Make date functions work; create negative intervals for depreciation,

Also renamed "months_until_depreciation" to "time_until_depreciation"
And renamed Depreciatable to Depreciable (which is an actual word in
English.) Also a cleanup/consistency-enforcement for interval display.

app/models/Asset.php

@@ -1,6 +1,6 @@
 <?php
 
-class Asset extends Depreciatable
+class Asset extends Depreciable
 {
 	use SoftDeletingTrait;
     protected $dates = ['deleted_at'];

app/models/Depreciable.php

@@ -1,14 +1,17 @@
 <?php
 
-class Depreciatable extends Elegant
+class Depreciable extends Elegant
 {
     /**
     * Depreciation Relation, and associated helper methods
     */
 
+    //REQUIRES a purchase_date field
+    //     and a purchase_cost field
+
     public function depreciation()
     {
-        return $this->model->belongsTo('Depreciation','depreciation_id');
+        return $this->belongsTo('Depreciation','depreciation_id');
     }
 
     /**
@@ -28,7 +31,7 @@ class Depreciatable extends Elegant
         }
 
         // fraction of value left
-        $current_value = round(($this->months_until_depreciated() / ($this->depreciation->months)) * $this->purchase_cost, 2);
+        $current_value = round(($this->time_until_depreciated() / ($this->depreciation->months)) * $this->purchase_cost, 2);
 
         if ($current_value < 0) {
             $current_value = 0;
@@ -36,15 +39,19 @@ class Depreciatable extends Elegant
         return $current_value;
     }
 
-    public function months_until_depreciated()
+    public function time_until_depreciated()
     {
         // @link http://www.php.net/manual/en/class.datetime.php
         $d1 = new DateTime();
-        $d2 = new DateTime($this->depreciated_date());
+        $d2 = $this->depreciated_date();
 
         // @link http://www.php.net/manual/en/class.dateinterval.php
         $interval = $d1->diff($d2);
-        return $interval;
+        if(!$interval->invert) {
+            return $interval;
+        } else {
+            return new DateInterval("PT0S"); //null interval (zero seconds from now)
+        }
     }
 
     public function depreciated_date()

app/models/License.php

@@ -1,6 +1,6 @@
 <?php
 
-class License extends Depreciatable
+class License extends Depreciable
 {
 	use SoftDeletingTrait;
     protected $dates = ['deleted_at'];

app/views/backend/hardware/view.blade.php

@@ -119,13 +119,13 @@
                 @lang('admin/hardware/form.months')
                 )</div>
             <div class="col-md-12" style="padding-bottom: 5px;"><strong>@lang('admin/hardware/form.fully_depreciated'): </strong>
-            {{{ $asset->months_until_depreciated()->m }}}
+            {{{ $asset->time_until_depreciated()->m }}}
             @lang('admin/hardware/form.months')
-             @if ($asset->months_until_depreciated()->y > 0)
-                , {{{ $asset->months_until_depreciated()->y }}}
+             @if ($asset->time_until_depreciated()->y > 0)
+                , {{{ $asset->time_until_depreciated()->y }}}
                 @lang('admin/hardware/form.years')
              @endif
-              ({{{ $asset->depreciation->depreciated_date() }}})
+              ({{{ $asset->depreciated_date()->format('Y-m-d') }}})
              </div>
         @endif
 

app/views/backend/licenses/view.blade.php

@@ -73,18 +73,18 @@
 
 	<div class="col-md-6" style="padding-bottom: 5px">
 		<strong>@lang('admin/hardware/form.depreciates_on'): </strong>
-		{{{ $license->depreciated_date() }}}
+		{{{ $license->depreciated_date()->format("Y-m-d") }}}
 	</div>
 
 	<div class="col-md-6" style="padding-bottom: 5px">
 		<strong>@lang('admin/hardware/form.fully_depreciated'): </strong>
-		{{{ $license->months_until_depreciated()->m }}}
+        @if ($license->time_until_depreciated()->y > 0)
+            {{{ $license->time_until_depreciated()->y }}}
+            @lang('admin/hardware/form.years'), 
+        @endif
+		{{{ $license->time_until_depreciated()->m }}}
 		@lang('admin/hardware/form.months')
 
-		@if ($license->months_until_depreciated()->y > 0)
-			, {{{ $license->months_until_depreciated()->y }}}
-			@lang('admin/hardware/form.years')
-		@endif
 	 </div>
 @endif