<?php

namespace App\Services;

use Carbon\CarbonImmutable;

class PeopleOperationalInsights
{
    /**
     * Derive facts only from the caller's already authorised, filtered workdesk.
     * No candidate data, new database queries or inferred access rights.
     *
     * @param  array<string,mixed>  $workdesk
     * @return array<string,mixed>
     */
    public function build(array $workdesk): array
    {
        $today = CarbonImmutable::parse($workdesk['updated_at'])->setTimezone(config('app.timezone'))->startOfDay();
        $overdue = [];
        foreach ($workdesk['alerts'] as $alert) {
            $days = (int) CarbonImmutable::parse($alert['due_on'], config('app.timezone'))->startOfDay()->diffInDays($today);
            if ($days > 0) {
                $overdue[] = ['id' => $alert['id'], 'process_id' => $alert['process_id'], 'reference' => $alert['reference'],
                    'label' => $alert['label'], 'due_on' => $alert['due_on'], 'days_overdue' => $days, 'href' => $alert['href']];
            }
        }
        usort($overdue, fn ($a, $b) => ($b['days_overdue'] <=> $a['days_overdue']) ?: strcmp((string) $a['id'], (string) $b['id']));

        $actions = [];
        foreach ($workdesk['tasks'] as $task) {
            $actions[$task['action']] = ($actions[$task['action']] ?? 0) + 1;
        }
        $withoutDeadline = count(array_filter($workdesk['tasks'], fn ($task) => $task['due_on'] === null));

        return ['method' => 'operational_facts_v1', 'generated_at' => $workdesk['updated_at'],
            'coverage' => ['processes' => $workdesk['counts']['processes'], 'tasks' => count($workdesk['tasks']), 'approvals' => count($workdesk['approvals'])],
            'overdue' => ['items' => count($overdue), 'processes' => count(array_unique(array_column($overdue, 'process_id'))),
                'maximum_days' => $overdue === [] ? null : $overdue[0]['days_overdue'], 'oldest' => array_slice($overdue, 0, 5)],
            'task_actions' => $actions, 'tasks_without_deadline' => $withoutDeadline];
    }
}