<?php

namespace App\Services;

use App\Models\Dynamic;
use App\Models\Ledger;
use App\Models\Message;
use App\Models\ReadCursor;
use App\Models\User;
use App\Notifications\NewActivityNotification;
use Carbon\CarbonInterface;
use Illuminate\Support\Carbon;

class ActivityService
{
    /**
     * Update the read cursor for a user on a specific entity.
     */
    public function updateCursor(User $user, $entity): void
    {
        ReadCursor::updateOrCreate(
            [
                'user_id' => $user->id,
                'cursorable_id' => $entity->id,
                'cursorable_type' => get_class($entity),
            ],
            [
                'read_at' => Carbon::now(),
            ]
        );
    }

    /**
     * Get the read cursor timestamp for a user on a specific entity.
     */
    public function getCursorReadAt(User $user, $entity): CarbonInterface
    {
        $cursor = ReadCursor::where([
            'user_id' => $user->id,
            'cursorable_id' => $entity->id,
            'cursorable_type' => get_class($entity),
        ])->first();

        // If no cursor exists, default to epoch (all activities are unread)
        return $cursor ? $cursor->read_at : Carbon::parse('1970-01-01');
    }

    public function createMessage($dynamic, $user, $content, $subject = null)
    {
        $chat = $dynamic->getOrCreateChat();
        $message = $chat->messages()->create([
            'user_id' => $user ? $user->id : null,
            'content' => $content,
            'subject_id' => $subject ? $subject->id : null,
            'subject_type' => $subject ? get_class($subject) : null,
        ]);

        $this->notify($message);

        return $message;
    }

    public function createMutation($ledger, $user, $type, $amount, $description, $status)
    {
        $mutation = $ledger->mutations()->create([
            'user_id' => $user->id,
            'type' => $type,
            'amount' => $amount,
            'description' => $description,
            'status' => $status,
        ]);

        return $mutation;
    }

    public function notify(Message $message)
    {
        $dynamic = $message->chat->chatable;

        if ($dynamic instanceof Dynamic) {
            $participants = $dynamic->participants;

            foreach ($participants as $participant) {
                if ($message->user_id !== $participant->id) {
                    $participant->notify(new NewActivityNotification($message));
                }
            }
        }
    }

    /**
     * Retrieve all activities for a given entity.
     */
    public function getActivitiesForDynamic(Dynamic $dynamic): array
    {
        $chat = $dynamic->getOrCreateChat();
        if (!$chat) {
            return [];
        }

        $participants = $dynamic->participants()->withPivot('display_name')->get();
        $participantsMap = $participants->reduce(function ($acc, $p) {
            $acc[$p->id] = $p->pivot->display_name ?? $p->name;

            return $acc;
        }, []);

        $messages = Message::where('chat_id', $chat->id)
            ->with(['user', 'subject'])
            ->latest()
            ->get();

        return $messages->map(function ($message) use ($participantsMap) {
            $messageData = $message->toArray();
            $messageData['url'] = $this->getUrlForMessage($message);

            // Resolve <user:id> placeholders to actual names/display names
            $messageData['content'] = preg_replace_callback('/<user:(\d+)>/', function ($matches) use ($participantsMap) {
                $userId = $matches[1];

                return $participantsMap[$userId] ?? "User #{$userId}";
            }, $message->content);

            return $messageData;
        })->all();
    }

    /**
     * Get unread activities grouped by active entities (Dynamics, Ledgers) for the given user.
     */
    public function getUnreadEntitiesGrouped(User $user): array
    {
        $groupedDynamics = [];
        $participatingDynamics = $user->dynamics()->with(['chat', 'ledgers'])->get();

        foreach ($participatingDynamics as $dynamic) {
            $readAt = $this->getCursorReadAt($user, $dynamic);
            $activities = $this->getActivitiesForDynamic($dynamic);

            $this->partitionAndGroupActivities($activities, $readAt, $dynamic, $groupedDynamics);
        }

        return $groupedDynamics;
    }

    /**
     * Partition activities into read and unread, and construct the grouped entity metadata.
     */
    private function partitionAndGroupActivities(array $activities, CarbonInterface $readAt, Dynamic $dynamic, array &$groupedDynamics): void
    {
        $alreadyRead = [];
        $unread = [];

        foreach ($activities as $act) {
            if (Carbon::parse($act['created_at'])->gt($readAt)) {
                $unread[] = $act;
            } else {
                $alreadyRead[] = $act;
            }
        }

        if (! empty($unread)) {
            $context = array_slice($alreadyRead, 0, 2);

            $groupedDynamics[] = [
                'id' => $dynamic->id,
                'name' => $dynamic->name,
                'url' => route('dynamics.show', $dynamic->uuid),
                'unread_count' => count($unread),
                'context_activities' => $context,
                'new_activities' => array_reverse($unread),
            ];
        }
    }

    private function getUrlForEntity($entity): string
    {
        if ($entity instanceof Dynamic) {
            return route('dynamics.show', $entity->uuid);
        }

        if ($entity instanceof Ledger) {
            return route('dynamics.ledgers.show', [$entity->dynamic->uuid, $entity->uuid]);
        }

        if ($entity instanceof Message) {
            $subject = $entity->subject;
            return $this->getUrlForEntity($subject);
        }

        return '';
    }

    private function getUrlForMessage(Message $message): string
    {
        if ($message->subject) {
            return $this->getUrlForEntity($message->subject);
        }

        if ($message->chat->chatable) {
            return $this->getUrlForEntity($message->chat->chatable);
        }

        return '';
    }
}