Add addEditSticker fuction. Still not fully working.

contexts/StickerContext.tsx

@@ -1,4 +1,5 @@
 import React, { createContext, useState, ReactNode } from "react";
+import { format, getDate, isBefore, startOfDay } from "date-fns";
 import stickersSeeder from "../data/stickerSeeder";
 
 const StickersContext = createContext({} as StickersContextState);
@@ -13,11 +14,39 @@ const StickersContextProvider = ({
   );
 
   // TODO: Add stickers functions here. (Add and edit stickers).
+  const addEditSticker = (date: Date, sticker: ValidStickerVal): void => {
+    const newStickersMonth = [...stickersMonth];
+    const index = getDate(date) - 1;
+    const currDate = newStickersMonth[index];
+
+    const edited = currDate.edited
+      ? true
+      : isBefore(currDate.date, startOfDay(new Date()))
+      ? true
+      : false;
+    currDate.edited = edited;
+    // Add manual here when necessary.
+
+    const id = format(date, "yyyyddLL") + sticker;
+
+    const newSticker: Sticker = {
+      id: id,
+      date: date,
+      sticker: sticker,
+      edited: edited,
+      manual: false
+    }
+
+    newStickersMonth[index] = newSticker;
+
+    setStickersMonth(newStickersMonth);
+  };
 
   // TODO: Add stickers validation function here.
 
   const stickersContextValues = {
-    stickersMonth
+    stickersMonth,
+    addEditSticker
   };
 
   return (