<?php

namespace App\Services;

use App\Models\Employee;
use App\Models\AttendanceRecord;
use Illuminate\Support\Facades\DB;
use Carbon\Carbon;

class PayrollService
{
    /**
     * Compute cumulative payroll: daily_rate × days_worked.
     * Philippine statutory contributions based on full monthly salary bracket.
     */
    public function calculateForPeriod(Employee $employee, $startDate, $endDate)
    {
        // 1. Fetch salary config
        $salaryData = \App\Models\EmployeeSalary::where('employee_id', $employee->user_id)->first();

        $grossMonthly = $salaryData ? $salaryData->basic_salary : 20000;
        $payFrequency = $salaryData ? $salaryData->pay_frequency : 'monthly';

        $isSemiMonthly = ($payFrequency === 'semi-monthly');
        $divisor = $isSemiMonthly ? 2 : 1;

        // Daily rate: monthly salary / 26 standard working days
        $actualDailyRate = $grossMonthly / 26;
        $hourlyRate = $actualDailyRate / 8;

        // 2. Fetch Attendance
        $attendances = AttendanceRecord::where('employee_id', $employee->user_id)
            ->whereBetween('date', [$startDate, $endDate])
            ->get();

        $daysWorked = 0;
        $renderedHours = 0;
        $lateHours = 0;
        $absencesCount = 0;
        $nightDiffHours = 0;
        $totalOvertimeHours = 0;
        $expectedWorkingDays = 0;
        $expectedHours = 0;

        $currentDate = Carbon::parse($startDate);
        $periodEndObj = Carbon::parse($endDate);

        // Index attendances by date for fast lookup
        $indexedAttendances = $attendances->keyBy(function($item) {
            return $item->date instanceof Carbon ? $item->date->toDateString() : substr((string)$item->date, 0, 10);
        });

        while ($currentDate->lte($periodEndObj)) {
            $dateString = $currentDate->toDateString();
            $att = $indexedAttendances->get($dateString);

            // Skip rest days — not a working day
            if ($att && $att->is_rest_day) {
                $currentDate->addDay();
                continue;
            }

            // Count expected working days
            $expectedWorkingDays++;
            $expectedHours += 9;

            if (!$att || $att->is_absent || $att->status === 'absent') {
                // Absent — simply not paid (cumulative model)
                $absencesCount++;
            } else {
                $daysWorked++;
                if ($att->total_hours) {
                    $renderedHours += $att->total_hours;
                }
                if ($att->is_late) {
                    $lateHours += (float) ($att->late_hours ?? 0);
                }

                // --- NIGHT DIFFERENTIAL ENGINE ---
                if (!empty($att->clock_in) && !empty($att->clock_out)) {
                    try {
                        $in = Carbon::parse($dateString . ' ' . $att->clock_in);
                        $out = Carbon::parse($dateString . ' ' . $att->clock_out);

                        if ($out->lt($in)) {
                            $out->addDay();
                        }

                        // DOLE ND Windows: 10PM–6AM
                        $windows = [
                            [Carbon::parse($dateString)->startOfDay(), Carbon::parse($dateString)->setTime(6, 0)],
                            [Carbon::parse($dateString)->setTime(22, 0), Carbon::parse($dateString)->addDay()->setTime(6, 0)]
                        ];

                        foreach ($windows as $window) {
                            $overlapStart = $in->copy()->max($window[0]);
                            $overlapEnd = $out->copy()->min($window[1]);

                            if ($overlapEnd->gt($overlapStart)) {
                                $nightDiffHours += $overlapEnd->diffInMinutes($overlapStart, true) / 60;
                            }
                        }
                    } catch (\Exception $e) {
                        // Skip malformed logs
                    }
                }

                // --- OVERTIME ENGINE ---
                if ($att->overtime_hours) {
                    $totalOvertimeHours += (float) $att->overtime_hours;
                }
            }

            $currentDate->addDay();
        }

        // Apply Time Exemption (salaried exempt employees)
        if ($salaryData && $salaryData->is_time_exempt) {
            $lateHours = 0;
            $nightDiffHours = 0;
            $totalOvertimeHours = 0;
        }

        $holidayPay = 0;

        // 3. CUMULATIVE EARNINGS: daily_rate × days_worked
        $earnedBasicSalary = $daysWorked * $actualDailyRate;

        // Late deduction remains as explicit hourly penalty
        $lateDeduction = $lateHours * $hourlyRate;

        // OT and ND premiums
        $regularOtTotal = $totalOvertimeHours * ($hourlyRate * 1.25);
        $nightDiffAmount = $nightDiffHours * ($hourlyRate * 0.10);

        // 4. Statutory Contributions — only if employee has earnings (prevents negative payroll)
        $sssCutoff = 0;
        $phCutoff = 0;
        $pagibigCutoff = 0;
        $tax = 0.00;

        if ($daysWorked > 0) {
            // Based on FULL monthly salary bracket (PH law)
            $msc = min(floor($grossMonthly / 500) * 500, 30000);

            $sssMonthly = $salaryData->sss_fixed ?? ($msc * 0.045);
            $philhealthMonthly = $salaryData->philhealth_fixed ?? ($grossMonthly * 0.025);
            if ($salaryData && is_null($salaryData->philhealth_fixed) && $grossMonthly <= 10000) $philhealthMonthly = 250;
            if ($salaryData && is_null($salaryData->philhealth_fixed) && $grossMonthly >= 100000) $philhealthMonthly = 2500;

            $pagibigMonthly = $salaryData->pagibig_fixed ?? (100 * $divisor);

            $sssCutoff = $sssMonthly / $divisor;
            $phCutoff = $philhealthMonthly / $divisor;
            $pagibigCutoff = $pagibigMonthly / $divisor;
        }

        // 5. Build earnings array
        $earnings = [
            ['name' => 'Basic Salary', 'amount' => number_format($earnedBasicSalary, 2, '.', '')],
            ['name' => 'Overtime (Regular)', 'amount' => number_format($regularOtTotal, 2, '.', '')],
            ['name' => 'Night Differential', 'amount' => number_format($nightDiffAmount, 2, '.', '')],
            ['name' => 'Holiday Pay', 'amount' => number_format($holidayPay, 2, '.', '')],
        ];

        // 6. Build deductions array — NO absence deduction (cumulative model)
        $deductions = [];
        if ($lateDeduction > 0) {
            $deductions[] = ['name' => 'Late Deduction', 'amount' => number_format($lateDeduction, 2, '.', '')];
        }
        $deductions[] = ['name' => 'SSS Contribution (EE)', 'amount' => number_format($sssCutoff, 2, '.', '')];
        $deductions[] = ['name' => 'PhilHealth Contribution (EE)', 'amount' => number_format($phCutoff, 2, '.', '')];
        $deductions[] = ['name' => 'Pag-IBIG Contribution (EE)', 'amount' => number_format($pagibigCutoff, 2, '.', '')];
        $deductions[] = ['name' => 'Withholding Tax', 'amount' => number_format($tax, 2, '.', '')];

        // 7. Totals
        $totalEarnings = $earnedBasicSalary + $nightDiffAmount + $regularOtTotal + $holidayPay;
        $totalDeductions = $lateDeduction + $sssCutoff + $phCutoff + $pagibigCutoff + $tax;
        $netPay = $totalEarnings - $totalDeductions;

        return [
            'gross_monthly' => $grossMonthly,
            'pay_type' => $isSemiMonthly ? 'Semi-Monthly' : 'Monthly',
            'daily_rate' => $actualDailyRate,
            'basic_salary' => $earnedBasicSalary,
            'earnings' => $earnings,
            'deductions' => $deductions,
            'total_earnings' => $totalEarnings,
            'total_deductions' => $totalDeductions,
            'net_pay' => $netPay,
            'summary' => [
                'days_worked' => $daysWorked,
                'expected_working_days' => $expectedWorkingDays,
                'expected_hours' => number_format($expectedHours, 2),
                'rendered_hours' => number_format($renderedHours, 2),
                'night_diff_hours' => number_format($nightDiffHours, 2),
                'absences' => $absencesCount,
                'leaves' => 0,
                'reg_ot_hours' => number_format($totalOvertimeHours, 2),
                'reg_ot_amount' => $regularOtTotal,
                'night_diff_amount' => $nightDiffAmount,
                'holiday' => 0,
            ]
        ];
    }
}