initial work for fs api forwarding (#49)

* implement fs api forwarding

* changes from first review

* fix cwd return to match original, rename constant

* second review updates

* fix missed arg, remove commented out code

filesys/fd.go

@@ -0,0 +1,7 @@
+//go:build darwin || linux
+
+package filesys
+
+func FdType(fd int) int {
+	return fd
+}

filesys/fd_windows.go

@@ -0,0 +1,7 @@
+package filesys
+
+import "syscall"
+
+func FdType(fd int) syscall.Handle {
+	return syscall.Handle(fd)
+}

filesys/handler.go

@@ -0,0 +1,319 @@
+package filesys
+
+import (
+	"encoding/base64"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"log"
+	"net/http"
+	"os"
+	"strings"
+	"syscall"
+)
+
+// Handler translates json payload data to and from system calls like syscall.Stat
+type Handler struct {
+	debug         bool
+	securityToken string
+	logger        *log.Logger
+}
+
+func NewHandler(securityToken string, logger *log.Logger) *Handler {
+	return &Handler{
+		debug:         false,
+		securityToken: securityToken,
+		logger:        logger,
+	}
+}
+
+func (fa *Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	if r.Header.Get("WBT-Token") != fa.securityToken {
+		fa.doError("not implemented", "ENOSYS", w, errors.New("missing WBT-token"))
+		return
+	}
+	switch r.URL.Path {
+	case "/fs/stat":
+		fa.handle(&Stat{}, w, r)
+	case "/fs/fstat":
+		fa.handle(&Fstat{}, w, r)
+	case "/fs/open":
+		fa.handle(&Open{}, w, r)
+	case "/fs/write":
+		fa.handle(&Write{}, w, r)
+	case "/fs/close":
+		fa.handle(&Close{}, w, r)
+	case "/fs/rename":
+		fa.handle(&Rename{}, w, r)
+	case "/fs/readdir":
+		fa.handle(&Readdir{}, w, r)
+	case "/fs/lstat":
+		fa.handle(&Lstat{}, w, r)
+	case "/fs/read":
+		fa.handle(&Read{}, w, r)
+	case "/fs/mkdir":
+		fa.handle(&Mkdir{}, w, r)
+	case "/fs/unlink":
+		fa.handle(&Unlink{}, w, r)
+	case "/fs/rmdir":
+		fa.handle(&Rmdir{}, w, r)
+	default:
+		fa.doError("not implemented", "ENOSYS", w,
+			fmt.Errorf("unsupported api path %q", r.URL.Path))
+	}
+}
+
+type Responder interface {
+	WriteResponse(fa *Handler, w http.ResponseWriter)
+}
+
+func (fa *Handler) handle(responder Responder, w http.ResponseWriter, r *http.Request) {
+	if err := json.NewDecoder(r.Body).Decode(responder); err != nil {
+		fa.logger.Printf("ERROR handle : %v\n", err)
+		w.WriteHeader(http.StatusBadRequest)
+		return
+	}
+	if fa.debug {
+		fa.logger.Printf("handle %s %+v\n", r.URL.Path, responder)
+	}
+	responder.WriteResponse(fa, w)
+}
+
+type ErrorCode struct {
+	Error string `json:"error"`
+	Code  string `json:"code"`
+}
+
+func (fa *Handler) doError(msg, code string, w http.ResponseWriter, err error) {
+	if fa.debug {
+		fa.logger.Printf("doError %s : %s\n", msg, code)
+	}
+	if err != nil {
+		fa.logger.Printf("Error: %v", err)
+	}
+
+	e := &ErrorCode{Error: msg, Code: code}
+
+	w.WriteHeader(http.StatusBadRequest)
+	w.Header().Set("Content-Type", "application/json")
+	if err := json.NewEncoder(w).Encode(e); err != nil {
+		fa.logger.Printf("Error encoding json: %v", err)
+	}
+}
+
+func (fa *Handler) okResponse(data any, w http.ResponseWriter) {
+	var marshal []byte
+	var err error
+	if marshal, err = json.Marshal(data); err != nil {
+		fa.logger.Println("okResponse json error:", err)
+		w.WriteHeader(http.StatusInternalServerError)
+		return
+	}
+	if fa.debug {
+		fa.logger.Printf("okResponse %s\n", string(marshal))
+	}
+
+	w.WriteHeader(http.StatusOK)
+	w.Header().Set("Content-Type", "application/json")
+	if _, err = w.Write(marshal); err != nil {
+		fa.logger.Printf("Error writing json: %v", err)
+	}
+}
+
+func fixPath(path string) string {
+	return strings.TrimPrefix(path, "/fs/")
+}
+
+type Stat struct {
+	Path string `json:"path,omitempty"`
+}
+
+type Open struct {
+	Path  string `json:"path"`
+	Flags int    `json:"flags"`
+	Mode  uint32 `json:"mode"`
+}
+
+func (o *Open) WriteResponse(fa *Handler, w http.ResponseWriter) {
+	fd, err := syscall.Open(fixPath(o.Path), o.Flags, o.Mode)
+	if fa.handleError(w, err, true) {
+		return
+	}
+	response := map[string]any{"fd": fd}
+	fa.okResponse(response, w)
+}
+
+type Fstat struct {
+	Fd int `json:"fd"`
+}
+
+type Write struct {
+	Fd       int    `json:"fd"`
+	Buffer   string `json:"buffer"`
+	Offset   int    `json:"offset"`
+	Length   int    `json:"length"`
+	Position *int   `json:"position,omitempty"`
+}
+
+func (wr *Write) WriteResponse(fa *Handler, w http.ResponseWriter) {
+	if wr.Offset != 0 {
+		fa.doError("not implemented", "ENOSYS", w,
+			fmt.Errorf("write offset %d not supported", wr.Offset))
+		return
+	}
+	if wr.Position != nil {
+		_, err := syscall.Seek(FdType(wr.Fd), int64(*wr.Position), 0)
+		if err != nil {
+			fa.doError("not implemented", "ENOSYS", w, err)
+			return
+		}
+	}
+
+	bytes, err := base64.StdEncoding.DecodeString(wr.Buffer)
+	if err != nil {
+		fa.doError("not implemented", "ENOSYS", w, err)
+		return
+	}
+
+	var written int
+	written, err = syscall.Write(FdType(wr.Fd), bytes)
+	if err != nil {
+		fa.doError("not implemented", "ENOSYS", w, err)
+		return
+	}
+
+	fa.okResponse(map[string]any{"written": written}, w)
+}
+
+type Close struct {
+	Fd int `json:"fd"`
+}
+
+func (c *Close) WriteResponse(fa *Handler, w http.ResponseWriter) {
+	err := syscall.Close(FdType(c.Fd))
+	if fa.handleError(w, err, false) {
+		return
+	}
+	fa.okResponse(map[string]any{}, w)
+}
+
+type Rename struct {
+	From string `json:"from"`
+	To   string `json:"to"`
+}
+
+func (r *Rename) WriteResponse(fa *Handler, w http.ResponseWriter) {
+	err := syscall.Rename(fixPath(r.From), fixPath(r.To))
+	if fa.handleError(w, err, true) {
+		return
+	}
+	fa.okResponse(map[string]any{}, w)
+}
+
+type Readdir struct {
+	Path string `json:"path"`
+}
+
+func (r *Readdir) WriteResponse(fa *Handler, w http.ResponseWriter) {
+	entries, err := os.ReadDir(fixPath(r.Path))
+	if fa.handleError(w, err, false) {
+		return
+	}
+	stringNames := make([]string, len(entries))
+	for i, entry := range entries {
+		stringNames[i] = entry.Name()
+	}
+	fa.okResponse(map[string]any{"entries": stringNames}, w)
+}
+
+type Lstat struct {
+	Path string `json:"path"`
+}
+
+type Read struct {
+	Fd       int  `json:"fd"`
+	Offset   int  `json:"offset"`
+	Length   int  `json:"length"`
+	Position *int `json:"position,omitempty"`
+}
+
+func (r *Read) WriteResponse(fa *Handler, w http.ResponseWriter) {
+	if r.Offset != 0 {
+		fa.doError("not implemented", "ENOSYS", w,
+			fmt.Errorf("read offset %d not supported", r.Offset))
+		return
+	}
+	if r.Position != nil {
+		_, err := syscall.Seek(FdType(r.Fd), int64(*r.Position), 0)
+		if err != nil {
+			fa.doError("not implemented", "ENOSYS", w, err)
+			return
+		}
+	}
+
+	buffer := make([]byte, r.Length)
+	read, err := syscall.Read(FdType(r.Fd), buffer)
+	if err != nil {
+		fa.doError("not implemented", "ENOSYS", w, err)
+		return
+	}
+	response := map[string]any{
+		"read":   read,
+		"buffer": base64.StdEncoding.EncodeToString(buffer[:read]),
+	}
+	fa.okResponse(response, w)
+
+}
+
+type Mkdir struct {
+	Path string `json:"path"`
+	Perm uint32 `json:"perm"`
+}
+
+func (m *Mkdir) WriteResponse(fa *Handler, w http.ResponseWriter) {
+	err := syscall.Mkdir(fixPath(m.Path), m.Perm)
+	if err != nil {
+		fa.doError("not implemented", "ENOSYS", w, err)
+		return
+	}
+	fa.okResponse(map[string]any{}, w)
+}
+
+type Unlink struct {
+	Path string `json:"path"`
+}
+
+func (u *Unlink) WriteResponse(fa *Handler, w http.ResponseWriter) {
+	err := syscall.Unlink(fixPath(u.Path))
+	if err != nil {
+		fa.doError("not implemented", "ENOSYS", w, err)
+		return
+	}
+	fa.okResponse(map[string]any{}, w)
+}
+
+type Rmdir struct {
+	Path string `json:"path"`
+}
+
+func (r *Rmdir) WriteResponse(fa *Handler, w http.ResponseWriter) {
+	err := syscall.Rmdir(fixPath(r.Path))
+	if fa.handleError(w, err, true) {
+		return
+	}
+	fa.okResponse(map[string]any{}, w)
+}
+
+func (fa *Handler) handleError(w http.ResponseWriter, err error, noEnt bool) bool {
+	if err == nil {
+		return false
+	}
+	if noEnt && os.IsNotExist(err) {
+		// We're not passing the error down for logging here since this is a
+		// file not found condition, not an actual error condition.
+		fa.doError(syscall.ENOENT.Error(), "ENOENT", w, nil)
+	} else {
+		fa.doError(syscall.ENOSYS.Error(), "ENOSYS", w, err)
+	}
+	return true
+}