import { JSDOM } from "jsdom";
import { fetchHtmlWithPlaywright } from "./playwright.ts";
import { createStreamResponse } from "./helpers.ts";

/**
 * Mutates the given JSDOM instance: rewrites all relevant URL-bearing attributes
 * to absolute URLs, resolving against the provided domain (e.g., "https://example.com").
 */
export function absolutizeDomUrls(dom: JSDOM, domain: string): void {
  const { document } = dom.window;
  const base = toBase(domain);

  const rewrite = (selector: string, attr: string) => {
    document.querySelectorAll<HTMLElement>(selector).forEach((el) => {
      const v = el.getAttribute(attr);
      if (!v) return;
      const abs = toAbsolute(v, base);
      if (abs !== v) el.setAttribute(attr, abs);
    });
  };

  // Common URL attributes
  rewrite("a[href]", "href");
  rewrite("area[href]", "href");
  rewrite("link[href]", "href");
  rewrite("use[href]", "href"); // SVG 2
  rewrite("use[xlink\\:href]", "xlink:href"); // legacy SVG
  rewrite("image[href]", "href"); // SVG
  rewrite("image[xlink\\:href]", "xlink:href"); // legacy SVG

  rewrite("script[src]", "src");
  rewrite("img[src]", "src");
  rewrite("source[src]", "src");
  rewrite("track[src]", "src");
  rewrite("iframe[src]", "src");
  rewrite("embed[src]", "src");
  rewrite("audio[src]", "src");
  rewrite("video[src]", "src");
  rewrite("object[data]", "data");
  rewrite("input[src]", "src");
  rewrite("form[action]", "action");
  rewrite("video[poster]", "poster");

  // srcset (img, source)
  document
    .querySelectorAll<HTMLElement>("img[srcset], source[srcset]")
    .forEach((el) => {
      const v = el.getAttribute("srcset");
      if (!v) return;
      const abs = absolutizeSrcset(v, base);
      if (abs !== v) el.setAttribute("srcset", abs);
    });

  // Inline CSS in style attributes: url(...)
  document.querySelectorAll<HTMLElement>("[style]").forEach((el) => {
    const v = el.getAttribute("style");
    if (!v) return;
    const abs = absolutizeCssUrls(v, base);
    if (abs !== v) el.setAttribute("style", abs);
  });

  // <style> blocks (inline CSS): url(...)
  document.querySelectorAll<HTMLStyleElement>("style").forEach((styleEl) => {
    const css = styleEl.textContent ?? "";
    const abs = absolutizeCssUrls(css, base);
    if (abs !== css) styleEl.textContent = abs;
  });

  // <meta http-equiv="refresh" content="5; url=/path">
  document
    .querySelectorAll<HTMLMetaElement>('meta[http-equiv="refresh" i][content]')
    .forEach((meta) => {
      const content = meta.getAttribute("content") || "";
      const abs = absolutizeMetaRefresh(content, base);
      if (abs !== content) meta.setAttribute("content", abs);
    });
}

/** Normalize the base to a valid absolute URL root. */
function toBase(domain: string): string {
  // Allow callers to pass "example.com" or "//example.com"
  let d = domain.trim();
  if (!/^[a-zA-Z][a-zA-Z0-9+\-.]*:/.test(d)) {
    d = d.startsWith("//") ? `https:${d}` : `https://${d}`;
  }
  // Ensure trailing slash does not matter for URL resolution
  try {
    // new URL('/', base) works whether base ends with slash or not
    return new URL("/", d).toString();
  } catch {
    // Fallback: if domain is irreparably bad, throw early
    throw new Error(`Invalid base domain: ${domain}`);
  }
}

/** Convert a possibly-relative URL to absolute, using the provided base. */
function toAbsolute(url: string, base: string): string {
  const trimmed = url.trim();

  // Leave already absolute or special schemes untouched by just parsing directly.
  // If it's not a valid absolute URL, resolve against base.
  try {
    // If parse succeeds without base and includes a scheme, keep as-is
    const abs = new URL(trimmed);
    return abs.toString();
  } catch {
    // Not absolute, resolve relative to base (handles #hash, ?q, //host, etc.)
    try {
      return new URL(trimmed, base).toString();
    } catch {
      // If still invalid (e.g., badly formed), return original
      return url;
    }
  }
}

/** Absolutize a srcset list. */
function absolutizeSrcset(srcset: string, base: string): string {
  // Split by commas but keep descriptors (1x, 2x, 100w, etc.)
  // Each candidate: <url> [<descriptor>]
  return srcset
    .split(",")
    .map((part) => {
      const s = part.trim();
      if (!s) return s;
      // First whitespace separates URL and descriptor
      const spaceIdx = s.search(/\s/);
      if (spaceIdx === -1) {
        return toAbsolute(s, base);
      }
      const url = s.slice(0, spaceIdx);
      const desc = s.slice(spaceIdx).trim();
      return `${toAbsolute(url, base)} ${desc}`;
    })
    .join(", ");
}

/** Replace url(...) in CSS text with absolute URLs. */
function absolutizeCssUrls(cssText: string, base: string): string {
  // Matches url("..."), url('...'), url(...)
  return cssText.replace(
    /url\(\s*(['"]?)([^'")]+)\1\s*\)/g,
    (_m, _q, rawUrl) => {
      const abs = toAbsolute(rawUrl, base);
      // Preserve quoting if present; browsers accept unquoted if safe, but keep simple.
      return `url(${abs})`;
    },
  );
}

/** Rewrite the URL in a meta refresh content value if present. */
function absolutizeMetaRefresh(content: string, base: string): string {
  // Format examples:
  // "5; url=/path", "0;URL='page.html'"
  const match = content.match(
    /^\s*([^;]+)\s*;\s*(url|URL)\s*=\s*('?)([^']+)\3\s*$/,
  );
  if (!match) return content;
  const delay = match[1].trim();
  const url = match[4].trim();
  const abs = toAbsolute(url, base);
  return `${delay}; url=${abs}`;
}

export async function webScrape(
  url: string,
  streamResponse: ReturnType<typeof createStreamResponse>,
): JSDOM {
  const u = new URL(url);
  const html = await fetchHtmlWithPlaywright(url, streamResponse);
  const dom = new JSDOM(html);
  absolutizeDomUrls(dom, u.origin);
  return dom;
}