From b405d6fba95b239182c03a018a3257b2515f1a12 Mon Sep 17 00:00:00 2001
From: sdomino <sdomino@pagodabox.com>
Date: Tue, 16 Dec 2014 14:30:28 -0700
Subject: [PATCH] using mutex over channels, and some other minor cleanups

---
 scribble.go | 129 +++++++++++++++++++++++++---------------------------
 1 file changed, 62 insertions(+), 67 deletions(-)

diff --git a/scribble.go b/scribble.go
index 11df0c8..99840b7 100644
--- a/scribble.go
+++ b/scribble.go
@@ -2,10 +2,12 @@ package scribble
 
 import (
 	"encoding/json"
+	"errors"
 	"fmt"
 	"io/ioutil"
 	"os"
 	"strings"
+	"sync"
 
 	"github.com/nanobox-core/hatchet"
 )
@@ -18,16 +20,16 @@ type (
 
 	// Driver
 	Driver struct {
-		channels map[string]chan int
+		mutexes map[string]sync.Mutex
 		dir      string
-		log      *hatchet.Logger
+		log      hatchet.Logger
 	}
 
 	// Transaction represents
 	Transaction struct {
 		Action     string
 		Collection string
-		Resource   string
+		ResourceID string
 		Container  interface{}
 	}
 )
@@ -36,9 +38,17 @@ type (
 func New(dir string, logger hatchet.Logger) (*Driver, error) {
 	fmt.Printf("Creating database directory at '%v'...\n", dir)
 
-	scribble := &Driver{}
-	scribble.dir = dir
-	scribble.channels = make(map[string]chan int)
+	//
+  if logger == nil {
+    logger = hatchet.DevNullLogger{}
+  }
+
+	//
+	scribble := &Driver{
+		dir: 		 dir,
+		mutexes: make(map[string]sync.Mutex),
+		log: 		 logger,
+	}
 
 	//
 	if err := mkDir(scribble.dir); err != nil {
@@ -52,92 +62,74 @@ func New(dir string, logger hatchet.Logger) (*Driver, error) {
 // Transact
 func (d *Driver) Transact(trans Transaction) error {
 
-	//
-	done := d.getOrCreateChan(trans.Collection)
-	fail := make(chan error)
-
 	//
 	switch trans.Action {
 	case "write":
-		go d.write(trans, done, fail)
+		return d.write(trans)
 	case "read":
-		go d.read(trans, done, fail)
+		return d.read(trans)
 	case "readall":
-		go d.readAll(trans, done, fail)
+		return d.readAll(trans)
 	case "delete":
-		go d.delete(trans, done, fail)
+		return d.delete(trans)
 	default:
-		fmt.Println("Unsupported action ", trans.Action)
+		return errors.New(fmt.Sprintf("Unsupported action %+v", trans.Action))
 	}
 
-	// wait until we're done, or error
-	select {
-	case <-done:
-		return nil
-	case err := <-fail:
-		return err
-	}
+	return nil
 }
 
 // private
 
 // write
-func (d *Driver) write(trans Transaction, done chan<- int, fail chan<- error) {
+func (d *Driver) write(trans Transaction) error {
+
+	mutex := d.getOrCreateMutex(trans.Collection)
+	mutex.Lock()
 
 	//
 	dir := d.dir + "/" + trans.Collection
 
-	//
-	if err := mkDir(dir); err != nil {
-		fail <- err
-	}
-
-	//
-	file, err := os.Create(dir + "/" + trans.Resource)
-	if err != nil {
-		fail <- err
-	}
-
-	defer file.Close()
-
 	//
 	b, err := json.MarshalIndent(trans.Container, "", "\t")
 	if err != nil {
-		fail <- err
+		return err
 	}
 
-	_, err = file.WriteString(string(b))
-	if err != nil {
-		fail <- err
+	//
+	if err := mkDir(dir); err != nil {
+		return err
 	}
 
-	// release...
-	done <- 0
+	//
+	if err := ioutil.WriteFile(trans.ResourceID, b, 0666); err != nil {
+		return err
+	}
+
+	mutex.Unlock()
+
+	return nil
 }
 
 // read
-func (d *Driver) read(trans Transaction, done chan<- int, fail chan<- error) interface{} {
+func (d *Driver) read(trans Transaction) error {
 
 	dir := d.dir + "/" + trans.Collection
 
-	b, err := ioutil.ReadFile(dir + "/" + trans.Resource)
+	b, err := ioutil.ReadFile(dir + "/" + trans.ResourceID)
 	if err != nil {
-		fmt.Printf("Unable to read file %v/%v: %v", trans.Collection, trans.Resource, err)
-		os.Exit(1)
+		return err
 	}
 
 	if err := json.Unmarshal(b, trans.Container); err != nil {
-		fail <- err
+		return err
 	}
 
-	// release...
-	done <- 0
-
-	return trans.Container
+	return nil
 }
 
 // readAll
-func (d *Driver) readAll(trans Transaction, done chan<- int, fail chan<- error) {
+func (d *Driver) readAll(trans Transaction) error {
 
 	dir := d.dir + "/" + trans.Collection
 
@@ -153,7 +145,7 @@ func (d *Driver) readAll(trans Transaction, done chan<- int, fail chan<- error)
 	for _, file := range files {
 		b, err := ioutil.ReadFile(dir + "/" + file.Name())
 		if err != nil {
-			fail <- err
+			return err
 		}
 
 		f = append(f, string(b))
@@ -161,38 +153,41 @@ func (d *Driver) readAll(trans Transaction, done chan<- int, fail chan<- error)
 
 	//
 	if err := json.Unmarshal([]byte("["+strings.Join(f, ",")+"]"), trans.Container); err != nil {
-		fail <- err
+		return err
 	}
 
-	// release...
-	done <- 0
+	return nil
 }
 
 // delete
-func (d *Driver) delete(trans Transaction, done chan<- int, fail chan<- error) {
+func (d *Driver) delete(trans Transaction) error {
+
+	mutex := d.getOrCreateMutex(trans.Collection)
+	mutex.Lock()
 
 	dir := d.dir + "/" + trans.Collection
 
-	err := os.Remove(dir + "/" + trans.Resource)
+	err := os.Remove(dir + "/" + trans.ResourceID)
 	if err != nil {
-		fail <- err
+		return err
 	}
 
-	// release...
-	done <- 0
+	mutex.Unlock()
+
+	return nil
 }
 
 // helpers
 
-// getChan
-func (d *Driver) getOrCreateChan(channel string) chan int {
+// getOrCreateMutex
+func (d *Driver) getOrCreateMutex(collection string) sync.Mutex {
 
-	c, ok := d.channels[channel]
+	c, ok := d.mutexes[collection]
 
-	// if the chan doesn't exist make it
+	// if the mutex doesn't exist make it
 	if !ok {
-		d.channels[channel] = make(chan int)
-		return d.channels[channel]
+		d.mutexes[collection] = sync.Mutex{}
+		return d.mutexes[collection]
 	}
 
 	return c