"use client";

/**
 * Code highlighting for editor code blocks (Prism, manual mode).
 *
 * The CodeBlock language dropdown exposes exactly these languages
 * (block-renderer.tsx); `LANGUAGE_GRAMMARS` is the single mapping from that
 * dropdown value to the Prism grammar to load. Unknown values fall back to
 * `plaintext` (rendered verbatim, never broken).
 *
 * `Prism.manual = true` is set at module scope: we always call
 * `Prism.highlight` ourselves, and the UMD default would otherwise also
 * auto-highlight every `code[class*=language-]` on DOMContentLoaded — a
 * second, uncontrolled pass over the same DOM.
 *
 * Pure enough to unit-test: `highlightCode` takes (text, language) and
 * returns an HTML string (or null for plaintext/empty), so the test asserts
 * deterministic token markup without a DOM.
 */
import Prism from "prismjs";
import "prismjs/components/prism-typescript";
import "prismjs/components/prism-python";
import "prismjs/components/prism-bash";
import "prismjs/components/prism-json";
import "prismjs/components/prism-sql";
import "prismjs/components/prism-go";
import "prismjs/components/prism-rust";
// `css` and `markup` ship in the prismjs default bundle (prism.js).

/** The exact languages the CodeBlock dropdown offers (keep in sync). */
export const CODE_LANGUAGES = [
  "plaintext",
  "javascript",
  "typescript",
  "python",
  "bash",
  "json",
  "sql",
  "go",
  "rust",
  "css",
  "html",
] as const;

export type CodeLanguage = (typeof CODE_LANGUAGES)[number];

const LANGUAGE_GRAMMARS: Record<CodeLanguage, string> = {
  plaintext: "plain",
  javascript: "javascript",
  typescript: "typescript",
  python: "python",
  bash: "bash",
  json: "json",
  sql: "sql",
  go: "go",
  rust: "rust",
  css: "css",
  html: "markup",
};

// Never let Prism re-highlight the DOM on its own.
Prism.manual = true;

/**
 * Highlight `text` as `language`. Returns `null` when nothing should be
 * wrapped (plaintext, unknown language, or empty input) — callers render the
 * raw text as-is then. The HTML uses `Prism.token` classes
 * (`token comment|keyword|string|number|function|punctuation|…`) that
 * globals.css colors for the theme.
 */
export function highlightCode(text: string, language: string): string | null {
  if (!text) return null;
  const key = (CODE_LANGUAGES as readonly string[]).includes(language)
    ? LANGUAGE_GRAMMARS[language as CodeLanguage]
    : "plain";
  // `plain` is a no-op grammar (Prism ships one); treat it as "no
  // highlighting" so callers get the unambiguous null → raw-text path.
  if (key === "plain" || !Prism.languages[key]) return null;
  return Prism.highlight(text, Prism.languages[key], key);
}

/** Escape a string for safe insertion as text into an HTML document. */
export function escapeHtml(text: string): string {
  return text
    .replace(/&/g, "&amp;")
    .replace(/</g, "&lt;")
    .replace(/>/g, "&gt;")
    .replace(/"/g, "&quot;")
    .replace(/'/g, "&#39;");
}

/**
 * Render `text` for a code block: Prism token HTML for a known language,
 * HTML-escaped raw text otherwise (plaintext / unknown language). Always
 * returns a string — the component can put the result straight into
 * `dangerouslySetInnerHTML` without a null branch.
 */
export function codeToHtml(text: string, language: string): string {
  const html = highlightCode(text, language);
  return html ?? escapeHtml(text);
}