Implement lazy parsing

lib/psd.coffee

 fs        = require 'fs'
 
 File      = require './psd/file.coffee'
+LazyExecute = require './psd/lazy_execute.coffee'
+
 Header    = require './psd/header.coffee'
 Resources = require './psd/resources.coffee'
 LayerMask = require './psd/layer_mask.coffee'
@@ -29,13 +31,22 @@ module.exports = class PSD
     @header.parse()
 
   parseResources: ->
-    @resources = new Resources(@file)
-    @resources.parse()
+    resources = new Resources(@file)
+    @resources = new LazyExecute(resources, @file)
+      .now('skip')
+      .later('parse')
+      .get()
 
   parseLayerMask: ->
-    @layerMask = new LayerMask(@file, @header)
-    @layerMask.parse()
+    layerMask = new LayerMask(@file, @header)
+    @layerMask = new LazyExecute(layerMask, @file)
+      .now('skip')
+      .later('parse')
+      .get()
 
   parseImage: ->
-    @image = new Image(@file, @header)
-    @image.parse()
\ No newline at end of file
+    image = new Image(@file, @header)
+    @image = new LazyExecute(image, @file)
+      .later('parse')
+      .ignore('width', 'height')
+      .get()
\ No newline at end of file

lib/psd/header.coffee

@@ -24,8 +24,8 @@ module.exports = class Header
     @sig = null
     @version = null
     @channels = null
-    @rows = null
-    @cols = null
+    @rows = @height = null
+    @cols = @width = null
     @depth = null
     @mode = null
 
@@ -36,8 +36,8 @@ module.exports = class Header
     @file.seek 6, true
 
     @channels = @file.readUShort()
-    @rows = @file.readUInt()
-    @cols = @file.readUInt()
+    @rows = @height = @file.readUInt()
+    @cols = @width = @file.readUInt()
     @depth = @file.readUShort()
     @mode = @file.readUShort()
 

lib/psd/image.coffee

 module.exports = class Image
   constructor: (@file, @header) ->
+    @width = @header.width
+    @height = @header.height
 
   parse: ->
+    console.log "parse!"
     
\ No newline at end of file

lib/psd/layer_mask.coffee

@@ -6,6 +6,8 @@ module.exports = class LayerMask
     @mergedAlpha = false
     @globalMask = null
 
+  skip: -> @file.seek @file.readInt()
+
   parse: ->
     maskSize = @file.readInt()
     finish = maskSize + @file.tell()

lib/psd/lazy_execute.coffee

+module.exports = class LazyExecute
+  constructor: (@obj, @file) ->
+    @startPos = @file.tell()
+    @loaded = false
+    @loadMethod = null
+    @loadArgs = []
+    @passthru = []
+
+  now: (method, args...) ->
+    @obj[method].apply(@obj, args)
+    return @
+
+  later: (method, args...) ->
+    @loadMethod = method
+    @loadArgs = args
+    return @
+
+  ignore: (args...) ->
+    @passthru.concat args
+    return @
+
+  get: ->
+    for own key, val of @obj then do (key, val) =>
+      return if @[key]?
+      Object.defineProperty @, key,
+        get: ->
+          @load() if not @loaded and not (key in @passthru)
+          @obj[key]
+
+    @
+
+  load: ->
+    origPos = @file.tell()
+    @file.seek @startPos
+
+    @obj[@loadMethod].apply(@obj, @loadArgs)
+
+    @file.seek origPos
+    @loaded = true

lib/psd/resources.coffee

@@ -4,6 +4,10 @@ module.exports = class Resources
     @typeIndex = {}
     @length = null
 
+  skip: ->
+    @length = @file.readInt()
+    @file.seek @length, true
+
   parse: ->
     @length = @file.readInt()
     @file.seek @length, true
\ No newline at end of file