<?php

namespace App\Services\Parents;

use App\Models\Invoice;
use App\Models\ParentAccount;
use App\Models\ParentBalanceTransfer;
use App\Models\User;
use Illuminate\Support\Facades\DB;
use Illuminate\Support\Facades\Schema;

class ParentInvoiceService
{
    public function listInvoices(int $parentId, ?string $schoolYear = null): array
    {
        $rows = Invoice::query()
            ->where('parent_id', $parentId)
            ->when($schoolYear, fn ($q) => $q->where('school_year', $schoolYear))
            ->orderByDesc('created_at')
            ->get();

        $invoiceIds = $rows
            ->pluck('id')
            ->map(fn ($id) => (int) $id)
            ->filter(fn ($id) => $id > 0)
            ->values()
            ->all();

        $paymentsByInvoice = $this->paymentsByInvoice($parentId, $invoiceIds);
        $adjustments = $this->invoiceAdjustments($invoiceIds);

        return $rows
            ->map(function (Invoice $invoice) use ($paymentsByInvoice, $adjustments): array {
                $invoiceRow = $invoice->toArray();
                $invoiceId = (int) $invoice->id;
                $payments = $paymentsByInvoice[(int) $invoice->id] ?? [];
                $paidAmount = round(array_sum(array_map(
                    static fn (array $payment): float => (float) ($payment['paid_amount'] ?? 0),
                    $payments
                )), 2);
                $discountAmount = round((float) ($adjustments['discounts'][$invoiceId] ?? 0), 2);
                $refundAmount = round((float) ($adjustments['refunds'][$invoiceId] ?? 0), 2);
                $totalAmount = round((float) ($invoice->total_amount ?? 0), 2);
                $balance = max(0.0, round($totalAmount - $paidAmount - $discountAmount - $refundAmount, 2));

                $invoiceRow['payments'] = $payments;
                $invoiceRow['paid_amount'] = $paidAmount;
                $invoiceRow['discount'] = $discountAmount;
                $invoiceRow['refund_amount'] = $refundAmount;
                $invoiceRow['balance'] = $balance;
                $invoiceRow['last_paid_amount'] = (float) ($payments[0]['paid_amount'] ?? 0);
                $invoiceRow['last_payment_date'] = $payments[0]['payment_date'] ?? null;
                $invoiceRow['status'] = $this->deriveInvoiceStatus($invoice->status, $paidAmount, $balance);

                return $invoiceRow;
            })
            ->all();
    }

    public function statement(int $parentId, ?string $schoolYear = null): array
    {
        $parent = User::query()->find($parentId);
        $account = $schoolYear
            ? ParentAccount::query()
                ->where('parent_id', $parentId)
                ->where('school_year', $schoolYear)
                ->first()
            : null;

        $columns = [
            'id',
            'invoice_number',
            'total_amount',
            'paid_amount',
            'balance',
            'status',
            'description',
            'school_year',
        ];

        if (Schema::hasColumn('invoices', 'invoice_type')) {
            $columns[] = 'invoice_type';
        }
        if (Schema::hasColumn('invoices', 'balance_transfer_id')) {
            $columns[] = 'balance_transfer_id';
        }

        $invoices = Invoice::query()
            ->where('parent_id', $parentId)
            ->when($schoolYear, fn ($q) => $q->where('school_year', $schoolYear))
            ->orderBy('created_at')
            ->get($columns);

        $transferSourceYears = $this->transferSourceYears($invoices->pluck('balance_transfer_id')->filter()->all());
        $invoiceIds = $invoices
            ->pluck('id')
            ->map(fn ($id) => (int) $id)
            ->filter(fn ($id) => $id > 0)
            ->values()
            ->all();
        $adjustments = $this->invoiceAdjustments($invoiceIds);

        $lines = $invoices
            ->map(function (Invoice $invoice) use ($transferSourceYears, $adjustments): array {
                $transferId = (int) ($invoice->balance_transfer_id ?? 0);
                $invoiceId = (int) $invoice->id;
                $totalAmount = round((float) ($invoice->total_amount ?? 0), 2);
                $paidAmount = round((float) ($adjustments['payments'][$invoiceId] ?? $invoice->paid_amount ?? 0), 2);
                $discountAmount = round((float) ($adjustments['discounts'][$invoiceId] ?? 0), 2);
                $refundAmount = round((float) ($adjustments['refunds'][$invoiceId] ?? 0), 2);
                $balance = max(0.0, round($totalAmount - $paidAmount - $discountAmount - $refundAmount, 2));

                return [
                    'label' => $invoice->description ?: ($invoice->invoice_number ?: sprintf('Invoice #%d', $invoice->id)),
                    'amount' => $balance,
                    'source_school_year' => $transferId > 0
                        ? ($transferSourceYears[$transferId] ?? $invoice->school_year)
                        : $invoice->school_year,
                    'invoice_id' => $invoice->id,
                ];
            })
            ->values()
            ->all();

        $openingBalance = round((float) ($account?->opening_balance ?? 0), 2);
        $currentBalance = round($openingBalance + array_sum(array_map(
            static fn (array $line): float => (float) ($line['amount'] ?? 0),
            $lines
        )), 2);

        return [
            'parent_id' => $parentId,
            'parent_name' => $this->parentName($parent),
            'school_year' => $schoolYear,
            'lines' => $lines,
            'opening_balance' => $openingBalance,
            'current_balance' => round($currentBalance, 2),
        ];
    }

    private function parentName(?User $parent): ?string
    {
        if (! $parent) {
            return null;
        }

        $parts = array_filter([
            trim((string) ($parent->firstname ?? '')),
            trim((string) ($parent->lastname ?? '')),
        ]);

        if ($parts !== []) {
            return implode(' ', $parts);
        }

        return $parent->name ?? $parent->email ?? null;
    }

    /**
     * @param list<int> $invoiceIds
     * @return array<int, list<array<string, mixed>>>
     */
    private function paymentsByInvoice(int $parentId, array $invoiceIds): array
    {
        if ($invoiceIds === [] || ! Schema::hasTable('payments')) {
            return [];
        }

        $columns = [
            'id',
            'parent_id',
            'invoice_id',
            'paid_amount',
            Schema::hasColumn('payments', 'balance') ? 'balance' : DB::raw('NULL AS balance'),
            Schema::hasColumn('payments', 'payment_method') ? 'payment_method' : DB::raw('NULL AS payment_method'),
            Schema::hasColumn('payments', 'payment_date') ? 'payment_date' : DB::raw('NULL AS payment_date'),
            Schema::hasColumn('payments', 'transaction_id') ? 'transaction_id' : DB::raw('NULL AS transaction_id'),
            Schema::hasColumn('payments', 'status') ? 'status' : DB::raw('NULL AS status'),
            Schema::hasColumn('payments', 'school_year') ? 'school_year' : DB::raw('NULL AS school_year'),
            Schema::hasColumn('payments', 'semester') ? 'semester' : DB::raw('NULL AS semester'),
            Schema::hasColumn('payments', 'created_at') ? 'created_at' : DB::raw('NULL AS created_at'),
        ];

        $query = DB::table('payments')
            ->select($columns)
            ->where('parent_id', $parentId)
            ->whereIn('invoice_id', $invoiceIds);

        if (Schema::hasColumn('payments', 'status')) {
            $query->whereNotIn(DB::raw('LOWER(status)'), ['pending', 'void', 'voided', 'cancelled', 'canceled', 'failed', 'rejected']);
        }
        if (Schema::hasColumn('payments', 'payment_date')) {
            $query->orderByDesc('payment_date');
        }
        if (Schema::hasColumn('payments', 'created_at')) {
            $query->orderByDesc('created_at');
        }

        $rows = $query
            ->get()
            ->map(static fn ($row): array => [
                'id' => (int) $row->id,
                'parent_id' => (int) $row->parent_id,
                'invoice_id' => (int) $row->invoice_id,
                'paid_amount' => (float) $row->paid_amount,
                'balance' => (float) $row->balance,
                'payment_method' => $row->payment_method,
                'payment_date' => $row->payment_date,
                'transaction_id' => $row->transaction_id,
                'status' => $row->status,
                'school_year' => $row->school_year,
                'semester' => $row->semester,
                'created_at' => $row->created_at,
            ])
            ->all();

        $grouped = [];
        foreach ($rows as $row) {
            $grouped[(int) $row['invoice_id']][] = $row;
        }

        return $grouped;
    }

    /**
     * @param list<int> $invoiceIds
     * @return array{payments: array<int, float>, discounts: array<int, float>, refunds: array<int, float>}
     */
    private function invoiceAdjustments(array $invoiceIds): array
    {
        $invoiceIds = array_values(array_unique(array_filter(array_map('intval', $invoiceIds))));
        $adjustments = [
            'payments' => [],
            'discounts' => [],
            'refunds' => [],
        ];

        if ($invoiceIds === []) {
            return $adjustments;
        }

        if (Schema::hasTable('payments')) {
            $paymentQuery = DB::table('payments')
                ->selectRaw('invoice_id, COALESCE(SUM(paid_amount),0) AS total')
                ->whereIn('invoice_id', $invoiceIds);

            if (Schema::hasColumn('payments', 'status')) {
                $paymentQuery->where(function ($query) {
                    $query->whereNotIn(DB::raw('LOWER(status)'), [
                        'pending',
                        'void',
                        'voided',
                        'cancelled',
                        'canceled',
                        'failed',
                        'rejected',
                        'refunded',
                        'chargeback',
                        'declined',
                        'reversed',
                    ])->orWhereNull('status');
                });
            }

            $adjustments['payments'] = $paymentQuery
                ->groupBy('invoice_id')
                ->pluck('total', 'invoice_id')
                ->map(fn ($value) => (float) $value)
                ->all();
        }

        if (Schema::hasTable('discount_usages')) {
            $adjustments['discounts'] = DB::table('discount_usages')
                ->selectRaw('invoice_id, COALESCE(SUM(discount_amount),0) AS total')
                ->whereIn('invoice_id', $invoiceIds)
                ->groupBy('invoice_id')
                ->pluck('total', 'invoice_id')
                ->map(fn ($value) => (float) $value)
                ->all();
        }

        if (Schema::hasTable('refunds')) {
            $adjustments['refunds'] = DB::table('refunds')
                ->selectRaw('invoice_id, COALESCE(SUM(refund_paid_amount),0) AS total')
                ->whereIn('invoice_id', $invoiceIds)
                ->whereIn('status', ['Partial', 'Paid'])
                ->groupBy('invoice_id')
                ->pluck('total', 'invoice_id')
                ->map(fn ($value) => (float) $value)
                ->all();
        }

        return $adjustments;
    }

    private function deriveInvoiceStatus(?string $storedStatus, float $paidAmount, float $balance): string
    {
        if ($paidAmount <= 0 && $balance > 0) {
            return 'Unpaid';
        }

        if ($balance <= 0) {
            return 'Paid';
        }

        if ($paidAmount > 0) {
            return 'Partially Paid';
        }

        return $storedStatus ?: 'Unpaid';
    }

    /**
     * @param array<int|string> $transferIds
     * @return array<int, string|null>
     */
    private function transferSourceYears(array $transferIds): array
    {
        $ids = array_values(array_unique(array_map('intval', $transferIds)));
        if ($ids === []) {
            return [];
        }

        return ParentBalanceTransfer::query()
            ->whereIn('id', $ids)
            ->pluck('from_school_year', 'id')
            ->all();
    }
}