using System;
using System.Drawing;
using System.IO;
using System.Net;

namespace HanvonF710XAttendanceService
{
    internal sealed class HrmsEmployeePhotoDownloadResult
    {
        public bool Success { get; set; }
        public int StatusCode { get; set; }
        public string ContentType { get; set; }
        public string Url { get; set; }
        public byte[] ImageBytes { get; set; }
        public int Width { get; set; }
        public int Height { get; set; }
        public int Base64Length { get; set; }
        public string Error { get; set; }
    }

    internal static class HrmsEmployeePhotoClient
    {
        /// <param name="hrmsEmployeeId">employees.id used in the portal photo path. Not the device serial.</param>
        public static string BuildPhotoUrl(string baseUrl, string hrmsEmployeeId)
        {
            if (string.IsNullOrWhiteSpace(baseUrl))
            {
                throw new ArgumentException("Employee photo base URL is required.");
            }

            if (string.IsNullOrWhiteSpace(hrmsEmployeeId))
            {
                throw new ArgumentException("HRMS employee ID (employees.id) is required.");
            }

            string trimmedBase = baseUrl.Trim();
            if (!trimmedBase.EndsWith("/", StringComparison.Ordinal))
            {
                trimmedBase += "/";
            }

            return trimmedBase + hrmsEmployeeId.Trim() + ".jpeg";
        }

        /// <param name="hrmsEmployeeId">employees.id for EmployeePhotoBaseUrl + id + ".jpeg".</param>
        public static bool TryDownloadEmployeePhoto(string hrmsEmployeeId, out HrmsEmployeePhotoDownloadResult result)
        {
            result = new HrmsEmployeePhotoDownloadResult();
            if (!EmployeePhotoSourceSettings.IsEnabled())
            {
                result.Error = "employee_photo_source_disabled";
                return false;
            }

            string baseUrl = EmployeePhotoSourceSettings.GetBaseUrl();
            if (string.IsNullOrWhiteSpace(baseUrl))
            {
                result.Error = "employee_photo_base_url_missing";
                return false;
            }

            if (string.IsNullOrWhiteSpace(hrmsEmployeeId))
            {
                result.Error = "hrms_employee_id_missing";
                return false;
            }

            result.Url = BuildPhotoUrl(baseUrl, hrmsEmployeeId);
            int timeoutMs = EmployeePhotoSourceSettings.GetTimeoutMs();

            try
            {
                var request = (HttpWebRequest)WebRequest.Create(result.Url);
                request.Method = "GET";
                request.Timeout = timeoutMs;
                request.ReadWriteTimeout = timeoutMs;
                request.AllowAutoRedirect = true;
                request.UserAgent = "HanvonF710XAttendanceService/1.0";

                using (var response = (HttpWebResponse)request.GetResponse())
                using (var stream = response.GetResponseStream())
                using (var memory = new MemoryStream())
                {
                    result.StatusCode = (int)response.StatusCode;
                    result.ContentType = response.ContentType;

                    if (response.StatusCode != HttpStatusCode.OK)
                    {
                        result.Error = "http_status_" + result.StatusCode;
                        return false;
                    }

                    if (stream == null)
                    {
                        result.Error = "empty_response_stream";
                        return false;
                    }

                    stream.CopyTo(memory);
                    result.ImageBytes = memory.ToArray();
                }
            }
            catch (WebException wex)
            {
                if (wex.Response is HttpWebResponse errResp)
                {
                    result.StatusCode = (int)errResp.StatusCode;
                    result.ContentType = errResp.ContentType;
                }

                result.Error = wex.Message;
                return false;
            }
            catch (Exception ex)
            {
                result.Error = ex.Message;
                return false;
            }

            if (!TryValidateDownloadedImage(result, out string validationError))
            {
                result.Error = validationError;
                result.ImageBytes = null;
                return false;
            }

            result.Base64Length = Convert.ToBase64String(result.ImageBytes).Length;
            result.Success = true;
            return true;
        }

        public static bool TryValidateDownloadedImage(HrmsEmployeePhotoDownloadResult result, out string error)
        {
            error = null;
            byte[] bytes = result?.ImageBytes;
            if (bytes == null || bytes.Length == 0)
            {
                error = "empty_image";
                return false;
            }

            if (bytes.Length < 4 || bytes[0] != 0xFF || bytes[1] != 0xD8)
            {
                error = "not_jpeg";
                return false;
            }

            if (!NedoPhotoPreprocessor.IsCompleteJpeg(bytes))
            {
                error = "incomplete_jpeg";
                return false;
            }

            string contentType = result.ContentType ?? "";
            if (!string.IsNullOrWhiteSpace(contentType)
                && contentType.IndexOf("image", StringComparison.OrdinalIgnoreCase) < 0
                && contentType.IndexOf("jpeg", StringComparison.OrdinalIgnoreCase) < 0
                && contentType.IndexOf("octet-stream", StringComparison.OrdinalIgnoreCase) < 0)
            {
                error = "invalid_content_type";
                return false;
            }

            try
            {
                using (var input = new MemoryStream(bytes))
                using (var image = Image.FromStream(input))
                {
                    result.Width = image.Width;
                    result.Height = image.Height;
                }
            }
            catch (Exception ex)
            {
                error = "invalid_image_data:" + ex.Message;
                return false;
            }

            int minShort = EmployeePhotoSourceSettings.GetMinShortSide();
            int maxShort = EmployeePhotoSourceSettings.GetMaxShortSide();
            int shortSide = Math.Min(result.Width, result.Height);
            int longSide = Math.Max(result.Width, result.Height);

            if (shortSide < minShort)
            {
                error = "image_too_small";
                return false;
            }

            if (longSide > maxShort)
            {
                error = "image_too_large";
                return false;
            }

            return true;
        }
    }
}