<?php

require_once __DIR__ . '/db.php';
require_once __DIR__ . '/account_service.php';

function add_months_keep_day(string $date, int $months, int $paymentDay): string
{
    $base = new DateTime($date);
    $base->modify('first day of this month');

    if ($months > 0) {
        $base->modify('+' . $months . ' month');
    }

    $lastDay = (int)$base->format('t');
    $day = min($paymentDay, $lastDay);
    $base->setDate((int)$base->format('Y'), (int)$base->format('m'), $day);

    return $base->format('Y-m-d');
}

function monthly_rate(float $annualRate): float
{
    return ($annualRate / 100.0) / 12.0;
}

function calc_equal_payment_monthly_amount(float $principal, float $annualRate, int $months): float
{
    if ($months <= 0) {
        return 0;
    }

    $r = monthly_rate($annualRate);

    if ($r <= 0) {
        return round($principal / $months, 2);
    }

    $payment = $principal * ($r * pow(1 + $r, $months)) / (pow(1 + $r, $months) - 1);
    return round($payment, 2);
}

function build_loan_schedule_rows(
    float $principal,
    float $annualRate,
    string $startDate,
    int $graceMonths,
    int $repaymentMonths,
    string $repaymentMethod,
    int $paymentDay
): array {
    $rows = [];
    $balance = round($principal, 2);
    $cycleNo = 1;
    $firstDueOffset = 1;

    for ($i = 0; $i < $graceMonths; $i++) {
        $dueDate = add_months_keep_day($startDate, $i + $firstDueOffset, $paymentDay);
        $interest = round($balance * monthly_rate($annualRate), 2);

        $rows[] = [
            'cycle_no' => $cycleNo++,
            'due_date' => $dueDate,
            'opening_principal' => $balance,
            'scheduled_principal' => 0.00,
            'scheduled_interest' => $interest,
            'scheduled_total' => round($interest, 2),
            'closing_principal' => $balance,
            'payment_phase' => 'grace',
        ];
    }

    $repaymentStartOffset = $graceMonths + $firstDueOffset;

    if ($repaymentMethod === 'interest_only_then_equal_payment' || $repaymentMethod === 'equal_payment') {
        $monthlyPayment = calc_equal_payment_monthly_amount($balance, $annualRate, $repaymentMonths);

        for ($i = 0; $i < $repaymentMonths; $i++) {
            $dueDate = add_months_keep_day($startDate, $repaymentStartOffset + $i, $paymentDay);
            $opening = $balance;
            $interest = round($opening * monthly_rate($annualRate), 2);
            $principalPart = round($monthlyPayment - $interest, 2);

            if ($i === $repaymentMonths - 1 || $principalPart > $balance) {
                $principalPart = $balance;
            }

            $total = round($principalPart + $interest, 2);
            $balance = round($balance - $principalPart, 2);

            $rows[] = [
                'cycle_no' => $cycleNo++,
                'due_date' => $dueDate,
                'opening_principal' => $opening,
                'scheduled_principal' => $principalPart,
                'scheduled_interest' => $interest,
                'scheduled_total' => $total,
                'closing_principal' => $balance,
                'payment_phase' => 'repayment',
            ];
        }
    } elseif ($repaymentMethod === 'interest_only_then_equal_principal' || $repaymentMethod === 'equal_principal') {
        $principalBase = round($balance / $repaymentMonths, 2);

        for ($i = 0; $i < $repaymentMonths; $i++) {
            $dueDate = add_months_keep_day($startDate, $repaymentStartOffset + $i, $paymentDay);
            $opening = $balance;
            $interest = round($opening * monthly_rate($annualRate), 2);

            $principalPart = $principalBase;
            if ($i === $repaymentMonths - 1 || $principalPart > $balance) {
                $principalPart = $balance;
            }

            $total = round($principalPart + $interest, 2);
            $balance = round($balance - $principalPart, 2);

            $rows[] = [
                'cycle_no' => $cycleNo++,
                'due_date' => $dueDate,
                'opening_principal' => $opening,
                'scheduled_principal' => $principalPart,
                'scheduled_interest' => $interest,
                'scheduled_total' => $total,
                'closing_principal' => $balance,
                'payment_phase' => 'repayment',
            ];
        }
    } elseif ($repaymentMethod === 'interest_only_then_bullet' || $repaymentMethod === 'bullet') {
        for ($i = 0; $i < $repaymentMonths; $i++) {
            $dueDate = add_months_keep_day($startDate, $repaymentStartOffset + $i, $paymentDay);
            $opening = $balance;
            $interest = round($opening * monthly_rate($annualRate), 2);

            $principalPart = 0.00;
            if ($i === $repaymentMonths - 1) {
                $principalPart = $balance;
            }

            $total = round($principalPart + $interest, 2);
            $balance = round($balance - $principalPart, 2);

            $rows[] = [
                'cycle_no' => $cycleNo++,
                'due_date' => $dueDate,
                'opening_principal' => $opening,
                'scheduled_principal' => $principalPart,
                'scheduled_interest' => $interest,
                'scheduled_total' => $total,
                'closing_principal' => $balance,
                'payment_phase' => 'repayment',
            ];
        }
    } else {
        throw new RuntimeException('지원하지 않는 상환 방식입니다.');
    }

    return $rows;
}

function get_category_id_by_name(int $userId, string $categoryType, string $name): ?int
{
    $pdo = db();

    $stmt = $pdo->prepare("
        SELECT id
        FROM categories
        WHERE user_id = ?
          AND category_type = ?
          AND name = ?
        LIMIT 1
    ");
    $stmt->execute([$userId, $categoryType, $name]);
    $row = $stmt->fetch();

    return $row ? (int)$row['id'] : null;
}

function build_tx_fingerprint(
    int $userId,
    int $accountId,
    ?int $relatedAccountId,
    int $categoryId,
    string $transactionType,
    float $amount,
    string $transactionDate,
    ?string $merchantName,
    ?string $description,
    ?int $sourceLoanId = null
): string {
    $raw = implode('|', [
        $userId,
        $accountId,
        $relatedAccountId ?? 0,
        $categoryId,
        $transactionType,
        number_format($amount, 2, '.', ''),
        $transactionDate,
        trim((string)$merchantName),
        trim((string)$description),
        $sourceLoanId ?? 0,
    ]);

    return hash('sha256', $raw);
}

function insert_transaction_row(array $data): int
{
    $pdo = db();

    $sourceLoanId = !empty($data['source_loan_id']) ? (int)$data['source_loan_id'] : null;

    $fingerprint = build_tx_fingerprint(
        (int)$data['user_id'],
        (int)$data['account_id'],
        !empty($data['related_account_id']) ? (int)$data['related_account_id'] : null,
        (int)$data['category_id'],
        (string)$data['transaction_type'],
        (float)$data['amount'],
        (string)$data['transaction_date'],
        $data['merchant_name'] ?? null,
        $data['description'] ?? null,
        $sourceLoanId
    );

    $stmt = $pdo->prepare("
        SELECT id
        FROM transactions
        WHERE user_id = ?
          AND fingerprint = ?
        LIMIT 1
    ");
    $stmt->execute([
        $data['user_id'],
        $fingerprint
    ]);
    $exists = $stmt->fetch();

    if ($exists) {
        return (int)$exists['id'];
    }

    $stmt = $pdo->prepare("
        INSERT INTO transactions
        (
            user_id,
            account_id,
            category_id,
            transaction_type,
            amount,
            is_installment,
            installment_months,
            installment_interest_rate,
            installment_interest_total,
            installment_total_billed,
            installment_prepay_amount,
            transaction_date,
            merchant_name,
            description,
            related_account_id,
            source_loan_id,
            fingerprint
        )
        VALUES (?, ?, ?, ?, ?, 0, NULL, 0, 0, NULL, 0, ?, ?, ?, ?, ?, ?)
    ");

    $stmt->execute([
        $data['user_id'],
        $data['account_id'],
        $data['category_id'],
        $data['transaction_type'],
        $data['amount'],
        $data['transaction_date'],
        $data['merchant_name'],
        $data['description'],
        $data['related_account_id'],
        $sourceLoanId,
        $fingerprint,
    ]);

    return (int)$pdo->lastInsertId();
}

function create_loan_schedule_only(
    int $loanId,
    float $principalAmount,
    float $annualInterestRate,
    string $startDate,
    int $graceMonths,
    int $repaymentMonths,
    string $repaymentMethod,
    int $paymentDay
): void {
    $pdo = db();

    $rows = build_loan_schedule_rows(
        $principalAmount,
        $annualInterestRate,
        $startDate,
        $graceMonths,
        $repaymentMonths,
        $repaymentMethod,
        $paymentDay
    );

    $stmt = $pdo->prepare("
        INSERT INTO loan_schedules
        (
            loan_id, cycle_no, due_date,
            opening_principal, scheduled_principal, scheduled_interest, scheduled_total,
            closing_principal, payment_phase, is_paid, paid_at
        )
        VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, 0, NULL)
    ");

    foreach ($rows as $row) {
        $stmt->execute([
            $loanId,
            $row['cycle_no'],
            $row['due_date'],
            $row['opening_principal'],
            $row['scheduled_principal'],
            $row['scheduled_interest'],
            $row['scheduled_total'],
            $row['closing_principal'],
            $row['payment_phase'],
        ]);
    }
}

function create_loan_with_schedule(array $data): int
{
    $pdo = db();
    $pdo->beginTransaction();

    try {
        $stmt = $pdo->prepare("
            INSERT INTO loans
            (
                user_id, account_id, loan_name, lender_name,
                principal_amount, annual_interest_rate,
                start_date, maturity_date,
                grace_period_months, repayment_months, repayment_method,
                payment_day, current_principal_balance, status, description
            )
            VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, 'active', ?)
        ");

        $stmt->execute([
            $data['user_id'],
            $data['account_id'] ?: null,
            $data['loan_name'],
            $data['lender_name'] ?: null,
            $data['principal_amount'],
            $data['annual_interest_rate'],
            $data['start_date'],
            $data['maturity_date'] ?: null,
            $data['grace_period_months'],
            $data['repayment_months'],
            $data['repayment_method'],
            $data['payment_day'],
            $data['principal_amount'],
            $data['description'] ?: null,
        ]);

        $loanId = (int)$pdo->lastInsertId();

        create_loan_schedule_only(
            $loanId,
            (float)$data['principal_amount'],
            (float)$data['annual_interest_rate'],
            (string)$data['start_date'],
            (int)$data['grace_period_months'],
            (int)$data['repayment_months'],
            (string)$data['repayment_method'],
            (int)$data['payment_day']
        );

        $pdo->commit();
        return $loanId;
    } catch (Throwable $e) {
        $pdo->rollBack();
        throw $e;
    }
}

function backfill_loan_transactions_and_mark_paid(
    int $userId,
    int $loanId,
    ?int $accountId,
    string $todayDate
): void {
    $pdo = db();
    $pdo->beginTransaction();

    try {
        $stmt = $pdo->prepare("
            SELECT *
            FROM loans
            WHERE id = ?
              AND user_id = ?
            LIMIT 1
        ");
        $stmt->execute([$loanId, $userId]);
        $loan = $stmt->fetch();

        if (!$loan) {
            throw new RuntimeException('대출 정보를 찾을 수 없습니다.');
        }

        if (empty($accountId)) {
            throw new RuntimeException('과거 거래 일괄 생성에는 입출금 계좌가 필요합니다.');
        }

        $incomeCategoryId = get_category_id_by_name($userId, 'income', '대출금');
        if (!$incomeCategoryId) {
            throw new RuntimeException('income 카테고리 "대출금"이 없습니다.');
        }

        $expenseCategoryId = get_category_id_by_name($userId, 'expense', '대출상환');
        if (!$expenseCategoryId) {
            throw new RuntimeException('expense 카테고리 "대출상환"이 없습니다.');
        }

		insert_transaction_row([
			'user_id' => $userId,
			'account_id' => $accountId,
			'category_id' => $incomeCategoryId,
			'transaction_type' => 'income',
			'amount' => (float)$loan['principal_amount'],
			'transaction_date' => $loan['start_date'],
			'merchant_name' => $loan['loan_name'],
			'description' => '[대출실행] ' . ($loan['lender_name'] ?: $loan['loan_name']),
			'related_account_id' => null,
			'source_loan_id' => $loanId,
		]);

        $stmt = $pdo->prepare("
            SELECT *
            FROM loan_schedules
            WHERE loan_id = ?
              AND due_date <= ?
            ORDER BY due_date ASC, cycle_no ASC
        ");
        $stmt->execute([$loanId, $todayDate]);
        $pastSchedules = $stmt->fetchAll();

        foreach ($pastSchedules as $schedule) {
            if ((int)$schedule['is_paid'] === 1) {
                continue;
            }

            $principal = (float)$schedule['scheduled_principal'];
            $interest = (float)$schedule['scheduled_interest'];
            $total = (float)$schedule['scheduled_total'];

            $stmt2 = $pdo->prepare("
                INSERT INTO loan_payments
                (
                    user_id, loan_id, loan_schedule_id, account_id,
                    payment_date, principal_amount, interest_amount, fee_amount,
                    total_amount, payment_type, is_auto_generated, description
                )
                VALUES (?, ?, ?, ?, ?, ?, ?, 0, ?, 'scheduled', 1, ?)
            ");
            $stmt2->execute([
                $userId,
                $loanId,
                $schedule['id'],
                $accountId,
                $schedule['due_date'],
                $principal,
                $interest,
                $total,
                '[자동반영] 대출 상환 회차 ' . $schedule['cycle_no'],
            ]);

			insert_transaction_row([
				'user_id' => $userId,
				'account_id' => $accountId,
				'category_id' => $expenseCategoryId,
				'transaction_type' => 'expense',
				'amount' => $total,
				'transaction_date' => $schedule['due_date'],
				'merchant_name' => $loan['loan_name'],
				'description' => '[대출상환] 원금 ' . number_format($principal, 0) . ' / 이자 ' . number_format($interest, 0),
				'related_account_id' => null,
				'source_loan_id' => $loanId,
			]);

            $stmt2 = $pdo->prepare("
                UPDATE loan_schedules
                SET is_paid = 1, paid_at = NOW()
                WHERE id = ?
            ");
            $stmt2->execute([$schedule['id']]);
        }

        $stmt = $pdo->prepare("
            SELECT
                COALESCE(SUM(CASE WHEN is_paid = 0 THEN scheduled_principal ELSE 0 END), 0) AS remaining_principal
            FROM loan_schedules
            WHERE loan_id = ?
        ");
        $stmt->execute([$loanId]);
        $remaining = $stmt->fetch();

        $remainingPrincipal = (float)($remaining['remaining_principal'] ?? 0);

        $stmt = $pdo->prepare("
            UPDATE loans
            SET
                current_principal_balance = ?,
                status = CASE WHEN ? <= 0.009 THEN 'closed' ELSE 'active' END
            WHERE id = ?
        ");
        $stmt->execute([$remainingPrincipal, $remainingPrincipal, $loanId]);

        $pdo->commit();
        recalculate_account_balance($accountId);
    } catch (Throwable $e) {
        $pdo->rollBack();
        throw $e;
    }
}

function create_loan_with_full_backfill(array $data): int
{
    $loanId = create_loan_with_schedule($data);

    if (!empty($data['create_full_history'])) {
        backfill_loan_transactions_and_mark_paid(
            (int)$data['user_id'],
            $loanId,
            !empty($data['account_id']) ? (int)$data['account_id'] : null,
            $data['today_date'] ?? date('Y-m-d')
        );
    }

    return $loanId;
}

function reset_loan_auto_history_and_reapply(
    int $userId,
    int $loanId,
    string $todayDate
): void {
    $pdo = db();
    $pdo->beginTransaction();

    try {
        $stmt = $pdo->prepare("
            SELECT *
            FROM loans
            WHERE id = ?
              AND user_id = ?
            LIMIT 1
        ");
        $stmt->execute([$loanId, $userId]);
        $loan = $stmt->fetch();

        if (!$loan) {
            throw new RuntimeException('대출 정보를 찾을 수 없습니다.');
        }

        if (empty($loan['account_id'])) {
            throw new RuntimeException('연결된 입출금 계좌가 없어 자동반영 리셋을 할 수 없습니다.');
        }

        // 자동 생성 거래 삭제
		$stmt = $pdo->prepare("
			DELETE FROM transactions
			WHERE user_id = ?
			AND source_loan_id = ?
		");
		$stmt->execute([$userId, $loanId]);

        // 자동반영 payment 삭제
        $stmt = $pdo->prepare("
            DELETE FROM loan_payments
            WHERE user_id = ?
              AND loan_id = ?
              AND is_auto_generated = 1
        ");
        $stmt->execute([$userId, $loanId]);

        // 스케줄 초기화
        $stmt = $pdo->prepare("DELETE FROM loan_schedules WHERE loan_id = ?");
        $stmt->execute([$loanId]);

        // 원금/상태 초기화
        $stmt = $pdo->prepare("
            UPDATE loans
            SET
                current_principal_balance = principal_amount,
                status = 'active'
            WHERE id = ?
        ");
        $stmt->execute([$loanId]);

        // 초기 스케줄 재생성
        create_loan_schedule_only(
            $loanId,
            (float)$loan['principal_amount'],
            (float)$loan['annual_interest_rate'],
            (string)$loan['start_date'],
            (int)$loan['grace_period_months'],
            (int)$loan['repayment_months'],
            (string)$loan['repayment_method'],
            (int)$loan['payment_day']
        );

        $pdo->commit();

        // 다시 자동반영 적용
        backfill_loan_transactions_and_mark_paid(
            $userId,
            $loanId,
            (int)$loan['account_id'],
            $todayDate
        );
    } catch (Throwable $e) {
        $pdo->rollBack();
        throw $e;
    }
}

function get_loan_remaining_summary(int $loanId): array
{
    $pdo = db();

    $stmt = $pdo->prepare("
        SELECT
            COALESCE(SUM(CASE WHEN is_paid = 0 THEN scheduled_principal ELSE 0 END), 0) AS remaining_principal,
            COALESCE(SUM(CASE WHEN is_paid = 0 THEN scheduled_interest ELSE 0 END), 0) AS remaining_interest,
            COALESCE(SUM(CASE WHEN is_paid = 0 THEN scheduled_total ELSE 0 END), 0) AS remaining_total
        FROM loan_schedules
        WHERE loan_id = ?
    ");
    $stmt->execute([$loanId]);
    $row = $stmt->fetch();

    return [
        'remaining_principal' => (float)($row['remaining_principal'] ?? 0),
        'remaining_interest' => (float)($row['remaining_interest'] ?? 0),
        'remaining_total' => (float)($row['remaining_total'] ?? 0),
    ];
}

function pay_loan_schedule(
    int $userId,
    int $loanScheduleId,
    ?int $accountId,
    string $paymentDate,
    ?string $description = null
): void {
    $pdo = db();
    $pdo->beginTransaction();

    try {
        $stmt = $pdo->prepare("
            SELECT
                ls.*,
                l.user_id,
                l.id AS loan_id,
                l.loan_name
            FROM loan_schedules ls
            JOIN loans l ON l.id = ls.loan_id
            WHERE ls.id = ?
              AND l.user_id = ?
        ");
        $stmt->execute([$loanScheduleId, $userId]);
        $schedule = $stmt->fetch();

        if (!$schedule) {
            throw new RuntimeException('상환 회차를 찾을 수 없습니다.');
        }

        if ((int)$schedule['is_paid'] === 1) {
            throw new RuntimeException('이미 납부된 회차입니다.');
        }

        $principal = (float)$schedule['scheduled_principal'];
        $interest = (float)$schedule['scheduled_interest'];
        $total = (float)$schedule['scheduled_total'];

        $stmt = $pdo->prepare("
            INSERT INTO loan_payments
            (
                user_id, loan_id, loan_schedule_id, account_id,
                payment_date, principal_amount, interest_amount, fee_amount,
                total_amount, payment_type, is_auto_generated, description
            )
            VALUES (?, ?, ?, ?, ?, ?, ?, 0, ?, 'scheduled', 0, ?)
        ");
        $stmt->execute([
            $userId,
            $schedule['loan_id'],
            $loanScheduleId,
            $accountId ?: null,
            $paymentDate,
            $principal,
            $interest,
            $total,
            $description,
        ]);

        if (!empty($accountId) && $total > 0) {
            $expenseCategoryId = get_category_id_by_name($userId, 'expense', '대출상환');

            if ($expenseCategoryId) {
                insert_transaction_row([
                    'user_id' => $userId,
                    'account_id' => $accountId,
                    'category_id' => $expenseCategoryId,
                    'transaction_type' => 'expense',
                    'amount' => $total,
                    'transaction_date' => $paymentDate,
                    'merchant_name' => $schedule['loan_name'],
                    'description' => '[대출상환] 원금 ' .
                        number_format($principal, 0) .
                        ' / 이자 ' .
                        number_format($interest, 0),
                    'related_account_id' => null,
                    'source_loan_id' => $schedule['loan_id'],
                ]);
            }
        }

        $stmt = $pdo->prepare("
            UPDATE loan_schedules
            SET is_paid = 1, paid_at = NOW()
            WHERE id = ?
        ");
        $stmt->execute([$loanScheduleId]);

        $stmt = $pdo->prepare("
            UPDATE loans
            SET current_principal_balance = GREATEST(current_principal_balance - ?, 0)
            WHERE id = ?
        ");
        $stmt->execute([$principal, $schedule['loan_id']]);

        $stmt = $pdo->prepare("
            SELECT current_principal_balance
            FROM loans
            WHERE id = ?
        ");
        $stmt->execute([$schedule['loan_id']]);
        $loan = $stmt->fetch();

        if ($loan && (float)$loan['current_principal_balance'] <= 0.009) {
            $stmt = $pdo->prepare("UPDATE loans SET status = 'closed' WHERE id = ?");
            $stmt->execute([$schedule['loan_id']]);
        }

        $pdo->commit();

        if (!empty($accountId)) {
            recalculate_account_balance((int)$accountId);
        }
    } catch (Throwable $e) {
        $pdo->rollBack();
        throw $e;
    }
}

function rebuild_remaining_loan_schedules(int $loanId): void
{
    $pdo = db();
    $pdo->beginTransaction();

    try {
        $stmt = $pdo->prepare("
            SELECT *
            FROM loans
            WHERE id = ?
            LIMIT 1
        ");
        $stmt->execute([$loanId]);
        $loan = $stmt->fetch();

        if (!$loan) {
            throw new RuntimeException('대출 정보를 찾을 수 없습니다.');
        }

        $stmt = $pdo->prepare("
            SELECT *
            FROM loan_schedules
            WHERE loan_id = ?
              AND is_paid = 0
            ORDER BY cycle_no ASC
        ");
        $stmt->execute([$loanId]);
        $remaining = $stmt->fetchAll();

        if (!$remaining) {
            $stmt = $pdo->prepare("UPDATE loans SET status = 'closed', current_principal_balance = 0 WHERE id = ?");
            $stmt->execute([$loanId]);
            $pdo->commit();
            return;
        }

        $remainingMonths = count($remaining);
        $firstUnpaid = $remaining[0];
        $newStartDate = $firstUnpaid['due_date'];

        if ($firstUnpaid['payment_phase'] === 'grace') {
            $graceCount = 0;
            foreach ($remaining as $r) {
                if ($r['payment_phase'] === 'grace') {
                    $graceCount++;
                } else {
                    break;
                }
            }
            $graceMonths = $graceCount;
            $repaymentMonths = $remainingMonths - $graceMonths;
        } else {
            $graceMonths = 0;
            $repaymentMonths = $remainingMonths;
        }

        $stmt = $pdo->prepare("
            DELETE FROM loan_schedules
            WHERE loan_id = ?
              AND is_paid = 0
        ");
        $stmt->execute([$loanId]);

        $rows = build_loan_schedule_rows(
            (float)$loan['current_principal_balance'],
            (float)$loan['annual_interest_rate'],
            $newStartDate,
            $graceMonths,
            $repaymentMonths,
            (string)$loan['repayment_method'],
            (int)$loan['payment_day']
        );

        $maxPaidCycleStmt = $pdo->prepare("
            SELECT COALESCE(MAX(cycle_no), 0) AS max_cycle
            FROM loan_schedules
            WHERE loan_id = ?
              AND is_paid = 1
        ");
        $maxPaidCycleStmt->execute([$loanId]);
        $maxPaidCycle = (int)($maxPaidCycleStmt->fetch()['max_cycle'] ?? 0);

        $stmt = $pdo->prepare("
            INSERT INTO loan_schedules
            (
                loan_id, cycle_no, due_date,
                opening_principal, scheduled_principal, scheduled_interest, scheduled_total,
                closing_principal, payment_phase, is_paid, paid_at
            )
            VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, 0, NULL)
        ");

        foreach ($rows as $row) {
            $stmt->execute([
                $loanId,
                $maxPaidCycle + (int)$row['cycle_no'],
                $row['due_date'],
                $row['opening_principal'],
                $row['scheduled_principal'],
                $row['scheduled_interest'],
                $row['scheduled_total'],
                $row['closing_principal'],
                $row['payment_phase'],
            ]);
        }

        $pdo->commit();
    } catch (Throwable $e) {
        $pdo->rollBack();
        throw $e;
    }
}

function prepay_loan(
    int $userId,
    int $loanId,
    ?int $accountId,
    string $paymentDate,
    float $principalAmount,
    float $interestAmount = 0.0,
    float $feeAmount = 0.0,
    ?string $description = null
): void {
    $pdo = db();
    $pdo->beginTransaction();

    try {
        $stmt = $pdo->prepare("
            SELECT *
            FROM loans
            WHERE id = ?
              AND user_id = ?
        ");
        $stmt->execute([$loanId, $userId]);
        $loan = $stmt->fetch();

        if (!$loan) {
            throw new RuntimeException('대출 정보를 찾을 수 없습니다.');
        }

        $principalAmount = round($principalAmount, 2);
        $interestAmount = round($interestAmount, 2);
        $feeAmount = round($feeAmount, 2);

        if ($principalAmount <= 0 && $interestAmount <= 0 && $feeAmount <= 0) {
            throw new RuntimeException('중도상환 금액이 0보다 커야 합니다.');
        }

        if ($principalAmount > (float)$loan['current_principal_balance']) {
            throw new RuntimeException('중도상환 원금이 남은 원금을 초과합니다.');
        }

        $totalAmount = round($principalAmount + $interestAmount + $feeAmount, 2);

        $stmt = $pdo->prepare("
            INSERT INTO loan_payments
            (
                user_id, loan_id, loan_schedule_id, account_id,
                payment_date, principal_amount, interest_amount, fee_amount,
                total_amount, payment_type, is_auto_generated, description
            )
            VALUES (?, ?, NULL, ?, ?, ?, ?, ?, ?, 'prepayment', 0, ?)
        ");
        $stmt->execute([
            $userId,
            $loanId,
            $accountId ?: null,
            $paymentDate,
            $principalAmount,
            $interestAmount,
            $feeAmount,
            $totalAmount,
            $description,
        ]);

        if ($principalAmount > 0) {
            $stmt = $pdo->prepare("
                UPDATE loans
                SET current_principal_balance = GREATEST(current_principal_balance - ?, 0)
                WHERE id = ?
            ");
            $stmt->execute([$principalAmount, $loanId]);
        }

        $stmt = $pdo->prepare("
            SELECT current_principal_balance
            FROM loans
            WHERE id = ?
        ");
        $stmt->execute([$loanId]);
        $updatedLoan = $stmt->fetch();

        if ((float)$updatedLoan['current_principal_balance'] <= 0.009) {
            $stmt = $pdo->prepare("UPDATE loans SET current_principal_balance = 0, status = 'closed' WHERE id = ?");
            $stmt->execute([$loanId]);

            $stmt = $pdo->prepare("
                DELETE FROM loan_schedules
                WHERE loan_id = ?
                  AND is_paid = 0
            ");
            $stmt->execute([$loanId]);
        } else {
            $pdo->commit();
            rebuild_remaining_loan_schedules($loanId);
            $pdo = db();
            $pdo->beginTransaction();
        }

        $pdo->commit();

        if (!empty($accountId)) {
            recalculate_account_balance((int)$accountId);
        }
    } catch (Throwable $e) {
        $pdo->rollBack();
        throw $e;
    }
}

function delete_loan_with_history(int $userId, int $loanId): void
{
    $pdo = db();
    $pdo->beginTransaction();

    try {
        $stmt = $pdo->prepare("
            SELECT *
            FROM loans
            WHERE id = ?
              AND user_id = ?
            LIMIT 1
        ");
        $stmt->execute([$loanId, $userId]);
        $loan = $stmt->fetch();

        if (!$loan) {
            throw new RuntimeException('대출 정보를 찾을 수 없습니다.');
        }

		$stmt = $pdo->prepare("
			DELETE FROM transactions
			WHERE user_id = ?
			AND source_loan_id = ?
		");
		$stmt->execute([$userId, $loanId]);

        $stmt = $pdo->prepare("
            DELETE FROM loans
            WHERE id = ?
              AND user_id = ?
        ");
        $stmt->execute([$loanId, $userId]);

        $pdo->commit();

        if (!empty($loan['account_id'])) {
            recalculate_account_balance((int)$loan['account_id']);
        }
    } catch (Throwable $e) {
        $pdo->rollBack();
        throw $e;
    }
}

function update_loan_and_rebuild_full_history(int $userId, int $loanId, array $data): void
{
    $pdo = db();
    $pdo->beginTransaction();

    try {
        $stmt = $pdo->prepare("
            SELECT *
            FROM loans
            WHERE id = ?
              AND user_id = ?
            LIMIT 1
        ");
        $stmt->execute([$loanId, $userId]);
        $oldLoan = $stmt->fetch();

        if (!$oldLoan) {
            throw new RuntimeException('대출 정보를 찾을 수 없습니다.');
        }

        if (!empty($data['create_full_history']) && empty($data['account_id'])) {
            throw new RuntimeException('완전 반영 방식을 사용할 때는 입출금 계좌를 선택하세요.');
        }

        $oldAccountId = !empty($oldLoan['account_id']) ? (int)$oldLoan['account_id'] : 0;
        $newAccountId = !empty($data['account_id']) ? (int)$data['account_id'] : 0;

        // 기존 자동 생성 거래/납부/스케줄 제거
        $stmt = $pdo->prepare("
            DELETE FROM transactions
            WHERE user_id = ?
              AND source_loan_id = ?
        ");
        $stmt->execute([$userId, $loanId]);

        $stmt = $pdo->prepare("
            DELETE FROM loan_payments
            WHERE loan_id = ?
        ");
        $stmt->execute([$loanId]);

        $stmt = $pdo->prepare("
            DELETE FROM loan_schedules
            WHERE loan_id = ?
        ");
        $stmt->execute([$loanId]);

        // 대출 기본정보 수정
        $stmt = $pdo->prepare("
            UPDATE loans
            SET
                account_id = ?,
                loan_name = ?,
                lender_name = ?,
                principal_amount = ?,
                annual_interest_rate = ?,
                start_date = ?,
                maturity_date = NULL,
                grace_period_months = ?,
                repayment_months = ?,
                repayment_method = ?,
                payment_day = ?,
                current_principal_balance = ?,
                status = 'active',
                description = ?,
                updated_at = NOW()
            WHERE id = ?
              AND user_id = ?
        ");
        $stmt->execute([
            $newAccountId ?: null,
            $data['loan_name'],
            $data['lender_name'] ?: null,
            $data['principal_amount'],
            $data['annual_interest_rate'],
            $data['start_date'],
            $data['grace_period_months'],
            $data['repayment_months'],
            $data['repayment_method'],
            $data['payment_day'],
            $data['principal_amount'],
            $data['description'] ?: null,
            $loanId,
            $userId
        ]);

        // 새 스케줄 생성
        create_loan_schedule_only(
            $loanId,
            (float)$data['principal_amount'],
            (float)$data['annual_interest_rate'],
            (string)$data['start_date'],
            (int)$data['grace_period_months'],
            (int)$data['repayment_months'],
            (string)$data['repayment_method'],
            (int)$data['payment_day']
        );

        $pdo->commit();

        if (!empty($data['create_full_history'])) {
            backfill_loan_transactions_and_mark_paid(
                $userId,
                $loanId,
                $newAccountId ?: null,
                $data['today_date'] ?? date('Y-m-d')
            );
        }

        if ($oldAccountId > 0) {
            recalculate_account_balance($oldAccountId);
        }
        if ($newAccountId > 0 && $newAccountId !== $oldAccountId) {
            recalculate_account_balance($newAccountId);
        }
    } catch (Throwable $e) {
        if ($pdo->inTransaction()) {
            $pdo->rollBack();
        }
        throw $e;
    }
}