<?php

namespace App\Services\Hosting;

use App\Models\HostingAccount;
use App\Models\HostingNode;
use App\Models\HostingProduct;
use App\Models\NodeCapacityAlert;

class NodeCapacityService
{
    public function __construct(
        private HostingNodePoolService $nodePool,
    ) {}

    public const WARNING_THRESHOLD = 80;
    public const CRITICAL_THRESHOLD = 95;
    public const LOCAL_NODE_LIMIT = 50;
    private const BYTES_PER_GB = 1073741824;

    public function checkAllNodes(): array
    {
        $alerts = [];

        $nodes = HostingNode::query()
            ->whereIn('status', [HostingNode::STATUS_ACTIVE, HostingNode::STATUS_FULL])
            ->where('type', HostingNode::TYPE_SHARED)
            ->get();

        foreach ($nodes as $node) {
            $alert = $this->checkNode($node);

            if ($alert) {
                $alerts[] = $alert;
            }
        }

        return $alerts;
    }

    public function checkNode(HostingNode $node): ?NodeCapacityAlert
    {
        $node = $this->refreshNodeResourceTotals($node);
        $capacityPercent = $this->nodePressurePercent($node);

        $existingAlert = NodeCapacityAlert::where('hosting_node_id', $node->id)
            ->where('is_resolved', false)
            ->whereIn('alert_type', [
                NodeCapacityAlert::TYPE_CAPACITY_WARNING,
                NodeCapacityAlert::TYPE_CAPACITY_CRITICAL,
                NodeCapacityAlert::TYPE_NEEDS_EXPANSION,
            ])
            ->first();

        if ($capacityPercent >= self::CRITICAL_THRESHOLD) {
            return $this->createOrUpdateAlert(
                $node,
                NodeCapacityAlert::TYPE_CAPACITY_CRITICAL,
                $capacityPercent,
                sprintf(
                    'Node %s is at %.1f%% pressure (%s). Immediate action required.',
                    $node->name,
                    $capacityPercent,
                    $this->dominantPressureLabel($node)
                ),
                $existingAlert
            );
        }

        if ($capacityPercent >= self::WARNING_THRESHOLD) {
            return $this->createOrUpdateAlert(
                $node,
                NodeCapacityAlert::TYPE_CAPACITY_WARNING,
                $capacityPercent,
                sprintf(
                    'Node %s is at %.1f%% pressure (%s). Capacity is nearing exhaustion.',
                    $node->name,
                    $capacityPercent,
                    $this->dominantPressureLabel($node)
                ),
                $existingAlert
            );
        }

        if ($existingAlert) {
            $existingAlert->update([
                'is_resolved' => true,
                'resolved_at' => now(),
                'resolution_notes' => 'Auto-resolved: Node pressure dropped below warning threshold.',
            ]);
        }

        return null;
    }

    public function canProvision(HostingNode|int $node, int $requestedDiskGb): bool
    {
        $node = $node instanceof HostingNode ? $node : HostingNode::query()->findOrFail($node);
        $node = $this->refreshNodeResourceTotals($node);

        return $node->canProvision($requestedDiskGb);
    }

    public function checkCapacityForProduct(HostingProduct $product): array
    {
        $requestedDiskGb = (int) ($product->disk_gb ?? 0);
        $segment = $product->preferredNodeSegment();
        $nodes = $this->preparedCandidateNodes($segment)
            ->map(fn (HostingNode $node): array => $this->nodeSnapshot($node, $requestedDiskGb, $segment))
            ->values();

        $selected = $this->findAvailableNodeForProduct($product);

        return [
            'available' => $selected !== null,
            'requested_disk_gb' => $requestedDiskGb,
            'segment' => $segment,
            'selected_node_id' => $selected?->id,
            'selected_node_name' => $selected?->name,
            'nodes' => $nodes,
        ];
    }

    public function findAvailableNode(int $requestedDiskGb = 0, ?string $segment = null): ?HostingNode
    {
        $primaries = $this->preparedCandidateNodes($segment)
            ->filter(fn (HostingNode $node) => $node->isPrimary());

        $bestMember = null;
        $bestLoad = PHP_FLOAT_MAX;

        foreach ($primaries as $primary) {
            $member = $this->nodePool->findProvisioningMember($primary, $requestedDiskGb, $segment);
            if (! $member) {
                continue;
            }

            if ($this->isLocalNode($member) && $member->accountCapacityPercent() >= self::LOCAL_NODE_LIMIT) {
                continue;
            }

            $load = (float) $member->current_load_percent;
            if ($load < $bestLoad) {
                $bestLoad = $load;
                $bestMember = $member;
            }
        }

        if ($bestMember) {
            return $bestMember;
        }

        foreach ($this->preparedCandidateNodes($segment) as $node) {
            if (! $node->canProvision($requestedDiskGb, $segment)) {
                continue;
            }

            if ($this->isLocalNode($node) && $node->accountCapacityPercent() >= self::LOCAL_NODE_LIMIT) {
                continue;
            }

            return $node;
        }

        return null;
    }

    public function findAvailableNodeForProduct(HostingProduct $product): ?HostingNode
    {
        return $this->findAvailableNode(
            (int) ($product->disk_gb ?? 0),
            $product->preferredNodeSegment()
        );
    }

    public function needsNewNode(): bool
    {
        return $this->findAvailableNode() === null;
    }

    public function getCapacitySummary(): array
    {
        $nodes = HostingNode::query()
            ->whereIn('status', [HostingNode::STATUS_ACTIVE, HostingNode::STATUS_FULL])
            ->where('type', HostingNode::TYPE_SHARED)
            ->get()
            ->map(fn (HostingNode $node): HostingNode => $this->refreshNodeResourceTotals($node));

        $totalDisk = $nodes->sum('disk_gb');
        $totalLogicalCapacity = $nodes->sum(fn (HostingNode $node): float => $node->logicalCapacityGb());
        $totalAllocated = $nodes->sum('allocated_disk_gb');
        $totalUsed = $nodes->sum('used_disk_gb');
        $totalAccountCapacity = $nodes->sum('max_accounts');
        $totalAccounts = $nodes->sum('current_accounts');

        return [
            'total_nodes' => $nodes->count(),
            'total_capacity' => $totalAccountCapacity,
            'total_used' => $totalAccounts,
            'available_slots' => max($totalAccountCapacity - $totalAccounts, 0),
            'overall_percent' => $totalAccountCapacity > 0 ? round(($totalAccounts / $totalAccountCapacity) * 100, 1) : 0,
            'physical_disk_gb' => $totalDisk,
            'logical_disk_gb' => round($totalLogicalCapacity, 2),
            'allocated_disk_gb' => $totalAllocated,
            'used_disk_gb' => $totalUsed,
            'logical_disk_percent' => $totalDisk > 0 ? round(($totalUsed / $totalDisk) * 100, 1) : 0,
            'physical_disk_percent' => $totalDisk > 0 ? round(($totalUsed / $totalDisk) * 100, 1) : 0,
            'needs_expansion' => $this->needsNewNode(),
            'unresolved_alerts' => NodeCapacityAlert::unresolved()->count(),
        ];
    }

    public function refreshNodeResourceTotals(HostingNode $node): HostingNode
    {
        $aggregate = HostingAccount::query()
            ->where('hosting_node_id', $node->id)
            ->where('type', HostingAccount::TYPE_SHARED)
            ->selectRaw('COUNT(*) as account_count')
            ->selectRaw('COALESCE(SUM(allocated_disk_gb), 0) as allocated_disk_gb')
            ->selectRaw('COALESCE(SUM(disk_used_bytes), 0) as used_disk_bytes')
            ->first();

        $currentAccounts = (int) ($aggregate->account_count ?? 0);
        $allocatedDiskGb = (int) ($aggregate->allocated_disk_gb ?? 0);
        $usedDiskGb = (int) ceil(((int) ($aggregate->used_disk_bytes ?? 0)) / self::BYTES_PER_GB);
        $logicalCapacity = $node->disk_gb && $node->disk_gb > 0
            ? $node->disk_gb * max((float) ($node->oversell_ratio ?: 1), 1)
            : 0;
        $physicalPercent = $node->disk_gb && $node->disk_gb > 0 ? ($usedDiskGb / $node->disk_gb) * 100 : 0;
        $accountPercent = $node->max_accounts && $node->max_accounts > 0 ? ($currentAccounts / $node->max_accounts) * 100 : 0;
        $currentLoadPercent = round(max($physicalPercent, $accountPercent), 2);

        $updates = [
            'current_accounts' => $currentAccounts,
            'allocated_disk_gb' => $allocatedDiskGb,
            'used_disk_gb' => $usedDiskGb,
            'current_load_percent' => $currentLoadPercent,
        ];

        if (in_array($node->status, [HostingNode::STATUS_ACTIVE, HostingNode::STATUS_FULL], true)) {
            $updates['status'] = $this->shouldMarkFull($node, $currentAccounts, $usedDiskGb)
                ? HostingNode::STATUS_FULL
                : HostingNode::STATUS_ACTIVE;
        }

        $node->forceFill($updates);

        if ($node->exists && $node->isDirty()) {
            $node->save();
        }

        return $node->refresh();
    }

    private function candidateNodes(?string $segment)
    {
        return HostingNode::query()
            ->whereIn('status', [HostingNode::STATUS_ACTIVE, HostingNode::STATUS_FULL])
            ->where('type', HostingNode::TYPE_SHARED)
            ->when($segment, function ($query) use ($segment) {
                $query->whereIn('segment', [$segment, HostingNode::SEGMENT_GENERAL]);
            })
            ->get();
    }

    private function preparedCandidateNodes(?string $segment)
    {
        return $this->candidateNodes($segment)
            ->map(fn (HostingNode $node): HostingNode => $this->refreshNodeResourceTotals($node))
            ->sortBy(fn (HostingNode $node) => sprintf(
                '%012.2f-%012d-%012d',
                (float) $node->current_load_percent,
                $node->allocated_disk_gb,
                $node->current_accounts
            ))
            ->values();
    }

    private function shouldMarkFull(HostingNode $node, int $currentAccounts, int $usedDiskGb): bool
    {
        if ($node->max_accounts && $currentAccounts >= $node->max_accounts) {
            return true;
        }

        if ($node->disk_gb && $node->disk_gb > 0) {
            return $usedDiskGb >= $node->disk_gb;
        }

        return false;
    }

    private function nodePressurePercent(HostingNode $node): float
    {
        return round(max(
            $node->physicalDiskPercent(),
            $node->accountCapacityPercent()
        ), 2);
    }

    private function dominantPressureLabel(HostingNode $node): string
    {
        $pressures = [
            'disk usage' => $node->physicalDiskPercent(),
            'account slots' => $node->accountCapacityPercent(),
        ];

        arsort($pressures);

        $label = array_key_first($pressures);

        return sprintf('%s %.1f%%', $label, $pressures[$label] ?? 0);
    }

    private function nodeSnapshot(HostingNode $node, int $requestedDiskGb, ?string $segment = null): array
    {
        return [
            'id' => $node->id,
            'name' => $node->name,
            'segment' => $node->segment,
            'can_provision' => $node->canProvision($requestedDiskGb, $segment),
            'requested_disk_gb' => $requestedDiskGb,
            'physical_disk_gb' => $node->disk_gb,
            'logical_disk_gb' => $node->logicalCapacityGb(),
            'allocated_disk_gb' => $node->allocated_disk_gb,
            'used_disk_gb' => $node->used_disk_gb,
            'available_logical_disk_gb' => $node->availableLogicalDiskGb(),
            'oversell_ratio' => (float) $node->oversell_ratio,
            'current_accounts' => $node->current_accounts,
            'max_accounts' => $node->max_accounts,
            'logical_capacity_percent' => $node->logicalCapacityPercent(),
            'physical_disk_percent' => $node->physicalDiskPercent(),
            'account_capacity_percent' => $node->accountCapacityPercent(),
            'current_load_percent' => (float) $node->current_load_percent,
        ];
    }

    private function isLocalNode(HostingNode $node): bool
    {
        return $node->provider === HostingNode::PROVIDER_LOCAL
            || $node->ip_address === '127.0.0.1'
            || $node->ip_address === 'localhost';
    }

    private function createOrUpdateAlert(
        HostingNode $node,
        string $type,
        float $capacityPercent,
        string $message,
        ?NodeCapacityAlert $existingAlert
    ): NodeCapacityAlert {
        $data = [
            'hosting_node_id' => $node->id,
            'alert_type' => $type,
            'current_accounts' => $node->current_accounts,
            'max_accounts' => $node->max_accounts ?? 0,
            'capacity_percent' => $capacityPercent,
            'resource_usage' => [
                'logical_capacity_percent' => $node->logicalCapacityPercent(),
                'physical_disk_percent' => $node->physicalDiskPercent(),
                'account_capacity_percent' => $node->accountCapacityPercent(),
                'allocated_disk_gb' => $node->allocated_disk_gb,
                'used_disk_gb' => $node->used_disk_gb,
                'logical_disk_gb' => $node->logicalCapacityGb(),
            ],
            'message' => $message,
        ];

        if ($existingAlert) {
            $existingAlert->update($data);

            return $existingAlert;
        }

        return NodeCapacityAlert::create($data);
    }
}