using System;
using System.Collections.Generic;
using System.Threading.Tasks;
using Windows.Storage;
using Windows.Storage.Search;
using Caliburn.Micro;
using Newtonsoft.Json;

namespace FileStorage
{
    public abstract class Service<T> : IService<T> where T : class
    {
        protected abstract IStorageFolder StorageFolder { get; }
        protected abstract string FolderName { get; }

        public virtual async Task<IEnumerable<T>> GetAll()
        {
            var files = new List<T>();
            foreach (var file in await Files())
                files.Add(JsonConvert.DeserializeObject<T>(await FileIO.ReadTextAsync(file)));

            return files;
        }

        public async Task Save(T schema, string fileName)
        {
            var folder = await Folder();
            var file = await folder.CreateFileAsync(fileName, CreationCollisionOption.OpenIfExists);
            return await FileIO.WriteTextAsync(file, JsonConvert.SerializeObject(schema));
        }

        public async Task<T> Get(string fileName)
        {
            var file = await GetFile(fileName);
            return file == null ? null : JsonConvert.DeserializeObject<T>(await FileIO.ReadTextAsync(file));
        }

        public async Task Delete(string fileName)
        {
            var file = await GetFile(fileName);
            if (file != null)
                await file.DeleteAsync();
        }

        protected async Task<StorageFile> GetFile(string fileName)
        {
            var folder = await Folder();
            var file = await folder.GetFileAsync(fileName);
            return file;
        }

        protected async Task<IEnumerable<IStorageFile>> Files()
        {
            var folder = await Folder();
            return await folder.GetFilesAsync(CommonFileQuery.OrderByName);
        }

        private async Task CreateFolder()
        {
            await StorageFolder.CreateFolderAsync(FolderName);
        }

        protected async Task<StorageFolder> Folder()
        {
            try
            {
                var folder = await StorageFolder.GetFolderAsync(FolderName);
                if (folder == null)
                    await CreateFolder();
                return folder;
            }
            catch (Exception ex)
            {
                LogManager.GetLog(GetType()).Error(ex);
                throw;
            }
        }
    }
}