<?php

namespace Modules\Crm\Services;

use Carbon\Carbon;
use Illuminate\Support\Facades\DB;
use Modules\Crm\Entities\CrmCallQueue;
use Modules\Crm\Entities\CrmCallSession;
use Modules\Crm\Entities\CrmPhoneFollowUp;
use Modules\Crm\Utils\TelemarketingUtil;

class CallQueueService
{
    public function syncQueueForBusiness(int $business_id): void
    {
        $this->pruneInvalidQueueEntries($business_id);

        $phones = CrmPhoneFollowUp::where('business_id', $business_id)
            ->where('status', 'pending')
            ->where('block_auto_recall', false)
            ->get();

        foreach ($phones as $phone) {
            $exists = CrmCallQueue::where('business_id', $business_id)
                ->where('phone_follow_up_id', $phone->id)
                ->exists();

            if (! $exists) {
                CrmCallQueue::create([
                    'business_id' => $business_id,
                    'phone_follow_up_id' => $phone->id,
                    'campaign_id' => $phone->campaign_id,
                    'status' => 'available',
                    'priority' => $phone->priority ?? 3,
                ]);
            }
        }
    }

    /**
     * Remove queue slots for numbers already called or no longer pending.
     */
    public function pruneInvalidQueueEntries(int $business_id): void
    {
        $now = Carbon::now();

        CrmCallQueue::where('business_id', $business_id)
            ->whereIn('status', ['available', 'locked'])
            ->whereHas('phoneFollowUp', function ($q) {
                $q->where('status', '!=', 'pending');
            })
            ->update([
                'status' => 'skipped',
                'completed_at' => $now,
                'locked_by' => null,
                'locked_at' => null,
                'expires_at' => null,
            ]);

        $donePhoneIds = CrmCallQueue::where('business_id', $business_id)
            ->whereIn('status', ['completed', 'skipped'])
            ->pluck('phone_follow_up_id')
            ->unique();

        if ($donePhoneIds->isNotEmpty()) {
            CrmCallQueue::where('business_id', $business_id)
                ->whereIn('status', ['available', 'locked'])
                ->whereIn('phone_follow_up_id', $donePhoneIds)
                ->update([
                    'status' => 'skipped',
                    'completed_at' => $now,
                    'locked_by' => null,
                    'locked_at' => null,
                    'expires_at' => null,
                ]);
        }
    }

    public function acquireNext(int $business_id, int $user_id, ?int $campaign_id = null): ?CrmCallQueue
    {
        return DB::transaction(function () use ($business_id, $user_id, $campaign_id) {
            $this->syncQueueForBusiness($business_id);

            $query = CrmCallQueue::where('crm_call_queues.business_id', $business_id)
                ->where('crm_call_queues.status', 'available')
                ->join('crm_phone_follow_ups', 'crm_call_queues.phone_follow_up_id', '=', 'crm_phone_follow_ups.id')
                ->where('crm_phone_follow_ups.status', 'pending')
                ->where('crm_phone_follow_ups.block_auto_recall', false)
                ->select('crm_call_queues.*')
                ->orderBy('crm_call_queues.priority')
                ->orderBy('crm_call_queues.id');

            if (! auth()->user()->can('crm.telemarketing.view_all_queue') && ! auth()->user()->can('superadmin')) {
                $query->where(function ($q) use ($user_id) {
                    $q->whereNull('crm_phone_follow_ups.assigned_to')
                        ->orWhere('crm_phone_follow_ups.assigned_to', $user_id);
                });
            }

            if (! empty($campaign_id)) {
                $query->where('crm_call_queues.campaign_id', $campaign_id);
            }

            $queue = $query->lockForUpdate()->first();

            if (empty($queue)) {
                return null;
            }

            $lockMinutes = TelemarketingUtil::callLockMinutes($business_id);
            $now = Carbon::now();

            $queue->update([
                'status' => 'locked',
                'locked_by' => $user_id,
                'locked_at' => $now,
                'expires_at' => $now->copy()->addMinutes($lockMinutes),
            ]);

            return $queue->fresh(['phoneFollowUp']);
        });
    }

    public function release(int $queue_id, int $user_id, ?int $business_id = null): bool
    {
        $query = CrmCallQueue::query()->where('id', $queue_id);
        if ($business_id) {
            $query->where('business_id', $business_id);
        }
        $queue = $query->first();
        if (empty($queue) || $queue->locked_by != $user_id) {
            return false;
        }

        if ($queue->status === 'in_call') {
            return false;
        }

        $queue->update([
            'status' => 'available',
            'locked_by' => null,
            'locked_at' => null,
            'expires_at' => null,
        ]);

        return true;
    }

    public function startSession(int $queue_id, int $user_id, ?int $business_id = null): ?CrmCallSession
    {
        return DB::transaction(function () use ($queue_id, $user_id, $business_id) {
            $query = CrmCallQueue::query()->where('id', $queue_id);
            if ($business_id) {
                $query->where('business_id', $business_id);
            }
            $queue = $query->lockForUpdate()->first();

            if (empty($queue) || $queue->locked_by != $user_id) {
                return null;
            }

            $session = CrmCallSession::create([
                'business_id' => $queue->business_id,
                'queue_id' => $queue->id,
                'phone_follow_up_id' => $queue->phone_follow_up_id,
                'user_id' => $user_id,
                'started_at' => Carbon::now(),
            ]);

            $queue->update([
                'status' => 'in_call',
                'call_session_id' => $session->id,
            ]);

            return $session->load('phoneFollowUp');
        });
    }

    public function endSession(int $session_id, int $user_id, ?string $outcome = null, ?int $business_id = null): ?CrmCallSession
    {
        return DB::transaction(function () use ($session_id, $user_id, $outcome, $business_id) {
            $query = CrmCallSession::query()->where('id', $session_id);
            if ($business_id) {
                $query->where('business_id', $business_id);
            }
            $session = $query->first();

            if (empty($session) || $session->user_id != $user_id || ! empty($session->ended_at)) {
                return null;
            }

            $session->update([
                'ended_at' => Carbon::now(),
                'outcome' => $outcome,
            ]);

            if (! empty($session->queue_id)) {
                CrmCallQueue::where('id', $session->queue_id)->update([
                    'status' => 'completed',
                    'completed_at' => Carbon::now(),
                ]);
            }

            return $session->fresh();
        });
    }

    public function getActiveSession(int $business_id, int $user_id): ?CrmCallSession
    {
        return CrmCallSession::where('business_id', $business_id)
            ->where('user_id', $user_id)
            ->whereNull('ended_at')
            ->with(['phoneFollowUp', 'queue'])
            ->latest('started_at')
            ->first();
    }

    public function getActiveQueue(int $business_id, int $user_id): ?CrmCallQueue
    {
        return CrmCallQueue::where('business_id', $business_id)
            ->where('locked_by', $user_id)
            ->whereIn('status', ['locked', 'in_call'])
            ->with('phoneFollowUp')
            ->latest('locked_at')
            ->first();
    }

    public function expireStaleLocks(): int
    {
        $expired = CrmCallQueue::whereIn('status', ['locked', 'in_call'])
            ->whereNotNull('expires_at')
            ->where('expires_at', '<', Carbon::now())
            ->get();

        $count = 0;
        foreach ($expired as $queue) {
            if ($queue->status === 'in_call') {
                continue;
            }
            $queue->update([
                'status' => 'available',
                'locked_by' => null,
                'locked_at' => null,
                'expires_at' => null,
            ]);
            $count++;
        }

        return $count;
    }
}