/**
 * CodeMirror 6 language support for Decodal.
 *
 * This module exports the Decodal language extension, parser metadata, and the
 * bundled highlight style used by the official Decodal playground. Add
 * {@link decodal} to a CodeMirror extension set to enable highlighting,
 * indentation, and folding for Decodal documents.
 *
 * @module
 */
import { HighlightStyle, LRLanguage, LanguageSupport, delimitedIndent, foldNodeProp, indentNodeProp, syntaxHighlighting } from 'npm:@codemirror/language@^6.12.4';
import { styleTags, tags as t } from 'npm:@lezer/highlight@^1.2.3';
import { parser } from './decodal-parser-jsr.js';

const parserWithMetadata = parser.configure({
  props: [
    styleTags({
      'Let In Match Import Default As': t.keyword,
      'True False': t.bool,
      Identifier: t.variableName,
      String: t.string,
      Regex: t.regexp,
      'Integer Float': t.number,
      Comment: t.lineComment,
      'Plus Minus Star Slash PlusPlus Ellipsis Equal EqualEqual Bang BangEqual Amp AmpAmp PipePipe SlashSlash Gt Gte Lt Lte Arrow': t.operator,
      'LBrace RBrace': t.brace,
      'LBracket RBracket': t.squareBracket,
      'LParen RParen': t.paren,
      'Semicolon Comma Dot Colon': t.punctuation,
    }),
    indentNodeProp.add({
      Object: delimitedIndent({ closing: '}', align: false }),
      MapConstraint: delimitedIndent({ closing: '}', align: false }),
      Array: delimitedIndent({ closing: ']', align: false }),
      ArrayConstraint: delimitedIndent({ closing: ']', align: false }),
      MatchExpression: delimitedIndent({ closing: '}', align: false }),
      LetExpression: context => context.column(context.node.from) + context.unit,
    }),
    foldNodeProp.add({
      Object: foldDelimited('{', '}'),
      MapConstraint: foldDelimited('{', '}'),
      Array: foldDelimited('[', ']'),
      ArrayConstraint: foldDelimited('[', ']'),
      MatchExpression: foldDelimited('{', '}'),
    }),
  ],
});

function foldDelimited(open: string, close: string) {
  return (node: { from: number; to: number }, state: { doc: { sliceString(from: number, to: number): string } }) => {
    const text = state.doc.sliceString(node.from, node.to);
    const openIndex = text.indexOf(open);
    const closeIndex = text.lastIndexOf(close);
    if (openIndex < 0 || closeIndex <= openIndex) return null;
    const from = node.from + openIndex + open.length;
    const to = node.from + closeIndex;
    return from < to ? { from, to } : null;
  };
}

/** Decodal LR language definition for CodeMirror 6. */
export const decodalLanguage: LRLanguage = LRLanguage.define({
  parser: parserWithMetadata,
  languageData: {
    commentTokens: { line: '#' },
    closeBrackets: { brackets: ['(', '[', '{', '"'] },
  },
});

/** Default Decodal highlight style used by the playground. */
export const decodalHighlightStyle: HighlightStyle = HighlightStyle.define([
  { tag: t.keyword, color: '#93c5fd', fontWeight: '700' },
  { tag: t.variableName, color: 'inherit' },
  { tag: t.bool, color: '#fbbf24' },
  { tag: t.number, color: '#fbbf24' },
  { tag: t.string, color: '#86efac' },
  { tag: t.regexp, color: '#86efac' },
  { tag: t.lineComment, color: '#94a3b8', fontStyle: 'italic' },
  { tag: t.operator, color: '#f9a8d4' },
  { tag: [t.brace, t.squareBracket, t.paren, t.punctuation], color: '#f9a8d4' },
]);

/** Options for {@link decodal}. */
export interface DecodalOptions {
  /** Include the bundled {@link decodalHighlightStyle}. Defaults to `true`. */
  highlight?: boolean;
}

/**
 * Create CodeMirror language support for Decodal.
 *
 * @param options - Optional language support options.
 * @returns A CodeMirror extension bundle containing the Decodal language and,
 * unless disabled, the default highlight style.
 */
export function decodal(options: DecodalOptions = {}): LanguageSupport {
  const { highlight = true } = options;
  return new LanguageSupport(
    decodalLanguage,
    highlight ? [syntaxHighlighting(decodalHighlightStyle)] : [],
  );
}