1 files changed, 62 insertions, 0 deletions
diff --git a/src/inventory.lisp b/src/inventory.lisp
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+++ b/src/inventory.lisp
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+(defpackage inventory
+  (:use :cl)
+  (:export :inventory
+		   :add-item
+		   :remove-item))
+
+(in-package :inventory)
+
+
+(defclass inventory ()
+  ((size :initarg :size
+		 :reader size)
+   (filled :initform 0
+		   :accessor filled)
+   (items :initform '()
+    	  :accessor items)))
+
+(defmethod find-item ((inv inventory) name)
+  (with-slots (items) inv
+	(find-if
+	 #'(lambda (i)
+		 (equal (commodities:name (car i)) name))
+	 items)))
+
+(defmethod delete-item ((inv inventory) item)
+  ;; removes <item> from inventory list and substracts
+  ;; its stored quantity from the filled attribute
+  (with-slots (filled items) inv
+	(setq items (remove item items))
+	(setq filled (- filled (cdr item)))))
+
+(defmethod add-item ((inv inventory) item quantity)
+  ;; add <quantity> of <item> to inventory
+  (with-slots (size filled items) inv
+	(when (> size (+ filled quantity))
+	  (let* ((old-item
+			  (find-item inv (commodities:name item)))
+			 (qt (if old-item
+					 (progn
+					   (delete-item inv old-item)
+					   (+ quantity (cdr old-item)))
+					 quantity)))
+		(prog1
+		  (setq filled (+ filled qt))
+		  (push (cons item qt)
+				items))))))
+
+(defmethod remove-item ((inv inventory) name quantity)
+  ;; remove <quantity> of <item> from inventory
+  ;; quantity must be positive or zero
+  (assert (>= quantity 0))
+  (with-slots (filled items) inv
+	(let ((item (find-item inv name)))
+	  (when item
+		(delete-item inv item)
+	    (if (< quantity (cdr item))
+			(progn
+			  (add-item inv
+						(car item)
+						(- (cdr item) quantity))
+			  (cons (car item) quantity))
+			item)))))