remove obsolete existence check for milageStart/End

db/bill.ts

@@ -28,8 +28,31 @@ const BillSchema = new mongoose.Schema<BillDocument>(
       ref: 'Booking',
       required: true,
     },
-    milageStart: { type: Number, required: true },
-    milageEnd: { type: Number, required: true },
+    milageStart: {
+      type: Number,
+      required: true,
+      validate: {
+        validator: function (v: number) {
+          const bill = this as BillDocument
+
+          return v <= bill.milageEnd
+        },
+        message: (props) => `${props.value} is bigger than milageEnd!`,
+      },
+    },
+    milageEnd: {
+      type: Number,
+      required: true,
+
+      validate: {
+        validator: function (v: number) {
+          const bill = this as BillDocument
+
+          return v >= bill.milageStart
+        },
+        message: (props) => `${props.value} is smaller than milageStart!`,
+      },
+    },
     rate: {
       type: Number,
       enum: Object.values(MILAGE_RATES),
@@ -54,19 +77,12 @@ const BillSchema = new mongoose.Schema<BillDocument>(
 
 BillSchema.virtual('milage').get(function () {
   const bill = this as BillDocument
-
-  if (!bill.milageStart || !bill.milageEnd) {
-    return null
-  }
   return bill.milageEnd - bill.milageStart
 })
 
 BillSchema.virtual('total').get(function () {
   const bill = this as BillDocument
 
-  if (!bill.milageStart || !bill.milageEnd) {
-    return null
-  }
   const milageCosts = bill.milage * bill.rate
   const additionalCostSum = bill.additionalCosts
     .map(({ value }) => value)