<?php

namespace App\Http\Controllers\Api;

use App\Models\Configuration;
use App\Models\FamilyGuardian;
use App\Models\Invoice;
use App\Models\Payment;
use App\Models\PaymentNotificationLog;
use App\Models\User;
use App\Services\EmailService;
use Illuminate\Http\JsonResponse;
use Illuminate\Support\Facades\DB;
use Illuminate\Support\Facades\Log;
use Symfony\Component\HttpFoundation\Response;

class PaymentNotificationController extends BaseApiController
{
    protected PaymentNotificationLog $log;
    protected User $user;
    protected Configuration $config;
    protected Invoice $invoice;
    protected Payment $payment;
    protected FamilyGuardian $familyGuardian;
    protected EmailService $emailService;

    public function __construct()
    {
        parent::__construct();
        $this->log = model(PaymentNotificationLog::class);
        $this->user = model(User::class);
        $this->config = model(Configuration::class);
        $this->invoice = model(Invoice::class);
        $this->payment = model(Payment::class);
        $this->familyGuardian = model(FamilyGuardian::class);
        $this->emailService = app(EmailService::class);
    }

    /**
     * GET /api/v1/payments/notifications
     * List payment notification logs with optional filters
     */
    public function index(): JsonResponse
    {
        $page = max(1, (int) ($this->request->getGet('page') ?? 1));
        $perPage = min(100, max(1, (int) ($this->request->getGet('per_page') ?? 20)));
        $from = $this->request->getGet('from');
        $to = $this->request->getGet('to');
        $type = $this->request->getGet('type');

        try {
            $rows = $this->log->listLogs($from, $to, $type);

            // Preload parent names
            $parents = [];
            foreach ($rows as $r) {
                $pid = (int) ($r['parent_id'] ?? 0);
                if ($pid && !isset($parents[$pid])) {
                    $u = $this->user->select('firstname,lastname')->find($pid);
                    $parents[$pid] = trim(($u['firstname'] ?? '') . ' ' . ($u['lastname'] ?? ''));
                }
            }

            // Add parent names to rows
            foreach ($rows as &$row) {
                $pid = (int) ($row['parent_id'] ?? 0);
                $row['parent_name'] = $parents[$pid] ?? '';
            }
            unset($row);

            $offset = ($page - 1) * $perPage;
            $total = count($rows);
            $paginatedRows = array_slice($rows, $offset, $perPage);

            $result = [
                'data' => $paginatedRows,
                'pagination' => [
                    'current_page' => $page,
                    'per_page' => $perPage,
                    'total' => $total,
                    'total_pages' => (int) ceil($total / $perPage),
                ],
            ];

            return $this->success($result, 'Payment notification logs retrieved successfully');
        } catch (\Throwable $e) {
            Log::error('Payment notification logs error: ' . $e->getMessage());
            return $this->respondError('Failed to retrieve payment notification logs', Response::HTTP_INTERNAL_SERVER_ERROR);
        }
    }

    /**
     * POST /api/v1/payments/notifications/send
     * Send payment reminder notifications
     * 
     * Body: parent_id? (int), type? ('no_payment'|'installment'), school_year?, force? (0|1)
     * - When parent_id provided: send for that parent only (if balance > 0 or force=1)
     * - Otherwise: send to all parents with positive balance for selected school year
     *   respecting idempotency (1 email per month/type) unless force=1.
     */
    public function send(): JsonResponse
    {
        $payload = $this->payloadData();
        
        $parentId = (int) ($payload['parent_id'] ?? 0);
        $typeInput = (string) ($payload['type'] ?? '');
        $force = (int) ($payload['force'] ?? 0) === 1;
        $schoolYear = (string) ($payload['school_year'] ?? ($this->config->getConfig('school_year') ?? date('Y')));

        $tzName = (string) (config('School')->attendance['timezone'] ?? user_timezone());
        $tz = new \DateTimeZone($tzName);
        $now = new \DateTime('now', $tz);
        $year = (int) $now->format('Y');
        $month = (int) $now->format('n');

        // Helper: compute current total balance across invoices for this parent/year
        $computeBalance = function (int $pid) use ($schoolYear): array {
            $rows = DB::table('invoices')
                ->select('id', 'total_amount')
                ->where('parent_id', $pid)
                ->where('school_year', $schoolYear)
                ->get()
                ->toArray();

            $paymentsTbl = 'payments';
            $hasStatus = DB::getSchemaBuilder()->hasColumn($paymentsTbl, 'status');
            $hasVoid = DB::getSchemaBuilder()->hasColumn($paymentsTbl, 'is_void');

            $sumBalance = 0.0;
            $latestId = null;

            foreach ($rows as $ir) {
                $ir = (array) $ir; // Convert to array for consistent access
                $iid = (int) ($ir['id'] ?? 0);
                if ($latestId === null) {
                    $latestId = $iid;
                }
                $total = (float) ($ir['total_amount'] ?? 0);

                $qb = DB::table('payments')->select(DB::raw('COALESCE(SUM(paid_amount),0) AS tot'))->where('invoice_id', $iid);

                if ($hasStatus) {
                    $qb->where(function ($query) {
                        $query->whereNotIn('status', ['void', 'voided', 'refunded', 'failed', 'chargeback', 'declined', 'reversed', 'canceled', 'cancelled'])
                            ->orWhereNull('status');
                    });
                }

                if ($hasVoid) {
                    $qb->where(function ($query) {
                        $query->where('is_void', 0)
                            ->orWhereNull('is_void');
                    });
                }

                $paidRow = $qb->first();
                $paid = (float) (($paidRow && isset($paidRow->tot)) ? $paidRow->tot : 0);

                $discRow = DB::table('discount_usages')
                    ->select(DB::raw('COALESCE(SUM(discount_amount),0) AS tot'))
                    ->where('invoice_id', $iid)
                    ->first();
                $disc = (float) (($discRow && isset($discRow->tot)) ? $discRow->tot : 0);

                $rfndRow = DB::table('refunds')
                    ->select(DB::raw('COALESCE(SUM(refund_paid_amount),0) AS tot'))
                    ->where('invoice_id', $iid)
                    ->whereIn('status', ['Partial', 'Paid'])
                    ->first();
                $rfnd = (float) (($rfndRow && isset($rfndRow->tot)) ? $rfndRow->tot : 0);

                $sumBalance += max(0.0, round($total - $disc - $paid - $rfnd, 2));
            }

            return [$sumBalance, $latestId];
        };

        // Helper: get secondary guardian email
        $getSecondary = function (int $primaryUserId): ?string {
            $row = $this->familyGuardian->where('user_id', $primaryUserId)->first();
            if (!$row || empty($row['family_id'])) {
                return null;
            }

            $others = $this->familyGuardian
                ->where('family_id', (int) $row['family_id'])
                ->where('user_id', '!=', $primaryUserId)
                ->where('receive_emails', 1)
                ->findAll();

            foreach ($others as $g) {
                $email = $this->user->select('email')->find((int) $g['user_id'])['email'] ?? null;
                if ($email && filter_var($email, FILTER_VALIDATE_EMAIL)) {
                    return $email;
                }
            }

            return null;
        };

        // Compose subject/body using same content as CLI command
        $compose = function (int $pid, float $balance) use ($schoolYear, $now, $tzName): array {
            $u = $this->user->find($pid) ?: [];
            $parentName = trim(($u['firstname'] ?? '') . ' ' . ($u['lastname'] ?? ''));
            $greeting = $parentName !== '' ? "Dear {$parentName}," : 'Dear Parent,';

            $monthYear = $now->format('F Y');
            $subject = sprintf('Monthly Tuition Reminder — %s', $schoolYear);
            $balanceFmt = '$' . number_format($balance, 2);

            $intro = 'This is your monthly installment reminder for ' . $schoolYear . '.';

            // Compute remaining/max installments similar to Manual Payment UI
            $installmentEndRaw = (string) $this->config->getConfig('installment_date');
            $tz = new \DateTimeZone($tzName);
            $today = new \DateTimeImmutable('today', $tz);
            $end = null;

            try {
                if ($installmentEndRaw) {
                    $end = new \DateTimeImmutable($installmentEndRaw, $tz);
                }
            } catch (\Throwable $e) {
                $end = null;
            }

            $remMonths = 0;
            if ($end) {
                $y = (int) $end->format('Y') - (int) $today->format('Y');
                $m = (int) $end->format('n') - (int) $today->format('n');
                $remMonths = $y * 12 + $m;
                if ((int) $end->format('j') > (int) $today->format('j')) {
                    $remMonths += 1;
                }
                if ($remMonths < 0) {
                    $remMonths = 0;
                }
            }

            $remainingInst = max(1, $remMonths);
            $maxInst = max(($remMonths ?: 0), ($balance > 0 ? 2 : 0));
            $instDueFmt = '$' . number_format($remainingInst > 0 ? ($balance / $remainingInst) : 0, 2);

            $bodyHtml = <<<HTML
                <div style="font-family:Arial,Helvetica,sans-serif; font-size:14px; color:#212529; line-height:1.5;">
                  <h2 style="margin:0 0 10px; font-size:18px;">Monthly Tuition Reminder</h2>
                  <p>{$greeting}</p>
                  <p>{$intro}</p>
                  <p><strong>Current Outstanding Balance:</strong> {$balanceFmt}</p>
                  <ul>
                    <li><strong>Remaining installments:</strong> {$remainingInst}</li>
                    <li><strong>Suggested installment this month:</strong> {$instDueFmt}</li>
                    <li><strong>Maximum installments available:</strong> {$maxInst}</li>
                  </ul>
                  <p>As a friendly reminder, our tuition installments are due at the beginning of each month.</p>
                  <p>You can review your invoice and payment options by logging in to your parent portal.</p>
                  <p>Thank you for your prompt attention.</p>
                  <p><em>Reminder Period:</em> {$monthYear}</p>
                </div>
            HTML;

            // Try to wrap in email layout view, fallback to plain HTML
            try {
                $body = view('emails._wrap_layout', [
                    'title' => 'Monthly Tuition Reminder',
                    'body_html' => $bodyHtml,
                ], ['saveData' => false]);
            } catch (\Throwable $e) {
                // Fallback if view doesn't exist
                $body = $bodyHtml;
            }

            return [$subject, $body];
        };

        $results = [
            'sent' => 0,
            'skipped' => 0,
            'failed' => 0,
            'details' => [],
        ];

        if ($parentId > 0) {
            // Single parent mode
            [$balance, $latestInv] = $computeBalance($parentId);

            // Detect type if not provided
            if ($typeInput === 'no_payment' || $typeInput === 'installment') {
                $type = $typeInput;
            } else {
                $hasPayments = $this->payment
                    ->where('parent_id', $parentId)
                    ->where('school_year', $schoolYear)
                    ->countAllResults() > 0;
                $type = $hasPayments ? 'installment' : 'no_payment';
            }

            // Idempotency: skip if already sent this month for this type
            if (!$force && $this->log->existsForPeriod($parentId, $year, $month, $type)) {
                $results['skipped']++;
                $results['details'][] = ['parent_id' => $parentId, 'result' => 'already_sent'];
            } elseif ($balance <= 0 && !$force) {
                $results['skipped']++;
                $results['details'][] = ['parent_id' => $parentId, 'result' => 'no_balance'];
            } else {
                // Compute current-month installment suggestion
                $installmentEndRaw = (string) $this->config->getConfig('installment_date');
                $tz = new \DateTimeZone($tzName);
                $nowD = new \DateTimeImmutable('today', $tz);
                $endD = null;

                try {
                    if ($installmentEndRaw) {
                        $endD = new \DateTimeImmutable($installmentEndRaw, $tz);
                    }
                } catch (\Throwable $e) {
                    $endD = null;
                }

                $remMonths = 0;
                if ($endD) {
                    $y = (int) $endD->format('Y') - (int) $nowD->format('Y');
                    $m = (int) $endD->format('n') - (int) $nowD->format('n');
                    $remMonths = $y * 12 + $m;
                    if ((int) $endD->format('j') > (int) $nowD->format('j')) {
                        $remMonths += 1;
                    }
                    if ($remMonths < 0) {
                        $remMonths = 0;
                    }
                }

                $remInst = max(1, $remMonths);
                $instDue = round($balance / $remInst, 2);

                $toEmail = $this->user->select('email')->find($parentId)['email'] ?? null;
                $toEmail = $toEmail && filter_var($toEmail, FILTER_VALIDATE_EMAIL) ? $toEmail : null;
                $ccEmail = $getSecondary($parentId);

                [$subject, $body] = $compose($parentId, $balance);

                $ok = $toEmail ? $this->emailService->send($toEmail, $subject, $body, 'finance') : false;

                if ($ok && $ccEmail && strcasecmp($ccEmail, (string) $toEmail) !== 0) {
                    $this->emailService->send($ccEmail, $subject, $body, 'finance');
                }

                $this->log->insert([
                    'parent_id' => $parentId,
                    'invoice_id' => $latestInv,
                    'school_year' => $schoolYear,
                    'period_year' => $year,
                    'period_month' => $month,
                    'type' => $type,
                    'to_email' => $toEmail,
                    'cc_email' => $ccEmail,
                    'head_fa_notified' => 0,
                    'subject' => $subject,
                    'body' => $body,
                    'status' => $ok ? 'sent' : 'failed',
                    'error_message' => $ok ? null : 'Missing/invalid email or send failed',
                    'balance_snapshot' => $balance,
                    'sent_at' => $now->format('Y-m-d H:i:s'),
                ]);

                if ($ok) {
                    $results['sent']++;
                    $results['details'][] = [
                        'parent_id' => $parentId,
                        'result' => 'sent',
                        'balance' => $balance,
                        'installment_due' => $instDue,
                        'remaining' => $remInst,
                    ];
                } else {
                    $results['failed']++;
                    $results['details'][] = ['parent_id' => $parentId, 'result' => 'failed'];
                }
            }
        } else {
            // Bulk mode: parents with positive balance in selected year
            $rows = DB::table('invoices')
                ->select(DB::raw('DISTINCT parent_id'))
                ->where('school_year', $schoolYear)
                ->get();

            $pids = array_values(array_unique($rows->pluck('parent_id')->map(fn($id) => (int) $id)->toArray()));

            foreach ($pids as $pid) {
                [$balance, $latestInv] = $computeBalance($pid);

                if ($balance <= 0 && !$force) {
                    $results['skipped']++;
                    continue;
                }

                $hasPayments = $this->payment
                    ->where('parent_id', $pid)
                    ->where('school_year', $schoolYear)
                    ->countAllResults() > 0;
                $type = $hasPayments ? 'installment' : 'no_payment';

                if (!$force && $this->log->existsForPeriod($pid, $year, $month, $type)) {
                    $results['skipped']++;
                    continue;
                }

                $toEmail = $this->user->select('email')->find($pid)['email'] ?? null;
                $toEmail = $toEmail && filter_var($toEmail, FILTER_VALIDATE_EMAIL) ? $toEmail : null;
                $ccEmail = $getSecondary($pid);

                [$subject, $body] = $compose($pid, $balance);

                $ok = $toEmail ? $this->emailService->send($toEmail, $subject, $body, 'finance') : false;

                if ($ok && $ccEmail && strcasecmp($ccEmail, (string) $toEmail) !== 0) {
                    $this->emailService->send($ccEmail, $subject, $body, 'finance');
                }

                // Optional: notify head of finance in-app
                $this->notifyHeadOfFinance($pid, $type, $balance);

                $this->log->insert([
                    'parent_id' => $pid,
                    'invoice_id' => $latestInv,
                    'school_year' => $schoolYear,
                    'period_year' => $year,
                    'period_month' => $month,
                    'type' => $type,
                    'to_email' => $toEmail,
                    'cc_email' => $ccEmail,
                    'head_fa_notified' => 1,
                    'subject' => $subject,
                    'body' => $body,
                    'status' => $ok ? 'sent' : 'failed',
                    'error_message' => $ok ? null : 'Missing/invalid email or send failed',
                    'balance_snapshot' => $balance,
                    'sent_at' => $now->format('Y-m-d H:i:s'),
                ]);

                if ($ok) {
                    $results['sent']++;
                } else {
                    $results['failed']++;
                }
            }
        }

        return $this->success([
            'ok' => true,
        ] + $results + [
            'csrf_token' => csrf_token(),
            'csrf_hash' => csrf_hash(),
        ], 'Payment notifications processed');
    }

    /**
     * Notify head of finance users about payment reminder sent
     */
    private function notifyHeadOfFinance(int $parentId, string $type, float $balance): void
    {
        try {
            $heads = $this->getHeadOfFinanceUsers();
            foreach ($heads as $u) {
                // Create in-app notification if notification system exists
                // This is optional functionality - can be implemented later
                Log::info(sprintf(
                    'Payment reminder sent: %s reminder to parent #%d (balance: $%0.2f)',
                    $type,
                    $parentId,
                    $balance
                ));
            }
        } catch (\Throwable $e) {
            // Silently fail - this is optional
            Log::debug('Failed to notify head of finance: ' . $e->getMessage());
        }
    }

    /**
     * Get head of finance users
     */
    private function getHeadOfFinanceUsers(): array
    {
        $heads = $this->user->getUsersByRole('head of department (finance)');
        if (!empty($heads)) {
            return $heads;
        }

        $acct = $this->user->getUsersByRole('accountant');
        return $acct ?: [];
    }
}