Add method to automatically create integer IDs

README.md

@@ -51,6 +51,18 @@ if err := db.Delete("fish", ""); err != nil {
 }
 ```
 
+Also supports automatically generating integer IDs.
+
+```
+// Write a fish to the database
+fish := Fish{}
+id, err := db.WriteAutoId("fish", fish); if err != nil {
+  fmt.Println("Error", err)
+}
+
+// ID == 1
+```
+
 ## Documentation
 - Complete documentation is available on [godoc](http://godoc.org/github.com/nanobox-io/golang-scribble).
 - Coverage Report is available on [gocover](https://gocover.io/github.com/nanobox-io/golang-scribble)

scribble.go

@@ -10,13 +10,15 @@ import (
 	"sync"
 
 	"github.com/jcelliott/lumber"
+	"path"
+	"strings"
+	"strconv"
 )
 
 // Version is the current version of the project
 const Version = "1.0.4"
 
 type (
-
 	// Logger is a generic logger interface
 	Logger interface {
 		Fatal(string, ...interface{})
@@ -98,6 +100,11 @@ func (d *Driver) Write(collection, resource string, v interface{}) error {
 	mutex.Lock()
 	defer mutex.Unlock()
 
+	return d.writeFile(collection, resource, v)
+}
+
+// Writes a file to disk
+func (d *Driver) writeFile(collection string, resource string, v interface{}) error {
 	//
 	dir := filepath.Join(d.dir, collection)
 	fnlPath := filepath.Join(dir, resource+".json")
@@ -123,6 +130,51 @@ func (d *Driver) Write(collection, resource string, v interface{}) error {
 	return os.Rename(tmpPath, fnlPath)
 }
 
+// Locks the database, gets the next available integer resource ID and attempts to write the
+// record to the database under the [collection] specified with the generated [resource] ID
+func (d *Driver) WriteAutoId(collection string, v interface{}) (resourceId int64, err error) {
+	resourceId = -1
+
+	// ensure there is a place to save record
+	if collection == "" {
+		return resourceId, fmt.Errorf("Missing collection - no place to save record!")
+	}
+
+	mutex := d.getOrCreateMutex(collection)
+	mutex.Lock()
+	defer mutex.Unlock()
+
+	// list the directory, sort it, take the last entry then parse and increment the last ID
+	files, err := ioutil.ReadDir(d.dir)
+	if err != nil {
+		fmt.Printf("Error listing directory %s: %s", d.dir, err.Error())
+		return resourceId, err
+	}
+
+	if len(files) == 0 {
+		resourceId = 1
+	} else {
+		lastFile := files[len(files)-1]
+
+		ext := path.Ext(lastFile.Name())
+
+		baseName := strings.TrimSuffix(lastFile.Name(), ext)
+
+		resourceId, err := strconv.ParseInt(baseName, 10, 8)
+		if err != nil {
+			fmt.Printf("Error parsing string '%s' as integer", baseName, err.Error())
+			return resourceId, err
+		}
+	}
+
+	stringResourceId := fmt.Sprintf("%d", resourceId)
+
+	fmt.Printf("Writing resource under auto-generated ID '%s'\n", stringResourceId)
+	err = d.writeFile(collection, stringResourceId, v)
+
+	return resourceId, err
+}
+
 // Read a record from the database
 func (d *Driver) Read(collection, resource string, v interface{}) error {
 

scribble_test.go

@@ -3,6 +3,7 @@ package scribble
 import (
 	"os"
 	"testing"
+	"fmt"
 )
 
 //
@@ -85,6 +86,36 @@ func TestWriteAndRead(t *testing.T) {
 	destroySchool()
 }
 
+//
+func TestWriteAutoIdAndRead(t *testing.T) {
+
+	createDB()
+
+	// add fish to database
+	id, err := db.WriteAutoId(collection, redfish);
+	if err != nil {
+		t.Error("Create fish failed: ", err.Error())
+	}
+
+	if id <= 0 {
+		t.Error("Auto-generated ID should have been > 0")
+	}
+
+	stringId := fmt.Sprintf("%d", id)
+
+	// read fish from database
+	if err := db.Read(collection, stringId, &onefish); err != nil {
+		t.Error("Failed to read: ", err.Error())
+	}
+
+	//
+	if onefish.Type != "red" {
+		t.Error("Expected red fish, got: ", onefish.Type)
+	}
+
+	destroySchool()
+}
+
 //
 func TestReadall(t *testing.T) {