import type { AnchorHTMLAttributes } from "react";
import { CITE_SCHEME } from "../../lib/citations/inline";
import type { CitationView } from "../../lib/report/views";
import { Markdown } from "../Markdown";
import { CitationsProvider } from "./CitationsContext";
import { InlineCite } from "./InlineCite";

// Report markdown with its citations live: every `[label](cite:<id>)` link
// (lib/citations/inline.ts) becomes an InlineCite for that id; every other
// link renders as Markdown's own external link, except a `#<id>` link to a
// place on the same page, which stays in the tab. The house markdown setup
// (Markdown.tsx — markdown-to-jsx, raw HTML escaped, token-styled) is
// unchanged; this only swaps its link component. A `cite:` link inside code is
// code, never a citation: markdown-to-jsx makes no link there.
//
// The views come from the page's one CitationsProvider (a page with many
// markdown blocks serializes its citation map once). A block rendered on its
// own may pass `citations`, and gets a provider of its own.

const EXTERNAL_LINK_CLASS = "text-brand underline decoration-brand/40 hover:decoration-brand";

export function citeIdOf(href: string | undefined): string | null {
  return href?.startsWith(CITE_SCHEME) ? href.slice(CITE_SCHEME.length).trim() : null;
}

type Citations = Readonly<Record<string, CitationView>>;

// The `<a>` of cited markdown: one stable component.
function CiteLink({ href, children: label, ...rest }: AnchorHTMLAttributes<HTMLAnchorElement>) {
  const id = citeIdOf(href);
  if (id !== null) return <InlineCite id={id}>{label}</InlineCite>;
  if (href?.startsWith("#")) {
    return (
      <a {...rest} href={href} className={EXTERNAL_LINK_CLASS}>
        {label}
      </a>
    );
  }
  return (
    <a {...rest} href={href} target="_blank" rel="noopener noreferrer" className={EXTERNAL_LINK_CLASS}>
      {label}
    </a>
  );
}

export function CitedMarkdown({
  children,
  citations,
  className,
}: {
  children: string;
  citations?: Citations;
  className?: string;
}) {
  const md = (
    <Markdown className={className} linkComponent={CiteLink}>
      {children}
    </Markdown>
  );
  return citations ? <CitationsProvider citations={citations}>{md}</CitationsProvider> : md;
}