// Pure helpers for MarkdownText. Kept free of React/RN deps so they can be
// unit-tested directly (see markdownTextUtils.test.ts).
import type { ASTNode } from 'react-native-markdown-display';

/** Only http(s) URLs are considered safe to open or to load as images. */
export function isSafeUrl(url: string): boolean {
  return /^https?:\/\//i.test(url.trim());
}

/** GitHub-style heading slug: lowercase, drop punctuation, spaces -> hyphens. */
export function slugify(text: string): string {
  return text.toLowerCase().trim().replace(/[^\w\s-]/g, '').replace(/\s+/g, '-');
}

/** Percent-decode a URL fragment; returns the input unchanged if malformed. */
export function decodeFragment(fragment: string): string {
  try {
    return decodeURIComponent(fragment);
  } catch {
    return fragment;
  }
}

/** Plain visible text of a markdown AST node (used for heading anchor slugs). */
export function getNodeText(node?: ASTNode): string {
  if (!node) return '';
  if (node.type === 'text' || node.type === 'code_inline') return node.content ?? '';
  return (node.children ?? []).map(getNodeText).join('');
}

/** All `tr` nodes under a table node, in document order. */
export function collectTableRows(node: ASTNode, acc: ASTNode[] = []): ASTNode[] {
  if (node.type === 'tr') acc.push(node);
  for (const child of node.children ?? []) collectTableRows(child, acc);
  return acc;
}

/**
 * Split a table AST node into its header cells and body rows' cells. A row with
 * any `th` cell is treated as the header; the rest are body rows.
 */
export function extractTableData(tableNode: ASTNode): { header: ASTNode[]; rows: ASTNode[][] } {
  const rows: ASTNode[][] = [];
  let header: ASTNode[] = [];
  for (const tr of collectTableRows(tableNode)) {
    const cells = (tr.children ?? []).filter((cell) => cell.type === 'th' || cell.type === 'td');
    if (cells.some((cell) => cell.type === 'th')) header = cells;
    else rows.push(cells);
  }
  return { header, rows };
}

// A table separator row: |---|:--:|---| (>= 2 columns, dashes with optional
// alignment colons). Used to detect GFM tables.
const TABLE_SEPARATOR = /^\s*\|?\s*:?-{3,}:?\s*(?:\|\s*:?-{3,}:?\s*)+\|?\s*$/;
// Markdown image syntax: ![alt](url).
const IMAGE_PATTERN = /!\[[^\]]*\]\([^)]+\)/;

/**
 * True when the content contains a block that should be allowed to expand to
 * the full bubble width (and scroll horizontally): a fenced code block, a
 * table, or an image. Mirrors the host's `hasScrollableMarkdown` heuristic in
 * conversationParts so the bubble layout and the renderer agree.
 */
export function hasWideContent(content: string): boolean {
  if (!content) return false;
  if (/```|~~~/.test(content)) return true;
  if (IMAGE_PATTERN.test(content)) return true;

  const lines = content.replace(/\r\n/g, '\n').split('\n');
  return lines.some((line, index) => line.includes('|') && TABLE_SEPARATOR.test(lines[index + 1] ?? ''));
}