<?php

namespace App\Libraries;

use App\Models\AdditionalChargeModel;

class InvoiceAdjustmentService
{
    private \CodeIgniter\Database\BaseConnection $db;
    private AdditionalChargeModel $additionalChargeModel;
    private InvoiceLedgerService $invoiceLedgerService;

    public function __construct(
        ?\CodeIgniter\Database\BaseConnection $db = null,
        ?AdditionalChargeModel $additionalChargeModel = null,
        $invoiceLineModel = null,
        ?InvoiceLedgerService $invoiceLedgerService = null
    ) {
        $this->db = $db ?? db_connect();
        $this->additionalChargeModel = $additionalChargeModel ?? new AdditionalChargeModel();
        $this->invoiceLedgerService = $invoiceLedgerService ?? new InvoiceLedgerService();
    }

    public function applyAdditionalCharge(int $chargeId, int $invoiceId, int $actorId): InvoiceLedgerResult
    {
        $this->db->transBegin();

        try {
            $charge = $this->lockCharge($chargeId);
            $invoice = $this->lockInvoice($invoiceId);

            $this->assertInvoiceAcceptsAdjustment($invoice);
            $this->assertChargeMatchesInvoice($charge, $invoice);
            if ((string)($charge['status'] ?? '') !== FinancialStatus::ADDITIONAL_CHARGE_APPROVED) {
                throw new \RuntimeException('Only approved charges can be applied.');
            }

            $amountCents = $this->signedChargeAmountCents($charge);
            if ($amountCents === 0) {
                throw new \RuntimeException('Zero amount additional charges cannot be applied.');
            }

            $now = utc_now();
            $this->requireWrite($this->additionalChargeModel->update($chargeId, [
                'status' => FinancialStatus::ADDITIONAL_CHARGE_APPLIED,
                'invoice_id' => $invoiceId,
                'parent_id' => (int)$invoice['parent_id'],
                'school_year' => (string)$invoice['school_year'],
                'semester' => (string)($invoice['semester'] ?? ''),
                'applied_invoice_line_id' => null,
                'applied_by' => $actorId > 0 ? $actorId : null,
                'applied_at' => $now,
            ]), 'ADDITIONAL_CHARGE_APPLY_UPDATE_FAILED', $this->additionalChargeModel);

            $ledger = $this->invoiceLedgerService->recalculateInvoice($invoiceId);
            $this->requireTransactionStatus();
            $this->db->transCommit();

            return new InvoiceLedgerResult($invoiceId, 0, $ledger);
        } catch (\Throwable $e) {
            $this->db->transRollback();
            throw $e;
        }
    }

    public function reverseAdditionalCharge(int $chargeId, string $reason, int $actorId): InvoiceLedgerResult
    {
        $reason = trim($reason);
        if ($reason === '') {
            throw new \RuntimeException('Reversal reason is required.');
        }

        $this->db->transBegin();

        try {
            $charge = $this->lockCharge($chargeId);
            if ((string)($charge['status'] ?? '') !== FinancialStatus::ADDITIONAL_CHARGE_APPLIED) {
                throw new \RuntimeException('Only applied charges can be reversed.');
            }

            $invoiceId = (int)($charge['invoice_id'] ?? 0);
            $invoice = $this->lockInvoice($invoiceId);
            $this->assertInvoiceAcceptsAdjustment($invoice);

            if ($this->signedChargeAmountCents($charge) === 0) {
                throw new \RuntimeException('Zero amount additional charges cannot be reversed.');
            }

            $now = utc_now();
            $this->requireWrite($this->additionalChargeModel->update($chargeId, [
                'status' => 'reversed',
                'voided_by' => $actorId > 0 ? $actorId : null,
                'voided_at' => $now,
                'void_reason' => $reason,
            ]), 'ADDITIONAL_CHARGE_REVERSE_UPDATE_FAILED', $this->additionalChargeModel);

            $ledger = $this->invoiceLedgerService->recalculateInvoice($invoiceId);
            $this->requireTransactionStatus();
            $this->db->transCommit();

            return new InvoiceLedgerResult($invoiceId, 0, $ledger);
        } catch (\Throwable $e) {
            $this->db->transRollback();
            throw $e;
        }
    }

    private function lockCharge(int $chargeId): array
    {
        $charge = $this->db->query('SELECT * FROM additional_charges WHERE id = ? FOR UPDATE', [$chargeId])->getRowArray();
        if (!$charge) {
            throw new \RuntimeException('Additional charge not found.');
        }

        return $charge;
    }

    private function lockInvoice(int $invoiceId): array
    {
        $invoice = $this->db->query('SELECT * FROM invoices WHERE id = ? FOR UPDATE', [$invoiceId])->getRowArray();
        if (!$invoice) {
            throw new \RuntimeException('Invoice not found.');
        }

        return $invoice;
    }

    private function assertInvoiceAcceptsAdjustment(array $invoice): void
    {
        if (FinancialStatus::normalizeInvoiceStatus($invoice['status'] ?? null) === FinancialStatus::INVOICE_VOIDED) {
            throw new \RuntimeException('Voided invoices cannot be adjusted.');
        }
    }

    private function assertChargeMatchesInvoice(array $charge, array $invoice): void
    {
        if ((int)($charge['parent_id'] ?? 0) !== (int)($invoice['parent_id'] ?? 0)) {
            throw new \RuntimeException('Charge parent does not match invoice parent.');
        }
        if ((string)($charge['school_year'] ?? '') !== (string)($invoice['school_year'] ?? '')) {
            throw new \RuntimeException('Charge school year does not match invoice school year.');
        }
        if ((string)($charge['semester'] ?? '') !== (string)($invoice['semester'] ?? '')) {
            throw new \RuntimeException('Charge semester does not match invoice semester.');
        }
    }

    private function signedChargeAmountCents(array $charge): int
    {
        $amount = (int)round(abs((float)($charge['amount'] ?? 0)) * 100);
        return (string)($charge['charge_type'] ?? 'add') === 'deduct' ? -1 * $amount : $amount;
    }

    private function chargeDescription(array $charge): string
    {
        $title = trim((string)($charge['title'] ?? 'Additional charge'));
        return $title !== '' ? $title : 'Additional charge';
    }

    private function requireWrite($result, string $code, $model = null): void
    {
        if ($result === false || $result === null || $result === 0) {
            $details = is_object($model) && method_exists($model, 'errors') ? (array)$model->errors() : [];
            throw new FinancialPersistenceException($code, $details);
        }
    }

    private function requireTransactionStatus(string $code = 'TRANSACTION_FAILED'): void
    {
        if (method_exists($this->db, 'transStatus') && $this->db->transStatus() === false) {
            throw new FinancialPersistenceException($code);
        }
    }
}