// Shared by the server and canvas; no storage or network work happens here.
export type ArchivedImageUrlMap = Record<string, string>;

export function isGeneratedImageSource(value: string) {
  return (
    /^https?:\/\//i.test(value) || /^data:image\/[a-z0-9.+-]+;base64,[a-z0-9+/=]+$/i.test(value)
  );
}

export function collectImageArchiveSources(value: unknown): string[] {
  const urls = new Set<string>();
  const visit = (item: unknown) => {
    if (typeof item === "string") {
      if (isGeneratedImageSource(item)) urls.add(item);
      else
        for (const match of item.matchAll(/!\[[^\]]*\]\(([^)]+)\)/g)) {
          if (isGeneratedImageSource(match[1])) urls.add(match[1]);
        }
    } else if (Array.isArray(item)) item.forEach(visit);
    else if (item && typeof item === "object" && !(item instanceof Date))
      Object.values(item).forEach(visit);
  };
  visit(value);
  return [...urls];
}

// Structural sharing preserves unaffected nodes and Date values; no undo step is added.
export function replaceArchivedImageUrls<T>(value: T, replacements: ArchivedImageUrlMap): T {
  if (typeof value === "string") {
    if (replacements[value]) return replacements[value] as T;
    // URLs inside generated-image Markdown carry both preview and original URLs.
    return value.replace(/!\[([^\]]*)\]\(([^)]+)\)/g, (_match, alt: string, url: string) => {
      const nextAlt = alt
        .split("|||")
        .map((part) => replacements[part] || part)
        .join("|||");
      return `![${nextAlt}](${replacements[url] || url})`;
    }) as T;
  }
  if (!value || typeof value !== "object" || value instanceof Date) return value;
  let changed = false;
  if (Array.isArray(value)) {
    const next = value.map((item) => {
      const replaced = replaceArchivedImageUrls(item, replacements);
      if (replaced !== item) changed = true;
      return replaced;
    });
    return (changed ? next : value) as T;
  }
  const next: Record<string, unknown> = {};
  for (const [key, item] of Object.entries(value)) {
    next[key] = replaceArchivedImageUrls(item, replacements);
    if (next[key] !== item) changed = true;
  }
  return (changed ? next : value) as T;
}