using Microsoft.AspNetCore.Authorization;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;
using Oqtane.Infrastructure;
using Oqtane.Shared;
using System;
using System.Collections.Generic;
using System.IO;
using System.Threading;
using System.Threading.Tasks;

namespace Oqtane.Controllers
{
    [Route("{site}/api/[controller]")]
    public class FileController : Controller
    {
        private readonly IWebHostEnvironment environment;
        private readonly ILogManager logger;
        private readonly string WhiteList = "jpg,jpeg,jpe,gif,bmp,png,mov,wmv,avi,mp4,mp3,doc,docx,xls,xlsx,ppt,pptx,pdf,txt,zip,nupkg";

        public FileController(IWebHostEnvironment environment, ILogManager logger)
        {
            this.environment = environment;
            this.logger = logger;
        }

        // GET: api/<controller>?folder=x
        [HttpGet]
        public IEnumerable<string> Get(string folder)
        {
            List<string> files = new List<string>();
            folder = GetFolder(folder);
            if (Directory.Exists(folder))
            {
                foreach (string file in Directory.GetFiles(folder))
                {
                    files.Add(Path.GetFileName(file));
                }
            }
            return files;
        }

        // POST api/<controller>/upload
        [HttpPost("upload")]
        [Authorize(Roles = Constants.AdminRole)]
        public async Task UploadFile(string folder, IFormFile file)
        {
            if (file.Length > 0)
            {
                folder = GetFolder(folder);
                if (!Directory.Exists(folder))
                {
                    Directory.CreateDirectory(folder);
                }
                using (var stream = new FileStream(Path.Combine(folder, file.FileName), FileMode.Create))
                {
                    await file.CopyToAsync(stream);
                }
                await MergeFile(folder, file.FileName);
            }
        }

        private async Task MergeFile(string folder, string filename)
        {
            // parse the filename which is in the format of filename.ext.part_x_y 
            string token = ".part_";
            string parts = Path.GetExtension(filename).Replace(token, ""); // returns "x_y"
            int totalparts = int.Parse(parts.Substring(parts.IndexOf("_") + 1));
            filename = filename.Substring(0, filename.IndexOf(token)); // base filename
            string[] fileparts = Directory.GetFiles(folder, filename + token + "*"); // list of all file parts

            // if all of the file parts exist ( note that file parts can arrive out of order )
            if (fileparts.Length == totalparts && CanAccessFiles(fileparts))
            {
                // merge file parts
                bool success = true;
                using (var stream = new FileStream(Path.Combine(folder, filename + ".tmp"), FileMode.Create))
                {
                    foreach (string filepart in fileparts)
                    {
                        try
                        {
                            using (FileStream chunk = new FileStream(filepart, FileMode.Open))
                            {
                                await chunk.CopyToAsync(stream);
                            }
                        }
                        catch
                        {
                            success = false;
                        }
                    }
                }

                // delete file parts and rename file
                if (success)
                {
                    foreach (string filepart in fileparts)
                    {
                        System.IO.File.Delete(filepart);
                    }

                    // check for allowable file extensions
                    if (!WhiteList.Contains(Path.GetExtension(filename).Replace(".", "")))
                    {
                        System.IO.File.Delete(Path.Combine(folder, filename + ".tmp"));
                    }
                    else
                    {
                        // rename file now that the entire process is completed
                        System.IO.File.Move(Path.Combine(folder, filename + ".tmp"), Path.Combine(folder, filename));
                        logger.Log(LogLevel.Information, this.GetType().AssemblyQualifiedName, LogFunction.Create, "File Uploaded {File}", Path.Combine(folder, filename));
                    }
                }
            }

            // clean up file parts which are more than 2 hours old ( which can happen if a prior file upload failed )
            fileparts = Directory.GetFiles(folder, "*" + token + "*");
            foreach (string filepart in fileparts)
            {
                DateTime createddate = System.IO.File.GetCreationTime(filepart);
                if (createddate < DateTime.Now.AddHours(-2))
                {
                    System.IO.File.Delete(filepart);
                }
            }
        }

        private bool CanAccessFiles(string[] files)
        {
            // ensure files are not locked by another process ( ie. still being written to )
            bool canaccess = true;
            FileStream stream = null;
            foreach (string file in files)
            {
                int attempts = 0;
                bool locked = true;
                while (attempts < 5 && locked == true)
                {
                    try
                    {
                        stream = System.IO.File.Open(file, FileMode.Open, FileAccess.Read, FileShare.None);
                        locked = false;
                    }
                    catch // file is locked by another process
                    {                    
                        Thread.Sleep(1000); // wait 1 second
                    }
                    finally
                    {
                        if (stream != null)
                        {
                            stream.Close();
                        }
                    }
                    attempts += 1;
                }
                if (locked && canaccess)
                {
                    canaccess = false;
                }
            }
            return canaccess;
        }

        // DELETE api/<controller>/?folder=x&file=y
        [HttpDelete]
        [Authorize(Roles = Constants.AdminRole)]
        public void Delete(string folder, string file)
        {
            file = Path.Combine(GetFolder(folder) + file);
            if (System.IO.File.Exists(file))
            {
                System.IO.File.Delete(file);
                logger.Log(LogLevel.Information, this.GetType().AssemblyQualifiedName, LogFunction.Delete, "File Deleted {File}", file);
            }
        }

        private string GetFolder(string folder)
        {
            folder = folder.Replace("/", "\\");
            if (folder.StartsWith("\\")) folder = folder.Substring(1);
            return Path.Combine(environment.WebRootPath, folder);
        }
    }
}