<?php

namespace App\Services\Qms;

use App\Models\Counter;
use App\Models\Organization;
use App\Models\ServiceQueue;
use App\Models\Ticket;
use App\Models\TicketEvent;
use Illuminate\Support\Facades\DB;
use Illuminate\Support\Str;

class QueueEngine
{
    public function issueTicket(
        ServiceQueue $queue,
        string $ownerRef,
        array $attributes = [],
    ): Ticket {
        return DB::transaction(function () use ($queue, $ownerRef, $attributes) {
            $queue = ServiceQueue::query()->lockForUpdate()->findOrFail($queue->id);

            if ($queue->is_paused || ! $queue->is_active) {
                throw new \RuntimeException('Queue is not accepting tickets.');
            }

            $sourceQueueId = $queue->id;
            [$queue, $attributes] = app(QueueRuleService::class)->apply($queue, $attributes);
            app(WorkflowService::class)->attachOnIssue($queue, $attributes);

            if ($queue->id !== $sourceQueueId) {
                $queue = ServiceQueue::query()->lockForUpdate()->findOrFail($queue->id);
            }

            if ($queue->is_paused || ! $queue->is_active) {
                throw new \RuntimeException('Queue is not accepting tickets.');
            }

            if ($queue->max_capacity) {
                $waiting = Ticket::query()
                    ->where('service_queue_id', $queue->id)
                    ->whereIn('status', ['waiting', 'called', 'serving', 'on_hold'])
                    ->count();
                if ($waiting >= $queue->max_capacity) {
                    throw new \RuntimeException('Queue has reached maximum capacity.');
                }
            }

            $queue->increment('ticket_sequence');
            $queue->refresh();

            $number = sprintf('%s%03d', $queue->prefix, $queue->ticket_sequence);
            $waitingCount = Ticket::query()
                ->where('service_queue_id', $queue->id)
                ->where('status', 'waiting')
                ->count();
            $estimatedWait = $waitingCount * (int) $queue->avg_service_seconds;

            $assignedCounterId = $this->resolveAssignedCounterId($queue, $attributes);

            $ticket = Ticket::create([
                'owner_ref' => $ownerRef,
                'organization_id' => $queue->organization_id,
                'branch_id' => $queue->branch_id,
                'service_queue_id' => $queue->id,
                'assigned_counter_id' => $assignedCounterId,
                'ticket_number' => $number,
                'status' => 'waiting',
                'priority' => $attributes['priority'] ?? 'walk_in',
                'position' => $waitingCount + 1,
                'customer_name' => $attributes['customer_name'] ?? null,
                'customer_phone' => $attributes['customer_phone'] ?? null,
                'customer_email' => $attributes['customer_email'] ?? null,
                'source' => $attributes['source'] ?? 'kiosk',
                'barcode' => $attributes['barcode'] ?? Str::upper(Str::random(10)),
                'estimated_wait_seconds' => $estimatedWait,
                'issued_at' => now(),
                'metadata' => $attributes['metadata'] ?? null,
            ]);

            $this->recordEvent($ticket, 'issued', $attributes['actor_ref'] ?? null, null, [
                'assigned_counter_id' => $assignedCounterId,
            ]);

            AuditLogger::record(
                $ownerRef,
                'ticket.issued',
                $queue->organization_id,
                $attributes['actor_ref'] ?? null,
                Ticket::class,
                $ticket->id,
                ['ticket_number' => $number, 'queue' => $queue->name],
            );

            $ticket = $ticket->fresh(['serviceQueue', 'branch', 'assignedCounter']);
            app(QueueNotificationService::class)->ticketIssued($ticket);

            return $ticket;
        });
    }

    public function callNext(ServiceQueue $queue, Counter $counter, ?string $actorRef = null): ?Ticket
    {
        $ticket = $this->nextWaitingTicket($queue, $counter);
        if (! $ticket) {
            return null;
        }

        return $this->callTicket($ticket, $counter, $actorRef);
    }

    public function callTicket(Ticket $ticket, Counter $counter, ?string $actorRef = null): Ticket
    {
        if ($ticket->assigned_counter_id && (int) $ticket->assigned_counter_id !== (int) $counter->id) {
            throw new \RuntimeException('Ticket is assigned to another service point.');
        }

        $ticket->update([
            'status' => 'called',
            'counter_id' => $counter->id,
            'assigned_counter_id' => $ticket->assigned_counter_id ?: $counter->id,
            'called_at' => now(),
        ]);

        $counter->update(['status' => 'busy']);
        $this->recordEvent($ticket, 'called', $actorRef, $counter->id);
        $this->audit($ticket, 'ticket.called', $actorRef, ['counter_id' => $counter->id]);

        app(VoiceAnnouncementService::class)->announceCalled($ticket, $counter);

        $ticket = $ticket->fresh(['serviceQueue', 'counter']);
        app(QueueNotificationService::class)->ticketCalled($ticket);
        $this->notifyWaitingPositions($ticket->serviceQueue);

        return $ticket;
    }

    public function recall(Ticket $ticket, ?string $actorRef = null): Ticket
    {
        $ticket->load(['serviceQueue', 'counter']);
        $this->recordEvent($ticket, 'recalled', $actorRef, $ticket->counter_id);
        $this->audit($ticket, 'ticket.recalled', $actorRef);

        if ($ticket->counter) {
            app(VoiceAnnouncementService::class)->announceCalled($ticket, $ticket->counter);
        }

        return $ticket->fresh(['serviceQueue', 'counter']);
    }

    public function startServing(Ticket $ticket, ?string $actorRef = null): Ticket
    {
        $ticket->update([
            'status' => 'serving',
            'serving_started_at' => now(),
        ]);
        $this->recordEvent($ticket, 'serving', $actorRef, $ticket->counter_id);
        app(ServiceSessionTracker::class)->start($ticket, $actorRef);

        return $ticket->fresh();
    }

    public function hold(Ticket $ticket, ?string $actorRef = null): Ticket
    {
        $ticket->update(['status' => 'on_hold']);
        $this->recordEvent($ticket, 'held', $actorRef, $ticket->counter_id);
        $this->audit($ticket, 'ticket.held', $actorRef);

        return $ticket->fresh();
    }

    public function skip(Ticket $ticket, ?string $actorRef = null): Ticket
    {
        $ticket->update([
            'status' => 'waiting',
            'counter_id' => null,
            'called_at' => null,
        ]);
        $this->recordEvent($ticket, 'skipped', $actorRef);
        $this->audit($ticket, 'ticket.skipped', $actorRef);

        return $ticket->fresh();
    }

    public function completeTicket(Ticket $ticket, ?string $actorRef = null): Ticket
    {
        $ticket->update([
            'status' => 'completed',
            'completed_at' => now(),
        ]);

        if ($ticket->counter_id) {
            Counter::where('id', $ticket->counter_id)->update(['status' => 'available']);
        }

        $this->recordEvent($ticket, 'completed', $actorRef, $ticket->counter_id);
        $this->audit($ticket, 'ticket.completed', $actorRef);
        app(ServiceSessionTracker::class)->endForTicket($ticket);

        $ticket = $ticket->fresh(['serviceQueue', 'counter']);
        app(QueueNotificationService::class)->ticketCompleted($ticket);
        app(WorkflowService::class)->advanceAfterCompletion($ticket);

        return $ticket;
    }

    public function markNoShow(Ticket $ticket, ?string $actorRef = null): Ticket
    {
        $ticket->update([
            'status' => 'no_show',
            'completed_at' => now(),
        ]);

        if ($ticket->counter_id) {
            Counter::where('id', $ticket->counter_id)->update(['status' => 'available']);
        }

        $this->recordEvent($ticket, 'no_show', $actorRef, $ticket->counter_id);
        $this->audit($ticket, 'ticket.no_show', $actorRef);

        $ticket = $ticket->fresh(['serviceQueue', 'counter']);
        app(QueueNotificationService::class)->ticketMissed($ticket);

        return $ticket;
    }

    public function cancel(Ticket $ticket, ?string $actorRef = null): Ticket
    {
        $ticket->update(['status' => 'cancelled', 'completed_at' => now()]);
        $this->recordEvent($ticket, 'cancelled', $actorRef, $ticket->counter_id);
        $this->audit($ticket, 'ticket.cancelled', $actorRef);

        return $ticket->fresh();
    }

    public function transfer(
        Ticket $ticket,
        ServiceQueue $toQueue,
        ?Counter $counter = null,
        ?string $reason = null,
        ?string $actorRef = null,
        ?Counter $assignToCounter = null,
    ): Ticket {
        return DB::transaction(function () use ($ticket, $toQueue, $counter, $reason, $actorRef, $assignToCounter) {
            $ticket = Ticket::query()->lockForUpdate()->findOrFail($ticket->id);
            $toQueue = ServiceQueue::query()->lockForUpdate()->findOrFail($toQueue->id);

            if ($toQueue->id === $ticket->service_queue_id) {
                throw new \RuntimeException('Ticket is already in that queue.');
            }

            if ($ticket->organization_id !== $toQueue->organization_id || $ticket->owner_ref !== $toQueue->owner_ref) {
                throw new \RuntimeException('Cannot hand off to a queue outside this organization.');
            }

            if (! $toQueue->is_active || $toQueue->is_paused) {
                throw new \RuntimeException('Target queue is not accepting tickets.');
            }

            if ($toQueue->max_capacity) {
                $waiting = Ticket::query()
                    ->where('service_queue_id', $toQueue->id)
                    ->whereIn('status', ['waiting', 'called', 'serving', 'on_hold'])
                    ->count();
                if ($waiting >= $toQueue->max_capacity) {
                    throw new \RuntimeException('Target queue has reached maximum capacity.');
                }
            }

            $assignedCounterId = null;
            if ($assignToCounter) {
                if ((int) $assignToCounter->organization_id !== (int) $toQueue->organization_id) {
                    throw new \RuntimeException('Assigned service point is outside this organization.');
                }
                $assignedCounterId = $assignToCounter->id;
            } elseif ($toQueue->usesAssignedOnlyRouting()) {
                throw new \RuntimeException('Target queue requires an assigned service point.');
            }

            $fromQueueId = $ticket->service_queue_id;
            $fromCounterId = $counter?->id ?? $ticket->counter_id;
            $ticketNumber = $ticket->ticket_number;

            $waitingCount = Ticket::query()
                ->where('service_queue_id', $toQueue->id)
                ->where('status', 'waiting')
                ->count();
            $estimatedWait = $waitingCount * (int) $toQueue->avg_service_seconds;

            // Same ticket row and number — only the queue assignment changes.
            $ticket->update([
                'service_queue_id' => $toQueue->id,
                'branch_id' => $toQueue->branch_id,
                'status' => 'waiting',
                'position' => $waitingCount + 1,
                'estimated_wait_seconds' => $estimatedWait,
                'counter_id' => null,
                'assigned_counter_id' => $assignedCounterId,
                'called_at' => null,
                'serving_started_at' => null,
                'completed_at' => null,
            ]);

            if ($fromCounterId) {
                Counter::where('id', $fromCounterId)->update(['status' => 'available']);
            }

            app(ServiceSessionTracker::class)->endForTicket($ticket);

            DB::table('queue_ticket_transfers')->insert([
                'owner_ref' => $ticket->owner_ref,
                'ticket_id' => $ticket->id,
                'from_service_queue_id' => $fromQueueId,
                'to_service_queue_id' => $toQueue->id,
                'from_counter_id' => $fromCounterId,
                'reason' => $reason,
                'transferred_by' => $actorRef,
                'transferred_at' => now(),
            ]);

            $this->recordEvent($ticket, 'transferred', $actorRef, $fromCounterId, [
                'from_queue_id' => $fromQueueId,
                'to_queue_id' => $toQueue->id,
                'ticket_number' => $ticketNumber,
                'reason' => $reason,
            ]);
            $this->audit($ticket, 'ticket.transferred', $actorRef, [
                'to_queue' => $toQueue->name,
                'ticket_number' => $ticketNumber,
            ]);

            $ticket = $ticket->fresh(['serviceQueue', 'counter']);
            app(QueueNotificationService::class)->ticketTransferred($ticket);
            $this->notifyWaitingPositions($toQueue);

            return $ticket;
        });
    }

    public function pauseQueue(ServiceQueue $queue, ?string $actorRef = null): ServiceQueue
    {
        $queue->update(['is_paused' => true]);
        AuditLogger::record($queue->owner_ref, 'service_queue.paused', $queue->organization_id, $actorRef, ServiceQueue::class, $queue->id);

        $org = Organization::find($queue->organization_id);
        if ($org) {
            app(StaffNotifier::class)->queueEvent(
                $org,
                'Queue paused',
                "{$queue->name} is no longer accepting tickets.",
                route('qms.queues.show', $queue),
                'pause',
            );
        }

        return $queue->fresh();
    }

    public function resumeQueue(ServiceQueue $queue, ?string $actorRef = null): ServiceQueue
    {
        $queue->update(['is_paused' => false]);
        AuditLogger::record($queue->owner_ref, 'service_queue.resumed', $queue->organization_id, $actorRef, ServiceQueue::class, $queue->id);

        return $queue->fresh();
    }

    public function delayArrival(Ticket $ticket, int $minutes, ?string $actorRef = null): Ticket
    {
        $metadata = $ticket->metadata ?? [];
        $metadata['delayed_until'] = now()->addMinutes($minutes)->toIso8601String();
        $ticket->update(['metadata' => $metadata]);
        $this->recordEvent($ticket, 'delayed', $actorRef, null, ['minutes' => $minutes]);

        return $ticket->fresh();
    }

    /**
     * @return list<Ticket>
     */
    public function waitingTickets(ServiceQueue $queue, int $limit = 50, ?Counter $forCounter = null): array
    {
        return $this->waitingTicketQuery($queue, $forCounter)
            ->limit($limit)
            ->get()
            ->all();
    }

    protected function nextWaitingTicket(ServiceQueue $queue, ?Counter $counter = null): ?Ticket
    {
        return $this->waitingTicketQuery($queue, $counter)->first();
    }

    /**
     * Tickets visible/callable for a service point:
     * - assigned_only: only tickets assigned to this counter
     * - shared_pool: unassigned tickets, or tickets assigned to this counter
     * - no counter: all waiting (admin/list views)
     */
    protected function waitingTicketQuery(ServiceQueue $queue, ?Counter $counter = null)
    {
        $query = Ticket::query()
            ->where('service_queue_id', $queue->id)
            ->where('status', 'waiting')
            ->orderByRaw($this->priorityOrderSql())
            ->orderBy('issued_at');

        if (! $counter) {
            return $query;
        }

        if ($queue->usesAssignedOnlyRouting()) {
            return $query->where('assigned_counter_id', $counter->id);
        }

        return $query->where(function ($q) use ($counter) {
            $q->whereNull('assigned_counter_id')
                ->orWhere('assigned_counter_id', $counter->id);
        });
    }

    /**
     * @param  array<string, mixed>  $attributes
     */
    protected function resolveAssignedCounterId(ServiceQueue $queue, array $attributes): ?int
    {
        $counter = null;

        if (! empty($attributes['assigned_counter_id'])) {
            $value = $attributes['assigned_counter_id'];
            $counter = is_numeric($value)
                ? Counter::query()->find((int) $value)
                : Counter::query()->where('uuid', (string) $value)->first();
        } elseif (! empty($attributes['assigned_counter_uuid'])) {
            $counter = Counter::query()->where('uuid', (string) $attributes['assigned_counter_uuid'])->first();
        }

        if (! $counter) {
            if ($queue->usesAssignedOnlyRouting()) {
                throw new \RuntimeException('This queue requires an assigned service point.');
            }

            return null;
        }

        if ((int) $counter->organization_id !== (int) $queue->organization_id
            || (string) $counter->owner_ref !== (string) $queue->owner_ref) {
            throw new \RuntimeException('Assigned service point is outside this organization.');
        }

        return (int) $counter->id;
    }

    protected function priorityOrderSql(): string
    {
        $priorityOrder = array_keys(config('qms.ticket_priorities'));

        if (\Illuminate\Support\Facades\DB::connection()->getDriverName() === 'sqlite') {
            $cases = collect($priorityOrder)
                ->map(fn ($p, $i) => "WHEN priority = '{$p}' THEN {$i}")
                ->implode(' ');

            return "CASE {$cases} ELSE 99 END";
        }

        return 'FIELD(priority, '.implode(',', array_map(fn ($p) => "'{$p}'", $priorityOrder)).')';
    }

    protected function notifyWaitingPositions(?ServiceQueue $queue): void
    {
        if (! $queue) {
            return;
        }

        $notifications = app(QueueNotificationService::class);
        foreach ($this->waitingTickets($queue, 20) as $position => $waitingTicket) {
            $notifications->customersAhead($waitingTicket, $position);
        }
    }

    protected function audit(Ticket $ticket, string $action, ?string $actorRef, ?array $metadata = null): void
    {
        AuditLogger::record(
            $ticket->owner_ref,
            $action,
            $ticket->organization_id,
            $actorRef,
            Ticket::class,
            $ticket->id,
            $metadata,
        );
    }

    /**
     * @param  array<string, mixed>|null  $metadata
     */
    protected function recordEvent(
        Ticket $ticket,
        string $event,
        ?string $actorRef = null,
        ?int $counterId = null,
        ?array $metadata = null,
    ): void {
        TicketEvent::create([
            'owner_ref' => $ticket->owner_ref,
            'ticket_id' => $ticket->id,
            'event' => $event,
            'actor_ref' => $actorRef,
            'counter_id' => $counterId,
            'metadata' => $metadata,
            'created_at' => now(),
        ]);
    }
}