<?php

namespace App\Services\Billing;

use App\Models\StripeAddonPrice;
use App\Models\Subscription;
use App\Services\Stripe\StripeClient;
use Illuminate\Database\UniqueConstraintViolationException;

/**
 * The Stripe Price a module is billed on, found or minted.
 *
 * Modules had no place in Stripe at all, which is why they were charged in the
 * month they were booked and never again: nothing ever became an item on the
 * subscription. This is the missing half of the catalogue mirror — the module
 * side of what stripe:sync-catalogue does for packages.
 *
 * **Why a module needs more than one Price.** A booking is frozen at the price
 * it was booked at, and a Stripe Price is immutable. So a customer who took
 * storage at ten euros keeps billing against the ten-euro Price while everyone
 * who books it tomorrow bills against the twelve-euro one, and both stay live.
 * The interval belongs to the Price as well, and every item on one subscription
 * has to share it — so a module on a yearly contract is a yearly Price of twelve
 * times the monthly figure, which is exactly what a yearly customer pays for it.
 *
 * **Minting on demand, not only from the sweep.** The command pre-creates
 * today's prices so the ordinary booking finds one waiting. It cannot cover a
 * discounted grant, or a customer grandfathered on a figure the catalogue left
 * behind years ago — and refusing to bill those would be the same bug in a new
 * place. Stripe's idempotency key makes the on-demand path safe to repeat.
 */
final class AddonPrices
{
    public function __construct(private readonly StripeClient $stripe) {}

    /**
     * The Stripe Price for this module at this money on this term, creating it
     * if Stripe has never been told about it.
     *
     * Null when there is nothing to bill: a module given away costs nothing, and
     * a zero-amount item on a subscription is a line on every invoice that says
     * the customer owes nothing for it.
     */
    public function ensure(string $addonKey, int $unitNetCents, string $currency, string $term): ?string
    {
        if ($unitNetCents <= 0) {
            return null;
        }

        $interval = $term === Subscription::TERM_YEARLY ? 'year' : 'month';
        $currency = strtoupper($currency);

        // A module is priced per month; a yearly contract bills a year of it at
        // once, in step with the package beside it. Twelve months exactly, so
        // the figure the customer was shown times twelve is the figure charged.
        $amount = $interval === 'year' ? $unitNetCents * 12 : $unitNetCents;

        $existing = $this->find($addonKey, $amount, $currency, $interval);

        if ($existing !== null) {
            return $existing;
        }

        $productId = $this->product($addonKey);

        $priceId = $this->stripe->createPrice(
            productId: $productId,
            amountCents: $amount,
            currency: $currency,
            interval: $interval,
            metadata: [
                // Read back when a Stripe invoice line has to be turned into
                // wording a customer can read — see StripeInvoiceLines.
                'addon' => $addonKey,
            ],
            // Keyed on what the Price IS, so a crash between Stripe creating it
            // and us storing its id gives back the same Price on the next
            // attempt rather than a second one at the same money.
            idempotencyKey: "clupilot-addon-price-{$addonKey}-{$interval}-{$amount}-{$currency}",
        );

        $this->remember($addonKey, $amount, $currency, $interval, $productId, $priceId);

        return $priceId;
    }

    /** The Price we already have for this combination, or null. */
    public function find(string $addonKey, int $amountCents, string $currency, string $interval): ?string
    {
        $id = StripeAddonPrice::query()
            ->where('addon_key', $addonKey)
            ->where('amount_cents', $amountCents)
            ->where('currency', strtoupper($currency))
            ->where('interval', $interval)
            ->value('stripe_price_id');

        return is_string($id) && $id !== '' ? $id : null;
    }

    /**
     * The Stripe Product every Price for this module hangs off.
     *
     * One per module, however many Prices it accumulates — that is what a
     * Product is for, and it is what makes the module readable in Stripe's own
     * dashboard rather than a list of anonymous amounts.
     */
    private function product(string $addonKey): string
    {
        $existing = StripeAddonPrice::query()
            ->where('addon_key', $addonKey)
            ->value('stripe_product_id');

        if (is_string($existing) && $existing !== '') {
            return $existing;
        }

        return $this->stripe->createProduct(
            app(AddonCatalogue::class)->name($addonKey),
            ['addon' => $addonKey],
            idempotencyKey: "clupilot-addon-product-{$addonKey}",
        );
    }

    private function remember(
        string $addonKey,
        int $amountCents,
        string $currency,
        string $interval,
        string $productId,
        string $priceId,
    ): void {
        try {
            StripeAddonPrice::create([
                'addon_key' => $addonKey,
                'amount_cents' => $amountCents,
                'currency' => $currency,
                'interval' => $interval,
                'stripe_product_id' => $productId,
                'stripe_price_id' => $priceId,
            ]);
        } catch (UniqueConstraintViolationException) {
            // Two bookings of the same module landed together. Stripe replayed
            // one Price for both — the idempotency key saw to that — so there is
            // nothing to correct here beyond letting the first row stand.
        }
    }
}