adding a delta logger facility for easier recovery in case of bugs

acedoc.go

@@ -10,6 +10,8 @@ type Document struct {
 	lines   []string
 	deltas  []Delta
 	clients []*Client
+
+	logger *Client
 }
 
 type DeltaHandler interface {

client.go

@@ -1,6 +1,9 @@
 package acedoc
 
 import (
+	"encoding/json"
+	"os"
+	"path"
 	"sync"
 	"time"
 )
@@ -15,8 +18,8 @@ func (d *Document) Client(h DeltaHandler) *Client {
 
 	go func() {
 		for {
-			dls := c.pullDeltas()
+			dls, ok := c.pullDeltas()
-			if dls != nil && c.handler != nil {
+			if len(dls) > 0 && c.handler != nil {
 				go func() {
 					err := c.handler.Handle(dls)
 					if err != nil {
@@ -29,6 +32,9 @@ func (d *Document) Client(h DeltaHandler) *Client {
 					}
 				}()
 			}
+			if !ok {
+				return
+			}
 		}
 	}()
 
@@ -40,6 +46,12 @@ func (d *Document) Client(h DeltaHandler) *Client {
 	return c
 }
 
+func (d *Document) Close() {
+	if d.logger != nil {
+		d.logger.Close()
+	}
+}
+
 func (d *Document) removeClient(c *Client) {
 	d.mtx.Lock()
 	defer d.mtx.Unlock()
@@ -104,7 +116,7 @@ func (c *Client) PushDeltas(d ...Delta) error {
 	return c.doc.Apply(ds...)
 }
 
-func (c *Client) pullDeltas() []Delta {
+func (c *Client) pullDeltas() ([]Delta, bool) {
 	maxSize := c.maxDeltaBucket
 	if maxSize == 0 {
 		maxSize = 50
@@ -120,26 +132,89 @@ func (c *Client) pullDeltas() []Delta {
 
 		select {
 		case d, ok = <-c.ch:
+			if !ok {
+				return ds, false
+			}
 		case <-timer:
-			return ds
+			return ds, true
-		}
-
-		timer = time.After(timeout)
-
-		if !ok {
-			return ds
 		}
 
 		if d.Equal(Delta{}) {
 			continue
 		}
+
 		if d.source == c {
 			continue
 		}
 
+		timer = time.After(timeout)
+
 		ds = append(ds, d)
 		if len(ds) == maxSize {
-			return ds
+			return ds, true
 		}
 	}
 }
+
+func (d *Document) LogToFile(filename string) error {
+	if d.logger != nil {
+		return nil
+	}
+
+	var f *os.File
+	var err error
+	var mtx sync.Mutex
+	var closeTimer *time.Timer
+
+	err = os.MkdirAll(path.Dir(filename), 0755)
+	if err != nil {
+		return err
+	}
+
+	getFile := func() {
+		if f != nil {
+			return
+		}
+		f, err = os.OpenFile(filename, os.O_CREATE|os.O_APPEND|os.O_WRONLY, 0644)
+		closeTimer.Reset(1 * time.Minute)
+	}
+
+	closeFile := func() {
+		mtx.Lock()
+		defer mtx.Unlock()
+
+		if f != nil {
+			err = f.Close()
+			f = nil
+		}
+	}
+
+	closeTimer = time.AfterFunc(1*time.Minute, closeFile)
+
+	getFile()
+	if err != nil {
+		return err
+	}
+
+	d.logger = d.Client(DeltaHandlerFunc(func(dls []Delta) error {
+		mtx.Lock()
+		defer mtx.Unlock()
+
+		getFile()
+		if err != nil {
+			return err
+		}
+
+		enc := json.NewEncoder(f)
+		for _, dl := range dls {
+			err = enc.Encode(dl)
+			if err != nil {
+				return err
+			}
+		}
+
+		return nil
+	}))
+
+	return nil
+}

delta.go

@@ -196,9 +196,7 @@ func (d *Document) Apply(dls ...Delta) error {
 		if err != nil {
 			return fmt.Errorf("delta does not apply to document: %v", err)
 		}
-	}
 
-	for _, dl := range dls {
 		switch dl.Action {
 		case DeltaInsert:
 			d.applyInsert(dl)