using System;
using System.IO;
using System.Linq;
using System.Text;
using UglyToad.PdfPig;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Http;
using xCommons.Extensions;

namespace xAiModels.Extensions
{
    public static class IFormFileExtensions
    {
        /// <summary>
        /// Read a IFormFile Content as byte array ...
        /// </summary>
        /// <param name="source"></param>
        /// <param name="cancellationToken"></param>
        /// <returns></returns>
        public static async Task<byte[]> ReadAsBytes(
            this IFormFile source,
            CancellationToken cancellationToken = default
        )
        {
            //
            // Create and use a Memory Stream ...
            using var stream = new MemoryStream();

            //
            // Copy File Content to Stream ...
            await source.CopyToAsync(
                target: stream,
                cancellationToken: cancellationToken
            );

            //
            // Read Stream Content as byte array ...
            var result = stream.ToArray();

            //
            return result;
        }

        /// <summary>
        /// Read a File Content by it's Path as byte array ...
        /// </summary>
        /// <param name="filePath"></param>
        /// <param name="bufferSize"></param>
        /// <param name="cancellationToken"></param>
        /// <returns></returns>
        /// <exception cref="Exception"></exception>
        public static async Task<byte[]> ReadAsBytes(
            this string filePath,
            int bufferSize = 81920,
            CancellationToken cancellationToken = default
        )
        {
            //
            if (string.IsNullOrWhiteSpace(filePath))
            {
                throw new Exception("Invalid Args ...");
            }

            //
            // Create and use a Memory Stream ...
            using var memStream = new MemoryStream();

            //
            using var stream = new FileStream(
                path: filePath,
                mode: FileMode.Open,
                access: FileAccess.Read,
                share: FileShare.ReadWrite
            );

            //
            // Copy File Content to Stream ...
            await stream.CopyToAsync(
                destination: memStream,
                bufferSize: bufferSize,
                cancellationToken: cancellationToken
            );

            //
            // Read Stream Content as byte array ...
            var result = memStream.ToArray();

            //
            return result;
        }

        /// <summary>
        /// Read Text Content of Document ...
        /// </summary>
        /// <param name="source"></param>
        /// <param name="cancellationToken"></param>
        /// <returns></returns>
        public static async Task<string> ReadContent(
            this IFormFile source,
            CancellationToken cancellationToken = default
        )
        {
            //
            // Check if File PDF or not ...
            var isPDF = source.ContentType
                .ToNormalString()
                .Contains("pdf"
                    .ToNormalString());

            //
            var result = string.Empty;

            //
            var isValidFileType = isPDF;
            if (!isValidFileType)
            {
                return result;
            }

            //
            if (isPDF)
            {
                //
                // Reading File Content as Byte array ...
                var fileBytes = await source.ReadAsBytes(cancellationToken);

                //
                // Create a PDF Document ...
                using var stream = new MemoryStream(fileBytes);
                using var document = PdfDocument.Open(stream);

                //
                // Extract PDF Text ...
                var textBuilder = new StringBuilder();
                foreach (var page in document.GetPages())
                {
                    textBuilder.Append(page.Text);
                }

                //
                result = textBuilder.ToString();
            }

            //
            return result;
        }
    }
}