<?php

namespace App\Services\Hosting;

use App\Models\HostingAccount;
use App\Models\HostingProduct;
use App\Models\User;
use Illuminate\Support\Collection;

class UpsellRecommendationService
{
    private const STORAGE_THRESHOLD = 70.0;
    private const TRAFFIC_THRESHOLD = 70.0;
    private const EMAIL_ADDON_QUANTITY = 10;
    private const EMAIL_ADDON_UNIT_PRICE = 5;
    private const BYTES_PER_GB = 1073741824;

    /**
     * @return Collection<int, array<string, mixed>>
     */
    public function recommendationsForUser(User $user): Collection
    {
        $accountsQuery = HostingAccount::query()
            ->where('user_id', $user->id)
            ->where('status', HostingAccount::STATUS_ACTIVE)
            ->with(['product']);

        if (HostingAccount::tracksLocalMailboxes()) {
            $accountsQuery->with(['mailboxes:id,hosting_account_id,is_paid']);
        }

        $accounts = $accountsQuery->get();

        return $accounts
            ->flatMap(fn (HostingAccount $account): array => $this->recommendationsForAccount($account))
            ->sortByDesc(fn (array $recommendation): float => (float) ($recommendation['priority_score'] ?? 0))
            ->values();
    }

    /**
     * @return array<int, array<string, mixed>>
     */
    public function recommendationsForAccount(HostingAccount $account): array
    {
        $account->loadMissing(['product']);

        $recommendations = [];
        $upgradeProduct = $this->nextUpgradeProduct($account);
        $diskPercent = $account->diskUsagePercent();
        $trafficPercent = $this->bandwidthUsagePercent($account);
        $trafficTriggered = $trafficPercent !== null && $trafficPercent >= self::TRAFFIC_THRESHOLD;
        $storageTriggered = $diskPercent >= self::STORAGE_THRESHOLD;

        if ($upgradeProduct && ($storageTriggered || $trafficTriggered)) {
            $recommendations[] = [
                'id' => sprintf('account-%d-upgrade', $account->id),
                'type' => 'plan_upgrade',
                'trigger' => $storageTriggered && $trafficTriggered
                    ? 'storage_and_traffic'
                    : ($storageTriggered ? 'storage_usage' : 'traffic_spike'),
                'account_id' => $account->id,
                'account_label' => $account->primary_domain ?: $account->username,
                'title' => $storageTriggered && $trafficTriggered
                    ? sprintf('%s is outgrowing its current plan', $account->primary_domain ?: $account->username)
                    : ($storageTriggered
                        ? sprintf('Storage usage is high on %s', $account->primary_domain ?: $account->username)
                        : sprintf('Traffic is climbing on %s', $account->primary_domain ?: $account->username)),
                'message' => $this->upgradeMessage($account, $upgradeProduct, $diskPercent, $trafficPercent),
                'cta_label' => sprintf('Upgrade to %s', $upgradeProduct->name),
                'cta_url' => route('hosting.accounts.show', $account),
                'target_product_id' => $upgradeProduct->id,
                'target_product_name' => $upgradeProduct->name,
                'target_product_type' => $upgradeProduct->type,
                'priority_score' => max($diskPercent, $trafficPercent ?? 0),
                'metrics' => [
                    'disk_usage_percent' => round($diskPercent, 2),
                    'traffic_usage_percent' => $trafficPercent !== null ? round($trafficPercent, 2) : null,
                ],
            ];
        }

        $freeAllowance = $account->freeEmailAllowance();
        $mailboxCount = $account->loadedMailboxes()->count();
        if (HostingAccount::tracksLocalMailboxes() && $freeAllowance !== null && $mailboxCount > $freeAllowance) {
            $extraMailboxes = $mailboxCount - $freeAllowance;
            $addonAmount = self::EMAIL_ADDON_QUANTITY * self::EMAIL_ADDON_UNIT_PRICE;

            $recommendations[] = [
                'id' => sprintf('account-%d-email-addon', $account->id),
                'type' => 'email_addon',
                'trigger' => 'email_overage',
                'account_id' => $account->id,
                'account_label' => $account->primary_domain ?: $account->username,
                'title' => sprintf('Mailbox overage on %s', $account->primary_domain ?: $account->username),
                'message' => sprintf(
                    'This account is using %d mailbox%s on a plan with %d included. Adding %d more mailboxes would be GHS %d/month.',
                    $mailboxCount,
                    $mailboxCount === 1 ? '' : 'es',
                    $freeAllowance,
                    self::EMAIL_ADDON_QUANTITY,
                    $addonAmount
                ),
                'cta_label' => 'Manage Email Add-ons',
                'cta_url' => route('hosting.accounts.show', $account),
                'suggested_quantity' => self::EMAIL_ADDON_QUANTITY,
                'estimated_amount' => (float) $addonAmount,
                'priority_score' => 50 + ($extraMailboxes * 5),
                'metrics' => [
                    'mailbox_count' => $mailboxCount,
                    'free_allowance' => $freeAllowance,
                    'extra_mailboxes' => $extraMailboxes,
                ],
            ];
        }

        return $recommendations;
    }

    private function nextUpgradeProduct(HostingAccount $account): ?HostingProduct
    {
        $current = $account->product;
        if (! $current) {
            return null;
        }

        return HostingProduct::query()
            ->active()
            ->visible()
            ->where('category', HostingProduct::CATEGORY_SHARED)
            ->whereKeyNot($current->id)
            ->get()
            ->filter(function (HostingProduct $candidate) use ($current): bool {
                $candidateDomains = $candidate->max_domains ?? 0;
                $currentDomains = $current->max_domains ?? 0;

                return ($candidate->disk_gb ?? 0) > ($current->disk_gb ?? 0)
                    || ($candidate->max_email_accounts ?? 0) > ($current->max_email_accounts ?? 0)
                    || ($candidateDomains === -1 && $currentDomains !== -1)
                    || ($candidateDomains > $currentDomains && $currentDomains !== -1);
            })
            ->sortBy(fn (HostingProduct $candidate): string => sprintf(
                '%d-%08d-%012.2f',
                $candidate->type === $current->type ? 0 : 1,
                (int) ($candidate->sort_order ?? 0),
                (float) ($candidate->price_monthly ?? 0)
            ))
            ->first();
    }

    private function bandwidthUsagePercent(HostingAccount $account): ?float
    {
        $limitBytes = $this->bandwidthLimitBytes($account);
        if ($limitBytes === null || $limitBytes <= 0) {
            return null;
        }

        return ($account->bandwidth_used_bytes / $limitBytes) * 100;
    }

    private function bandwidthLimitBytes(HostingAccount $account): ?int
    {
        $limitBytes = data_get($account->resource_limits, 'bandwidth_limit_bytes');
        if (is_numeric($limitBytes) && (int) $limitBytes > 0) {
            return (int) $limitBytes;
        }

        $bandwidthGb = data_get($account->resource_limits, 'bandwidth_gb');
        if (is_numeric($bandwidthGb) && (int) $bandwidthGb > 0) {
            return (int) $bandwidthGb * self::BYTES_PER_GB;
        }

        if ($account->product?->bandwidth_gb && $account->product->bandwidth_gb > 0) {
            return (int) $account->product->bandwidth_gb * self::BYTES_PER_GB;
        }

        return null;
    }

    private function upgradeMessage(HostingAccount $account, HostingProduct $target, float $diskPercent, ?float $trafficPercent): string
    {
        $parts = [];

        if ($diskPercent >= self::STORAGE_THRESHOLD) {
            $parts[] = sprintf('disk usage is at %.1f%%', $diskPercent);
        }

        if ($trafficPercent !== null && $trafficPercent >= self::TRAFFIC_THRESHOLD) {
            $parts[] = sprintf('traffic usage is at %.1f%%', $trafficPercent);
        }

        $reason = $parts === [] ? 'usage is increasing' : implode(' and ', $parts);

        return sprintf(
            '%s. Moving this account to %s gives you %s storage%s.',
            ucfirst($reason),
            $target->name,
            $target->formatDiskSize(),
            $target->formatDomainLimit() ? ' and '.$target->formatDomainLimit() : ''
        );
    }
}