Add Store to go runtime

v2/internal/runtime/goruntime/store.go

@@ -0,0 +1,290 @@
+// Package goruntime contains all the methods and data structures related to the
+// runtime library of Wails. This includes both Go and JS runtimes.
+package goruntime
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"log"
+	"reflect"
+	"sync"
+)
+
+// Options defines the optional data that may be used
+// when creating a Store
+type Options struct {
+
+	// The name of the store
+	Name string
+
+	// The runtime to attach the store to
+	Runtime *Runtime
+
+	// Indicates if notifying Go listeners should be notified of updates
+	// synchronously (on the current thread) or asynchronously using
+	// goroutines
+	NotifySynchronously bool
+}
+
+// StoreProvider is a struct that creates Stores
+type StoreProvider struct {
+	runtime *Runtime
+}
+
+// NewStoreProvider creates new stores using the provided Runtime reference.
+func NewStoreProvider(runtime *Runtime) *StoreProvider {
+	return &StoreProvider{
+		runtime: runtime,
+	}
+}
+
+// Store is where we keep named data
+type Store struct {
+	name                string
+	data                reflect.Value
+	dataType            reflect.Type
+	eventPrefix         string
+	callbacks           []reflect.Value
+	runtime             *Runtime
+	notifySynchronously bool
+
+	// Lock
+	mux sync.Mutex
+
+	// Error handler
+	errorHandler func(error)
+}
+
+// New creates a new store
+func (p *StoreProvider) New(name string, defaultValue interface{}) *Store {
+
+	dataType := reflect.TypeOf(defaultValue)
+
+	result := Store{
+		name:     name,
+		runtime:  p.runtime,
+		data:     reflect.ValueOf(defaultValue),
+		dataType: dataType,
+	}
+
+	// Setup the sync listener
+	result.setupListener()
+
+	return &result
+}
+
+// OnError takes a function that will be called
+// whenever an error occurs
+func (s *Store) OnError(callback func(error)) {
+	s.errorHandler = callback
+}
+
+// Processes the updates sent by the front end
+func (s *Store) processUpdatedData(data string) error {
+
+	// Decode incoming data
+	var rawdata json.RawMessage
+	d := json.NewDecoder(bytes.NewBufferString(data))
+	err := d.Decode(&rawdata)
+	if err != nil {
+		return err
+	}
+
+	// Create a new instance of our data and unmarshal
+	// the received value into it
+	newData := reflect.New(s.dataType).Interface()
+	err = json.Unmarshal(rawdata, &newData)
+	if err != nil {
+		return err
+	}
+
+	// Lock mutex for writing
+	s.mux.Lock()
+
+	// Handle nulls
+	if newData == nil {
+		s.data = reflect.Zero(s.dataType)
+	} else {
+		// Store the resultant value in the data store
+		s.data = reflect.ValueOf(newData).Elem()
+	}
+
+	// Unlock mutex
+	s.mux.Unlock()
+
+	return nil
+}
+
+// Setup listener for front end changes
+func (s *Store) setupListener() {
+
+	// Listen for updates from the front end
+	s.runtime.Events.On("wails:sync:store:updatedbyfrontend:"+s.name, func(data ...interface{}) {
+
+		// Process the incoming data
+		err := s.processUpdatedData(data[0].(string))
+
+		if err != nil {
+			if s.errorHandler != nil {
+				s.errorHandler(err)
+				return
+			}
+		}
+
+		// Notify listeners
+		s.notify()
+	})
+}
+
+// notify the listeners of the current data state
+func (s *Store) notify() {
+
+	// Execute callbacks
+	for _, callback := range s.callbacks {
+
+		// Build args
+		args := []reflect.Value{s.data}
+
+		if s.notifySynchronously {
+			callback.Call(args)
+		} else {
+			go callback.Call(args)
+		}
+
+	}
+}
+
+// Set will update the data held by the store
+// and notify listeners of the change
+func (s *Store) Set(data interface{}) error {
+
+	inType := reflect.TypeOf(data)
+
+	if inType != s.dataType {
+		return fmt.Errorf("invalid data given in Store.Set(). Expected %s, got %s", s.dataType.String(), inType.String())
+	}
+
+	// Save data
+	s.mux.Lock()
+	s.data = reflect.ValueOf(data)
+	s.mux.Unlock()
+
+	// Stringify data
+	newdata, err := json.Marshal(data)
+	if err != nil {
+		if s.errorHandler != nil {
+			return err
+		}
+	}
+
+	// Emit event to front end
+	s.runtime.Events.Emit("wails:sync:store:updatedbybackend:"+s.name, string(newdata))
+
+	// Notify subscribers
+	s.notify()
+
+	return nil
+}
+
+// callbackCheck ensures the given function to Subscribe() is
+// of the correct signature. Absolutely cannot wait for
+// generics to land rather than writing this nonsense.
+func (s *Store) callbackCheck(callback interface{}) error {
+
+	// Get type
+	callbackType := reflect.TypeOf(callback)
+
+	// Check callback is a function
+	if callbackType.Kind() != reflect.Func {
+		return fmt.Errorf("invalid value given to store.Subscribe(). Expected 'func(%s)'", s.dataType.String())
+	}
+
+	// Check input param
+	if callbackType.NumIn() != 1 {
+		return fmt.Errorf("invalid number of parameters given in callback function. Expected 1")
+	}
+
+	// Check input data type
+	if callbackType.In(0) != s.dataType {
+		return fmt.Errorf("invalid type for input parameter given in callback function. Expected %s, got %s", s.dataType.String(), callbackType.In(0))
+	}
+
+	// Check output param
+	if callbackType.NumOut() != 0 {
+		return fmt.Errorf("invalid number of return parameters given in callback function. Expected 0")
+	}
+
+	return nil
+}
+
+// Subscribe will subscribe to updates to the store by
+// providing a callback. Any updates to the store are sent
+// to the callback
+func (s *Store) Subscribe(callback interface{}) {
+
+	err := s.callbackCheck(callback)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	callbackFunc := reflect.ValueOf(callback)
+
+	s.callbacks = append(s.callbacks, callbackFunc)
+}
+
+// updaterCheck ensures the given function to Update() is
+// of the correct signature. Absolutely cannot wait for
+// generics to land rather than writing this nonsense.
+func (s *Store) updaterCheck(updater interface{}) error {
+
+	// Get type
+	updaterType := reflect.TypeOf(updater)
+
+	// Check updater is a function
+	if updaterType.Kind() != reflect.Func {
+		return fmt.Errorf("invalid value given to store.Update(). Expected 'func(%s) %s'", s.dataType.String(), s.dataType.String())
+	}
+
+	// Check input param
+	if updaterType.NumIn() != 1 {
+		return fmt.Errorf("invalid number of parameters given in updater function. Expected 1")
+	}
+
+	// Check input data type
+	if updaterType.In(0) != s.dataType {
+		return fmt.Errorf("invalid type for input parameter given in updater function. Expected %s, got %s", s.dataType.String(), updaterType.In(0))
+	}
+
+	// Check output param
+	if updaterType.NumOut() != 1 {
+		return fmt.Errorf("invalid number of return parameters given in updater function. Expected 1")
+	}
+
+	// Check output data type
+	if updaterType.Out(0) != s.dataType {
+		return fmt.Errorf("invalid type for return parameter given in updater function. Expected %s, got %s", s.dataType.String(), updaterType.Out(0))
+	}
+
+	return nil
+}
+
+// Update takes a function that is passed the current state.
+// The result of that function is then set as the new state
+// of the store. This will notify listeners of the change
+func (s *Store) Update(updater interface{}) {
+
+	err := s.updaterCheck(updater)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	// Build args
+	args := []reflect.Value{s.data}
+
+	// Make call
+	results := reflect.ValueOf(updater).Call(args)
+
+	// We will only have 1 result. Set the store to it
+	s.Set(results[0].Interface())
+}