diff --git a/index.js b/index.js
index 525c9de1..1edf7649 100644
--- a/index.js
+++ b/index.js
@@ -2,10 +2,16 @@ import { Drug, Pharmacy } from "./pharmacy";
 import fs from "fs";
 
 const drugs = [
-  new Drug("Doliprane", 20, 30),
-  new Drug("Herbal Tea", 10, 5),
-  new Drug("Fervex", 5, 40),
-  new Drug("Magic Pill", 15, 40)
+  // Normal Drugs decrease benefit by 1 each day, do not expire after expir date and have a linear evolution.
+  new Drug("Doliprane", 20, 30, 1, 1, false, true),
+  // Herbal tea increases in benefit over time, normal evolution (twice after expiration date).
+  new Drug("Herbal Tea", 10, 5, 1, -1, false, true),
+  // Fervex increases in benefit over time, not a linear evolution.
+  new Drug("Fervex", 5, 40, 1, -1, true, false, [10, 5]),
+  // magic pill will not decrease benefit nor expiration date.
+  new Drug("Magic Pill", 15, 40, 0, 0, false, true),
+  // Dafalgan is a normal drug but decreases benefit twice as fast.
+  new Drug("Dafalgan", 20, 30, 1, 2, false, true)
 ];
 const trial = new Pharmacy(drugs);
 
@@ -23,4 +29,5 @@ fs.writeFile("output.txt", log.toString(), err => {
     console.log("success");
   }
 });
+
 /* eslint-enable no-console */
diff --git a/pharmacy.js b/pharmacy.js
index cda44c41..30310f3b 100644
--- a/pharmacy.js
+++ b/pharmacy.js
@@ -1,8 +1,58 @@
 export class Drug {
-  constructor(name, expiresIn, benefit) {
+  constructor(name, expiresIn, benefit, exipreEvol = 1, benefitEvol = 1, expire = false, isLinear = true, evolArray = []) {
     this.name = name;
     this.expiresIn = expiresIn;
     this.benefit = benefit;
+    this.exipreEvol = exipreEvol;
+    this.benefitEvol = benefitEvol;
+    this.expire = expire;
+    this.isLinear = isLinear;
+    this.evolArray = evolArray;
+  }
+  
+  updateLinear() {
+    // benefit degrades with time
+    this.benefit = this.benefit - this.benefitEvol;
+    // once theexpiration date is reached, benefit degrades twice as fast
+    if (this.expiresIn == 0)
+      this.benefit = this.benefit - this.benefitEvol;
+  }
+
+  updateEvolveWithTime() {
+
+    for (let i = 0; i < this.evolArray.length; i++) {
+      if (this.expiresIn <= this.evolArray[i]) {
+        this.benefit = this.benefit - this.benefitEvol;
+      }
+    }
+    this.benefit = this.benefit - this.benefitEvol;
+  }
+
+  ExpireAtExpirationDate() {
+    if (this.expire == true && this.expiresIn == 0) {
+      this.benefit = 0;
+    }
+  }
+
+  checkBenefit() {
+    this.ExpireAtExpirationDate();
+    // benefit is never negative.
+    if (this.benefit < 0)
+      this.benefit = 0;
+    // benefit is never more than 50.
+    else if (this.benefit > 50)
+      this.benefit = 50;
+  }
+
+  updateDrug() {
+    if (this.isLinear == true)
+      this.updateLinear();
+    else
+      this.updateEvolveWithTime();
+    this.checkBenefit();
+    // a date should never be negative ?
+    if (this.expiresIn > 0)
+      this.expiresIn = this.expiresIn - this.exipreEvol;
   }
 }
 
@@ -10,57 +60,11 @@ export class Pharmacy {
   constructor(drugs = []) {
     this.drugs = drugs;
   }
+
   updateBenefitValue() {
-    for (var i = 0; i < this.drugs.length; i++) {
-      if (
-        this.drugs[i].name != "Herbal Tea" &&
-        this.drugs[i].name != "Fervex"
-      ) {
-        if (this.drugs[i].benefit > 0) {
-          if (this.drugs[i].name != "Magic Pill") {
-            this.drugs[i].benefit = this.drugs[i].benefit - 1;
-          }
-        }
-      } else {
-        if (this.drugs[i].benefit < 50) {
-          this.drugs[i].benefit = this.drugs[i].benefit + 1;
-          if (this.drugs[i].name == "Fervex") {
-            if (this.drugs[i].expiresIn < 11) {
-              if (this.drugs[i].benefit < 50) {
-                this.drugs[i].benefit = this.drugs[i].benefit + 1;
-              }
-            }
-            if (this.drugs[i].expiresIn < 6) {
-              if (this.drugs[i].benefit < 50) {
-                this.drugs[i].benefit = this.drugs[i].benefit + 1;
-              }
-            }
-          }
-        }
-      }
-      if (this.drugs[i].name != "Magic Pill") {
-        this.drugs[i].expiresIn = this.drugs[i].expiresIn - 1;
-      }
-      if (this.drugs[i].expiresIn < 0) {
-        if (this.drugs[i].name != "Herbal Tea") {
-          if (this.drugs[i].name != "Fervex") {
-            if (this.drugs[i].benefit > 0) {
-              if (this.drugs[i].name != "Magic Pill") {
-                this.drugs[i].benefit = this.drugs[i].benefit - 1;
-              }
-            }
-          } else {
-            this.drugs[i].benefit =
-              this.drugs[i].benefit - this.drugs[i].benefit;
-          }
-        } else {
-          if (this.drugs[i].benefit < 50) {
-            this.drugs[i].benefit = this.drugs[i].benefit + 1;
-          }
-        }
-      }
+    for (let i = 0; i < this.drugs.length; i++) {
+      this.drugs[i].updateDrug();
     }
-
     return this.drugs;
   }
 }