<?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']);

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

        // 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, ?string $category = null): array
    {
        $tenantId = $this->tenantId();

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

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

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

        // 상품권 카테고리: holding/used/disposed 상태별 집계 추가
        $isGiftCertificate = $category === Loan::CATEGORY_GIFT_CERTIFICATE;

        $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
        ';
        $bindings = [Loan::STATUS_OUTSTANDING, Loan::STATUS_SETTLED, Loan::STATUS_PARTIAL];

        if ($isGiftCertificate) {
            $selectRaw .= ',
                SUM(CASE WHEN status = ? THEN 1 ELSE 0 END) as holding_count,
                SUM(CASE WHEN status = ? THEN amount ELSE 0 END) as holding_amount,
                SUM(CASE WHEN status = ? THEN 1 ELSE 0 END) as used_count,
                SUM(CASE WHEN status = ? THEN amount ELSE 0 END) as used_amount,
                SUM(CASE WHEN status = ? THEN 1 ELSE 0 END) as disposed_count
            ';
            $bindings = array_merge($bindings, [
                Loan::STATUS_HOLDING, Loan::STATUS_HOLDING,
                Loan::STATUS_USED, Loan::STATUS_USED,
                Loan::STATUS_DISPOSED,
            ]);
        }

        $stats = $query->selectRaw($selectRaw, $bindings)->first();

        $result = [
            '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,
        ];

        if ($isGiftCertificate) {
            $result['holding_count'] = (int) $stats->holding_count;
            $result['holding_amount'] = (float) $stats->holding_amount;
            $result['used_count'] = (int) $stats->used_count;
            $result['used_amount'] = (float) $stats->used_amount;
            $result['disposed_count'] = (int) $stats->disposed_count;
        }

        return $result;
    }

    // =========================================================================
    // 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;
            }

            // 상품권: user_id 미지정 시 현재 사용자로 대체
            $loanUserId = $data['user_id'] ?? $userId;

            // 상태 결정: 상품권은 holding, 그 외는 outstanding
            $category = $data['category'] ?? null;
            $status = $data['status']
                ?? ($category === Loan::CATEGORY_GIFT_CERTIFICATE ? Loan::STATUS_HOLDING : Loan::STATUS_OUTSTANDING);

            return Loan::create([
                'tenant_id' => $tenantId,
                'user_id' => $loanUserId,
                'loan_date' => $data['loan_date'],
                'amount' => $data['amount'],
                'purpose' => $data['purpose'] ?? null,
                'status' => $status,
                'category' => $category,
                'metadata' => $data['metadata'] ?? null,
                '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'));
            }
        }

        $fillData = [
            '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,
        ];

        if (isset($data['category'])) {
            $fillData['category'] = $data['category'];
        }
        if (array_key_exists('metadata', $data)) {
            $fillData['metadata'] = $data['metadata'];
        }
        if (isset($data['status'])) {
            $fillData['status'] = $data['status'];
        }
        if (array_key_exists('settlement_date', $data)) {
            $fillData['settlement_date'] = $data['settlement_date'];
        }

        $loan->fill($fillData);

        $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,
        ];
    }

    /**
     * 가지급금 대시보드 데이터
     *
     * CEO 대시보드 카드/가지급금 관리 섹션 데이터 제공
     * D1.7: category_breakdown 추가 (카드/경조사/상품권/접대비 분류)
     *
     * @return array{
     *     summary: array{
     *         total_outstanding: float,
     *         recognized_interest: float,
     *         outstanding_count: int
     *     },
     *     category_breakdown: array<string, array{
     *         outstanding_amount: float,
     *         total_count: int,
     *         unverified_count: int
     *     }>,
     *     loans: array
     * }
     */
    public function dashboard(?string $startDate = null, ?string $endDate = null): array
    {
        $tenantId = $this->tenantId();
        $currentYear = now()->year;

        // 날짜 필터 조건 클로저
        $applyDateFilter = function ($query) use ($startDate, $endDate) {
            if ($startDate) {
                $query->where('loan_date', '>=', $startDate);
            }
            if ($endDate) {
                $query->where('loan_date', '<=', $endDate);
            }
            return $query;
        };

        // 1. Summary 데이터 (날짜 필터 적용)
        $summaryQuery = Loan::query()->where('tenant_id', $tenantId);
        $applyDateFilter($summaryQuery);

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

        // 2. 인정이자 계산 (현재 연도 기준, 날짜 필터 무관)
        $interestData = $this->calculateInterest($currentYear);
        $recognizedInterest = $interestData['summary']['total_recognized_interest'] ?? 0;

        // 3. 카테고리별 집계 (날짜 필터 적용)
        $categoryBreakdown = $this->getCategoryBreakdown($tenantId, $startDate, $endDate);

        // 4. 가지급금 목록 (미정산 우선, 날짜 필터 적용)
        $loansQuery = Loan::query()
            ->where('tenant_id', $tenantId)
            ->with(['user:id,name,email', 'withdrawal']);
        $applyDateFilter($loansQuery);

        $loans = $loansQuery
            ->orderByRaw('CASE WHEN status = ? THEN 0 WHEN status = ? THEN 1 ELSE 2 END', [
                Loan::STATUS_OUTSTANDING,
                Loan::STATUS_PARTIAL,
            ])
            ->orderByDesc('loan_date')
            ->limit(50)
            ->get()
            ->map(function ($loan) {
                return [
                    'id' => $loan->id,
                    'loan_date' => $loan->loan_date->format('Y-m-d'),
                    'user_name' => $loan->user?->name ?? '미지정',
                    'category' => $loan->category_label,
                    'amount' => (float) $loan->amount,
                    'status' => $loan->status,
                    'content' => $loan->purpose ?? '',
                ];
            })
            ->toArray();

        return [
            'summary' => [
                'total_outstanding' => (float) ($stats->total_outstanding ?? 0),
                'recognized_interest' => (float) $recognizedInterest,
                'outstanding_count' => (int) ($stats->outstanding_count ?? 0),
            ],
            'category_breakdown' => $categoryBreakdown,
            'loans' => $loans,
        ];
    }

    /**
     * 카테고리별 가지급금 집계
     *
     * @return array<string, array{outstanding_amount: float, total_count: int, unverified_count: int}>
     */
    private function getCategoryBreakdown(int $tenantId, ?string $startDate = null, ?string $endDate = null): array
    {
        // 기본값: 4개 카테고리 모두 0으로 초기화
        $breakdown = [];
        foreach (Loan::CATEGORIES as $category) {
            $breakdown[$category] = [
                'outstanding_amount' => 0.0,
                'total_count' => 0,
                'unverified_count' => 0,
            ];
        }

        // 카테고리별 집계 (summary와 동일하게 전체 대상, 날짜 필터 적용)
        $query = Loan::query()
            ->where('tenant_id', $tenantId);

        if ($startDate) {
            $query->where('loan_date', '>=', $startDate);
        }
        if ($endDate) {
            $query->where('loan_date', '<=', $endDate);
        }

        // NOTE: SQL alias를 'cat_outstanding'으로 사용 — Loan 모델의
        // getOutstandingAmountAttribute() accessor와 이름 충돌 방지
        $stats = $query
            ->selectRaw('category, COUNT(*) as total_count, SUM(amount - COALESCE(settlement_amount, 0)) as cat_outstanding')
            ->selectRaw('SUM(CASE WHEN purpose IS NULL OR purpose = \'\' THEN 1 ELSE 0 END) as unverified_count')
            ->groupBy('category')
            ->get();

        foreach ($stats as $stat) {
            $cat = $stat->category ?? Loan::CATEGORY_CARD;
            if (isset($breakdown[$cat])) {
                $breakdown[$cat] = [
                    'outstanding_amount' => (float) $stat->cat_outstanding,
                    'total_count' => (int) $stat->total_count,
                    'unverified_count' => (int) $stat->unverified_count,
                ];
            }
        }

        return $breakdown;
    }

    /**
     * 세금 시뮬레이션 데이터
     *
     * CEO 대시보드 카드/가지급금 관리 섹션(cm2) 세금 비교 분석용 데이터 제공
     *
     * @param  int  $year  시뮬레이션 연도
     * @return array{
     *     year: int,
     *     loan_summary: array{
     *         total_outstanding: float,
     *         recognized_interest: float,
     *         interest_rate: float
     *     },
     *     corporate_tax: array{
     *         without_loan: array{taxable_income: float, tax_amount: float},
     *         with_loan: array{taxable_income: float, tax_amount: float},
     *         difference: float,
     *         rate_info: string
     *     },
     *     income_tax: array{
     *         without_loan: array{taxable_income: float, tax_rate: string, tax_amount: float},
     *         with_loan: array{taxable_income: float, tax_rate: string, tax_amount: float},
     *         difference: float,
     *         breakdown: array{income_tax: float, local_tax: float, insurance: float}
     *     }
     * }
     */
    public function taxSimulation(int $year): array
    {
        // 1. 가지급금 요약 데이터
        $summaryData = $this->summary();
        $totalOutstanding = (float) $summaryData['total_outstanding'];

        // 2. 인정이자 계산
        $interestData = $this->calculateInterest($year);
        $recognizedInterest = $interestData['summary']['total_recognized_interest'] ?? 0;
        $interestRate = Loan::getInterestRate($year);

        // 3. 법인세 비교 계산
        // - 가지급금이 없을 때: 인정이자가 비용으로 처리되지 않음
        // - 가지급금이 있을 때: 인정이자만큼 추가 과세
        $corporateTaxRate = Loan::CORPORATE_TAX_RATE;
        $corporateTaxWithout = [
            'taxable_income' => 0.0,
            'tax_amount' => 0.0,
        ];
        $corporateTaxWith = [
            'taxable_income' => $recognizedInterest,
            'tax_amount' => round($recognizedInterest * $corporateTaxRate, 2),
        ];
        $corporateTaxDifference = $corporateTaxWith['tax_amount'] - $corporateTaxWithout['tax_amount'];

        // 4. 소득세 비교 계산 (대표이사 상여처분 시)
        $incomeTaxRate = Loan::INCOME_TAX_RATE;
        $localTaxRate = Loan::LOCAL_TAX_RATE;
        $insuranceRate = 0.09; // 4대보험 약 9%

        $incomeTaxWithout = [
            'taxable_income' => 0.0,
            'tax_rate' => '0%',
            'tax_amount' => 0.0,
        ];

        $incomeTaxAmount = round($recognizedInterest * $incomeTaxRate, 2);
        $localTaxAmount = round($incomeTaxAmount * $localTaxRate, 2);
        $insuranceAmount = round($recognizedInterest * $insuranceRate, 2);

        $incomeTaxWith = [
            'taxable_income' => $recognizedInterest,
            'tax_rate' => ($incomeTaxRate * 100).'%',
            'tax_amount' => $incomeTaxAmount + $localTaxAmount,
        ];

        $incomeTaxDifference = $incomeTaxWith['tax_amount'] - $incomeTaxWithout['tax_amount'];

        return [
            'year' => $year,
            'loan_summary' => [
                'total_outstanding' => $totalOutstanding,
                'recognized_interest' => (float) $recognizedInterest,
                'interest_rate' => $interestRate,
            ],
            'corporate_tax' => [
                'without_loan' => $corporateTaxWithout,
                'with_loan' => $corporateTaxWith,
                'difference' => round($corporateTaxDifference, 2),
                'rate_info' => '법인세 '.($corporateTaxRate * 100).'% 적용',
            ],
            'income_tax' => [
                'without_loan' => $incomeTaxWithout,
                'with_loan' => $incomeTaxWith,
                'difference' => round($incomeTaxDifference, 2),
                'breakdown' => [
                    'income_tax' => $incomeTaxAmount,
                    'local_tax' => $localTaxAmount,
                    'insurance' => $insuranceAmount,
                ],
            ],
        ];
    }

    /**
     * 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,
        ];
    }
}