<?php

namespace App\Services\Billing;

use Illuminate\Http\Client\PendingRequest;
use Illuminate\Support\Facades\Cache;
use Illuminate\Support\Facades\Http;

/**
 * Client for the platform Billing HTTP API — the one UserWallet lives on the
 * platform; QR Plus only consumes it. Amounts are integer minor units; the user is
 * identified by public_id. Authenticates with the per-consumer config('billing.service') key.
 *
 * When BILLING_API_FORCE_IP is set (e.g. 127.0.0.1), requests resolve the billing
 * host to that IP so same-server apps avoid a public hairpin (~400ms TLS each call).
 */
class BillingClient
{
    private const BALANCE_CACHE_TTL_SECONDS = 8;

    private function configuredBase(): string
    {
        return rtrim((string) config('billing.api_url'), '/');
    }

    /**
     * Public billing URL rewritten to a same-host IP when force_ip is set.
     * Example: https://ladill.com/api/billing + 127.0.0.1
     *       → https://127.0.0.1/api/billing (Host: ladill.com)
     */
    private function base(): string
    {
        $base = $this->configuredBase();
        $forceIp = trim((string) config('billing.force_ip', ''));
        if ($forceIp === '') {
            return $base;
        }

        $parts = parse_url($base);
        if (! is_array($parts) || empty($parts['host'])) {
            return $base;
        }

        $scheme = $parts['scheme'] ?? 'https';
        $path = $parts['path'] ?? '';
        $port = isset($parts['port']) ? ':'.$parts['port'] : '';

        return $scheme.'://'.$forceIp.$port.$path;
    }

    private function token(): string
    {
        return (string) (config('billing.api_key') ?? '');
    }

    private function client(): PendingRequest
    {
        $pending = Http::withToken($this->token())
            ->acceptJson()
            ->timeout((int) config('billing.timeout', 10))
            ->connectTimeout((int) config('billing.connect_timeout', 2));

        $forceIp = trim((string) config('billing.force_ip', ''));
        if ($forceIp === '') {
            return $pending;
        }

        $host = parse_url($this->configuredBase(), PHP_URL_HOST);
        if (! is_string($host) || $host === '') {
            return $pending;
        }

        $pending = $pending->withHeaders(['Host' => $host]);

        // Loopback TLS cert is issued for the public host, not the IP.
        if (in_array($forceIp, ['127.0.0.1', '::1', 'localhost'], true)
            || filter_var($forceIp, FILTER_VALIDATE_IP)) {
            $pending = $pending->withOptions(['verify' => false]);
        }

        return $pending;
    }

    private function get(string $path, array $query): array
    {
        $res = $this->client()->get($this->base().$path, $query);
        $res->throw();

        return (array) $res->json();
    }

    public function balanceMinor(string $publicId): int
    {
        return (int) Cache::remember(
            $this->balanceCacheKey($publicId),
            self::BALANCE_CACHE_TTL_SECONDS,
            fn () => (int) ($this->get('/balance', ['user' => $publicId])['balance_minor'] ?? 0),
        );
    }

    /**
     * Start a Paystack checkout to top up the central wallet; returns the
     * checkout URL. Backs the in-app two-step "Add funds" modal.
     */
    public function topup(string $publicId, float $amount, string $returnUrl): string
    {
        $res = $this->client()->timeout(15)->post($this->base().'/topup', [
            'user' => $publicId,
            'amount' => $amount,
            'return_url' => $returnUrl,
        ]);
        $res->throw();

        return (string) ($res->json()['checkout_url'] ?? '');
    }

    public function canAfford(string $publicId, int $amountMinor): bool
    {
        // Prefer a single balance lookup (cached) over a dedicated can-afford round-trip.
        return $this->balanceMinor($publicId) >= $amountMinor;
    }

    public function serviceLedger(string $publicId, string $service): array
    {
        return $this->get('/service-ledger', ['user' => $publicId, 'service' => $service]);
    }

    /**
     * Debit the wallet. Returns the API payload on success (includes
     * balance_after_minor), or null on insufficient balance (HTTP 402).
     * Idempotent by $reference.
     *
     * @return array<string, mixed>|null
     */
    public function debit(string $publicId, int $amountMinor, string $service, string $source, string $reference, ?int $serviceId = null, ?string $description = null): ?array
    {
        $res = $this->client()->post($this->base().'/debit', array_filter([
            'user' => $publicId,
            'amount_minor' => $amountMinor,
            'service' => $service,
            'source' => $source,
            'reference' => $reference,
            'service_id' => $serviceId,
            'description' => $description,
        ], static fn ($v) => $v !== null));

        if ($res->status() === 402) {
            $this->forgetBalance($publicId);
            if (is_numeric($res->json('balance_minor'))) {
                Cache::put(
                    $this->balanceCacheKey($publicId),
                    (int) $res->json('balance_minor'),
                    self::BALANCE_CACHE_TTL_SECONDS,
                );
            }

            return null;
        }

        $res->throw();
        $payload = (array) $res->json();

        if (isset($payload['balance_after_minor'])) {
            Cache::put(
                $this->balanceCacheKey($publicId),
                (int) $payload['balance_after_minor'],
                self::BALANCE_CACHE_TTL_SECONDS,
            );
        } else {
            $this->forgetBalance($publicId);
        }

        return $payload;
    }

    /**
     * @return array<string, mixed>
     */
    public function credit(string $publicId, int $amountMinor, string $service, string $source, string $reference, ?int $serviceId = null, ?string $description = null): array
    {
        $res = $this->client()->post($this->base().'/credit', array_filter([
            'user' => $publicId,
            'amount_minor' => $amountMinor,
            'service' => $service,
            'source' => $source,
            'reference' => $reference,
            'service_id' => $serviceId,
            'description' => $description,
        ], static fn ($v) => $v !== null));
        $res->throw();

        $payload = (array) $res->json();
        if (isset($payload['balance_after_minor'])) {
            Cache::put(
                $this->balanceCacheKey($publicId),
                (int) $payload['balance_after_minor'],
                self::BALANCE_CACHE_TTL_SECONDS,
            );
        } else {
            $this->forgetBalance($publicId);
        }

        return $payload;
    }

    public function forgetBalance(string $publicId): void
    {
        Cache::forget($this->balanceCacheKey($publicId));
    }

    private function balanceCacheKey(string $publicId): string
    {
        return 'billing:balance_minor:'.$publicId;
    }
}