/** Container tags an app may widen with `allowedStyles`. */
const EXTENSION_TAGS = new Set(['td', 'th', 'table', 'p', 'h1', 'h2', 'h3', 'h4', 'h5', 'h6']);

/** Properties an app can never allow, whatever its config. */
export const EXTENSION_DENYLIST = new Set([
  'position', 'top', 'right', 'bottom', 'left', 'inset', 'inset-block',
  'inset-block-start', 'inset-block-end', 'inset-inline', 'inset-inline-start',
  'inset-inline-end', 'z-index', 'content', 'behavior', '-moz-binding',
  'transform', 'transform-origin', 'transform-box', 'filter', 'backdrop-filter',
  'perspective', 'perspective-origin', 'display', 'visibility', 'opacity',
  'pointer-events', 'clip', 'clip-path', 'mask', 'mask-image', 'mask-repeat',
  'mask-position', 'mask-size', 'animation', 'animation-name', 'transition',
  'transition-property', 'will-change', 'cursor', 'float', 'clear', 'overflow',
  'overflow-x', 'overflow-y', 'background', 'background-image',
  'list-style-image', 'border-image', 'border-image-source',
]);

/** Properties a built-in fidelity path already handles; kept in sync with `sanitize.ts`. */
const BUILTIN_HANDLED = new Set([
  // ALLOWED_STYLES
  'color', 'background-color', 'font-family', 'font-size', 'font-style',
  'font-weight', 'text-align', 'text-decoration', 'text-decoration-line',
  'vertical-align', 'margin-left', 'margin-inline-start', 'list-style-type',
  'line-height',
  // CONTAINER_DROP
  'text-decoration-style', 'text-decoration-color',
  // CELL_LAYOUT
  'padding', 'padding-top', 'padding-right', 'padding-bottom', 'padding-left',
  'width', 'border', 'border-top', 'border-right', 'border-bottom',
  'border-left', 'border-radius',
  // TABLE_LAYOUT
  'max-width', 'margin-right',
  // BLOCK_LAYOUT
  'margin', 'margin-top', 'margin-bottom',
]);

/** Lowercase name (optionally `mso-`), not denylisted and not built in. */
export function isExtensionPropValid(name: string): boolean {
  if (!/^(?:mso-)?[a-z]+(?:-[a-z]+)*$/.test(name)) return false;
  if (EXTENSION_DENYLIST.has(name)) return false;
  if (BUILTIN_HANDLED.has(name)) return false;
  return true;
}

/** Strict value grammar: no functions except numeric colours, no escape characters. */
export function isExtensionValueValid(value: string): boolean {
  const v = value.trim();
  if (!v || v.length > 128) return false;
  // eslint-disable-next-line no-control-regex
  if (/[^\x00-\x7f]/.test(v)) return false;
  if (/\b(?:url|expression|var|calc|attr|env|image-set)\b/i.test(v)) return false;
  if (/[\\<>{};@]/.test(v)) return false;
  if (/\/\*/.test(v)) return false;
  if (/\//.test(v)) return false;
  if (/!important/i.test(v)) return false;
  if (/[()]/.test(v)) {
    if ((v.match(/\(/g) ?? []).length !== 1) return false;
    const fn = /(?:rgba?|hsla?)\(\s*[\d.]+%?(?:\s*,\s*[\d.]+%?){2,3}\s*\)/i.exec(v);
    if (!fn || /[()]/.test(v.replace(fn[0], ''))) return false;
  }
  return true;
}

/** tag → set of accepted extension property names. */
export type NormalizedAllowedStyles = Map<string, Set<string>>;

/** Validated tag → props map; warns once per dropped entry. */
export function normalizeEmailAllowedStyles(
  config: Record<string, string[]>
): NormalizedAllowedStyles {
  const out: NormalizedAllowedStyles = new Map();
  if (!config || typeof config !== 'object') return out;
  for (const [rawTag, rawProps] of Object.entries(config)) {
    const tag = String(rawTag).toLowerCase();
    if (!EXTENSION_TAGS.has(tag)) {
      // eslint-disable-next-line no-console
      console.warn(
        `[nile-wysiwyg-editor] allowedStyles: ignoring tag "${rawTag}" (unsupported tag)`
      );
      continue;
    }
    if (!Array.isArray(rawProps)) continue;
    const props = out.get(tag) ?? new Set<string>();
    for (const rawProp of rawProps) {
      const prop = String(rawProp);
      if (!isExtensionPropValid(prop)) {
        const reason = EXTENSION_DENYLIST.has(prop)
          ? 'denylisted'
          : BUILTIN_HANDLED.has(prop)
            ? 'already handled by a built-in'
            : 'invalid property name';
        // eslint-disable-next-line no-console
        console.warn(
          `[nile-wysiwyg-editor] allowedStyles: ignoring "${tag}: ${rawProp}" (${reason})`
        );
        continue;
      }
      props.add(prop);
    }
    if (props.size) out.set(tag, props);
  }
  return out;
}

/** `"td: letter-spacing; p: text-indent"` → `{ td: ['letter-spacing'], p: ['text-indent'] }`. */
export function parseAllowedStylesAttr(raw: string): Record<string, string[]> {
  const out: Record<string, string[]> = {};
  for (const group of raw.split(';')) {
    const idx = group.indexOf(':');
    if (idx === -1) continue;
    const tag = group.slice(0, idx).trim();
    if (!tag) continue;
    const props = group
      .slice(idx + 1)
      .split(',')
      .map(p => p.trim())
      .filter(Boolean);
    if (props.length) out[tag] = props;
  }
  return out;
}

/** Re-validates a stored `extraStyle` on write-back, where the per-app allowlist isn't visible. */
export function sanitizeExtraStyleForWrite(s: string): string {
  const kept: string[] = [];
  for (const decl of String(s ?? '').split(';')) {
    const idx = decl.indexOf(':');
    if (idx === -1) continue;
    const name = decl.slice(0, idx).trim().toLowerCase();
    const value = decl.slice(idx + 1).trim();
    if (isExtensionPropValid(name) && isExtensionValueValid(value)) {
      kept.push(`${name}: ${value}`);
    }
  }
  return kept.join('; ');
}