[#203] Réceptions — Parcours de pesée multi-étapes (première partie) (!3)

| Numéro du ticket | Titre du ticket |
|------------------|-----------------|
|        #203          |      Réceptions — Parcours de pesée multi-étapes         |

## Description de la PR
[#203] Réceptions — Parcours de pesée multi-étapes

## Modification du .env

## Check list

- [x] Pas de régression
- [x] TU/TI/TF rédigée
- [x] TU/TI/TF OK
- [x] CHANGELOG modifié

Reviewed-on: #3
Reviewed-by: THOLOT DECHENE Matthieu <matthieu@yuno.malio.fr>
Co-authored-by: AUTIN Tristan <tristan@yuno.malio.fr>
Co-committed-by: AUTIN Tristan <tristan@yuno.malio.fr>

src/Service/PontBasculePayloadDecoder.php

@@ -0,0 +1,68 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Service;
+
+use App\Dto\PontBasculeReading;
+use App\Exception\PontBasculeException;
+
+final class PontBasculePayloadDecoder
+{
+    public function decode(string $body): PontBasculeReading
+    {
+        // Payload is JSON with a "response_ascii" string containing STX (0x02) segments.
+        $payload = json_decode($body, true);
+        if (!is_array($payload)) {
+            throw PontBasculeException::invalidPayload();
+        }
+
+        $ascii = $payload['response_ascii'] ?? null;
+        if (!is_string($ascii)) {
+            throw PontBasculeException::missingPayloadField('response_ascii');
+        }
+
+        $dsd = null;
+        $net = null;
+
+        // Each segment starts with a 2-digit code followed by the numeric value.
+        $segments = preg_split('/\\x02/', $ascii) ?: [];
+        foreach ($segments as $segment) {
+            $segment = trim($segment);
+            if ('' === $segment) {
+                continue;
+            }
+
+            if (!preg_match('/^(\d{2})(\d+)(?:\.kg)?/', $segment, $matches)) {
+                continue;
+            }
+
+            $code  = $matches[1];
+            $value = $matches[2];
+
+            // Code 99 holds the DSD value.
+            if ('99' === $code) {
+                $dsd = (int) ltrim($value, '0');
+                if (0 === $dsd && '' !== $value) {
+                    $dsd = 0;
+                }
+
+                continue;
+            }
+
+            // Code 03 is the net weight; other codes are ignored for now.
+            if ('03' === $code) {
+                $net = (float) ltrim($value, '0');
+                if (0.0 === $net && '' !== $value) {
+                    $net = 0.0;
+                }
+            }
+        }
+
+        if (null === $dsd && null === $net) {
+            throw PontBasculeException::unreadableValues();
+        }
+
+        return new PontBasculeReading($dsd, $net);
+    }
+}