import { availableLanguages, detectLanguage as sniffLanguage, highlight } from "@arborium/arborium";
import { detectLanguage } from "./languages.ts";

const available = new Set<string>(availableLanguages);

function languageOf(path: string, source: string): string | null {
  const candidate = detectLanguage(path);
  if (candidate && available.has(candidate)) return candidate;
  const detected = sniffLanguage(source);
  return detected && available.has(detected) ? detected : null;
}

export async function highlightedHtml(path: string, source: string): Promise<string | null> {
  const language = languageOf(path, source);
  return language ? await highlight(language, source) : null;
}

function splitHighlighted(nodes: Node[]): Node[][] {
  const lines: Node[][] = [[]];
  for (const node of nodes) {
    let parts: Node[][];
    if (node instanceof Text) {
      parts = node.data.split("\n").map(text => text ? [document.createTextNode(text)] : []);
    } else if (node instanceof Element) {
      parts = splitHighlighted([...node.childNodes]).map(children => {
        if (children.length === 0) return [];
        const clone = node.cloneNode(false) as Element;
        clone.append(...children);
        return [clone];
      });
    } else {
      parts = splitHighlighted([...node.childNodes]);
    }
    lines.at(-1)!.push(...parts[0]);
    for (const part of parts.slice(1)) lines.push(part);
  }
  return lines;
}

export async function highlightedLines(path: string, source: string): Promise<Node[][] | null> {
  const html = await highlightedHtml(path, source);
  if (html === null) return null;
  const template = document.createElement("template");
  template.innerHTML = html;
  return splitHighlighted([...template.content.childNodes]);
}