<?php

namespace App\Services;

use App\Models\ChecklistTemplate;
use App\Models\Submission;

/**
 * Mengira hasil formula seksyen (A, B, C, D, E ...) berdasarkan jawapan serahan.
 *
 * Token tersedia kepada formula:
 *  - formula_token bagi setiap checklist_item (cth: SKOP1, EE, RE, D4I)
 *  - result_token bagi setiap formula yang telah dikira sebelumnya (cth: A, B)
 *
 * Formula dinilai mengikut turutan `order` supaya C boleh merujuk A & B, dsb.
 */
class FormulaService
{
    public function __construct(protected ExpressionEvaluator $evaluator) {}

    /**
     * Kira semua hasil formula bagi satu serahan.
     *
     * @return array<int, array{result_token:string,label:?string,value:?float,unit:?string}>
     */
    public function computeForSubmission(Submission $submission): array
    {
        $template = $submission->checklistTemplate
            ?: ($submission->checklist_template_id ? ChecklistTemplate::find($submission->checklist_template_id) : ChecklistTemplate::activeTemplate());

        if (! $template) {
            return [];
        }

        // Bina peta token => nilai daripada jawapan item.
        $variables = [];
        $answers = $submission->relationLoaded('answers')
            ? $submission->answers
            : $submission->answers()->with('item')->get();

        foreach ($answers as $answer) {
            $item = $answer->item;
            if ($item && $item->formula_token) {
                $variables[$item->formula_token] = is_numeric($answer->value) ? (float) $answer->value : 0.0;
            }
        }

        return $this->compute($template, $variables);
    }

    /**
     * Kira hasil formula daripada peta pemboleh ubah mentah (berguna untuk ujian).
     *
     * @param  array<string, float|int|null>  $variables
     * @return array<int, array{result_token:string,label:?string,value:?float,unit:?string}>
     */
    public function compute(ChecklistTemplate $template, array $variables): array
    {
        $formulas = $template->relationLoaded('formulas')
            ? $template->formulas->sortBy('order')
            : $template->formulas()->orderBy('order')->get();

        $results = [];

        foreach ($formulas as $formula) {
            $value = $this->evaluator->evaluate($formula->expression, $variables, $formula->guard_div_zero);

            // Hasil ini menjadi token yang boleh dirujuk oleh formula seterusnya.
            $variables[$formula->result_token] = $value ?? 0.0;

            $results[] = [
                'result_token' => $formula->result_token,
                'label' => $formula->label,
                'value' => $value,
                'unit' => $formula->unit,
            ];
        }

        return $results;
    }

    /**
     * Kira semula dan simpan hasil ke dalam jadual submission_results.
     */
    public function recalculateAndStore(Submission $submission): void
    {
        $results = $this->computeForSubmission($submission);

        foreach ($results as $r) {
            $submission->results()->updateOrCreate(
                ['result_token' => $r['result_token']],
                [
                    'label' => $r['label'],
                    'value' => $r['value'],
                    'unit' => $r['unit'],
                ]
            );
        }
    }
}