refactor(sick-leave): remake methods to calculate and update sick leave available

prisma/schema.prisma

@@ -55,6 +55,7 @@ model Employees {
   user                Users            @relation("UserEmployee", fields: [user_id], references: [id])
   leave_request       LeaveRequests[]  @relation("LeaveRequestEmployee")
   timesheet           Timesheets[]     @relation("TimesheetEmployee")
+  paid_time_off       PaidTimeOff?     @relation("EmployeePaidTimeOff")
 
   @@map("employees")
 }
@@ -321,6 +322,18 @@ model Preferences {
   @@map("preferences")
 }
 
+model PaidTimeOff {
+    id Int @id @default(autoincrement())
+    employee_id Int @unique
+    vacation_hours Int @default(0)
+    sick_hours Int @default(0)
+    last_updated DateTime @db.Date
+
+    employee Employees @relation("EmployeePaidTimeOff", fields: [employee_id], references: [id])
+
+    @@map("paid_time_off")
+}
+
 view PayPeriods {
   pay_year      Int
   pay_period_no Int

src/time-and-attendance/domains/services/sick-leave.service.ts

@@ -2,11 +2,114 @@
 import { Injectable, Logger } from "@nestjs/common";
 import { PrismaService } from "src/prisma/prisma.service";
 import { Result } from "src/common/errors/result-error.factory";
+import { Prisma } from "@prisma/client";
 
 @Injectable()
 export class SickLeaveService {
     constructor(private readonly prisma: PrismaService) { }
 
+    async updateSickLeaveHours(employee_id: number): Promise<Result<boolean, string>> {
+        const THIRTY_DAYS = 1000 * 60 * 60 * 24 * 30;
+        const FOURTEEN_DAYS = 1000 * 60 * 60 * 24 * 14;
+        const today = new Date();
+
+        // get employee info
+        const employee = await this.prisma.employees.findUnique({
+            where: { id: employee_id },
+            select: {
+                first_work_day: true,
+                last_work_day: true,
+                id: true,
+            }
+        })
+
+        if (!employee) return { success: false, error: 'EMPLOYEE_NOT_FOUND' };
+
+        // check if employee has been inactive for more than 2 weeks
+        if (employee.last_work_day) {
+            if (today.getTime() - employee.last_work_day.getTime() >= FOURTEEN_DAYS) {
+                return { success: false, error: "EMPLOYEE_NOT_ACTIVE" };
+            }
+        }
+
+        // get employee's PTO info, or create new details if not yet existing
+        let pto_details: Prisma.Result<typeof this.prisma.paidTimeOff, Prisma.PaidTimeOffDefaultArgs, 'findUnique' | 'create'>;
+
+        pto_details = await this.prisma.paidTimeOff.findUnique({
+            where: { employee_id: employee.id },
+        })
+
+        if (!pto_details) {
+            const new_pto_entry = await this.createNewPTORow(employee.id, today);
+
+            if (!new_pto_entry.success) return { success: false, error: "FAILED_TO_CREATE_EMPLOYEE_PTO" };
+
+            pto_details = new_pto_entry.data;
+        }
+
+        // check if employee has gotten his 3 days from completing his 30-day qualifying period from hiring date
+        if (today.getTime() - employee.first_work_day.getTime() >= THIRTY_DAYS && employee.first_work_day.toISOString() === pto_details?.last_updated?.toISOString()) {
+            const updated_pto = await this.addHoursToPTO(3 * 8, employee.id, today);
+
+            if (!updated_pto.success) return { success: updated_pto.success, error: updated_pto.error }
+        }
+        
+        const year_difference = today.getFullYear() - (pto_details!.last_updated.getFullYear() ?? today.getFullYear());
+        const months_since_last_update = (today.getMonth() + year_difference * 12) - pto_details!.last_updated.getMonth();
+
+        if (months_since_last_update > 0) {
+            const updated_pto = await this.addHoursToPTO(months_since_last_update * 8, employee.id, today);
+
+            if (updated_pto.success) {
+                return {success: true, data: true}
+            }
+        }
+
+        return { success: false, error: 'UNKNOWN_PTO_UPDATE_ERROR' };
+    }
+
+    // create a new PTO row
+    async createNewPTORow(employee_id: number, today: Date): Promise<Result<Prisma.Result<typeof this.prisma.paidTimeOff, Prisma.PaidTimeOffDefaultArgs, 'findUnique' | 'create'>, string>> {
+        try {
+            const new_pto_entry = await this.prisma.paidTimeOff.create({
+                data: {
+                    employee_id: employee_id,
+                    last_updated: today,
+                },
+                select: {
+                    id: true,
+                    employee_id: true,
+                    sick_hours: true,
+                    vacation_hours: true,
+                    last_updated: true,
+                }
+            });
+
+            return { success: true, data: new_pto_entry };
+        } catch (error) {
+            return { success: false, error };
+        }
+    }
+
+    // add n number of sick PTO hours to employee PTO
+    async addHoursToPTO(sick_hours: number, employee_id: number, last_updated: Date) {
+        try {
+            const update_pto = await this.prisma.paidTimeOff.update({
+                where: {
+                    employee_id,
+                },
+                data: {
+                    sick_hours,
+                    last_updated,
+                }
+            })
+
+            return { success: true, data: update_pto };
+        } catch (error) {
+            return { success: false, error };
+        }
+    };
+
     // switch employeeId for email
     async calculateSickLeavePay(
         employee_id: number,