export const labels = { section: 'Sektion', row: 'Zeile', column: 'Spalte', heading: 'Überschrift', text: 'Text', image: 'Bild', button: 'Button', gallery: 'Galerie', postlist: 'Beitragsliste', iconcard: 'Symbolkarte', stat: 'Kennzahl', quote: 'Kundenstimme', logos: 'Logoleiste', cta: 'Aufruf-Band', contact: 'Kontaktdaten', divider: 'Trennlinie', spacer: 'Abstand', accordion: 'Akkordeon', accordionitem: 'Akkordeon-Eintrag', tabs: 'Tabs', tabitem: 'Tab', form: 'Formular', breadcrumb: 'Brotkrumen', menu: 'Navigation', partialref: 'Verknüpfte Sektion', embed: 'Externer Inhalt', icon: 'Symbol', progress: 'Fortschritt', slider: 'Slider' , legal: 'Rechtszeile'};
export const icons = { section: '▣', row: '☰', column: '▥', heading: 'H', text: 'T', image: '▧', button: '↗', gallery: '▦', postlist: '☷', iconcard: '◈', stat: '№', quote: '❝', logos: '⬚', cta: '◉', contact: '✆', divider: '—', spacer: '⇳', accordion: '⌵', accordionitem: '·', tabs: '▭', tabitem: '▫', form: '✉', breadcrumb: '⟩', menu: '☰', partialref: '⧉', legal: '§', embed: '⬓', icon: '◆', progress: '▰', slider: '⇄' };
// A namespaced type belongs to a plugin this installation may not have. Such blocks stay in the
// document, stay selectable and movable, but the editor never edits or fills them.
export const PLUGIN_TYPE = /^[a-z][a-z0-9]{1,30}\.[a-z][a-z0-9-]{1,40}$/;
export const isPluginBlock = block => typeof block?.type === 'string' && PLUGIN_TYPE.test(block.type);
export const blockLabel = block => labels[block?.type] ?? (isPluginBlock(block) ? `Baustein ${block.type}` : 'Unbekannt');
export const blockIcon = block => icons[block?.type] ?? '❔';
export const isContainer = block => ['section', 'row', 'column', 'gallery', 'logos', 'accordion', 'accordionitem', 'tabs', 'tabitem', 'slider'].includes(block?.type);
// Nothing may be dropped into a plugin block: the core does not know its layout contract.
// Containers that accept only one kind of child, mirrored by the server side validator.
export const ONLY_CHILD = { gallery: 'image', logos: 'image', accordion: 'accordionitem', tabs: 'tabitem' };
export const canContain = (parent, block) => isContainer(parent) && !isPluginBlock(parent)
  && (ONLY_CHILD[parent.type] === undefined || ONLY_CHILD[parent.type] === block.type)
  && (block.type !== 'accordionitem' || parent.type === 'accordion')
  && (block.type !== 'tabitem' || parent.type === 'tabs');
export const clone = value => structuredClone(value);

export function locate(blocks, id, parent = null) {
  for (let index = 0; index < blocks.length; index++) {
    const block = blocks[index];
    if (block.id === id) return { block, siblings: blocks, index, parent };
    const child = locate(block.children || [], id, block);
    if (child) return child;
  }
  return null;
}

export function createBlock(type) {
  if (!Object.hasOwn(labels, type)) throw new Error('Unbekannter Block.');
  const block = { id: `b_${crypto.randomUUID().replaceAll('-', '')}`, type };
  if (isContainer(block)) block.children = [];
  if (type === 'accordion') block.children = [createBlock('accordionitem')];
  // A single tab is not a tab group, and the script needs at least two to enhance anything.
  if (type === 'tabs') block.children = [createBlock('tabitem'), createBlock('tabitem')];
  if (type === 'heading') block.props = { text: 'Deine neue Überschrift', level: 2 };
  if (type === 'text') block.props = { text: 'Hier beginnt dein neuer Inhalt.' };
  if (type === 'button') block.props = { text: 'Mehr erfahren', href: '/' };
  if (type === 'postlist') block.props = { count: 3, category: '', tag: '', layout: 'karten' };
  if (type === 'postnav') block.props = { previousLabel: 'Vorheriger Beitrag', nextLabel: 'Nächster Beitrag' };
  if (type === 'legal') block.props = { label: 'Rechtliches' };
  if (type === 'iconcard') block.props = { icon: 'check', title: 'Deine Leistung', text: 'Beschreibe hier kurz, worum es geht.', href: '' };
  if (type === 'stat') block.props = { value: '15+', label: 'Jahre Erfahrung' };
  if (type === 'quote') block.props = { text: 'Ein Satz, den eine Kundin oder ein Kunde über dich gesagt hat.', author: 'Name', role: '', rating: 5 };
  if (type === 'cta') block.props = { title: 'Bereit für den nächsten Schritt?', text: '', buttonText: 'Jetzt anfragen', href: '/' };
  if (type === 'contact') block.props = { phone: '', email: '', address: '' };
  if (type === 'spacer') block.props = { size: 'medium' };
  if (type === 'accordionitem') block.props = { title: 'Eine Frage', open: false };
  if (type === 'tabitem') block.props = { title: 'Neuer Tab' };
  if (type === 'form') block.props = { form: '' };
  if (type === 'menu') block.props = { slot: 'header', layout: 'horizontal' };
  if (type === 'partialref') block.props = { partial: '' };
  // An embed starts empty and blocked: no address, so nothing loads before someone enters one.
  if (type === 'embed') block.props = { group: 'external', title: '', provider: '', url: '', hint: '', height: 400 };
  if (type === 'icon') block.props = { icon: 'star', size: 48, decorative: true, label: '', href: '' };
  if (type === 'progress') block.props = { label: 'Fortschritt', value: 70, showValue: true };
  if (type === 'slider') block.props = { desktopVisible: 3, tabletVisible: 2, mobileVisible: 1, snap: true, dots: true, autoplay: 0 };
  if (type === 'image') block.props = { src: '/assets/image-placeholder.svg', alt: 'Abstrakte Landschaft als Platzhalter', decorative: false, width: 1000, height: 600 };
  return block;
}

export function insertBlock(document, type, selected) {
  const block = createBlock(type);
  if (type === 'gallery') upgradeDocument(document, 3);
  if (type === 'postlist') upgradeDocument(document, 5);
  if (type === 'postnav') upgradeDocument(document, 18);
  if (type === 'legal') upgradeDocument(document, 19);
  if (['iconcard', 'stat', 'quote', 'logos', 'cta', 'contact', 'divider', 'spacer', 'accordion', 'accordionitem'].includes(type)) upgradeDocument(document, 6);
  if (type === 'tabs' || type === 'tabitem') upgradeDocument(document, 7);
  if (type === 'form') upgradeDocument(document, 8);
  if (type === 'breadcrumb') upgradeDocument(document, 9);
  if (type === 'menu' || type === 'partialref') upgradeDocument(document, 11);
  if (type === 'embed') upgradeDocument(document, 14);
  if (['icon', 'progress', 'slider'].includes(type)) upgradeDocument(document, 15);
  let target = locate(document.blocks, selected);
  if (target?.block.type === 'gallery' && type !== 'image') { target.siblings.splice(target.index + 1, 0, block); return block.id; }
  if (target?.parent?.type === 'gallery' && type !== 'image') target = locate(document.blocks, target.parent.id);
  if (!target) document.blocks.push(block);
  else if (canContain(target.block, block)) (target.block.children ??= []).push(block);
  else target.siblings.splice(target.index + 1, 0, block);
  return block.id;
}

export function duplicateBlock(document, selected) {
  const target = locate(document.blocks, selected);
  if (!target) return null;
  const copy = clone(target.block);
  const rekey = block => {
    block.id = `b_${crypto.randomUUID().replaceAll('-', '')}`;
    if (block.type === 'heading' && block.props.level === 1) block.props.level = 2;
    (block.children || []).forEach(rekey);
  };
  rekey(copy);
  target.siblings.splice(target.index + 1, 0, copy);
  return copy.id;
}

export function moveBlock(document, selected, targetId, inside = false) {
  const source = locate(document.blocks, selected);
  const target = locate(document.blocks, targetId);
  if (!source || !target || selected === targetId || locate(source.block.children || [], targetId)) return false;
  if (inside && !isContainer(target.block)) return false;
  if (inside && !canContain(target.block, source.block)) return false;
  if (!inside && target.parent && !canContain(target.parent, source.block)) return false;
  source.siblings.splice(source.index, 1);
  const destination = locate(document.blocks, targetId);
  if (inside) (destination.block.children ??= []).push(source.block);
  else destination.siblings.splice(destination.index, 0, source.block);
  return true;
}

export const devices = { desktop: 'Desktop', tablet: 'Tablet', mobile: 'Mobil' };

// Called only inside a history transaction: all other fields and IDs stay untouched.
// Die höchste Fassung, die dieser Editor kennt. Sie stand bisher als Liste an zwei Stellen und
// blieb bei 12 stehen, während Bausteine schon v13 bis v15 verlangten: in einem aktuellen Dokument
// liess sich dann gar nichts mehr einfügen, und ein Symbol, ein Slider oder ein externer Inhalt
// nirgends. Eine Zahl, an einer Stelle.
export const SCHEMA_VERSION = 19;
const known = version => Number.isInteger(version) && version >= 1 && version <= SCHEMA_VERSION;

export function upgradeDocument(document, version = 2) {
  if (!known(document.schemaVersion) || !known(version) || version < 2) throw new Error('Unbekanntes Dokumentschema.');
  document.schemaVersion = Math.max(document.schemaVersion, version);
  return document;
}

export function effectiveDesign(block, device, key) {
  let value, source;
  for (const name of Object.keys(devices)) {
    if (block.layout?.design?.[name]?.[key] !== undefined) {
      value = block.layout.design[name][key]; source = name;
    }
    if (name === device) break;
  }
  return { value, source };
}

export function setDesign(document, id, device, key, value) {
  if (!known(document.schemaVersion)) throw new Error('Unbekanntes Dokumentschema.');
  if (!Object.hasOwn(devices, device)) throw new Error('Unbekannte Vorschaugröße.');
  const block = locate(document.blocks, id)?.block;
  if (!block) return;
  if (value === '') {
    const design = block.layout?.design;
    if (!design?.[device] || !Object.hasOwn(design[device], key)) return;
    delete design[device][key];
    if (!Object.keys(design[device]).length) delete design[device];
    if (!Object.keys(design).length) delete block.layout.design;
  } else {
    upgradeDocument(document);
    ((block.layout ??= {}).design ??= {})[device] ??= {};
    block.layout.design[device][key] = value;
  }
}

export function blockPath(blocks, id) {
  const found = locate(blocks, id);
  return found ? [...(found.parent ? blockPath(blocks, found.parent.id) : []), found.block] : [];
}

export function setEffect(document, id, key, value) {
  const block = locate(document.blocks, id)?.block;
  if (!block) return;
  upgradeDocument(document, 3);
  ((block.layout ??= {}).effects ??= {})[key] = value;
}

export function mediaProps(media) {
  const largest = media.variants.at(-1);
  return { mediaId: media.id, src: largest.src, width: largest.width, height: largest.height, alt: media.decorative ? '' : media.alt, decorative: Boolean(media.decorative), caption: '', sources: media.variants.map(({ src, width }) => ({ src, width })) };
}

export function insertMedia(document, selected, items) {
  const target = locate(document.blocks, selected)?.block;
  upgradeDocument(document, 3);
  if (target?.type === 'image') { target.props = mediaProps(items[0]); return target.id; }
  let parent = target;
  if (target?.type !== 'gallery') {
    const id = insertBlock(document, 'gallery', selected); parent = locate(document.blocks, id).block;
  }
  for (const item of items) { const image = createBlock('image'); image.props = mediaProps(item); (parent.children ??= []).push(image); }
  return parent.id;
}

/**
 * A row with a given number of columns, inserted where the selection is.
 *
 * A row on its own looks like nothing, which is why "add a row" was hard to find: what people
 * want is a row that already has columns in it.
 */
/**
 * A full screen hero: edge to edge, as tall as the screen, content centred, with room for a
 * background image and a dark overlay so text stays readable on any photo.
 *
 * The parts all exist on their own - width "full", min-height in dvh, display flex, overlay - but
 * finding that combination is a research project. This is the one click.
 */
export function insertHero(document, selected) {
  const section = createBlock('section');
  section.layout = { tone: 'ink', width: 'full' };
  section.style = {
    desktop: {
      // dvh, not vh: on a phone 100vh is taller than the screen.
      minHeight: '100dvh', display: 'flex', alignItems: 'center',
      backgroundSize: 'cover', backgroundPosition: 'center', backgroundRepeat: 'no-repeat',
      overlayColor: '#000000', overlayOpacity: 0.4,
      padding: { top: '80px', right: '32px', bottom: '80px', left: '32px' },
      textAlign: 'center',
    },
    mobile: { minHeight: '80dvh', padding: { top: '56px', right: '20px', bottom: '56px', left: '20px' } },
  };
  // A hero at the top of a page carries its main heading - but a page has exactly one, and
  // inserting a second would produce a document the editor refuses to save.
  const hasMainHeading = blocks => blocks.some(block =>
    (block.type === 'heading' && block.props?.level === 1) || hasMainHeading(block.children ?? []));
  const heading = createBlock('heading');
  heading.props = { text: 'Deine Botschaft, ganzflächig.', level: hasMainHeading(document.blocks) ? 2 : 1 };
  const paragraph = createBlock('text');
  paragraph.props = { text: 'Ein Satz, der sagt, worum es geht. Wähle im Designbereich unter Hintergrund ein Bild und stelle die Deckkraft der Überlagerung so ein, dass der Text lesbar bleibt.' };
  const button = createBlock('button');
  section.children = [heading, paragraph, button];
  upgradeDocument(document, 10);
  const top = blockPath(document.blocks, selected)[0];
  const index = top ? document.blocks.findIndex(block => block.id === top.id) + 1 : document.blocks.length;
  document.blocks.splice(index, 0, section);
  return section.id;
}

export function insertRow(document, columns, selected) {
  const count = Math.max(1, Math.min(6, Number(columns) || 2));
  const names = { 1: 'one', 2: 'two', 3: 'three', 4: 'four' };
  const row = createBlock('row');
  row.layout = { design: { desktop: { columns: names[count] ?? 'auto', gap: 'medium' }, mobile: { columns: 'one' } } };
  row.children = Array.from({ length: count }, () => createBlock('column'));
  upgradeDocument(document);
  const target = locate(document.blocks, selected);
  if (!target) document.blocks.push(row);
  else if (canContain(target.block, row)) (target.block.children ??= []).push(row);
  else target.siblings.splice(target.index + 1, 0, row);
  return row.id;
}

export function insertPreset(document, name, selected) {
  if (name === 'hero') return insertHero(document, selected);
  if (!['intro', 'columns', 'cta'].includes(name)) throw new Error('Unbekannte Vorlage.');
  const section = createBlock('section');
  const heading = text => { const block = createBlock('heading'); block.props.text = text; return block; };
  const paragraph = text => { const block = createBlock('text'); block.props.text = text; return block; };
  section.layout = { tone: name === 'cta' ? 'ink' : 'paper', width: name === 'columns' ? 'normal' : 'narrow' };
  section.children = [heading(name === 'cta' ? 'Lass uns gemeinsam starten.' : name === 'columns' ? 'Was wir für dich tun.' : 'Raum für deine nächste Idee.'), paragraph('Erzähle hier, was dein Angebot besonders macht und welchen Nutzen deine Besucher davon haben.')];
  if (name === 'columns') {
    const row = createBlock('row');
    row.layout = { design: { desktop: { columns: 'two', gap: 'medium' }, mobile: { columns: 'one' } } };
    row.children = ['Persönlich beraten', 'Gemeinsam umsetzen'].map(text => {
      const column = createBlock('column');
      const title = heading(text); title.props.level = 3;
      column.children = [title, paragraph('Beschreibe dein Angebot in wenigen verständlichen Sätzen.')];
      return column;
    });
    section.children.push(row);
    upgradeDocument(document);
  } else section.children.push(createBlock('button'));
  const top = blockPath(document.blocks, selected)[0];
  const index = top ? document.blocks.findIndex(block => block.id === top.id) + 1 : document.blocks.length;
  document.blocks.splice(index, 0, section);
  return section.id;
}

export class EditorHistory {
  constructor(document) { this.reset(document); }
  reset(document) {
    this.document = clone(document);
    this.past = [];
    this.future = [];
    this.mergeKey = null;
    this.saved = JSON.stringify(document);
  }
  change(mutator, mergeKey = null) {
    const next = clone(this.document);
    const result = mutator(next);
    if (JSON.stringify(next) === JSON.stringify(this.document)) return result;
    if (!mergeKey || this.mergeKey !== mergeKey) this.past.push(this.document);
    if (this.past.length > 100) this.past.shift();
    this.document = next;
    this.future = [];
    this.mergeKey = mergeKey;
    return result;
  }
  undo() {
    if (!this.past.length) return;
    this.future.push(this.document);
    this.document = this.past.pop();
    this.mergeKey = null;
  }
  redo() {
    if (!this.future.length) return;
    this.past.push(this.document);
    this.document = this.future.pop();
    this.mergeKey = null;
  }
  markSaved(document) { this.saved = JSON.stringify(document); this.mergeKey = null; }
  get dirty() { return JSON.stringify(this.document) !== this.saved; }
}

// ---------------------------------------------------------------------------------------------
// Free block styles (document schema v10).
//
// A style is { device: { property: value, hover: { property: value } } }. Desktop is the base,
// tablet and mobile override it. Everything mirrors StyleSchema on the server: the editor can only
// offer what the server accepts, and a value the server would reject never reaches a document.
// ---------------------------------------------------------------------------------------------

/** The value that actually applies on a device, plus the device it was inherited from. */
export function effectiveStyle(block, device, key, side = null) {
  let value, source;
  for (const name of Object.keys(devices)) {
    const stored = block?.style?.[name]?.[key];
    const candidate = side === null ? stored : stored?.[side];
    if (candidate !== undefined) { value = candidate; source = name; }
    if (name === device) break;
  }
  return { value, source };
}

export function hoverStyle(block, device, key) {
  return block?.style?.[device]?.hover?.[key];
}

/** Removes empty objects so an untouched block never carries a style skeleton. */
function prune(block) {
  for (const device of Object.keys(block.style ?? {})) {
    const values = block.style[device];
    for (const key of Object.keys(values)) {
      if (values[key] && typeof values[key] === 'object' && Object.keys(values[key]).length === 0) delete values[key];
    }
    if (Object.keys(values).length === 0) delete block.style[device];
  }
  if (block.style && Object.keys(block.style).length === 0) delete block.style;
}

/**
 * Sets one style value. An empty value removes it, which makes the block fall back to the wider
 * device and finally to the theme. Called inside a history transaction like every other change.
 */
export function setStyle(document, id, device, key, value, { side = null, hover = false } = {}) {
  if (!Object.hasOwn(devices, device)) throw new Error('Unbekannte Vorschaugröße.');
  const block = locate(document.blocks, id)?.block;
  if (!block) return;
  const empty = value === '' || value === null || value === undefined;
  if (!empty) upgradeDocument(document, 10);

  block.style ??= {};
  block.style[device] ??= {};
  let target = block.style[device];
  if (hover) { target.hover ??= {}; target = target.hover; }

  if (side !== null) {
    if (empty) { if (target[key]) delete target[key][side]; }
    else { target[key] ??= {}; target[key][side] = value; }
  } else if (empty) {
    delete target[key];
  } else {
    target[key] = value;
  }
  prune(block);
}

/** Drops every style of one device, so it inherits again. */
export function resetStyleDevice(document, id, device) {
  const block = locate(document.blocks, id)?.block;
  if (!block?.style) return;
  delete block.style[device];
  prune(block);
}

/** Drops the whole styling of a block. */
export function clearStyle(document, id) {
  const block = locate(document.blocks, id)?.block;
  if (!block) return;
  delete block.style;
}

/** Copies the styling of one block onto another, with fresh objects. */
export function copyStyle(document, fromId, toId) {
  const source = locate(document.blocks, fromId)?.block;
  const target = locate(document.blocks, toId)?.block;
  if (!source || !target) return false;
  if (!source.style) { delete target.style; return true; }
  upgradeDocument(document, 10);
  target.style = structuredClone(source.style);
  return true;
}