/*
 * Der Formulareditor in der Verwaltung.
 *
 * Ohne Skript ist die Seite vollständig bedienbar: Felder sind Karten mit Eingaben, ein Feld ohne
 * Beschriftung wird nicht gespeichert, die Vorschau zeigt den gespeicherten Stand. Das Skript
 * macht daraus einen Editor: Felder hinzufügen und entfernen, den technischen Namen aus der
 * Beschriftung ableiten, Optionen nur bei einer Auswahl zeigen, Farben aus der Palette wählen -
 * und eine Vorschau, die jeder Eingabe folgt, mit dem Standardbutton der Website.
 */
import { createColorControl } from './color-control.js';
import { buttonSample } from './button-design.js';

const root = document.querySelector('[data-form-schema]');
if (root) {
  const schema = JSON.parse(root.dataset.formSchema);
  const bilder = JSON.parse(root.dataset.formImages || '[]');
  const defaults = {
    fieldBorderColor: schema.base.color,
    fieldBackgroundColor: '#ffffff',
    buttonColor: schema.buttons.backgroundColor,
    buttonInk: schema.buttons.color,
  };
  const hex = value => /^#[0-9a-f]{6}/i.test(value || '') ? value.slice(0, 7) : schema.colors.find(color => `@${color.key}` === value)?.value || '';
  // Dunkler beim Überfahren, so wie es die Seite selbst tut (82 % Farbe, Rest Schwarz).
  const darker = value => {
    const rgb = hex(value); if (!rgb) return value;
    return '#' + [1, 3, 5].map(index => Math.round(parseInt(rgb.slice(index, index + 2), 16) * 0.82).toString(16).padStart(2, '0')).join('');
  };
  const luminance = rgb => {
    const [r, g, b] = [1, 3, 5].map(index => parseInt(rgb.slice(index, index + 2), 16) / 255)
      .map(channel => channel <= 0.03928 ? channel / 12.92 : ((channel + 0.055) / 1.055) ** 2.4);
    return 0.2126 * r + 0.7152 * g + 0.0722 * b;
  };
  const contrast = (back, front) => {
    if (!back || !front) return null;
    const [light, dark] = [luminance(back), luminance(front)].sort((a, b) => b - a);
    return (light + 0.05) / (dark + 0.05);
  };
  const slug = text => text.toLowerCase()
    .replace(/ä/g, 'ae').replace(/ö/g, 'oe').replace(/ü/g, 'ue').replace(/ß/g, 'ss')
    .replace(/[^a-z0-9]+/g, '_').replace(/^[^a-z]+/, '').replace(/_+$/, '').slice(0, 32);
  const el = (tag, className, text) => {
    const node = document.createElement(tag); node.className = className;
    if (text !== undefined) node.textContent = text; return node;
  };

  for (const form of root.querySelectorAll('[data-form-editor]')) {
    const list = form.querySelector('[data-field-list]'), template = form.querySelector('[data-field-template]');
    const preview = form.querySelector('[data-form-preview]'), add = form.querySelector('[data-add-field]');
    const buttonLabel = form.querySelector('[data-form-button-label]');
    const colorInputs = {};
    const cards = () => [...list.querySelectorAll('[data-field]')];
    let next = cards().length;

    const renderPreview = () => {
      preview.replaceChildren();
      preview.style.color = hex(schema.base.color) || '#203b34';
      preview.style.background = hex(schema.base.backgroundColor) || '#ffffff';
      preview.style.setProperty('--form-border', hex(colorInputs.fieldBorderColor.value) || 'currentColor');
      preview.style.setProperty('--form-bg', hex(colorInputs.fieldBackgroundColor.value) || '#ffffff');
      let shown = 0;
      for (const card of cards()) {
        const label = card.querySelector('[data-field-label]').value.trim();
        if (!label) continue;
        shown++;
        const type = card.querySelector('[data-field-type]').value;
        const help = card.querySelector('[data-field-help]').value.trim();
        if (type === 'step') {
          // Ein Schritt ist eine Zwischenüberschrift in der Vorschau, mit seiner Einleitung.
          const step = el('div', 'form-preview-step');
          step.append(el('span', 'form-preview-step-title', label));
          if (help) step.append(el('span', 'form-preview-help', help));
          preview.append(step);
          continue;
        }
        const required = type === 'consent' || card.querySelector('[data-field-required]').checked;
        const showIf = card.querySelector('[data-field-showif]').value.trim();
        const field = el('div', `form-preview-field${showIf ? ' form-preview-conditional' : ''}`);
        const options = () => card.querySelector('[data-field-options-input]').value.split(',').map(option => option.trim()).filter(Boolean);
        if (type === 'consent') {
          const check = el('span', 'form-preview-check');
          check.append(el('span', 'form-preview-box'), document.createTextNode(`${label} *`));
          field.append(check);
        } else if (type === 'radio' || type === 'checkboxes') {
          field.append(el('span', 'form-preview-label', label + (required ? ' *' : '')));
          for (const option of options()) {
            const check = el('span', 'form-preview-check');
            check.append(el('span', `form-preview-box${type === 'radio' ? ' form-preview-radio' : ''}`), document.createTextNode(option));
            field.append(check);
          }
        } else {
          field.append(el('span', 'form-preview-label', label + (required ? ' *' : '')));
          const unit = type === 'number' ? card.querySelector('[data-field-unit]').value.trim() : '';
          field.append(el('span', `form-preview-input${type === 'textarea' ? ' form-preview-area' : ''}${type === 'select' ? ' form-preview-select' : ''}${type === 'number' ? ' form-preview-number' : ''}`, type === 'select' ? '— bitte wählen —' : unit));
        }
        if (help) field.append(el('span', 'form-preview-help', help));
        if (showIf) field.append(el('span', 'form-preview-help', `Nur wenn ${showIf} = ${card.querySelector('[data-field-showvalues]').value.split(',').map(v => v.trim()).filter(Boolean).join(' oder ') || '…'}`));
        preview.append(field);
      }
      if (!shown) preview.append(el('p', 'form-preview-empty', 'Noch kein Feld mit Beschriftung.'));
      const values = { ...schema.buttons };
      const fill = colorInputs.buttonColor.value, ink = colorInputs.buttonInk.value;
      if (fill) { values.backgroundColor = fill; values.hoverBackgroundColor = darker(fill); }
      if (ink) { values.color = ink; values.hoverColor = ink; }
      preview.append(buttonSample(buttonLabel.value.trim() || 'Absenden', values, schema));
      // Der Kontrast der Buttonschrift auf der Buttonfarbe, nach WCAG: unter 4,5:1 ist der Text
      // fuer viele nicht mehr lesbar - das soll man sehen, bevor es auf der Website steht.
      const ratio = contrast(hex(values.backgroundColor), hex(values.color));
      note.hidden = ratio === null;
      if (ratio !== null) {
        note.className = `contrast-note ${ratio >= 4.5 ? 'contrast-ok' : ratio >= 3 ? 'contrast-warn' : 'contrast-bad'}`;
        note.textContent = `Buttonschrift auf Buttonfarbe: Kontrast ${ratio.toFixed(1).replace('.', ',')}:1 – ${ratio >= 4.5 ? 'gut lesbar.' : ratio >= 3 ? 'nur für große Schrift ausreichend, für den Button zu wenig.' : 'zu wenig, der Text ist kaum lesbar.'}`;
      }
    };
    const note = el('p', 'contrast-note'); note.hidden = true; note.setAttribute('role', 'status');
    preview.after(note);

    // Statt Kennungen zu tippen: je Option eine Liste der Mediathek. Das Textfeld bleibt das
    // gespeicherte Original und wird aus den Listen geschrieben; ohne Skript tippt man hinein.
    const renderImagePickers = card => {
      const area = card.querySelector('[data-field-images-input]');
      const options = card.querySelector('[data-field-options-input]').value.split(',').map(o => o.trim()).filter(Boolean);
      let box = card.querySelector('[data-image-pickers]');
      if (!box) {
        box = el('div', 'field-image-pickers'); box.dataset.imagePickers = '';
        area.hidden = true; area.after(box);
      }
      if (box.dataset.signature === options.join('|')) return;
      const current = Object.fromEntries(area.value.split('\n').filter(l => l.includes('=')).map(l => l.split('=').map(x => x.trim())));
      box.dataset.signature = options.join('|');
      box.replaceChildren();
      for (const option of options) {
        const row = el('label', 'field-image-picker');
        row.append(el('span', 'field-image-picker-option', option));
        const select = document.createElement('select');
        select.append(new Option('Kein Bild', ''));
        for (const bild of bilder) select.append(new Option(bild.title, bild.id, false, current[option] === bild.id));
        select.dataset.option = option;
        select.addEventListener('change', () => {
          const map = {};
          for (const picker of box.querySelectorAll('select')) if (picker.value) map[picker.dataset.option] = picker.value;
          area.value = Object.entries(map).map(([o, id]) => `${o} = ${id}`).join('\n');
          renderPreview();
        });
        row.append(select); box.append(row);
      }
    };

    const refresh = () => {
      cards().forEach((card, index) => {
        card.querySelector('[data-field-index]').textContent = String(index + 1);
        const type = card.querySelector('[data-field-type]').value;
        card.querySelector('[data-field-options]').hidden = !['select', 'radio', 'checkboxes'].includes(type);
        card.querySelector('[data-field-images]').hidden = !['radio', 'checkboxes'].includes(type);
        if (['radio', 'checkboxes'].includes(type)) renderImagePickers(card);
        card.querySelector('[data-field-number]').hidden = type !== 'number';
        const remove = card.querySelector('[data-remove-field]');
        remove.hidden = false; remove.setAttribute('aria-label', `Feld ${index + 1} entfernen`);
        const required = card.querySelector('[data-field-required]');
        // Eine Einwilligung ist immer Pflicht - das Kästchen sagt es, statt es zu verstecken.
        if (type === 'consent') { required.checked = true; required.disabled = true; }
        else if (type === 'step') { required.checked = false; required.disabled = true; }
        else required.disabled = false;
      });
      renderPreview();
    };

    // Die leere Karte für ein neues Feld braucht es nur, solange es kein Feld gibt: mit Skript
    // kommt jedes weitere über den Knopf.
    const empty = cards().filter(card => card.classList.contains('field-card-new'));
    if (cards().length > empty.length) empty.forEach(card => card.remove());
    add.hidden = false;
    add.addEventListener('click', () => {
      list.insertAdjacentHTML('beforeend', template.innerHTML.replaceAll('__n__', String(next++)));
      const card = list.lastElementChild; card.classList.remove('field-card-new');
      refresh(); card.querySelector('[data-field-label]').focus();
    });
    list.addEventListener('click', event => {
      const button = event.target.closest('[data-remove-field]');
      if (!button) return;
      button.closest('[data-field]').remove(); refresh(); add.focus();
    });
    list.addEventListener('input', event => {
      const card = event.target.closest('[data-field]');
      if (event.target.matches('[data-field-label]')) {
        // Der technische Name folgt der Beschriftung, bis jemand ihn selbst schreibt.
        const name = card.querySelector('[data-field-name]');
        if (!name.dataset.touched) name.value = slug(event.target.value);
      }
      if (event.target.matches('[data-field-name]')) event.target.dataset.touched = event.target.value ? '1' : '';
      refresh();
    });
    list.addEventListener('change', refresh);
    for (const card of cards()) {
      const name = card.querySelector('[data-field-name]');
      if (name.value) name.dataset.touched = '1';
    }

    for (const input of form.querySelectorAll('[data-form-color]')) {
      const key = input.dataset.formColor, label = form.querySelector(`label[for="${input.id}"]`).textContent;
      const id = input.id; input.type = 'hidden'; input.id += '-value';
      colorInputs[key] = input;
      const control = createColorControl({
        id, label, value: input.value, inheritedValue: defaults[key], colors: schema.colors,
        onChange: value => { input.value = value; renderPreview(); }, onComplete: () => {},
      });
      control.querySelector('.color-inherit').textContent = 'Wie die Website';
      input.after(control);
    }
    buttonLabel.addEventListener('input', renderPreview);
    refresh();
  }
}