte) int32

//go:extern environ
var libc_environ *unsafe.Pointer