<?php

namespace App\Services\StudyRouter;

use App\Domain\ACL\Role;
use App\Models\AssignmentPanel;
use App\Models\DicomRoutingRule;
use App\Models\Organization;
use App\Models\User;
use Illuminate\Support\Collection;
use Illuminate\Support\Facades\Cache;
use Symfony\Component\ExpressionLanguage\ExpressionLanguage;

final class DicomStudyRouter
{
    private static ?Collection $rules = null;
    private static ?Collection $activeRads = null;
    private static int $catchAll = -1;

    const int CACHE_TTL = 15;

    public static function matchStudy(array $dicomHeaders): array
    {
        self::initialize();

        if (blank($dicomHeaders)) {
            return self::fallbackRouting();
        }

        $expression = new ExpressionLanguage;
        foreach (self::$rules as $rule) {
            $matches = (bool) $expression->evaluate($rule->condition, ['study' => $dicomHeaders]);

            if ($matches) {
                return [
                    'organization_id' => $rule->organization_id,
                    'department_id' => $rule->department_id,
                    'rule_id' => $rule->id,
                    'rule_name' => $rule->name,
                    'radiologists' => self::getRadiologists($rule),
                ];
            }
        }

        return self::fallbackRouting();
    }

    private static function fallbackRouting(): array
    {
        return [
            'organization_id' => self::$catchAll,
            'department_id' => null,
            'rule_id' => null,
            'radiologists' => null,
        ];
    }

    private static function initialize(): void
    {
        if (is_null(self::$rules)) {
            self::$rules = Cache::remember('dicom.rules',
                now()->addMinutes(self::CACHE_TTL),
                fn () => DicomRoutingRule::active()
                    ->orderByDesc('priority')
                    ->get()
            );
        }

        if (is_null(self::$activeRads)) {
            self::$activeRads = Cache::remember('dicom.rads',
                now()->addMinutes(self::CACHE_TTL),
                fn () => User::active()
                    ->role(Role::Radiologist)
                    ->pluck('id')
            );
        }

        if (self::$catchAll < 0) {
            self::$catchAll = Organization::where('name', 'CATCH-ALL')
                ->first('id')
                ->id;
        }
    }

    private static function getRadiologists(DicomRoutingRule $rule): array
    {
        if (! is_null($rule->assignment_panel_id)) {
            $panel = AssignmentPanel::active()
                ->with('radiologists:id')
                ->find($rule->assignment_panel_id);
            if ($panel) {
                $rads = $panel->radiologists->pluck('id')->toArray();
                if (! empty($rads)) {
                    // return only existing id from self::$activeRads
                    return array_intersect($rads, self::$activeRads->toArray());
                }
            }
        } elseif (! is_null($rule->user_id)) {
            if (self::$activeRads->contains($rule->user_id)) {
                return [$rule->user_id];
            }
        }

        return [];
    }
}