using System.Collections.Generic;
using System.IO;
using System.Text;
using Umbraco.Cms.Core.IO;
using Umbraco.Cms.Core.Models;
using Umbraco.Cms.Core.Models.Entities;
using Umbraco.Cms.Core.Persistence;
using Umbraco.Extensions;

namespace Umbraco.Cms.Infrastructure.Persistence.Repositories.Implement
{
    internal abstract class FileRepository<TId, TEntity> : IReadRepository<TId, TEntity>, IWriteRepository<TEntity>
        where TEntity : IFile
    {
        protected FileRepository(IFileSystem fileSystem) => FileSystem = fileSystem;

        protected IFileSystem FileSystem { get; }

        public virtual void AddFolder(string folderPath) => PersistNewItem(new Folder(folderPath));

        public virtual void DeleteFolder(string folderPath) => PersistDeletedItem(new Folder(folderPath));

        #region Implementation of IRepository<TId,TEntity>

        public virtual void Save(TEntity entity)
        {
            if (FileSystem.FileExists(entity.OriginalPath) == false)
            {
                PersistNewItem(entity);
            }
            else
            {
                PersistUpdatedItem(entity);
            }
        }

        public virtual void Delete(TEntity entity) => PersistDeletedItem(entity);

        public abstract TEntity Get(TId id);

        public abstract IEnumerable<TEntity> GetMany(params TId[] ids);

        public virtual bool Exists(TId id) => FileSystem.FileExists(id.ToString());

        #endregion

        #region Implementation of IUnitOfWorkRepository

        public void PersistNewItem(IEntity entity)
        {
            //special case for folder
            if (entity is Folder folder)
            {
                PersistNewFolder(folder);
            }
            else
            {
                PersistNewItem((TEntity)entity);
            }
        }

        public void PersistUpdatedItem(IEntity entity) => PersistUpdatedItem((TEntity)entity);

        public void PersistDeletedItem(IEntity entity)
        {
            //special case for folder
            if (entity is Folder folder)
            {
                PersistDeletedFolder(folder);
            }
            else
            {
                PersistDeletedItem((TEntity)entity);
            }
        }

        #endregion

        internal virtual void PersistNewFolder(Folder entity) => FileSystem.CreateFolder(entity.Path);

        internal virtual void PersistDeletedFolder(Folder entity) => FileSystem.DeleteDirectory(entity.Path);

        #region Abstract IUnitOfWorkRepository Methods

        protected virtual void PersistNewItem(TEntity entity)
        {
            using (Stream stream = GetContentStream(entity.Content))
            {
                FileSystem.AddFile(entity.Path, stream, true);
                entity.CreateDate = FileSystem.GetCreated(entity.Path).UtcDateTime;
                entity.UpdateDate = FileSystem.GetLastModified(entity.Path).UtcDateTime;
                //the id can be the hash
                entity.Id = entity.Path.GetHashCode();
                entity.Key = entity.Path.EncodeAsGuid();
                entity.VirtualPath = FileSystem.GetUrl(entity.Path);
            }
        }

        protected virtual void PersistUpdatedItem(TEntity entity)
        {
            using (Stream stream = GetContentStream(entity.Content))
            {
                FileSystem.AddFile(entity.Path, stream, true);
                entity.CreateDate = FileSystem.GetCreated(entity.Path).UtcDateTime;
                entity.UpdateDate = FileSystem.GetLastModified(entity.Path).UtcDateTime;
                //the id can be the hash
                entity.Id = entity.Path.GetHashCode();
                entity.Key = entity.Path.EncodeAsGuid();
                entity.VirtualPath = FileSystem.GetUrl(entity.Path);
            }

            //now that the file has been written, we need to check if the path had been changed
            if (entity.Path.InvariantEquals(entity.OriginalPath) == false)
            {
                //delete the original file
                FileSystem.DeleteFile(entity.OriginalPath);
                //reset the original path on the file
                entity.ResetOriginalPath();
            }
        }

        protected virtual void PersistDeletedItem(TEntity entity)
        {
            if (FileSystem.FileExists(entity.Path))
            {
                FileSystem.DeleteFile(entity.Path);
            }
        }

        #endregion

        /// <summary>
        /// Gets a stream that is used to write to the file
        /// </summary>
        /// <param name="content"></param>
        /// <returns></returns>
        protected virtual Stream GetContentStream(string content) => new MemoryStream(Encoding.UTF8.GetBytes(content));

        /// <summary>
        /// Returns all files in the file system
        /// </summary>
        /// <param name="path"></param>
        /// <param name="filter"></param>
        /// <returns>
        /// Returns a list of all files with their paths. For example:
        ///
        /// \hello.txt
        /// \folder1\test.txt
        /// \folder1\blah.csv
        /// \folder1\folder2\blahhhhh.svg
        /// </returns>
        protected IEnumerable<string> FindAllFiles(string path, string filter)
        {
            var list = new List<string>();
            list.AddRange(FileSystem.GetFiles(path, filter));

            IEnumerable<string> directories = FileSystem.GetDirectories(path);
            foreach (var directory in directories)
            {
                list.AddRange(FindAllFiles(directory, filter));
            }

            return list;
        }

        protected string GetFileContent(string filename)
        {
            if (FileSystem.FileExists(filename) == false)
            {
                return null;
            }

            try
            {
                using (Stream stream = FileSystem.OpenFile(filename))
                using (var reader = new StreamReader(stream, Encoding.UTF8, true))
                {
                    return reader.ReadToEnd();
                }
            }
            catch
            {
                return null; // deal with race conds
            }
        }

        public Stream GetFileContentStream(string filepath)
        {
            if (FileSystem.FileExists(filepath) == false)
            {
                return null;
            }

            try
            {
                return FileSystem.OpenFile(filepath);
            }
            catch
            {
                return null; // deal with race conds
            }
        }

        public void SetFileContent(string filepath, Stream content) => FileSystem.AddFile(filepath, content, true);

        public long GetFileSize(string filename)
        {
            if (FileSystem.FileExists(filename) == false)
            {
                return -1;
            }

            try
            {
                return FileSystem.GetSize(filename);
            }
            catch
            {
                return -1; // deal with race conds
            }
        }
    }
}