<?php

namespace App\Services;

use App\Enums\PurchasingRole;
use App\Models\Budget;
use App\Models\BudgetConsumption;
use App\Models\BudgetEntry;
use App\Models\GoodsReceiptItem;
use App\Models\Invoice;
use App\Models\InvoiceItem;
use App\Models\PurchaseOrder;
use App\Models\Requisition;
use App\Models\User;
use Brick\Math\BigDecimal;
use Brick\Math\RoundingMode;
use Illuminate\Support\Facades\DB;
use Illuminate\Support\Str;
use Illuminate\Validation\ValidationException;

class InvoiceWorkflow
{
    private function access(User $user): void
    {
        abort_unless(auth()->id() === $user->id && $user->tenant_id !== null && $user->purchasing_role === PurchasingRole::Finance, 403);
    }

    private function invalid(string $message): never
    {
        throw ValidationException::withMessages(['invoice' => $message]);
    }

    /** @param list<array<string,mixed>> $inputs
     * @return list<array<string,mixed>>
     */
    private function lines(PurchaseOrder $order, array $inputs): array
    {
        $sources = $order->items()->get()->keyBy('id');
        $seen = [];
        $lines = [];
        foreach ($inputs as $input) {
            $source = $sources->get($input['purchase_order_item_id']);
            if (! $source || in_array($source->id, $seen, true)) {
                $this->invalid('Linhas distintas e pertencentes à ordem são obrigatórias.');
            }
            $seen[] = $source->id;
            $quantity = ReceiptWorkflow::milli((string) $input['quantity']);
            $previous = InvoiceItem::query()->where('purchase_order_item_id', $source->id)->whereIn('invoice_id', Invoice::query()->where('status', 'validated')->select('id'))->sum('quantity_milli');
            $accepted = GoodsReceiptItem::query()->where('purchase_order_item_id', $source->id)->sum('accepted_milli');
            if ($quantity <= 0 || (int) $previous + $quantity > (int) $accepted || (int) $previous + $quantity > ReceiptWorkflow::milli($source->quantity)) {
                $this->invalid('Quantidade superior à recepção aceite ainda não facturada. Serviços também exigem aceitação.');
            }
            if (BigDecimal::of((string) $input['unit_price'])->multipliedBy(100)->compareTo($source->unit_price_minor) !== 0 || BigDecimal::of((string) $input['tax_rate'])->compareTo((string) $source->tax_rate) !== 0 || trim((string) $input['unit']) !== $source->unit) {
                $this->invalid('Preço, unidade e IVA devem coincidir exactamente com a ordem. Não há tolerância ou excepção configurada.');
            }
            // Cumulative rounding ensures partial invoices sum exactly to the frozen order.
            $subtotal = fn (int $milli) => BigDecimal::of($milli)->multipliedBy($source->unit_price_minor)->dividedBy(1000, 0, RoundingMode::HalfUp)->toInt();
            $tax = fn (int $minor) => BigDecimal::of($minor)->multipliedBy((string) $source->tax_rate)->dividedBy(100, 0, RoundingMode::HalfUp)->toInt();
            $before = $subtotal((int) $previous);
            $after = $subtotal((int) $previous + $quantity);
            $lines[] = ['tenant_id' => $order->tenant_id, 'purchase_order_item_id' => $source->id, 'quantity_milli' => $quantity, 'subtotal_minor' => $after - $before, 'tax_minor' => $tax($after) - $tax($before), 'snapshot' => $source->only(['description', 'unit', 'unit_price_minor', 'tax_rate'])];
        }
        if ($lines === []) {
            $this->invalid('Indique pelo menos uma linha.');
        }

        return $lines;
    }

    /** @param array<string,mixed> $data */
    public function register(User $user, PurchaseOrder $order, array $data): Invoice
    {
        $this->access($user);
        abort_unless($order->tenant_id === $user->tenant_id, 403);

        return DB::transaction(function () use ($user, $order, $data) {
            app(ConflictGuard::class)->lockCompany($user);
            $order = PurchaseOrder::query()->lockForUpdate()->findOrFail($order->id);
            $request = Requisition::query()->findOrFail($order->requisition_id);
            app(ConflictGuard::class)->assertProcess($request, $order->supplier_id, $user);
            $number = Str::upper(Str::squish($data['number']));
            if ($number === '' || Invoice::query()->where('supplier_id', $order->supplier_id)->where('number', $number)->exists()) {
                $this->invalid('Número de factura vazio ou já registado para este fornecedor.');
            }
            if ($order->status !== 'issued' || $order->currency !== 'MZN' || substr($data['issued_on'], 0, 4) !== now()->format('Y') || $data['issued_on'] > today()->format('Y-m-d') || $data['issued_on'] < substr((string) $order->getRawOriginal('issued_at'), 0, 10)) {
                $this->invalid('Factura deve referir ordem emitida em MZN, com data válida no exercício actual e posterior à emissão.');
            }
            $lines = $this->lines($order, $data['items']);
            $subtotal = array_sum(array_column($lines, 'subtotal_minor'));
            $tax = array_sum(array_column($lines, 'tax_minor'));
            foreach (['subtotal' => $subtotal, 'tax' => $tax, 'total' => $subtotal + $tax] as $key => $expected) {
                if (BigDecimal::of((string) $data[$key])->multipliedBy(100)->compareTo($expected) !== 0) {
                    $this->invalid('Totais da factura divergem da conferência com a ordem e recepção. Verifique os arredondamentos das facturas parciais.');
                }
            }
            $invoice = Invoice::query()->create(['tenant_id' => $user->tenant_id, 'purchase_order_id' => $order->id, 'supplier_id' => $order->supplier_id, 'created_by' => $user->id, 'number' => $number, 'issued_on' => $data['issued_on'], 'subtotal_minor' => $subtotal, 'tax_minor' => $tax, 'total_minor' => $subtotal + $tax, 'snapshot' => ['supplier' => $order->snapshot['supplier'], 'order_number' => $order->number, 'author' => $user->only(['id', 'name']), 'currency' => 'MZN', 'development_only' => true, 'matching_tolerance' => 'zero', 'rounding' => 'cumulative_half_up']]);
            $invoice->items()->createMany($lines);
            app(RequisitionWorkflow::class)->audit($user, 'invoice.created', $request, null, $invoice->load('items')->toArray());

            return $invoice;
        });
    }

    public function validate(User $user, Invoice $invoice): void
    {
        $this->access($user);
        abort_unless($invoice->tenant_id === $user->tenant_id && $invoice->created_by !== $user->id, 403);
        DB::transaction(function () use ($user, $invoice) {
            app(ConflictGuard::class)->lockCompany($user);
            $invoice = Invoice::query()->lockForUpdate()->findOrFail($invoice->id);
            if ($invoice->status === 'validated') {
                return;
            }
            $order = PurchaseOrder::query()->lockForUpdate()->findOrFail($invoice->purchase_order_id);
            $request = Requisition::query()->findOrFail($order->requisition_id);
            app(ConflictGuard::class)->assertProcess($request, $order->supplier_id, $user);
            if (substr((string) $invoice->issued_on, 0, 4) !== now()->format('Y')) {
                $this->invalid('Conferência entre exercícios não suportada.');
            }
            $stored = $invoice->items()->orderBy('id')->get();
            $inputs = [];
            foreach ($stored as $line) {
                $inputs[] = ['purchase_order_item_id' => $line->purchase_order_item_id, 'quantity' => (string) BigDecimal::of($line->quantity_milli)->dividedBy(1000, 3), 'unit' => $line->snapshot['unit'], 'unit_price' => (string) BigDecimal::of($line->snapshot['unit_price_minor'])->dividedBy(100, 2), 'tax_rate' => $line->snapshot['tax_rate']];
            }
            $current = $this->lines($order, $inputs);
            foreach ($current as $index => $line) {
                if ($line['subtotal_minor'] !== $stored[$index]->subtotal_minor || $line['tax_minor'] !== $stored[$index]->tax_minor) {
                    $this->invalid('Conferência alterada por outra factura; a validação está bloqueada.');
                }
            }
            $commit = BudgetEntry::query()->where('requisition_id', $request->id)->where('kind', 'commit')->first();
            if (! $commit) {
                $this->invalid('A ordem não possui compromisso orçamental. Factura permanece pendente; não é criado saldo retroactivo.');
            }
            $budget = Budget::query()->lockForUpdate()->findOrFail($commit->budget_id);
            if (! $budget->approved_by || (int) $budget->year !== now()->year) {
                $this->invalid('Orçamento não aprovado ou fora do exercício.');
            }
            $amount = (int) ($budget->includes_tax ? $invoice->total_minor : $invoice->subtotal_minor);
            $remaining = (int) BudgetEntry::query()->where('requisition_id', $request->id)->sum('committed_minor');
            if ($amount > $remaining) {
                $this->invalid('Compromisso insuficiente para a factura.');
            }
            BudgetEntry::query()->create(['tenant_id' => $user->tenant_id, 'budget_id' => $budget->id, 'requisition_id' => $request->id, 'created_by' => $user->id, 'kind' => 'invoice-'.$invoice->id, 'reserved_minor' => 0, 'committed_minor' => -$amount, 'created_at' => now()]);
            BudgetConsumption::query()->create(['tenant_id' => $user->tenant_id, 'budget_id' => $budget->id, 'invoice_id' => $invoice->id, 'created_by' => $user->id, 'amount_minor' => $amount, 'created_at' => now()]);
            $invoice->update(['status' => 'validated', 'validated_by' => $user->id, 'validated_at' => now()]);
            app(RequisitionWorkflow::class)->audit($user, 'invoice.validated', $request, null, ['invoice_id' => $invoice->id, 'budget_id' => $budget->id, 'consumed_minor' => $amount]);
        });
    }
}