//go:build js || nintendoswitch || wasip1 || wasip2

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 Dup(fd int) (fd2 int, err error) {
	fd2 = int(libc_dup(int32(fd)))
	if fd2 < 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 Pwrite(fd int, p []byte, offset int64) (n int, err error) {
	buf, count := splitSlice(p)
	n = libc_pwrite(int32(fd), buf, uint(count), offset)
	if n < 0 {
		err = getErrno()
	}
	return
}

func Seek(fd int, offset int64, whence int) (newoffset int64, err error) {
	newoffset = libc_lseek(int32(fd), offset, whence)
	if newoffset < 0 {
		err = getErrno()
	}
	return
}

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 Fsync(fd int) (err error) {
	if libc_fsync(int32(fd)) < 0 {
		err = getErrno()
	}
	return
}

func Readlink(path string, p []byte) (n int, err error) {
	data := cstring(path)
	buf, count := splitSlice(p)
	n = libc_readlink(&data[0], buf, uint(count))
	if n < 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 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 Link(oldname, newname string) (err error) {
	fromdata := cstring(oldname)
	todata := cstring(newname)
	fail := int(libc_link(&fromdata[0], &todata[0]))
	if fail < 0 {
		err = getErrno()
	}
	return
}

func Symlink(from, to string) (err error) {
	fromdata := cstring(from)
	todata := cstring(to)
	fail := int(libc_symlink(&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 Chown(path string, uid, gid int) (err error) {
	data := cstring(path)
	fail := int(libc_chown(&data[0], uid, gid))
	if fail < 0 {
		err = getErrno()
	}
	return
}

func Fork() (err error) {
	fail := int(libc_fork())
	if fail < 0 {
		err = getErrno()
	}
	return
}

func Execve(pathname string, argv []string, envv []string) (err error) {
	argv0 := cstring(pathname)

	// transform argv and envv into the format expected by execve
	argv1 := make([]*byte, len(argv)+1)
	for i, arg := range argv {
		argv1[i] = &cstring(arg)[0]
	}
	argv1[len(argv)] = nil

	env1 := make([]*byte, len(envv)+1)
	for i, env := range envv {
		env1[i] = &cstring(env)[0]
	}
	env1[len(envv)] = nil

	fail := int(libc_execve(&argv0[0], &argv1[0], &env1[0]))
	if fail < 0 {
		err = getErrno()
	}
	return
}

func Truncate(path string, length int64) (err error) {
	data := cstring(path)
	fail := int(libc_truncate(&data[0], length))
	if fail < 0 {
		err = getErrno()
	}
	return
}

func Faccessat(dirfd int, path string, mode uint32, flags int) (err error)

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

type SysProcAttr struct{}

// TODO
type WaitStatus uint32

func (w WaitStatus) Exited() bool       { return false }
func (w WaitStatus) ExitStatus() int    { return 0 }
func (w WaitStatus) Signaled() bool     { return false }
func (w WaitStatus) Signal() Signal     { return 0 }
func (w WaitStatus) CoreDump() bool     { return false }
func (w WaitStatus) Stopped() bool      { return false }
func (w WaitStatus) Continued() bool    { return false }
func (w WaitStatus) StopSignal() Signal { return 0 }
func (w WaitStatus) TrapCause() int     { return 0 }

// since rusage is quite a big struct and we stub it out anyway no need to define it here
func Wait4(pid int, wstatus *WaitStatus, options int, rusage uintptr) (wpid int, err error) {
	return 0, ENOSYS // TODO
}

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 Munmap(b []byte) (err error) {
	errCode := libc_munmap(unsafe.Pointer(&b[0]), uintptr(len(b)))
	if errCode != 0 {
		err = getErrno()
	}
	return err
}

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
}

// BytePtrFromString returns a pointer to a NUL-terminated array of
// bytes containing the text of s. If s contains a NUL byte at any
// location, it returns (nil, EINVAL).
func BytePtrFromString(s string) (*byte, error) {
	for i := 0; i < len(s); i++ {
		if s[i] == 0 {
			return nil, EINVAL
		}
	}
	return &cstring(s)[0], nil
}

// 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
}

// These two functions are provided by the runtime.
func runtimeSetenv(key, value string)
func runtimeUnsetenv(key string)

//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

// 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

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

// ssize_t lseek(int fd, off_t offset, int whence);
//
//export lseek
func libc_lseek(fd int32, offset int64, whence int) int64

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

// int dup(int fd)
//
//export dup
func libc_dup(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 munmap(void *addr, size_t length);
//
//export munmap
func libc_munmap(addr unsafe.Pointer, length uintptr) int32

// 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 chown(const char *pathname, uid_t owner, gid_t group);
//
//export chown
func libc_chown(pathname *byte, owner, group int) 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, to *byte) int32

// int symlink(const char *from, *to);
//
//export symlink
func libc_symlink(from, to *byte) int32

// int link(const char *oldname, *newname);
//
//export link
func libc_link(oldname, newname *byte) int32

// int fsync(int fd);
//
//export fsync
func libc_fsync(fd int32) int32

// ssize_t readlink(const char *path, void *buf, size_t count);
//
//export readlink
func libc_readlink(path *byte, buf *byte, count uint) int

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

// pid_t fork(void);
//
//export fork
func libc_fork() int32

// int execve(const char *filename, char *const argv[], char *const envp[]);
//
//export execve
func libc_execve(filename *byte, argv **byte, envp **byte) int

// int truncate(const char *path, off_t length);
//
//export truncate
func libc_truncate(path *byte, length int64) int32