<?php

declare(strict_types=1);

require_once __DIR__ . '/bootstrap.php';

/**
 * Single source of truth for the pricing tiers, matching preise.php and
 * agb.php. max_participants = null means "no upper limit defined, contact
 * us" (the "auf Anfrage" tier).
 *
 * @return array<string, array{label: string, max_participants: ?int, price_cents: int}>
 */
function billing_plans(): array
{
    return [
        'free' => ['label' => 'Kostenlos', 'max_participants' => 10, 'price_cents' => 0],
        'basic' => ['label' => 'Basic', 'max_participants' => 25, 'price_cents' => 399],
        'plus' => ['label' => 'Plus', 'max_participants' => 50, 'price_cents' => 799],
        'pro' => ['label' => 'Pro', 'max_participants' => 150, 'price_cents' => 1299],
        'enterprise' => ['label' => 'Enterprise (auf Anfrage)', 'max_participants' => null, 'price_cents' => 0],
    ];
}

/**
 * Returns the cheapest plan whose participant limit still covers
 * $activeParticipantCount. Used both to show customers which plan they
 * need and, once Stripe is wired up, to detect required upgrades.
 */
function billing_required_plan_code(int $activeParticipantCount): string
{
    foreach (billing_plans() as $code => $plan) {
        if ($plan['max_participants'] === null || $activeParticipantCount <= $plan['max_participants']) {
            return $code;
        }
    }

    return 'enterprise';
}

function billing_count_active_participants(PDO $pdo, int $tenantId): int
{
    $stmt = $pdo->prepare('SELECT COUNT(*) FROM participants WHERE tenant_id = ? AND active = 1');
    $stmt->execute([$tenantId]);

    return (int)$stmt->fetchColumn();
}

/**
 * @return array{tenant_id: int, plan_code: string, subscription_status: string, stripe_customer_id: ?string, stripe_subscription_id: ?string, current_period_end: ?string}
 */
function billing_fetch_or_init(PDO $pdo, int $tenantId): array
{
    $stmt = $pdo->prepare('SELECT * FROM tenant_billing WHERE tenant_id = ?');
    $stmt->execute([$tenantId]);
    $row = $stmt->fetch();

    if ($row === false) {
        $pdo->prepare("INSERT INTO tenant_billing (tenant_id, plan_code, subscription_status) VALUES (?, 'free', 'active')")
            ->execute([$tenantId]);

        return [
            'tenant_id' => $tenantId,
            'plan_code' => 'free',
            'subscription_status' => 'active',
            'stripe_customer_id' => null,
            'stripe_subscription_id' => null,
            'current_period_end' => null,
        ];
    }

    return $row;
}

/**
 * Compares the tenant's currently booked plan against what their active
 * participant count actually requires. Purely informational until the
 * Stripe integration lands — nothing here blocks usage or auto-upgrades.
 *
 * @return array{current_plan: string, required_plan: string, active_participants: int, needs_upgrade: bool}
 */
function billing_check_tenant(PDO $pdo, int $tenantId): array
{
    $billing = billing_fetch_or_init($pdo, $tenantId);
    $activeCount = billing_count_active_participants($pdo, $tenantId);
    $requiredPlan = billing_required_plan_code($activeCount);

    $plans = array_keys(billing_plans());
    $currentRank = array_search($billing['plan_code'], $plans, true);
    $requiredRank = array_search($requiredPlan, $plans, true);

    return [
        'current_plan' => $billing['plan_code'],
        'required_plan' => $requiredPlan,
        'active_participants' => $activeCount,
        'needs_upgrade' => $requiredRank !== false && $currentRank !== false && $requiredRank > $currentRank,
    ];
}