Roughing out the demo app

node_modules/steno/index.js

@@ -0,0 +1,80 @@
+var fs = require('graceful-fs')
+var path = require('path')
+
+var writers = {}
+
+// Returns a temporary file
+// Example: for /some/file will return /some/.~file
+function getTempFile (file) {
+  return path.join(path.dirname(file), '.~' + path.basename(file))
+}
+
+function Writer (file) {
+  this.file = file
+  this.callbacks = []
+  this.nextData = null
+  this.nextCallbacks = []
+}
+
+Writer.prototype.write = function (data, cb) {
+  if (this.lock) {
+    // File is locked
+    // Save callback for later
+    this.nextCallbacks.push(cb)
+    // Set next data to be written
+    this.nextData = data
+  } else {
+    // File is not locked
+    // Lock it
+    this.lock = true
+
+    // Write data to a temporary file
+    var tmpFile = getTempFile(this.file)
+    fs.writeFile(tmpFile, data, function (err) {
+      if (err) {
+        // On error, call all the stored callbacks and the current one
+        // Then return
+        while (this.callbacks.length) this.callbacks.shift()(err)
+        cb(err)
+        return
+      }
+
+      // On success rename the temporary file to the real file
+      fs.rename(tmpFile, this.file, function (err) {
+        // call all the stored callbacks and the current one
+        while (this.callbacks.length) this.callbacks.shift()(err)
+        cb()
+
+        // Unlock file
+        this.lock = false
+
+        // Write next data if any
+        if (this.nextData) {
+          var data = this.nextData
+          this.callbacks = this.nextCallbacks
+
+          this.nextData = null
+          this.nextCallbacks = []
+
+          this.write(data, this.callbacks.pop())
+        }
+      }.bind(this))
+    }.bind(this))
+  }
+}
+
+module.exports.writeFile = function (file, data, cb) {
+  // Convert to absolute path
+  file = path.resolve(file)
+
+  // Create or get writer
+  writers[file] = writers[file] || new Writer(file)
+
+  // Write
+  writers[file].write(data, cb)
+}
+
+module.exports.writeFileSync = function (file, data) {
+  fs.writeFileSync(getTempFile(file), data)
+  fs.renameSync(getTempFile(file), file)
+}