cmd/serve: add serve docker command (#5415)

Fixes #4750

Co-authored-by: Ivan Andreev <ivandeex@gmail.com>

cmd/serve/docker/api.go

@@ -0,0 +1,175 @@
+package docker
+
+import (
+	"encoding/json"
+	"net/http"
+
+	"github.com/go-chi/chi/v5"
+	"github.com/rclone/rclone/fs"
+)
+
+const (
+	contentType  = "application/vnd.docker.plugins.v1.1+json"
+	activatePath = "/Plugin.Activate"
+	createPath   = "/VolumeDriver.Create"
+	getPath      = "/VolumeDriver.Get"
+	listPath     = "/VolumeDriver.List"
+	removePath   = "/VolumeDriver.Remove"
+	pathPath     = "/VolumeDriver.Path"
+	mountPath    = "/VolumeDriver.Mount"
+	unmountPath  = "/VolumeDriver.Unmount"
+	capsPath     = "/VolumeDriver.Capabilities"
+)
+
+// CreateRequest is the structure that docker's requests are deserialized to.
+type CreateRequest struct {
+	Name    string
+	Options map[string]string `json:"Opts,omitempty"`
+}
+
+// RemoveRequest structure for a volume remove request
+type RemoveRequest struct {
+	Name string
+}
+
+// MountRequest structure for a volume mount request
+type MountRequest struct {
+	Name string
+	ID   string
+}
+
+// MountResponse structure for a volume mount response
+type MountResponse struct {
+	Mountpoint string
+}
+
+// UnmountRequest structure for a volume unmount request
+type UnmountRequest struct {
+	Name string
+	ID   string
+}
+
+// PathRequest structure for a volume path request
+type PathRequest struct {
+	Name string
+}
+
+// PathResponse structure for a volume path response
+type PathResponse struct {
+	Mountpoint string
+}
+
+// GetRequest structure for a volume get request
+type GetRequest struct {
+	Name string
+}
+
+// GetResponse structure for a volume get response
+type GetResponse struct {
+	Volume *VolInfo
+}
+
+// ListResponse structure for a volume list response
+type ListResponse struct {
+	Volumes []*VolInfo
+}
+
+// CapabilitiesResponse structure for a volume capability response
+type CapabilitiesResponse struct {
+	Capabilities Capability
+}
+
+// Capability represents the list of capabilities a volume driver can return
+type Capability struct {
+	Scope string
+}
+
+// ErrorResponse is a formatted error message that docker can understand
+type ErrorResponse struct {
+	Err string
+}
+
+func newRouter(drv *Driver) http.Handler {
+	r := chi.NewRouter()
+	r.Post(activatePath, func(w http.ResponseWriter, r *http.Request) {
+		res := map[string]interface{}{
+			"Implements": []string{"VolumeDriver"},
+		}
+		encodeResponse(w, res, nil, activatePath)
+	})
+	r.Post(createPath, func(w http.ResponseWriter, r *http.Request) {
+		var req CreateRequest
+		if decodeRequest(w, r, &req) {
+			err := drv.Create(&req)
+			encodeResponse(w, nil, err, createPath)
+		}
+	})
+	r.Post(removePath, func(w http.ResponseWriter, r *http.Request) {
+		var req RemoveRequest
+		if decodeRequest(w, r, &req) {
+			err := drv.Remove(&req)
+			encodeResponse(w, nil, err, removePath)
+		}
+	})
+	r.Post(mountPath, func(w http.ResponseWriter, r *http.Request) {
+		var req MountRequest
+		if decodeRequest(w, r, &req) {
+			res, err := drv.Mount(&req)
+			encodeResponse(w, res, err, mountPath)
+		}
+	})
+	r.Post(pathPath, func(w http.ResponseWriter, r *http.Request) {
+		var req PathRequest
+		if decodeRequest(w, r, &req) {
+			res, err := drv.Path(&req)
+			encodeResponse(w, res, err, pathPath)
+		}
+	})
+	r.Post(getPath, func(w http.ResponseWriter, r *http.Request) {
+		var req GetRequest
+		if decodeRequest(w, r, &req) {
+			res, err := drv.Get(&req)
+			encodeResponse(w, res, err, getPath)
+		}
+	})
+	r.Post(unmountPath, func(w http.ResponseWriter, r *http.Request) {
+		var req UnmountRequest
+		if decodeRequest(w, r, &req) {
+			err := drv.Unmount(&req)
+			encodeResponse(w, nil, err, unmountPath)
+		}
+	})
+	r.Post(listPath, func(w http.ResponseWriter, r *http.Request) {
+		res, err := drv.List()
+		encodeResponse(w, res, err, listPath)
+	})
+	r.Post(capsPath, func(w http.ResponseWriter, r *http.Request) {
+		res := &CapabilitiesResponse{
+			Capabilities: Capability{Scope: pluginScope},
+		}
+		encodeResponse(w, res, nil, capsPath)
+	})
+	return r
+}
+
+func decodeRequest(w http.ResponseWriter, r *http.Request, req interface{}) bool {
+	if err := json.NewDecoder(r.Body).Decode(req); err != nil {
+		http.Error(w, err.Error(), http.StatusBadRequest)
+		return false
+	}
+	return true
+}
+
+func encodeResponse(w http.ResponseWriter, res interface{}, err error, path string) {
+	w.Header().Set("Content-Type", contentType)
+	if err != nil {
+		fs.Debugf(path, "Request returned error: %v", err)
+		w.WriteHeader(http.StatusInternalServerError)
+		res = &ErrorResponse{Err: err.Error()}
+	} else if res == nil {
+		res = struct{}{}
+	}
+	if err = json.NewEncoder(w).Encode(res); err != nil {
+		fs.Debugf(path, "Response encoding failed: %v", err)
+	}
+}