import { loader, type Monaco } from "@monaco-editor/react";
import * as monaco from "monaco-editor";
import editorWorker from "monaco-editor/esm/vs/editor/editor.worker?worker";

let initialized = false;
let monacoPromise: Promise<Monaco> | null = null;

// A Monarch tokenizer for Typst covering the common surface (headings,
// script keywords, math, comments, emphasis, strings, raw blocks). This is
// syntax-only; the LSP additionally provides diagnostics and (optionally)
// semantic tokens.
const typstLanguageDefinition: monaco.languages.IMonarchLanguage = {
  defaultToken: "",
  tokenPostfix: ".typst",
  brackets: [
    { open: "(", close: ")", token: "delimiter.parenthesis" },
    { open: "[", close: "]", token: "delimiter.square" },
    { open: "{", close: "}", token: "delimiter.curly" },
  ],
  tokenizer: {
    root: [
      [/^=+\s.*$/, "keyword.heading"],
      [/\*[^*]+\*/, "string.emphasis"],
      [/_[^_]+_/, "string.emphasis"],
      [/\/\/.*$/, "comment"],
      [/\/\*/, "comment", "@comment"],
      [/#\w+/, "keyword"], // #set, #let, #show, #if, ...
      [/\$/, { token: "string", next: "@math" }],
      [/"/, "string", "@string"],
      [/[{}()\[\]]/, "@brackets"],
    ],
    comment: [
      [/\*\//, "comment", "@pop"],
      [/[^*]+/, "comment"],
      [/\*/, "comment"],
    ],
    math: [
      [/\$/, { token: "string", next: "@pop" }],
      [/\\[a-zA-Z]+/, "keyword"],
      [/[a-zA-Z]+/, "variable"],
      [/[^\$]/, "string"],
    ],
    string: [
      [/[^"]/, "string"],
      [/"/, "string", "@pop"],
    ],
  },
};

function initEnvironment(): void {
  if (initialized) return;
  // Vite bundles the editor worker via `?worker`. Monaco only needs the base
  // editor worker for plaintext/typst (no language-specific workers required).
  self.MonacoEnvironment = {
    getWorker: () => new editorWorker(),
  };
  loader.config({ monaco });
  initialized = true;
}

export function loadMonaco(): Promise<Monaco> {
  if (!monacoPromise) {
    initEnvironment();
    // loader.init() resolves to the same `monaco` instance we configured above.
    monacoPromise = loader.init().then((m) => {
      m.languages.register({ id: "typst" });
      m.languages.setMonarchTokensProvider("typst", typstLanguageDefinition);
      return m;
    });
  }
  return monacoPromise;
}

export function getMonaco(): Monaco {
  return monaco as unknown as Monaco;
}