<?php

namespace App\Services;

use App\Models\Tenants\Loan;
use App\Models\Tenants\Withdrawal;
use Illuminate\Contracts\Pagination\LengthAwarePaginator;
use Illuminate\Support\Facades\DB;
use Symfony\Component\HttpKernel\Exception\BadRequestHttpException;

class LoanService extends Service
{
    // =========================================================================
    // 가지급금 목록/상세
    // =========================================================================

    /**
     * 가지급금 목록
     */
    public function index(array $params): LengthAwarePaginator
    {
        $tenantId = $this->tenantId();

        $query = Loan::query()
            ->where('tenant_id', $tenantId)
            ->with(['user:id,name,email', 'creator:id,name']);

        // 사용자 필터
        if (! empty($params['user_id'])) {
            $query->where('user_id', $params['user_id']);
        }

        // 상태 필터
        if (! empty($params['status'])) {
            $query->where('status', $params['status']);
        }

        // 날짜 범위 필터
        if (! empty($params['start_date'])) {
            $query->where('loan_date', '>=', $params['start_date']);
        }
        if (! empty($params['end_date'])) {
            $query->where('loan_date', '<=', $params['end_date']);
        }

        // 검색 (사용자명, 목적)
        if (! empty($params['search'])) {
            $search = $params['search'];
            $query->where(function ($q) use ($search) {
                $q->whereHas('user', function ($userQ) use ($search) {
                    $userQ->where('name', 'like', "%{$search}%");
                })->orWhere('purpose', 'like', "%{$search}%");
            });
        }

        // 정렬
        $sortBy = $params['sort_by'] ?? 'loan_date';
        $sortDir = $params['sort_dir'] ?? 'desc';
        $query->orderBy($sortBy, $sortDir);

        $perPage = $params['per_page'] ?? 20;

        return $query->paginate($perPage);
    }

    /**
     * 가지급금 상세
     */
    public function show(int $id): Loan
    {
        $tenantId = $this->tenantId();

        return Loan::query()
            ->where('tenant_id', $tenantId)
            ->with([
                'user:id,name,email',
                'withdrawal',
                'creator:id,name',
                'updater:id,name',
            ])
            ->findOrFail($id);
    }

    /**
     * 가지급금 요약 (특정 사용자 또는 전체)
     */
    public function summary(?int $userId = null): array
    {
        $tenantId = $this->tenantId();

        $query = Loan::query()
            ->where('tenant_id', $tenantId);

        if ($userId) {
            $query->where('user_id', $userId);
        }

        $stats = $query->selectRaw('
            COUNT(*) as total_count,
            SUM(CASE WHEN status = ? THEN 1 ELSE 0 END) as outstanding_count,
            SUM(CASE WHEN status = ? THEN 1 ELSE 0 END) as settled_count,
            SUM(CASE WHEN status = ? THEN 1 ELSE 0 END) as partial_count,
            SUM(amount) as total_amount,
            SUM(COALESCE(settlement_amount, 0)) as total_settled,
            SUM(amount - COALESCE(settlement_amount, 0)) as total_outstanding
        ', [Loan::STATUS_OUTSTANDING, Loan::STATUS_SETTLED, Loan::STATUS_PARTIAL])
            ->first();

        return [
            'total_count' => (int) $stats->total_count,
            'outstanding_count' => (int) $stats->outstanding_count,
            'settled_count' => (int) $stats->settled_count,
            'partial_count' => (int) $stats->partial_count,
            'total_amount' => (float) $stats->total_amount,
            'total_settled' => (float) $stats->total_settled,
            'total_outstanding' => (float) $stats->total_outstanding,
        ];
    }

    // =========================================================================
    // 가지급금 생성/수정/삭제
    // =========================================================================

    /**
     * 가지급금 생성
     */
    public function store(array $data): Loan
    {
        $tenantId = $this->tenantId();
        $userId = $this->apiUserId();

        return DB::transaction(function () use ($data, $tenantId, $userId) {
            // 출금 내역 연결 검증
            $withdrawalId = null;
            if (! empty($data['withdrawal_id'])) {
                $withdrawal = Withdrawal::query()
                    ->where('tenant_id', $tenantId)
                    ->where('id', $data['withdrawal_id'])
                    ->first();

                if (! $withdrawal) {
                    throw new BadRequestHttpException(__('error.loan.invalid_withdrawal'));
                }
                $withdrawalId = $withdrawal->id;
            }

            return Loan::create([
                'tenant_id' => $tenantId,
                'user_id' => $data['user_id'],
                'loan_date' => $data['loan_date'],
                'amount' => $data['amount'],
                'purpose' => $data['purpose'] ?? null,
                'status' => Loan::STATUS_OUTSTANDING,
                'withdrawal_id' => $withdrawalId,
                'created_by' => $userId,
                'updated_by' => $userId,
            ]);
        });
    }

    /**
     * 가지급금 수정
     */
    public function update(int $id, array $data): Loan
    {
        $tenantId = $this->tenantId();
        $userId = $this->apiUserId();

        $loan = Loan::query()
            ->where('tenant_id', $tenantId)
            ->findOrFail($id);

        if (! $loan->isEditable()) {
            throw new BadRequestHttpException(__('error.loan.not_editable'));
        }

        // 출금 내역 연결 검증
        if (isset($data['withdrawal_id']) && $data['withdrawal_id']) {
            $withdrawal = Withdrawal::query()
                ->where('tenant_id', $tenantId)
                ->where('id', $data['withdrawal_id'])
                ->first();

            if (! $withdrawal) {
                throw new BadRequestHttpException(__('error.loan.invalid_withdrawal'));
            }
        }

        $loan->fill([
            'user_id' => $data['user_id'] ?? $loan->user_id,
            'loan_date' => $data['loan_date'] ?? $loan->loan_date,
            'amount' => $data['amount'] ?? $loan->amount,
            'purpose' => $data['purpose'] ?? $loan->purpose,
            'withdrawal_id' => $data['withdrawal_id'] ?? $loan->withdrawal_id,
            'updated_by' => $userId,
        ]);

        $loan->save();

        return $loan->fresh(['user:id,name,email', 'creator:id,name']);
    }

    /**
     * 가지급금 삭제
     */
    public function destroy(int $id): bool
    {
        $tenantId = $this->tenantId();
        $userId = $this->apiUserId();

        $loan = Loan::query()
            ->where('tenant_id', $tenantId)
            ->findOrFail($id);

        if (! $loan->isDeletable()) {
            throw new BadRequestHttpException(__('error.loan.not_deletable'));
        }

        $loan->deleted_by = $userId;
        $loan->save();
        $loan->delete();

        return true;
    }

    // =========================================================================
    // 정산 처리
    // =========================================================================

    /**
     * 가지급금 정산
     */
    public function settle(int $id, array $data): Loan
    {
        $tenantId = $this->tenantId();
        $userId = $this->apiUserId();

        return DB::transaction(function () use ($id, $data, $tenantId, $userId) {
            $loan = Loan::query()
                ->where('tenant_id', $tenantId)
                ->findOrFail($id);

            if (! $loan->isSettleable()) {
                throw new BadRequestHttpException(__('error.loan.not_settleable'));
            }

            $settlementAmount = (float) $data['settlement_amount'];
            $currentSettled = (float) ($loan->settlement_amount ?? 0);
            $totalSettled = $currentSettled + $settlementAmount;
            $loanAmount = (float) $loan->amount;

            // 정산 금액이 가지급금액을 초과하는지 확인
            if ($totalSettled > $loanAmount) {
                throw new BadRequestHttpException(__('error.loan.settlement_exceeds'));
            }

            // 상태 결정
            $status = Loan::STATUS_PARTIAL;
            if (abs($totalSettled - $loanAmount) < 0.01) { // 부동소수점 비교
                $status = Loan::STATUS_SETTLED;
            }

            $loan->settlement_date = $data['settlement_date'];
            $loan->settlement_amount = $totalSettled;
            $loan->status = $status;
            $loan->updated_by = $userId;
            $loan->save();

            return $loan->fresh(['user:id,name,email']);
        });
    }

    // =========================================================================
    // 인정이자 계산
    // =========================================================================

    /**
     * 인정이자 일괄 계산
     *
     * @param  int  $year  계산 연도
     * @param  int|null  $userId  특정 사용자 (미지정시 전체)
     */
    public function calculateInterest(int $year, ?int $userId = null): array
    {
        $tenantId = $this->tenantId();

        $query = Loan::query()
            ->where('tenant_id', $tenantId)
            ->whereIn('status', [Loan::STATUS_OUTSTANDING, Loan::STATUS_PARTIAL]);

        if ($userId) {
            $query->where('user_id', $userId);
        }

        $loans = $query->with('user:id,name,email')->get();

        $interestRate = Loan::getInterestRate($year);
        $baseDate = now()->endOfYear()->year === $year
            ? now()
            : now()->setYear($year)->endOfYear();

        $results = [];
        $totalBalance = 0;
        $totalInterest = 0;
        $totalCorporateTax = 0;
        $totalIncomeTax = 0;
        $totalLocalTax = 0;

        foreach ($loans as $loan) {
            // 연도 내 경과일수 계산
            $startOfYear = now()->setYear($year)->startOfYear();
            $effectiveStartDate = $loan->loan_date->greaterThan($startOfYear)
                ? $loan->loan_date
                : $startOfYear;

            $elapsedDays = $effectiveStartDate->diffInDays($baseDate);
            $balance = $loan->outstanding_amount;

            $interest = $loan->calculateRecognizedInterest($elapsedDays, $year);
            $taxes = $loan->calculateTaxes($interest);

            $results[] = [
                'loan_id' => $loan->id,
                'user' => [
                    'id' => $loan->user->id,
                    'name' => $loan->user->name,
                    'email' => $loan->user->email,
                ],
                'loan_date' => $loan->loan_date->toDateString(),
                'amount' => (float) $loan->amount,
                'settlement_amount' => (float) ($loan->settlement_amount ?? 0),
                'outstanding_amount' => $balance,
                'elapsed_days' => $elapsedDays,
                'interest_rate' => $interestRate,
                'recognized_interest' => $taxes['recognized_interest'],
                'corporate_tax' => $taxes['corporate_tax'],
                'income_tax' => $taxes['income_tax'],
                'local_tax' => $taxes['local_tax'],
                'total_tax' => $taxes['total_tax'],
            ];

            $totalBalance += $balance;
            $totalInterest += $taxes['recognized_interest'];
            $totalCorporateTax += $taxes['corporate_tax'];
            $totalIncomeTax += $taxes['income_tax'];
            $totalLocalTax += $taxes['local_tax'];
        }

        return [
            'year' => $year,
            'interest_rate' => $interestRate,
            'base_date' => $baseDate->toDateString(),
            'summary' => [
                'total_balance' => round($totalBalance, 2),
                'total_recognized_interest' => round($totalInterest, 2),
                'total_corporate_tax' => round($totalCorporateTax, 2),
                'total_income_tax' => round($totalIncomeTax, 2),
                'total_local_tax' => round($totalLocalTax, 2),
                'total_tax' => round($totalCorporateTax + $totalIncomeTax + $totalLocalTax, 2),
            ],
            'details' => $results,
        ];
    }

    /**
     * 인정이자 리포트 (연도별 요약)
     */
    public function interestReport(int $year): array
    {
        $tenantId = $this->tenantId();

        // 사용자별 가지급금 집계
        $userLoans = Loan::query()
            ->where('tenant_id', $tenantId)
            ->whereYear('loan_date', '<=', $year)
            ->whereIn('status', [Loan::STATUS_OUTSTANDING, Loan::STATUS_PARTIAL])
            ->select('user_id')
            ->selectRaw('SUM(amount) as total_amount')
            ->selectRaw('SUM(COALESCE(settlement_amount, 0)) as total_settled')
            ->selectRaw('SUM(amount - COALESCE(settlement_amount, 0)) as total_outstanding')
            ->selectRaw('COUNT(*) as loan_count')
            ->groupBy('user_id')
            ->with('user:id,name,email')
            ->get();

        $interestRate = Loan::getInterestRate($year);
        $results = [];

        foreach ($userLoans as $userLoan) {
            $userInterest = $this->calculateInterest($year, $userLoan->user_id);

            $results[] = [
                'user' => [
                    'id' => $userLoan->user_id,
                    'name' => $userLoan->user?->name ?? 'Unknown',
                    'email' => $userLoan->user?->email ?? '',
                ],
                'loan_count' => $userLoan->loan_count,
                'total_amount' => (float) $userLoan->total_amount,
                'total_settled' => (float) $userLoan->total_settled,
                'total_outstanding' => (float) $userLoan->total_outstanding,
                'recognized_interest' => $userInterest['summary']['total_recognized_interest'],
                'total_tax' => $userInterest['summary']['total_tax'],
            ];
        }

        // 전체 합계
        $grandTotal = [
            'total_amount' => array_sum(array_column($results, 'total_amount')),
            'total_outstanding' => array_sum(array_column($results, 'total_outstanding')),
            'recognized_interest' => array_sum(array_column($results, 'recognized_interest')),
            'total_tax' => array_sum(array_column($results, 'total_tax')),
        ];

        return [
            'year' => $year,
            'interest_rate' => $interestRate,
            'users' => $results,
            'grand_total' => $grandTotal,
        ];
    }
}