/**
 *  Copyright (c) 2021 GraphQL Contributors.
 *
 *  This source code is licensed under the MIT license found in the
 *  LICENSE file in the root directory of this source tree.
 */
import escapeHTML from 'escape-html';
import MD from 'markdown-it';

import {
  GraphQLNonNull,
  GraphQLList
} from 'graphql';

const md = new MD();

/**
 * Render a custom UI for CodeMirror's hint which includes additional info
 * about the type and description for the selected context.
 */
export default function onHasCompletion(
  _cm,
  data,
  onHintInformationRender,
) {
  const CodeMirror = require('codemirror');

  let information;
  let deprecation;

  // When a hint result is selected, we augment the UI with information.
  CodeMirror.on(
    data,
    'select',
    (ctx, el) => {
      // Only the first time (usually when the hint UI is first displayed)
      // do we create the information nodes.
      if (!information) {
        const hintsUl = el.parentNode;

        // This "information" node will contain the additional info about the
        // highlighted typeahead option.
        information = document.createElement('div');
        information.className = 'CodeMirror-hint-information';
        hintsUl.appendChild(information);

        // This "deprecation" node will contain info about deprecated usage.
        deprecation = document.createElement('div');
        deprecation.className = 'CodeMirror-hint-deprecation';
        hintsUl.appendChild(deprecation);

        // When CodeMirror attempts to remove the hint UI, we detect that it was
        // removed and in turn remove the information nodes.
        let onRemoveFn;
        hintsUl.addEventListener(
          'DOMNodeRemoved',
          (onRemoveFn = (event) => {
            if (event.target === hintsUl) {
              hintsUl.removeEventListener('DOMNodeRemoved', onRemoveFn);
              information = null;
              deprecation = null;
              onRemoveFn = null;
            }
          }),
        );
      }

      // Now that the UI has been set up, add info to information.
      const description = ctx.description
        ? md.render(ctx.description)
        : 'Self descriptive.';
      const type = ctx.type
        ? '<span className="infoType">' + renderType(ctx.type) + '</span>'
        : '';

      information.innerHTML =
        '<div className="content">' +
        (description.slice(0, 3) === '<p>'
          ? '<p>' + type + description.slice(3)
          : type + description) +
        '</div>';

      if (ctx && deprecation && ctx.deprecationReason) {
        const reason = ctx.deprecationReason
          ? md.render(ctx.deprecationReason)
          : '';
        deprecation.innerHTML =
          '<span className="deprecation-label">Deprecated</span>' + reason;
        deprecation.style.display = 'block';
      } else if (deprecation) {
        deprecation.style.display = 'none';
      }

      // Additional rendering?
      if (onHintInformationRender) {
        onHintInformationRender(information);
      }
    },
  );
}

function renderType(type) {
  if (type instanceof GraphQLNonNull) {
    return `${renderType(type.ofType)}!`;
  }
  if (type instanceof GraphQLList) {
    return `[${renderType(type.ofType)}]`;
  }
  return `<a className="typeName">${escapeHTML(type.name)}</a>`;
}