Display error state when calculation is impossible

src/coffee/controllers/craft_page_controller.coffee

@@ -8,6 +8,7 @@ All rights reserved.
 _                          = require 'underscore'
 AdsenseController          = require './adsense_controller'
 CraftPage                  = require '../models/craft_page'
+Craftsman                  = require '../models/crafting/craftsman'
 CraftsmanWorkingController = require './craftsman_working_controller'
 {Event}                    = require '../constants'
 InventoryController        = require './inventory_controller'
@@ -144,21 +145,24 @@ module.exports = class CraftPageController extends PageController
     _refreshSectionVisibility: ->
         return unless @_rendered
 
+        toShow = []
+        toHide = []
+
         if @model.craftsman.want.isEmpty
-            for $el in [@$toolsSection, @$ingredientsSection, @$stepsSection]
-                @hide $el
-            @show @$instructionsSection
-            @hide @$workingSection
+            toShow.push el for el in [@$instructionsSection]
+            toHide.push el for el in [@$toolsSection, @$ingredientsSection, @$stepsSection, @$workingSection]
+        else if @model.craftsman.stage is Craftsman::STAGE.INVALID
+            toShow.push el for el in [@$workingSection]
+            toHide.push el for el in [@$instructionsSection, @$toolsSection, @$ingredientsSection, @$stepsSection]
         else if not @model.craftsman.complete
-            for $el in [@$toolsSection, @$ingredientsSection, @$stepsSection]
-                @hide $el
-            @hide @$instructionsSection
-            @show @$workingSection
+            toShow.push el for el in [@$workingSection]
+            toHide.push el for el in [@$instructionsSection, @$toolsSection, @$ingredientsSection, @$stepsSection]
         else
-            for $el in [@$toolsSection, @$ingredientsSection, @$stepsSection]
-                @show $el
-            @hide @$instructionsSection
-            @hide @$workingSection
+            toShow.push el for el in [@$toolsSection, @$ingredientsSection, @$stepsSection]
+            toHide.push el for el in [@$instructionsSection, @$workingSection]
+
+        @show $el for $el in toShow
+        @hide $el for $el in toHide
 
     _refreshSteps: ->
         steps = @model.craftsman.plan?.steps or []

src/coffee/controllers/craftsman_working_controller.coffee

@@ -25,6 +25,7 @@ module.exports = class CraftsmanWorkingController extends BaseController
     onDidRender: ->
         @$message = @$('.message p')
         @$count = @$('.count p')
+        @$waiting = @$('.waiting')
         super
 
     refresh: ->
@@ -36,6 +37,7 @@ module.exports = class CraftsmanWorkingController extends BaseController
     _refreshStatusText: ->
         return unless @$message? and @$count?
 
+        waitingVisible = true
         switch @model.stage
             when Craftsman::STAGE.WAITING
                 @$message.html 'Preparing crafting calculation...'
@@ -52,3 +54,9 @@ module.exports = class CraftsmanWorkingController extends BaseController
             when Craftsman::STAGE.COMPLETE
                 @$message.html 'All done!'
                 @$count.html ''
+            when Craftsman::STAGE.INVALID
+                @$message.html 'Couldn\'t make a crafting plan'
+                @$count.html ''
+                waitingVisible = false
+
+        if waitingVisible then @show @$waiting else @hide @$waiting

src/coffee/models/crafting/craftsman.coffee

@@ -30,6 +30,7 @@ module.exports = class Craftsman extends BaseModel
         PLANNING:  'computing plans'
         ANALYZING: 'analyzing plans'
         COMPLETE:  'complete'
+        INVALID:   'invalid'
 
     constructor: (modPack)->
         if not modPack? then throw new Error 'modPack is required'
@@ -41,7 +42,7 @@ module.exports = class Craftsman extends BaseModel
 
         @_modPack = modPack
 
-        reset = _.throttle (=> @reset()), 100
+        reset = _.debounce (=> @reset()), 100
 
         @_have = new Inventory modPack:@_modPack
         @_have.on Event.change, reset
@@ -71,6 +72,9 @@ module.exports = class Craftsman extends BaseModel
         else if not @_graphBuilder.complete
             @_graphBuilder.expandGraph @GRAPH_STEP_INCREMENT
             @stageCount = @_graphBuilder.stepCount
+        else if not @_graphBuilder.rootNode.valid
+            @stage = @STAGE.INVALID
+            @stageCount = 0
         else if not @_planBuilder?
             logger.debug => "Craftsman finished computing graph:\n#{@_graphBuilder.rootNode}"
 
@@ -92,7 +96,6 @@ module.exports = class Craftsman extends BaseModel
                 @_planEvaluator.findBestPlan PlanEvaluator::CRITERIA.FEWEST_STEPS
                 @_planEvaluator.findBestPlan PlanEvaluator::CRITERIA.LEAST_MATERIALS
             ]
-            @_plans[0].computeRequired()
             @stage = @STAGE.COMPLETE
             @stageCount = 0
 
@@ -118,7 +121,7 @@ module.exports = class Craftsman extends BaseModel
     Object.defineProperties @prototype,
 
         complete:
-            get: -> @_plans?
+            get: -> @stage in [@STAGE.COMPLETE, @STAGE.INVALID]
 
         have:
             get: -> @_have