import { POST_MEDIA_PUBLIC_PREFIX } from "../constants/media";

const MD_IMG_RE = /!\[[^\]]*]\(([^)]+)\)/g;

export type MergePostMediaUrlsOptions = {
  /**
   * 允许识别为「本站绝对地址」的 origin 列表（每项可为完整 URL，仅取其 `origin` 参与匹配）。
   * 为空时：不将含域名的绝对 URL 计为本站资源（仅 `${POST_MEDIA_PUBLIC_PREFIX}...` 相对路径有效）。
   */
  allowedAssetOrigins?: readonly string[];
};

function stripQueryHash(path: string): string {
  return path.split("?")[0]?.split("#")[0] ?? path;
}

function buildAllowedOriginSet(entries: readonly string[] | undefined): Set<string> {
  const s = new Set<string>();
  if (!entries?.length) {
    return s;
  }
  for (const e of entries) {
    const t = e.trim();
    if (!t) {
      continue;
    }
    try {
      s.add(new URL(t).origin);
    } catch {
      /* skip */
    }
  }
  return s;
}

/** 统一为 `${POST_MEDIA_PUBLIC_PREFIX}<key>`，供 `publicAssetUrlToStorageKey` 与引用同步使用。 */
function normalizeUrl(raw: string, allowedOrigins: Set<string>): string {
  const t = raw.trim().replace(/^<|>$/g, "").split(/\s+/)[0] ?? "";
  if (t.startsWith(POST_MEDIA_PUBLIC_PREFIX)) {
    return stripQueryHash(t);
  }
  if (allowedOrigins.size === 0) {
    return "";
  }
  try {
    const u = new URL(t);
    if (!allowedOrigins.has(u.origin)) {
      return "";
    }
    const path = stripQueryHash(u.pathname);
    if (path.startsWith(POST_MEDIA_PUBLIC_PREFIX)) {
      return path;
    }
  } catch {
    /* 非绝对 URL */
  }
  return "";
}

/** 从 markdown 中提取本站图片 URL（去重，顺序稳定） */
export function extractMediaUrlsFromMarkdown(markdown: string, options?: MergePostMediaUrlsOptions): string[] {
  const allowed = buildAllowedOriginSet(options?.allowedAssetOrigins);
  const out: string[] = [];
  const seen = new Set<string>();
  let m: RegExpExecArray | null;
  const re = new RegExp(MD_IMG_RE.source, MD_IMG_RE.flags);
  while ((m = re.exec(markdown)) !== null) {
    const u = normalizeUrl(m[1] ?? "", allowed);
    if (u && !seen.has(u)) {
      seen.add(u);
      out.push(u);
    }
  }
  return out;
}

export function extractMediaUrlsFromCover(
  coverUrl: string | null | undefined,
  options?: MergePostMediaUrlsOptions,
): string[] {
  if (!coverUrl) {
    return [];
  }
  const allowed = buildAllowedOriginSet(options?.allowedAssetOrigins);
  const u = normalizeUrl(coverUrl, allowed);
  return u ? [u] : [];
}

export function mergePostMediaUrls(
  bodyMarkdown: string,
  coverUrl: string | null | undefined,
  options?: MergePostMediaUrlsOptions,
): string[] {
  const a = extractMediaUrlsFromMarkdown(bodyMarkdown, options);
  const b = extractMediaUrlsFromCover(coverUrl, options);
  const seen = new Set<string>(a);
  for (const u of b) {
    if (!seen.has(u)) {
      seen.add(u);
      a.push(u);
    }
  }
  return a;
}

export function mergeProfileMediaUrls(
  bioMarkdown: string | null | undefined,
  avatar: string | null | undefined,
  options?: MergePostMediaUrlsOptions,
): string[] {
  return mergePostMediaUrls(bioMarkdown ?? "", avatar ?? null, options);
}

/** `${POST_MEDIA_PUBLIC_PREFIX}foo.webp` → `foo.webp` */
export function publicAssetUrlToStorageKey(url: string): string | null {
  const t = url.trim();
  if (!t.startsWith(POST_MEDIA_PUBLIC_PREFIX)) {
    return null;
  }
  const key = t.slice(POST_MEDIA_PUBLIC_PREFIX.length).replace(/^\/+/, "");
  if (!key || key.includes("..") || key.includes("/") || key.includes("\\")) {
    return null;
  }
  return key;
}