<?php

namespace App\Services\Hosting;

use App\Models\CustomerHostingOrder;
use App\Models\HostingAccount;
use App\Models\HostingBillingInvoice;
use App\Models\HostingPlanChange;
use App\Models\HostingProduct;
use App\Models\User;
use App\Services\Hosting\Providers\SharedNodeProvider;
use Illuminate\Support\Facades\DB;
use Illuminate\Validation\ValidationException;

class HostingPlanChangeService
{
    public function __construct(
        private NodeCapacityService $capacityService,
        private HostingResourcePolicyService $resourcePolicyService,
        private SharedNodeProvider $sharedNodeProvider,
    ) {
    }

    /**
     * @return \Illuminate\Database\Eloquent\Collection<int, HostingProduct>
     */
    public function availablePlans(): \Illuminate\Database\Eloquent\Collection
    {
        return HostingProduct::query()
            ->active()
            ->visible()
            ->where('category', HostingProduct::CATEGORY_SHARED)
            ->ordered()
            ->get();
    }

    /**
     * @return array<string, mixed>
     */
    public function quote(HostingAccount $account, HostingProduct $targetProduct): array
    {
        $account->loadMissing(['product', 'latestOrder', 'sites', 'databases', 'node']);
        $this->assertCanChange($account, $targetProduct);

        $currentProduct = $account->product;
        $order = $account->latestOrder;
        $billingCycle = $order?->billing_cycle ?? CustomerHostingOrder::CYCLE_MONTHLY;
        $cycleMonths = $order?->getCycleLengthInMonths() ?? 1;
        $currentCyclePrice = $this->cyclePriceFor($currentProduct, $billingCycle);
        $targetCyclePrice = $this->cyclePriceFor($targetProduct, $billingCycle);
        $remaining = $this->remainingCycleState($account, $order, $cycleMonths);
        $priceDelta = round($targetCyclePrice - $currentCyclePrice, 2);
        $direction = $priceDelta >= 0
            ? HostingPlanChange::DIRECTION_UPGRADE
            : HostingPlanChange::DIRECTION_DOWNGRADE;
        $proratedDelta = round($priceDelta * $remaining['ratio'], 2);
        $chargeAmount = $proratedDelta > 0 ? $proratedDelta : 0;
        $creditAmount = $proratedDelta < 0 ? abs($proratedDelta) : 0;

        return [
            'direction' => $direction,
            'billing_cycle' => $billingCycle,
            'cycle_months' => $cycleMonths,
            'remaining_days' => $remaining['days'],
            'proration_ratio' => $remaining['ratio'],
            'current_cycle_price' => $currentCyclePrice,
            'target_cycle_price' => $targetCyclePrice,
            'charge_amount' => $chargeAmount,
            'credit_amount' => $creditAmount,
            'net_amount' => round($chargeAmount - $creditAmount, 2),
            'currency' => $targetProduct->display_currency,
            'line_items' => $this->lineItems($account, $targetProduct, $direction, $chargeAmount, $creditAmount, $remaining['ratio']),
        ];
    }

    /**
     * @return array{change: HostingPlanChange, invoice: HostingBillingInvoice, account: HostingAccount, quote: array<string, mixed>}
     */
    public function apply(HostingAccount $account, HostingProduct $targetProduct, User $actor): array
    {
        $account->loadMissing(['product', 'latestOrder', 'sites', 'databases', 'node']);
        $quote = $this->quote($account, $targetProduct);
        $currentProduct = $account->product;

        return DB::transaction(function () use ($account, $targetProduct, $actor, $quote, $currentProduct): array {
            $change = HostingPlanChange::query()->create([
                'user_id' => $actor->id,
                'hosting_account_id' => $account->id,
                'from_hosting_product_id' => $currentProduct->id,
                'to_hosting_product_id' => $targetProduct->id,
                'direction' => $quote['direction'],
                'billing_cycle' => $quote['billing_cycle'],
                'cycle_months' => $quote['cycle_months'],
                'remaining_days' => $quote['remaining_days'],
                'proration_ratio' => $quote['proration_ratio'],
                'old_cycle_price' => $quote['current_cycle_price'],
                'new_cycle_price' => $quote['target_cycle_price'],
                'charge_amount' => $quote['charge_amount'],
                'credit_amount' => $quote['credit_amount'],
                'net_amount' => $quote['net_amount'],
                'currency' => $quote['currency'],
                'status' => 'applied',
                'applied_at' => now(),
                'metadata' => [
                    'actor_id' => $actor->id,
                    'sites_count' => $account->sites->count(),
                    'databases_count' => $account->databases->count(),
                ],
            ]);

            $invoiceStatus = $quote['charge_amount'] > 0
                ? HostingBillingInvoice::STATUS_PENDING
                : ($quote['credit_amount'] > 0
                    ? HostingBillingInvoice::STATUS_CREDITED
                    : HostingBillingInvoice::STATUS_WAIVED);

            $invoice = HostingBillingInvoice::query()->create([
                'user_id' => $actor->id,
                'hosting_account_id' => $account->id,
                'hosting_plan_change_id' => $change->id,
                'invoice_type' => HostingBillingInvoice::TYPE_PLAN_CHANGE,
                'status' => $invoiceStatus,
                'currency' => $quote['currency'],
                'subtotal_amount' => $quote['charge_amount'],
                'credit_amount' => $quote['credit_amount'],
                'total_amount' => max($quote['net_amount'], 0),
                'description' => sprintf(
                    '%s %s from %s to %s',
                    ucfirst($quote['direction']),
                    $account->primary_domain ?: $account->username,
                    $currentProduct->name,
                    $targetProduct->name
                ),
                'paid_at' => $invoiceStatus !== HostingBillingInvoice::STATUS_PENDING ? now() : null,
                'line_items' => $quote['line_items'],
                'metadata' => [
                    'direction' => $quote['direction'],
                    'billing_cycle' => $quote['billing_cycle'],
                    'remaining_days' => $quote['remaining_days'],
                ],
            ]);

            $this->applyProductToAccount($account, $targetProduct, $change, $actor);

            return [
                'change' => $change->fresh(['fromProduct', 'toProduct']),
                'invoice' => $invoice->fresh(),
                'account' => $account->fresh(['product', 'node']),
                'quote' => $quote,
            ];
        });
    }

    private function assertCanChange(HostingAccount $account, HostingProduct $targetProduct): void
    {
        if (! $account->product || ! $account->product->isSharedHosting()) {
            throw ValidationException::withMessages([
                'hosting_account_id' => 'Only shared hosting accounts can change packages.',
            ]);
        }

        if (! $targetProduct->isSharedHosting() || ! $targetProduct->is_active || ! $targetProduct->is_visible) {
            throw ValidationException::withMessages([
                'target_product_id' => 'Selected plan is not available for hosting upgrades.',
            ]);
        }

        if ((int) $account->hosting_product_id === (int) $targetProduct->id) {
            throw ValidationException::withMessages([
                'target_product_id' => 'Account is already on that plan.',
            ]);
        }

        $siteLimit = (int) ($targetProduct->max_domains ?? 0);
        if ($siteLimit >= 0 && $account->sites->count() > $siteLimit) {
            throw ValidationException::withMessages([
                'target_product_id' => "The target plan supports {$siteLimit} site(s), but this account already has {$account->sites->count()}.",
            ]);
        }

        $databaseLimit = $targetProduct->max_databases;
        if ($databaseLimit !== null && $databaseLimit >= 0 && $account->databases->count() > $databaseLimit) {
            throw ValidationException::withMessages([
                'target_product_id' => "The target plan supports {$databaseLimit} database(s), but this account already has {$account->databases->count()}.",
            ]);
        }

        $diskDelta = max((int) ($targetProduct->disk_gb ?? 0) - (int) ($account->allocated_disk_gb ?? 0), 0);
        if ($diskDelta > 0 && $account->node && ! $this->capacityService->canProvision($account->node, $diskDelta)) {
            throw ValidationException::withMessages([
                'target_product_id' => 'The assigned server does not have enough logical capacity for this upgrade.',
            ]);
        }
    }

    private function cyclePriceFor(?HostingProduct $product, string $billingCycle): float
    {
        if (! $product) {
            return 0;
        }

        $price = $product->getPriceForCycle($billingCycle);

        if ($price === null) {
            $price = $product->getPriceForCycle(CustomerHostingOrder::CYCLE_MONTHLY);
        }

        return round((float) $price, 2);
    }

    /**
     * @return array{ratio: float, days: int}
     */
    private function remainingCycleState(HostingAccount $account, ?CustomerHostingOrder $order, int $cycleMonths): array
    {
        $periodEnd = $account->expires_at
            ?? $order?->expires_at
            ?? now()->copy()->addMonthsNoOverflow($cycleMonths);

        if (! $periodEnd || $periodEnd->lte(now())) {
            return ['ratio' => 1.0, 'days' => 0];
        }

        $periodStart = $periodEnd->copy()->subMonthsNoOverflow(max($cycleMonths, 1));
        $totalSeconds = max($periodStart->diffInSeconds($periodEnd, false), 1);
        $remainingSeconds = max(now()->diffInSeconds($periodEnd, false), 0);

        return [
            'ratio' => round(min(max($remainingSeconds / $totalSeconds, 0), 1), 4),
            'days' => (int) ceil($remainingSeconds / 86400),
        ];
    }

    /**
     * @return array<int, array<string, mixed>>
     */
    private function lineItems(
        HostingAccount $account,
        HostingProduct $targetProduct,
        string $direction,
        float $chargeAmount,
        float $creditAmount,
        float $ratio
    ): array {
        $currentProduct = $account->product;

        return array_values(array_filter([
            [
                'code' => 'plan_change',
                'label' => sprintf('%s to %s', ucfirst($direction), $targetProduct->name),
                'description' => sprintf('Plan change from %s to %s.', $currentProduct?->name ?? 'Current plan', $targetProduct->name),
                'amount' => round($chargeAmount, 2),
            ],
            $creditAmount > 0 ? [
                'code' => 'proration_credit',
                'label' => 'Unused time credit',
                'description' => sprintf('Prorated credit at %.2f%% of the current cycle.', $ratio * 100),
                'amount' => round($creditAmount * -1, 2),
            ] : null,
        ]));
    }

    private function applyProductToAccount(HostingAccount $account, HostingProduct $targetProduct, HostingPlanChange $change, User $actor): void
    {
        $policyLimits = $this->resourcePolicyService->defaultLimitsForProduct($targetProduct);
        $resourceLimits = array_merge((array) ($account->resource_limits ?? []), [
            'disk_gb' => (int) ($targetProduct->disk_gb ?? 0),
            'bandwidth_gb' => $targetProduct->bandwidth_gb,
            'max_domains' => $targetProduct->max_domains,
            'max_databases' => $targetProduct->max_databases,
            'max_email_accounts' => $targetProduct->max_email_accounts,
            'max_ftp_accounts' => $targetProduct->max_ftp_accounts,
        ], $policyLimits);

        $metadata = array_merge((array) ($account->metadata ?? []), [
            'last_plan_change_id' => $change->id,
            'last_plan_change_at' => now()->toIso8601String(),
            'last_plan_changed_by' => $actor->id,
        ]);

        $account->update([
            'hosting_product_id' => $targetProduct->id,
            'allocated_disk_gb' => (int) ($targetProduct->disk_gb ?? 0),
            'cpu_limit_percent' => $policyLimits['cpu_limit_percent'] ?? $account->cpu_limit_percent,
            'memory_limit_mb' => $policyLimits['memory_limit_mb'] ?? $account->memory_limit_mb,
            'process_limit' => $policyLimits['process_limit'] ?? $account->process_limit,
            'io_limit_mb' => $policyLimits['io_limit_mb'] ?? $account->io_limit_mb,
            'inode_limit' => $policyLimits['inode_limit'] ?? $account->inode_limit,
            'resource_limits' => $resourceLimits,
            'metadata' => $metadata,
        ]);

        $account->refresh();

        $activeOrder = CustomerHostingOrder::query()
            ->where('hosting_account_id', $account->id)
            ->whereIn('status', [
                CustomerHostingOrder::STATUS_ACTIVE,
                CustomerHostingOrder::STATUS_SUSPENDED,
                CustomerHostingOrder::STATUS_PROVISIONING,
            ])
            ->latest('id')
            ->first();

        if ($activeOrder) {
            $activeOrder->update([
                'hosting_product_id' => $targetProduct->id,
                'currency' => $targetProduct->display_currency,
                'meta' => array_merge((array) ($activeOrder->meta ?? []), [
                    'last_plan_change_id' => $change->id,
                    'last_plan_change_direction' => $change->direction,
                ]),
            ]);
        }

        $this->sharedNodeProvider->syncAccountPackage($account);

        if ($account->node) {
            $this->capacityService->refreshNodeResourceTotals($account->node);
        }
    }
}