using Monaco.Languages;
using Newtonsoft.Json;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Windows.Data.Json;
using Windows.Foundation;

namespace Monaco
{
    /// <summary>
    /// Helper to static Monaco.Languages Namespace methods.
    /// https://microsoft.github.io/monaco-editor/api/modules/monaco.languages.html
    /// </summary>
    public sealed class LanguagesHelper
    {
        private WeakReference<CodeEditor> _editor;

        public LanguagesHelper(CodeEditor editor)
        {
            // We need the editor component in order to execute JavaScript within 
            // the WebView environment to retrieve data (even though this Monaco class is static).
            _editor = new WeakReference<CodeEditor>(editor);
        }

        public IAsyncOperation<IList<ILanguageExtensionPoint>> GetLanguagesAsync()
        {
            if (_editor.TryGetTarget(out CodeEditor editor))
            {
                return editor.SendScriptAsync<IList<ILanguageExtensionPoint>>("monaco.languages.getLanguages()").AsAsyncOperation();
            }

            return null;
        }

        public IAsyncAction RegisterAsync(ILanguageExtensionPoint language)
        {
            if (_editor.TryGetTarget(out CodeEditor editor))
            {
                return editor.InvokeScriptAsync("monaco.languages.register", language).AsAsyncAction();
            }

            return null;
        }

        public IAsyncAction RegisterCompletionItemProviderAsync(string languageId, CompletionItemProvider provider)
        {
            if (_editor.TryGetTarget(out CodeEditor editor))
            {
                // Wrapper around CompletionItem Provider to Monaco editor.
                // TODO: Add Incremented Id so that we can register multiple providers per language?
                editor._parentAccessor.RegisterEvent("CompletionItemProvider" + languageId, async (args) =>
                {
                    if (args != null && args.Length >= 2)
                    {
                        var items = await provider.ProvideCompletionItemsAsync(editor.GetModel(), JsonConvert.DeserializeObject<Position>(args[0]), JsonConvert.DeserializeObject<CompletionContext>(args[1]));

                        if (items != null)
                        {
                            return JsonConvert.SerializeObject(items);
                        }
                    }

                    return null;
                });

                return editor.InvokeScriptAsync("registerCompletionItemProvider", new object[] { languageId, provider.TriggerCharacters }).AsAsyncAction();
            }

            return null;
        }

        public IAsyncAction RegisterHoverProviderAsync(string languageId, HoverProvider provider)
        {
            if (_editor.TryGetTarget(out CodeEditor editor))
            {
                // Wrapper around Hover Provider to Monaco editor.
                // TODO: Add Incremented Id so that we can register multiple providers per language?
                editor._parentAccessor.RegisterEvent("HoverProvider" + languageId, async (args) =>
                {
                    if (args != null && args.Length >= 1)
                    {
                        var hover = await provider.Invoke(editor.GetModel(), JsonConvert.DeserializeObject<Position>(args[0]));

                        if (hover != null)
                        {
                            return JsonConvert.SerializeObject(hover);
                        }
                    }

                    return string.Empty;
                });

                return editor.InvokeScriptAsync("registerHoverProvider", languageId).AsAsyncAction();
            }

            return null;
        }
    }
}