<?php

namespace App\Services\Billing;

use App\Jobs\ArchiveInvoice;
use App\Models\Customer;
use App\Models\ExportTarget;
use App\Models\Invoice;
use App\Models\InvoiceSeries;
use App\Models\Order;
use App\Models\Subscription;
use App\Support\CompanyProfile;
use Illuminate\Support\Carbon;
use Illuminate\Support\Collection;
use Illuminate\Support\Facades\DB;
use RuntimeException;

/**
 * Turning what somebody bought into a document that cannot change afterwards.
 *
 * Everything the finished invoice says is copied into `snapshot` here, at the
 * moment the number is assigned: the issuer's registered details, the
 * customer's address, every line, the rate and the reason for it. The PDF is
 * rendered from that and never stored, so the same invoice re-rendered in seven
 * years is the page it was on the day it was issued — whatever has changed in
 * the settings in between.
 *
 * The number and the invoice commit together or not at all. A number taken and
 * then lost to a failure is a gap in a series that must not have one.
 */
final class IssueInvoice
{
    public function __construct(private readonly InvoiceNumbers $numbers) {}

    /**
     * One invoice covering several orders.
     *
     * Several rather than one-per-order on purpose: a customer who buys a plan
     * and two add-ons in one go has bought once, and sending them three
     * invoices for one purchase is three times the paperwork for the same
     * money. Each order becomes a line, which is also what was asked for —
     * every add-on listed on its own.
     *
     * @param  Collection<int, Order>  $orders
     */
    public function forOrders(Customer $customer, Collection $orders, ?InvoiceSeries $series = null): Invoice
    {
        // A full gift produces no invoice — no amount, no number drawn from
        // the series. A zero invoice with a sequential number is a bookkeeping
        // foreign body. A discounted grant is unaffected: it still charges
        // something and is invoiced exactly like an ordinary sale below.
        $orders = $orders->reject(fn (Order $order) => $order->isFreeGrant());

        if ($orders->isEmpty()) {
            throw new RuntimeException('Refusing to issue an invoice with no lines on it.');
        }

        $lines = $orders->map(fn (Order $order) => [
            'description' => $order->label(),
            'details' => array_values(array_filter([
                $order->isRecurring() ? __('invoice.line_recurring') : __('invoice.line_once'),
            ])),
            'quantity_milli' => 1000,
            'unit' => '',
            'unit_net_cents' => (int) $order->amount_cents,
        ])->all();

        return $this->issue(
            customer: $customer,
            lines: $lines,
            currency: strtoupper((string) ($orders->first()->currency ?: 'EUR')),
            series: $series,
            attributes: ['order_id' => $orders->first()->id],
        );
    }

    /**
     * One invoice for a term that was billed — a renewal.
     *
     * Deliberately NOT forOrders() with an Order made up for the occasion. An
     * Order is something a customer bought: it is created at a checkout, it sits
     * in their cart until it is paid, and provisioning and plan changes consume
     * it. A month rolling over is none of those things, and writing a purchase
     * nobody made would corrupt the one record that says what this customer has
     * actually ordered. The document points at the CONTRACT instead, which is
     * what a renewal renews.
     *
     * The line is the contract's own frozen price — `price_cents`, the
     * catalogue's NET figure — and not Stripe's `amount_paid`, which is a gross
     * total. What the customer is owed is what they agreed to; the register
     * records beside it what was actually taken, and `stripe_invoice_id` on the
     * row is how the two are reconciled afterwards.
     *
     * Booked modules are NOT on it. They are not items on the Stripe
     * subscription, so this renewal did not charge for them — putting them on
     * the document would invoice money nobody was asked for. (That they are
     * never billed after the month they were booked in is a real gap, and it is
     * a gap in the booking, not in this document.)
     *
     * `$stripeInvoiceId` is what makes issuing this idempotent: the column is
     * unique, so a redelivered webhook collides in the database and the
     * transaction takes its invoice number back with it.
     */
    public function forBilledPeriod(
        Subscription $subscription,
        Carbon $from,
        Carbon $to,
        ?string $stripeInvoiceId = null,
        ?InvoiceSeries $series = null,
    ): Invoice {
        $customer = $subscription->customer;

        if ($customer === null) {
            throw new RuntimeException('Refusing to issue an invoice for a contract with nobody on it.');
        }

        $lines = [[
            'description' => __('billing.cart.plan', ['plan' => ucfirst((string) $subscription->plan)]),
            'details' => [__('invoice.line_period', [
                'from' => $from->local()->format('d.m.Y'),
                // Stripe's period_end is the EXCLUSIVE boundary — the first
                // moment of the next term, which the next invoice will claim in
                // turn. Printed as it comes, the same day would appear on two
                // consecutive documents.
                'to' => $to->greaterThan($from)
                    ? $to->copy()->subDay()->local()->format('d.m.Y')
                    : $to->local()->format('d.m.Y'),
            ])],
            'quantity_milli' => 1000,
            'unit' => '',
            'unit_net_cents' => (int) $subscription->price_cents,
        ]];

        return $this->issue(
            customer: $customer,
            lines: $lines,
            currency: strtoupper((string) ($subscription->currency ?: 'EUR')),
            series: $series,
            attributes: [
                'subscription_id' => $subscription->id,
                // Left null on purpose. The contract's opening order is the
                // FIRST purchase and already has its own invoice; pointing this
                // one at it would file two documents under one sale.
                'order_id' => null,
                'stripe_invoice_id' => $stripeInvoiceId,
            ],
        );
    }

    /**
     * The part every document has in common: the number, the freeze, the copy
     * to the archive.
     *
     * @param  array<int, array<string, mixed>>  $lines
     * @param  array<string, mixed>  $attributes  what this document is FOR
     */
    /**
     * One invoice for work that was done, typed by a person.
     *
     * Not everything we are paid for is a package. Somebody asks whether their
     * data can be moved into Nextcloud, we look at it, we say yes, we do it —
     * and that is an invoice with no order and no contract behind it, because
     * nobody bought it from a price list.
     *
     * It goes through the same door as every other invoice on purpose: the same
     * series, so the number stays consecutive; the same tax treatment, so a
     * business in another member state gets its reverse charge here too; the
     * same immutable snapshot and the same archive jobs. A second way of making
     * invoices would be a second numbering — and a series with a document
     * missing from it is worth nothing at an audit.
     *
     * Lines arrive as a person typed them. Nothing here invents a price: the
     * caller is the operator, and what they wrote is what the customer agreed
     * to on the phone.
     *
     * @param  array<int, array{description: string, details?: array<int, string>, quantity_milli: int, unit?: string, unit_net_cents: int}>  $lines
     */
    public function forService(
        Customer $customer,
        array $lines,
        string $currency = 'EUR',
        ?InvoiceSeries $series = null,
    ): Invoice {
        if ($lines === []) {
            throw new RuntimeException('Refusing to issue an invoice with no lines on it.');
        }

        return $this->issue(
            customer: $customer,
            // Normalised here rather than trusted: the optional keys are
            // optional to the caller, and InvoiceMath and the renderer both
            // read them without asking whether they are there.
            lines: array_map(fn (array $line) => [
                'description' => (string) $line['description'],
                'details' => array_values(array_filter((array) ($line['details'] ?? []))),
                'quantity_milli' => (int) $line['quantity_milli'],
                'unit' => (string) ($line['unit'] ?? ''),
                'unit_net_cents' => (int) $line['unit_net_cents'],
            ], array_values($lines)),
            currency: strtoupper($currency),
            series: $series,
            // No order and no contract: this document points at neither, and
            // saying so with a null is more honest than inventing an Order
            // nobody placed just to have something to point at.
            attributes: [],
        );
    }

    private function issue(
        Customer $customer,
        array $lines,
        string $currency,
        ?InvoiceSeries $series,
        array $attributes,
    ): Invoice {
        $missing = CompanyProfile::missingForInvoicing();

        if ($missing !== []) {
            // Refusing is the correct outcome. An invoice without a registered
            // name, an address or a VAT number is not a valid invoice here, and
            // issuing one consumes a number that can never be reused.
            throw new RuntimeException(
                'Refusing to issue an invoice before the company details are complete: '.implode(', ', $missing)
            );
        }

        $series ??= InvoiceSeries::query()->where('kind', 'invoice')->where('active', true)->firstOrFail();

        $treatment = TaxTreatment::for($customer);
        $rate = (int) round($treatment->rate * 10000);

        $totals = InvoiceMath::totals($lines, null, $rate) + ['rate_basis_points' => $rate];

        $snapshot = [
            'issuer' => CompanyProfile::all(),
            'customer' => $this->customerBlock($customer),
            'lines' => $lines,
            'totals' => $totals,
            'meta' => $this->meta($customer, $treatment),
        ];

        $invoice = DB::transaction(function () use ($series, $customer, $snapshot, $totals, $currency, $attributes) {
            [$number, $sequence, $year] = $this->numbers->next($series);

            // The number is only true once it is on the document, so both are
            // written inside the same transaction the counter was advanced in.
            // That is also what keeps a redelivered Stripe invoice from eating a
            // number: the unique index rejects the row, the transaction rolls
            // back, and the counter comes back with it.
            $snapshot['meta']['number'] = $number;

            return Invoice::create([
                'invoice_series_id' => $series->id,
                'customer_id' => $customer->id,
                'number' => $number,
                'number_year' => $year,
                'number_sequence' => $sequence,
                'issued_on' => now()->toDateString(),
                'due_on' => now()->addDays((int) CompanyProfile::get('payment_days', 14))->toDateString(),
                'snapshot' => $snapshot,
                'net_cents' => $totals['net'],
                'tax_cents' => $totals['tax'],
                'gross_cents' => $totals['gross'],
                'currency' => $currency,
                ...$attributes,
            ]);
        });

        // After the commit, never inside it: a worker can pick a job up before
        // the transaction lands, and it would then look for an invoice that
        // does not exist yet.
        //
        // One job per destination. The reason for having a second is that the
        // first can fail, and a single job writing to both would retry the one
        // that worked every time the other did not.
        //
        // Dispatched rather than done here because a destination can be a
        // network mount that blocks for its whole timeout, and an invoice must
        // not fail to be issued because a NAS in an office is rebooting.
        foreach (ExportTarget::query()->where('active', true)->get() as $target) {
            ArchiveInvoice::dispatch($invoice, $target);
        }

        return $invoice;
    }

    /**
     * The recipient, as the document will show them.
     *
     * The billing address is one free-text field today, so it is carried as
     * lines rather than pulled apart into street and city here — guessing which
     * line is which would put a postcode where a street belongs on a document
     * nobody can correct afterwards.
     *
     * @return array<string, mixed>
     */
    private function customerBlock(Customer $customer): array
    {
        $address = trim((string) $customer->billing_address);

        return [
            'name' => (string) $customer->name,
            'address_lines' => $address === ''
                ? []
                : array_values(array_filter(array_map('trim', preg_split('/\R/', $address) ?: []))),
            'vat_id' => (string) $customer->vat_id,
            'email' => (string) $customer->email,
        ];
    }

    /** @return array<string, mixed> */
    private function meta(Customer $customer, TaxTreatment $treatment): array
    {
        $days = (int) CompanyProfile::get('payment_days', 14);

        return [
            'title' => __('invoice.title'),
            'number' => '',  // filled inside the transaction, once it is real
            'customer_number' => 'KN-'.str_pad((string) $customer->id, 4, '0', STR_PAD_LEFT),
            'issued_on' => now()->local()->format('d.m.Y'),
            'due_on' => now()->local()->addDays($days)->format('d.m.Y'),
            'currency' => 'EUR',
            'salutation' => __('invoice.salutation'),
            'intro' => __('invoice.intro'),
            'adjustment_label' => __('invoice.adjustment'),
            'payment_terms' => trim((string) CompanyProfile::get('payment_terms')) !== ''
                ? (string) CompanyProfile::get('payment_terms')
                : __('invoice.payment_default', ['days' => $days]),
            // The note that makes a zero-rated invoice lawful. Without it the
            // document says nothing about why no VAT was charged, which is the
            // one thing an auditor looks for.
            'closing' => $treatment->reverseCharge ? __('invoice.reverse_charge') : null,
        ];
    }
}