<?php

namespace Modules\QualityManagement\Services;

use Modules\QualityManagement\Models\SpcMeasurement;

class SpcAnalysisService
{
    public function recordMeasurement(int $businessId, array $data): SpcMeasurement
    {
        $inControl = $this->isInControl(
            (float) $data['measured_value'],
            isset($data['usl']) ? (float) $data['usl'] : null,
            isset($data['lsl']) ? (float) $data['lsl'] : null
        );

        return SpcMeasurement::create(array_merge($data, [
            'business_id' => $businessId,
            'measured_at' => $data['measured_at'] ?? now(),
            'in_control' => $inControl,
            'recorded_by' => $data['recorded_by'] ?? auth()->id(),
        ]));
    }

    public function isInControl(float $value, ?float $usl, ?float $lsl): bool
    {
        if ($usl !== null && $value > $usl) {
            return false;
        }
        if ($lsl !== null && $value < $lsl) {
            return false;
        }

        return true;
    }

    public function characteristicSummary(int $businessId, string $characteristic, int $days = 30): array
    {
        $measurements = SpcMeasurement::forBusiness($businessId)
            ->where('characteristic_name', $characteristic)
            ->where('measured_at', '>=', now()->subDays($days))
            ->orderBy('measured_at')
            ->get();

        if ($measurements->isEmpty()) {
            return ['count' => 0, 'mean' => 0, 'min' => 0, 'max' => 0, 'out_of_control' => 0];
        }

        $values = $measurements->pluck('measured_value')->map(fn ($v) => (float) $v);

        return [
            'count' => $measurements->count(),
            'mean' => round($values->avg(), 4),
            'min' => round($values->min(), 4),
            'max' => round($values->max(), 4),
            'out_of_control' => $measurements->where('in_control', false)->count(),
            'cpk_estimate' => $this->estimateCpk($values, $measurements->first()),
        ];
    }

    protected function estimateCpk($values, SpcMeasurement $sample): ?float
    {
        $usl = $sample->usl;
        $lsl = $sample->lsl;
        if ($usl === null || $lsl === null || $values->count() < 2) {
            return null;
        }

        $mean = $values->avg();
        $std = $this->stdDev($values->all());
        if ($std <= 0) {
            return null;
        }

        $cpu = ($usl - $mean) / (3 * $std);
        $cpl = ($mean - $lsl) / (3 * $std);

        return round(min($cpu, $cpl), 3);
    }

    protected function stdDev(array $values): float
    {
        $n = count($values);
        if ($n < 2) {
            return 0;
        }
        $mean = array_sum($values) / $n;
        $variance = array_sum(array_map(fn ($v) => ($v - $mean) ** 2, $values)) / ($n - 1);

        return sqrt($variance);
    }
}