<?php

namespace App\Http\Controllers;

use App\Models\Forum;
use Illuminate\Http\JsonResponse;
use Illuminate\Http\Request;
use Illuminate\Validation\Rule;

class ForumController extends Controller
{
    public function index(Request $request): JsonResponse
    {
        $query = Forum::query();

        $parentParam = $request->query('parent');
        if (is_array($parentParam) && array_key_exists('exists', $parentParam)) {
            $exists = filter_var($parentParam['exists'], FILTER_VALIDATE_BOOLEAN, FILTER_NULL_ON_FAILURE);
            if ($exists === false) {
                $query->whereNull('parent_id');
            } elseif ($exists === true) {
                $query->whereNotNull('parent_id');
            }
        } elseif (is_string($parentParam)) {
            $parentId = $this->parseIriId($parentParam);
            if ($parentId !== null) {
                $query->where('parent_id', $parentId);
            }
        }

        if ($request->filled('type')) {
            $query->where('type', $request->query('type'));
        }

        $forums = $query
            ->orderBy('position')
            ->orderBy('name')
            ->get()
            ->map(fn (Forum $forum) => $this->serializeForum($forum));

        return response()->json($forums);
    }

    public function show(Forum $forum): JsonResponse
    {
        return response()->json($this->serializeForum($forum));
    }

    public function store(Request $request): JsonResponse
    {
        $data = $request->validate([
            'name' => ['required', 'string', 'max:100'],
            'description' => ['nullable', 'string'],
            'type' => ['required', Rule::in(['category', 'forum'])],
            'parent' => ['nullable', 'string'],
        ]);

        $parentId = $this->parseIriId($data['parent'] ?? null);

        if ($parentId) {
            $parent = Forum::findOrFail($parentId);
            if ($parent->type !== 'category') {
                return response()->json(['message' => 'Parent must be a category.'], 422);
            }
        }

        $position = Forum::where('parent_id', $parentId)->max('position');

        $forum = Forum::create([
            'name' => $data['name'],
            'description' => $data['description'] ?? null,
            'type' => $data['type'],
            'parent_id' => $parentId,
            'position' => ($position ?? 0) + 1,
        ]);

        return response()->json($this->serializeForum($forum), 201);
    }

    public function update(Request $request, Forum $forum): JsonResponse
    {
        $data = $request->validate([
            'name' => ['sometimes', 'required', 'string', 'max:100'],
            'description' => ['nullable', 'string'],
            'type' => ['sometimes', Rule::in(['category', 'forum'])],
            'parent' => ['nullable', 'string'],
        ]);

        $parentId = $this->parseIriId($data['parent'] ?? null);

        if (array_key_exists('parent', $data)) {
            if ($parentId) {
                $parent = Forum::findOrFail($parentId);
                if ($parent->type !== 'category') {
                    return response()->json(['message' => 'Parent must be a category.'], 422);
                }
            }
            $forum->parent_id = $parentId;
        }

        if (array_key_exists('name', $data)) {
            $forum->name = $data['name'];
        }

        if (array_key_exists('description', $data)) {
            $forum->description = $data['description'];
        }

        if (array_key_exists('type', $data)) {
            $forum->type = $data['type'];
        }

        $forum->save();

        return response()->json($this->serializeForum($forum));
    }

    public function destroy(Forum $forum): JsonResponse
    {
        $forum->delete();

        return response()->json(null, 204);
    }

    public function reorder(Request $request): JsonResponse
    {
        $data = $request->validate([
            'parentId' => ['nullable'],
            'orderedIds' => ['required', 'array'],
            'orderedIds.*' => ['integer'],
        ]);

        $parentId = $data['parentId'] ?? null;
        if ($parentId === '' || $parentId === 'null') {
            $parentId = null;
        } elseif ($parentId !== null) {
            $parentId = (int) $parentId;
        }

        foreach ($data['orderedIds'] as $index => $forumId) {
            Forum::where('id', $forumId)
                ->where('parent_id', $parentId)
                ->update(['position' => $index + 1]);
        }

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

    private function parseIriId(?string $value): ?int
    {
        if (!$value) {
            return null;
        }

        if (preg_match('#/forums/(\d+)$#', $value, $matches)) {
            return (int) $matches[1];
        }

        if (is_numeric($value)) {
            return (int) $value;
        }

        return null;
    }

    private function serializeForum(Forum $forum): array
    {
        return [
            'id' => $forum->id,
            'name' => $forum->name,
            'description' => $forum->description,
            'type' => $forum->type,
            'parent' => $forum->parent_id ? "/api/forums/{$forum->parent_id}" : null,
            'position' => $forum->position,
            'created_at' => $forum->created_at?->toIso8601String(),
            'updated_at' => $forum->updated_at?->toIso8601String(),
        ];
    }
}