<?php

namespace App\Services\Admin\Management;

use App\Models\Position;
use App\Models\PositionQuota;
use App\Models\PusatMengundi;
use App\Models\SaluranMengundi;
use App\Models\StaffAssignment;
use Illuminate\Database\Eloquent\Collection;
use Illuminate\Support\Collection as BaseCollection;

class PennempatanService
{
    /**
     * Summary per pusat for the dashboard vacancy table.
     *
     * @return Collection<int, PusatMengundi>
     */
    public function pusatsWithVacancySummary(): Collection
    {
        return PusatMengundi::query()
            ->with([
                'dun',
                'election',
                'saluranMengundis',
                'positionQuotas',
            ])
            ->withCount(['saluranMengundis'])
            ->get()
            ->each(function (PusatMengundi $pusat): void {
                $totalQuota = $pusat->positionQuotas->sum('quota');
                $filled     = StaffAssignment::query()
                    ->where('pusat_mengundi_id', $pusat->id)
                    ->where('status', 'active')
                    ->count();

                $pusat->setAttribute('total_quota', $totalQuota);
                $pusat->setAttribute('filled', $filled);
                $pusat->setAttribute('vacant', max(0, $totalQuota - $filled));

                // PPM name
                $ppmPosition = Position::query()->where('code', 'PPM')->first();
                $ppmAssignment = $ppmPosition
                    ? StaffAssignment::query()
                        ->with('application')
                        ->where('pusat_mengundi_id', $pusat->id)
                        ->where('position_id', $ppmPosition->id)
                        ->where('status', 'active')
                        ->whereNull('saluran_mengundi_id')
                        ->first()
                    : null;

                $pusat->setAttribute('ppm_name', $ppmAssignment?->application?->name ?? '-');
            })
            ->filter(fn (PusatMengundi $p): bool => $p->vacant > 0)
            ->sortByDesc('vacant')
            ->values();
    }

    /**
     * Structured breakdown of quotas + assignments for a specific pusat.
     *
     * @return BaseCollection<int, array{saluran: SaluranMengundi|null, label: string, entries: BaseCollection}>
     */
    public function detailForPusat(PusatMengundi $pusat): BaseCollection
    {
        $quotas = PositionQuota::query()
            ->with('position')
            ->where('pusat_mengundi_id', $pusat->id)
            ->get()
            ->groupBy(fn (PositionQuota $q): string => $q->saluran_mengundi_id ?? 'pusat');

        $assignments = StaffAssignment::query()
            ->with(['application', 'position'])
            ->where('pusat_mengundi_id', $pusat->id)
            ->where('status', 'active')
            ->get()
            ->groupBy(fn (StaffAssignment $a): string => ($a->saluran_mengundi_id ?? 'pusat').'_'.$a->position_id);

        $salurans = SaluranMengundi::query()
            ->where('pusat_mengundi_id', $pusat->id)
            ->orderBy('number')
            ->get()
            ->keyBy('id');

        $sections = collect();

        // Pusat-level section first
        if ($quotas->has('pusat')) {
            $sections->push($this->buildSection(null, 'Peringkat Pusat (Saluran 0)', $quotas->get('pusat'), $assignments));
        }

        // Per-saluran sections
        foreach ($salurans as $saluran) {
            $saluranQuotas = $quotas->get((string) $saluran->id, collect());
            $sections->push($this->buildSection($saluran, 'Saluran '.$saluran->number, $saluranQuotas, $assignments));
        }

        return $sections;
    }

    /**
     * @param  Collection<int, PositionQuota>  $quotas
     * @param  BaseCollection<string, Collection>  $assignments
     * @return array{saluran: SaluranMengundi|null, label: string, entries: BaseCollection}
     */
    private function buildSection(?SaluranMengundi $saluran, string $label, $quotas, BaseCollection $assignments): array
    {
        $scopeKey = $saluran ? (string) $saluran->id : 'pusat';

        $entries = $quotas->map(function (PositionQuota $quota) use ($scopeKey, $assignments) {
            $key     = $scopeKey.'_'.$quota->position_id;
            $filled  = $assignments->get($key, collect());
            $vacant  = max(0, $quota->quota - $filled->count());

            return [
                'quota'       => $quota,
                'position'    => $quota->position,
                'assignments' => $filled,
                'vacant'      => $vacant,
            ];
        })->values();

        return [
            'saluran' => $saluran,
            'label'   => $label,
            'entries' => $entries,
        ];
    }
}