<?php

namespace App\Http\Controllers\Api\Messaging;

use App\Events\MessageSent;
use App\Http\Controllers\Controller;
use App\Models\Conversation;
use App\Models\ConversationParticipant;
use App\Models\Message;
use App\Models\MessageAttachment;
use App\Models\MessageReaction;
use App\Services\Messaging\MessageSearchIndexer;
use App\Services\Messaging\MessageNotificationService;
use Illuminate\Http\JsonResponse;
use Illuminate\Http\Request;
use Illuminate\Http\UploadedFile;
use Illuminate\Support\Facades\Cache;
use Illuminate\Support\Facades\Storage;

class MessageController extends Controller
{
    private const PAGE_SIZE = 30;

    // ── GET /api/messages/{conversation_id} ──────────────────────────────────

    public function index(Request $request, int $conversationId): JsonResponse
    {
        $this->assertParticipant($request, $conversationId);
        $cursor = $request->integer('cursor');

        $query = Message::withTrashed()
            ->where('conversation_id', $conversationId)
            ->with(['sender:id,username', 'reactions', 'attachments'])
            ->orderByDesc('created_at')
            ->orderByDesc('id');

        if ($cursor) {
            $query->where('id', '<', $cursor);
        }

        $chunk = $query->limit(self::PAGE_SIZE + 1)->get();
        $hasMore = $chunk->count() > self::PAGE_SIZE;
        $messages = $chunk->take(self::PAGE_SIZE)->reverse()->values();
        $nextCursor = $hasMore && $messages->isNotEmpty() ? (int) $messages->first()->id : null;

        return response()->json([
            'data' => $messages,
            'next_cursor' => $nextCursor,
        ]);
    }

    // ── POST /api/messages/{conversation_id} ─────────────────────────────────

    public function store(Request $request, int $conversationId): JsonResponse
    {
        $this->assertParticipant($request, $conversationId);

        $data = $request->validate([
            'body' => 'nullable|string|max:5000',
            'attachments' => 'sometimes|array|max:5',
            'attachments.*' => 'file|max:25600',
        ]);

        $body = trim((string) ($data['body'] ?? ''));
        $files = $request->file('attachments', []);
        abort_if($body === '' && empty($files), 422, 'Message body or attachment is required.');

        $message = Message::create([
            'conversation_id' => $conversationId,
            'sender_id'       => $request->user()->id,
            'body'            => $body,
        ]);

        foreach ($files as $file) {
            if ($file instanceof UploadedFile) {
                $this->storeAttachment($file, $message, (int) $request->user()->id);
            }
        }

        Conversation::where('id', $conversationId)
            ->update(['last_message_at' => $message->created_at]);

        $conversation = Conversation::findOrFail($conversationId);
        app(MessageNotificationService::class)->notifyNewMessage($conversation, $message, $request->user());
        app(MessageSearchIndexer::class)->indexMessage($message);
        event(new MessageSent($conversationId, $message->id, $request->user()->id));

        $participantUserIds = ConversationParticipant::where('conversation_id', $conversationId)
            ->whereNull('left_at')
            ->pluck('user_id')
            ->all();
        $this->touchConversationCachesForUsers($participantUserIds);

        $message->load(['sender:id,username', 'attachments']);

        return response()->json($message, 201);
    }

    // ── POST /api/messages/{conversation_id}/react ───────────────────────────

    public function react(Request $request, int $conversationId, int $messageId): JsonResponse
    {
        $this->assertParticipant($request, $conversationId);

        $data = $request->validate(['reaction' => 'required|string|max:32']);
        $this->assertAllowedReaction($data['reaction']);

        $existing = MessageReaction::where([
            'message_id' => $messageId,
            'user_id'    => $request->user()->id,
            'reaction'   => $data['reaction'],
        ])->first();

        if ($existing) {
            $existing->delete();
        } else {
            MessageReaction::create([
                'message_id' => $messageId,
                'user_id'    => $request->user()->id,
                'reaction'   => $data['reaction'],
            ]);
        }

        return response()->json($this->reactionSummary($messageId, (int) $request->user()->id));
    }

    // ── DELETE /api/messages/{conversation_id}/react ─────────────────────────

    public function unreact(Request $request, int $conversationId, int $messageId): JsonResponse
    {
        $this->assertParticipant($request, $conversationId);

        $data = $request->validate(['reaction' => 'required|string|max:32']);
        $this->assertAllowedReaction($data['reaction']);

        MessageReaction::where([
            'message_id' => $messageId,
            'user_id'    => $request->user()->id,
            'reaction'   => $data['reaction'],
        ])->delete();

        return response()->json($this->reactionSummary($messageId, (int) $request->user()->id));
    }

    public function reactByMessage(Request $request, int $messageId): JsonResponse
    {
        $message = Message::query()->findOrFail($messageId);
        $this->assertParticipant($request, (int) $message->conversation_id);

        $data = $request->validate(['reaction' => 'required|string|max:32']);
        $this->assertAllowedReaction($data['reaction']);

        $existing = MessageReaction::where([
            'message_id' => $messageId,
            'user_id' => $request->user()->id,
            'reaction' => $data['reaction'],
        ])->first();

        if ($existing) {
            $existing->delete();
        } else {
            MessageReaction::create([
                'message_id' => $messageId,
                'user_id' => $request->user()->id,
                'reaction' => $data['reaction'],
            ]);
        }

        return response()->json($this->reactionSummary($messageId, (int) $request->user()->id));
    }

    public function unreactByMessage(Request $request, int $messageId): JsonResponse
    {
        $message = Message::query()->findOrFail($messageId);
        $this->assertParticipant($request, (int) $message->conversation_id);

        $data = $request->validate(['reaction' => 'required|string|max:32']);
        $this->assertAllowedReaction($data['reaction']);

        MessageReaction::where([
            'message_id' => $messageId,
            'user_id' => $request->user()->id,
            'reaction' => $data['reaction'],
        ])->delete();

        return response()->json($this->reactionSummary($messageId, (int) $request->user()->id));
    }

    // ── PATCH /api/messages/message/{messageId} ───────────────────────────────

    public function update(Request $request, int $messageId): JsonResponse
    {
        $message = Message::findOrFail($messageId);

        abort_unless(
            $message->sender_id === $request->user()->id,
            403,
            'You may only edit your own messages.'
        );

        abort_if($message->deleted_at !== null, 422, 'Cannot edit a deleted message.');

        $data = $request->validate(['body' => 'required|string|max:5000']);

        $message->update([
            'body'      => $data['body'],
            'edited_at' => now(),
        ]);
        app(MessageSearchIndexer::class)->updateMessage($message);

        $participantUserIds = ConversationParticipant::where('conversation_id', $message->conversation_id)
            ->whereNull('left_at')
            ->pluck('user_id')
            ->all();
        $this->touchConversationCachesForUsers($participantUserIds);

        return response()->json($message->fresh());
    }

    // ── DELETE /api/messages/message/{messageId} ──────────────────────────────

    public function destroy(Request $request, int $messageId): JsonResponse
    {
        $message = Message::findOrFail($messageId);

        abort_unless(
            $message->sender_id === $request->user()->id || $request->user()->isAdmin(),
            403,
            'You may only delete your own messages.'
        );

        $participantUserIds = ConversationParticipant::where('conversation_id', $message->conversation_id)
            ->whereNull('left_at')
            ->pluck('user_id')
            ->all();
        app(MessageSearchIndexer::class)->deleteMessage($message);
        $message->delete();
        $this->touchConversationCachesForUsers($participantUserIds);

        return response()->json(['ok' => true]);
    }

    // ── Private helpers ──────────────────────────────────────────────────────

    private function assertParticipant(Request $request, int $conversationId): void
    {
        abort_unless(
            ConversationParticipant::where('conversation_id', $conversationId)
                ->where('user_id', $request->user()->id)
                ->whereNull('left_at')
                ->exists(),
            403,
            'You are not a participant of this conversation.'
        );
    }

    private function touchConversationCachesForUsers(array $userIds): void
    {
        foreach (array_unique($userIds) as $userId) {
            if (! $userId) {
                continue;
            }

            $versionKey = "messages:conversations:version:{$userId}";
            Cache::add($versionKey, 1, now()->addDay());
            Cache::increment($versionKey);
        }
    }

    private function assertAllowedReaction(string $reaction): void
    {
        $allowed = (array) config('messaging.reactions.allowed', []);
        abort_unless(in_array($reaction, $allowed, true), 422, 'Reaction is not allowed.');
    }

    private function reactionSummary(int $messageId, int $userId): array
    {
        $rows = MessageReaction::query()
            ->selectRaw('reaction, count(*) as aggregate_count')
            ->where('message_id', $messageId)
            ->groupBy('reaction')
            ->get();

        $summary = [];
        foreach ($rows as $row) {
            $summary[(string) $row->reaction] = (int) $row->aggregate_count;
        }

        $mine = MessageReaction::query()
            ->where('message_id', $messageId)
            ->where('user_id', $userId)
            ->pluck('reaction')
            ->values()
            ->all();

        $summary['me'] = $mine;

        return $summary;
    }

    private function storeAttachment(UploadedFile $file, Message $message, int $userId): void
    {
        $mime = (string) $file->getMimeType();
        $finfoMime = (string) finfo_file(finfo_open(FILEINFO_MIME_TYPE), $file->getPathname());
        $detectedMime = $finfoMime !== '' ? $finfoMime : $mime;

        $allowedImage = (array) config('messaging.attachments.allowed_image_mimes', []);
        $allowedFile = (array) config('messaging.attachments.allowed_file_mimes', []);

        $type = in_array($detectedMime, $allowedImage, true) ? 'image' : 'file';
        $allowed = $type === 'image' ? $allowedImage : $allowedFile;

        abort_unless(in_array($detectedMime, $allowed, true), 422, 'Unsupported attachment type.');

        $maxBytes = $type === 'image'
            ? ((int) config('messaging.attachments.max_image_kb', 10240) * 1024)
            : ((int) config('messaging.attachments.max_file_kb', 25600) * 1024);

        abort_if($file->getSize() > $maxBytes, 422, 'Attachment exceeds allowed size.');

        $year = now()->format('Y');
        $month = now()->format('m');
        $ext = strtolower($file->getClientOriginalExtension() ?: $file->extension() ?: 'bin');
        $path = "messages/{$message->conversation_id}/{$year}/{$month}/" . uniqid('att_', true) . ".{$ext}";

        $diskName = (string) config('messaging.attachments.disk', 'local');
        Storage::disk($diskName)->put($path, file_get_contents($file->getPathname()));

        $width = null;
        $height = null;
        if ($type === 'image') {
            $dimensions = @getimagesize($file->getPathname());
            $width = isset($dimensions[0]) ? (int) $dimensions[0] : null;
            $height = isset($dimensions[1]) ? (int) $dimensions[1] : null;
        }

        MessageAttachment::query()->create([
            'message_id' => $message->id,
            'user_id' => $userId,
            'type' => $type,
            'mime' => $detectedMime,
            'size_bytes' => (int) $file->getSize(),
            'width' => $width,
            'height' => $height,
            'sha256' => hash_file('sha256', $file->getPathname()),
            'original_name' => substr((string) $file->getClientOriginalName(), 0, 255),
            'storage_path' => $path,
            'created_at' => now(),
        ]);
    }
}