TS 2.3 Language Service Plugin for completion GraphQL Query

pluginModuleFactory.ts

import * as ts from 'typescript/lib/tsserverlibrary';

const { buildClientSchema } = require('graphql');
const { getAutocompleteSuggestions } = require('graphql-language-service-interface');

// TODO replace the result by introspection query
const introspectionJson = require('../schema.json');
const schema = buildClientSchema(introspectionJson.data);

function findNode(sourceFile: ts.SourceFile, position: number): ts.Node | undefined {
    function find(node: ts.Node): ts.Node|undefined {
        if (position >= node.getStart() && position < node.getEnd()) {
            return ts.forEachChild(node, find) || node;
        }
    }
    return find(sourceFile);
}

function create(info: ts.server.PluginCreateInfo): ts.LanguageService {
    const delegate = info.languageService.getCompletionsAtPosition;
    info.languageService.getCompletionsAtPosition = function(fileName: string, position: number) {
        const sourceFile = info.languageService.getProgram().getSourceFile(fileName);
        const node = findNode(sourceFile, position);
        if (!node || node.kind !== ts.SyntaxKind.NoSubstitutionTemplateLiteral) {
            return delegate(fileName, position);
        }
        const cursor = node.getStart() - position;
        const text = node.getText();
        const rawResults = getAutocompleteSuggestions(schema, text, cursor, '') as { label: string }[];
        const result: ts.CompletionInfo = {
            isGlobalCompletion: false,
            isMemberCompletion: false,
            isNewIdentifierLocation: false,
            entries: rawResults.map(r => {
                return {
                    name: r.label,
                    kindModifiers: 'declare',
                    kind: 'var',
                    sortText: '0',
                };
            }),
        };
        return result;
    };
    return info.languageService;
}

module.exports = function pluginModuleFactory() {
    return { create: create };
};