import { Injectable } from "@nestjs/common";
import { Result } from "src/common/errors/result-error.factory";
import { BankCodesResolver } from "src/common/mappers/bank-type-id.mapper";
import { EmailToIdResolver } from "src/common/mappers/email-id.mapper";
import { toStringFromDate, weekStartSunday } from "src/common/utils/date-utils";
import { PrismaService } from "prisma/postgres/prisma-postgres.service";
import { ExpenseDto } from "src/time-and-attendance/expenses/expense-create.dto";
import { normalizeAndParseExpenseDto } from "src/time-and-attendance/expenses/expense.utils";
import { PayPeriodEventService } from "src/time-and-attendance/pay-period/services/pay-period-event.service";
import { expense_select } from "src/time-and-attendance/utils/selects.utils";

@Injectable()
export class ExpenseCreateService {
    constructor(
        private readonly prisma: PrismaService,
        private readonly emailResolver: EmailToIdResolver,
        private readonly typeResolver: BankCodesResolver,
        private readonly payPeriodEventService: PayPeriodEventService,
    ) { }

    //_________________________________________________________________
    //                              CREATE
    //_________________________________________________________________
    async createExpense(dto: ExpenseDto, email: string): Promise<Result<ExpenseDto, string>> {
        try {
            //fetch employee_id using req.user.email
            const employee_id = await this.emailResolver.findIdByEmail(email);
            if (!employee_id.success) return { success: false, error: employee_id.error };

            //normalize strings and dates and Parse numbers
            const normed_expense = await normalizeAndParseExpenseDto(dto);
            if (!normed_expense.success) return { success: false, error: normed_expense.error }

            const type = await this.typeResolver.findBankCodeIDByType(dto.type);
            if (!type.success) return { success: false, error: 'INVALID_EXPENSE_TYPE' }

            //finds the timesheet using expense.date by finding the sunday
            const start_date = weekStartSunday(normed_expense.data.date);

            const timesheet = await this.prisma.timesheets.findFirst({
                where: { start_date, employee_id: employee_id.data },
                select: { id: true, employee_id: true },
            });
            if (!timesheet) return { success: false, error: `TIMESHEET_NOT_FOUND` };

            //create a new expense
            const expense = await this.prisma.expenses.create({
                data: {
                    ...normed_expense.data,
                    bank_code_id: type.data,
                    timesheet_id: timesheet.id,
                    is_approved: dto.is_approved,
                },
                //return the newly created expense with id
                select: expense_select,
            });
            if (!expense) return { success: false, error: `INVALID_EXPENSE` };

            //build an object to return to the frontend to display
            const created: ExpenseDto = {
                ...expense,
                type: dto.type,
                date: toStringFromDate(expense.date),
                amount: expense.amount?.toNumber() ?? undefined,
                mileage: expense.mileage?.toNumber(),
                attachment: expense.attachment ?? undefined,
                supervisor_comment: expense.supervisor_comment ?? undefined,
            };

            // notify timesheet approval observers of changes
            this.payPeriodEventService.emit({
                employee_email: email,
                event_type: 'expense',
                action: 'create',
            });

            return { success: true, data: created };
        } catch (error) {
            return { success: false, error: 'INVALID_EXPENSE' };
        }
    }
}