{% extends "op_zz_frame.html" %}
{% block centercontent %}
<main class="ct-docs-content-col" role="main">
  <h1 class="ct-docs-page-h1-title" id="content">{{ _('Plug & Charge – SECC check digit') }}</h1>
  <p class="text-muted">{{ _('Calculate the checksum for a SECC ID without the trailing digits.') }}</p>
  <div class="card shadow-sm">
    <div class="card-body">
      <div class="mb-3">
        <label for="secc-input" class="form-label">{{ _('SECC ID without check digit') }}</label>
        <input type="text" class="form-control" id="secc-input" value="{{ default_secc_id }}" autocomplete="off" />
        <div class="form-text">{{ _('Enter the SECC ID without the trailing two-digit checksum.') }}</div>
      </div>
      <div class="mb-3">
        <label for="secc-output" class="form-label">{{ _('Calculated SECC ID') }}</label>
        <input type="text" class="form-control" id="secc-output" readonly />
        <div id="secc-error" class="form-text text-danger d-none"></div>
      </div>
      <p class="mb-0 text-muted">{{ _('The check digit updates automatically while you type.') }}</p>
    </div>
  </div>
</main>
<script>
  function calculateSeccCheckDigit(seccIdWithoutCheckDigit) {
    const compact = seccIdWithoutCheckDigit.replace(/-/g, '');

    let numeric = '';
    for (const char of compact) {
      if (char >= 'A' && char <= 'Z') {
        numeric += (char.charCodeAt(0) - 55).toString();
      } else if (char >= '0' && char <= '9') {
        numeric += char;
      } else {
        throw new Error(`Ungültiges Zeichen: ${char}`);
      }
    }

    numeric += '00';

    let remainder = 0;
    for (let i = 0; i < numeric.length; i += 7) {
      remainder = Number(String(remainder) + numeric.substr(i, 7)) % 97;
    }

    const checkDigit = 98 - remainder;
    return checkDigit.toString().padStart(2, '0');
  }

  (function () {
    const input = document.getElementById('secc-input');
    const output = document.getElementById('secc-output');
    const error = document.getElementById('secc-error');

    function updateCheckDigit() {
      try {
        const value = input.value.trim();
        if (!value) {
          output.value = '';
          error.classList.add('d-none');
          return;
        }
        const checkDigit = calculateSeccCheckDigit(value);
        output.value = `${value}-${checkDigit}`;
        error.classList.add('d-none');
      } catch (err) {
        output.value = '';
        error.textContent = err.message || 'Error calculating check digit';
        error.classList.remove('d-none');
      }
    }

    input.addEventListener('input', updateCheckDigit);
    updateCheckDigit();
  })();
</script>
{% endblock %}