using System;
using System.Text;
using System.Text.RegularExpressions;

namespace HanvonF710XAttendanceService
{
    internal enum DbToDeviceTemplateFormat
    {
        Empty,
        NedoXml,
        HanvonJpegFace,
        HanvonRecord
    }

    internal enum NedoPhotoExtractResult
    {
        Found,
        Missing,
        Invalid
    }

    internal sealed class DbToDeviceUploadPlan
    {
        public DbToDeviceTemplateFormat Format { get; set; } = DbToDeviceTemplateFormat.Empty;
        public string PushMode { get; set; }
        public string Payload { get; set; }
        public bool UseProfileVerification { get; set; }
        public NedoPhotoExtractResult? NedoPhotoStatus { get; set; }
        public int PhotoByteLength { get; set; }
        public int PhotoBase64Length { get; set; }
        public int SourceBlobLength { get; set; }
        public string PrepareNote { get; set; }
        public int PreparedWidth { get; set; }
        public int PreparedHeight { get; set; }
        public string PhotoSourceLabel { get; set; }
        public string PhotoSourceUrl { get; set; }

        /// <param name="hrmsEmployeeId">employees.id used for portal photo URL. Must NOT be the device serial.</param>
        public bool TryResolveEmployeePhoto(string hrmsEmployeeId, out string error)
        {
            error = null;
            bool hadNedoPayload = HasUploadPayload;

            if (Format != DbToDeviceTemplateFormat.NedoXml || !EmployeePhotoSourceSettings.IsEnabled())
            {
                if (Format == DbToDeviceTemplateFormat.NedoXml && HasUploadPayload)
                {
                    PhotoSourceLabel = "NEDO_XML";
                }
                return HasUploadPayload;
            }

            if (string.IsNullOrWhiteSpace(hrmsEmployeeId))
            {
                error = "hrms_employee_id_missing";
                if (hadNedoPayload)
                {
                    PhotoSourceLabel = "NEDO_XML";
                    return true;
                }

                return false;
            }

            if (HrmsEmployeePhotoClient.TryDownloadEmployeePhoto(hrmsEmployeeId, out HrmsEmployeePhotoDownloadResult portalPhoto))
            {
                Payload = Convert.ToBase64String(portalPhoto.ImageBytes);
                PhotoByteLength = portalPhoto.ImageBytes.Length;
                PhotoBase64Length = portalPhoto.Base64Length;
                PhotoSourceLabel = "HRMS_PORTAL";
                PhotoSourceUrl = portalPhoto.Url;
                PreparedWidth = portalPhoto.Width;
                PreparedHeight = portalPhoto.Height;
                return true;
            }

            error = portalPhoto?.Error;
            if (hadNedoPayload)
            {
                PhotoSourceLabel = "NEDO_XML";
                return true;
            }

            return false;
        }

        public bool TryPrepareFacePayload(out string error)
        {
            error = null;
            if (Format != DbToDeviceTemplateFormat.NedoXml && Format != DbToDeviceTemplateFormat.HanvonJpegFace)
            {
                return true;
            }

            if (string.IsNullOrWhiteSpace(Payload))
            {
                error = "empty";
                return false;
            }

            if (!NedoPhotoPreprocessor.TryPrepareForHanvon(Payload, out string prepared, out int width, out int height, out string note))
            {
                error = note ?? "prepare_failed";
                return false;
            }

            Payload = prepared;
            PrepareNote = note;
            PreparedWidth = width;
            PreparedHeight = height;
            PhotoBase64Length = prepared?.Length ?? 0;
            PhotoByteLength = NedoTemplateConverter.GetDecodedJpegByteLength(prepared);
            return true;
        }

        public string FormatLabel
        {
            get
            {
                switch (Format)
                {
                    case DbToDeviceTemplateFormat.NedoXml: return "NEDO_XML";
                    case DbToDeviceTemplateFormat.HanvonJpegFace: return "HANVON_JPEG";
                    case DbToDeviceTemplateFormat.HanvonRecord: return "HANVON_RECORD";
                    default: return "EMPTY";
                }
            }
        }

        public bool HasUploadPayload => !string.IsNullOrWhiteSpace(Payload);

        public static DbToDeviceUploadPlan FromBlob(byte[] blob)
        {
            var plan = new DbToDeviceUploadPlan();
            plan.SourceBlobLength = blob?.Length ?? 0;
            if (blob == null || blob.Length == 0)
            {
                plan.Format = DbToDeviceTemplateFormat.Empty;
                return plan;
            }

            if (blob.Length >= 3 && blob[0] == 0xFF && blob[1] == 0xD8 && blob[2] == 0xFF)
            {
                plan.Format = DbToDeviceTemplateFormat.HanvonJpegFace;
                plan.PushMode = "face";
                plan.Payload = Convert.ToBase64String(blob);
                plan.PhotoByteLength = blob.Length;
                plan.UseProfileVerification = true;
                return plan;
            }

            string text = Encoding.UTF8.GetString(blob).Trim();
            if (string.IsNullOrWhiteSpace(text))
            {
                plan.Format = DbToDeviceTemplateFormat.Empty;
                return plan;
            }

            if (NedoTemplateConverter.IsNedoXml(text))
            {
                plan.Format = DbToDeviceTemplateFormat.NedoXml;
                plan.PushMode = "face";
                plan.UseProfileVerification = true;

                string photo;
                NedoPhotoExtractResult photoResult = NedoTemplateConverter.TryExtractPhoto(text, out photo);
                plan.NedoPhotoStatus = photoResult;
                if (photoResult == NedoPhotoExtractResult.Found)
                {
                    plan.Payload = photo;
                    plan.PhotoBase64Length = photo?.Length ?? 0;
                    plan.PhotoByteLength = NedoTemplateConverter.GetDecodedJpegByteLength(photo);
                }

                return plan;
            }

            string normalized = HanvonHttpApiClient.NormalizeFaceTemplatePayload(blob, out string pushMode);
            plan.Payload = normalized;
            plan.PushMode = pushMode;
            plan.Format = string.Equals(pushMode, "face", StringComparison.OrdinalIgnoreCase)
                ? DbToDeviceTemplateFormat.HanvonJpegFace
                : DbToDeviceTemplateFormat.HanvonRecord;
            plan.UseProfileVerification = plan.Format == DbToDeviceTemplateFormat.HanvonJpegFace;
            if (plan.Format == DbToDeviceTemplateFormat.HanvonJpegFace && !string.IsNullOrWhiteSpace(normalized))
            {
                plan.PhotoByteLength = NedoTemplateConverter.GetDecodedJpegByteLength(normalized);
            }

            return plan;
        }
    }

    internal static class NedoTemplateConverter
    {
        private static readonly Regex PhotoAttributeRegex = new Regex(
            @"photo\s*=\s*""([^""]*)""",
            RegexOptions.IgnoreCase | RegexOptions.CultureInvariant);

        public static bool IsNedoXml(string text)
        {
            if (string.IsNullOrWhiteSpace(text))
            {
                return false;
            }

            bool hasPhoto = text.IndexOf("photo=\"", StringComparison.OrdinalIgnoreCase) >= 0
                || text.IndexOf("photo =", StringComparison.OrdinalIgnoreCase) >= 0;
            if (!hasPhoto)
            {
                return false;
            }

            bool hasFaceData = text.IndexOf("face_data=\"", StringComparison.OrdinalIgnoreCase) >= 0;
            bool hasCheckTypeFace = text.IndexOf("check_type=\"face\"", StringComparison.OrdinalIgnoreCase) >= 0;
            bool hasIdAttribute = Regex.IsMatch(text, @"\bid\s*=\s*""", RegexOptions.IgnoreCase | RegexOptions.CultureInvariant);

            return hasFaceData || hasCheckTypeFace || hasIdAttribute;
        }

        public static NedoPhotoExtractResult TryExtractPhoto(string nedoText, out string photoBase64)
        {
            photoBase64 = null;
            if (string.IsNullOrWhiteSpace(nedoText))
            {
                return NedoPhotoExtractResult.Missing;
            }

            int photoAttrIndex = FindPhotoAttributeIndex(nedoText, out int valueStart);
            if (photoAttrIndex < 0)
            {
                return NedoPhotoExtractResult.Missing;
            }

            if (valueStart >= nedoText.Length)
            {
                return NedoPhotoExtractResult.Missing;
            }

            int faceDataIndex = nedoText.IndexOf("\"face_data", valueStart, StringComparison.OrdinalIgnoreCase);
            if (faceDataIndex < 0)
            {
                faceDataIndex = nedoText.IndexOf("\" face_data", valueStart, StringComparison.OrdinalIgnoreCase);
            }

            int valueEnd;
            if (faceDataIndex > valueStart)
            {
                valueEnd = faceDataIndex;
            }
            else
            {
                valueEnd = nedoText.IndexOf('"', valueStart);
            }

            if (valueEnd <= valueStart)
            {
                Match match = PhotoAttributeRegex.Match(nedoText);
                if (!match.Success || match.Groups.Count < 2)
                {
                    return NedoPhotoExtractResult.Missing;
                }

                return ValidateAndNormalizePhoto(match.Groups[1].Value, out photoBase64);
            }

            string raw = nedoText.Substring(valueStart, valueEnd - valueStart);
            return ValidateAndNormalizePhoto(raw, out photoBase64);
        }

        private static int FindPhotoAttributeIndex(string text, out int valueStart)
        {
            valueStart = -1;
            Match spaced = Regex.Match(text, @"photo\s*=\s*""", RegexOptions.IgnoreCase | RegexOptions.CultureInvariant);
            if (!spaced.Success)
            {
                return -1;
            }

            valueStart = spaced.Index + spaced.Length;
            return spaced.Index;
        }

        private static NedoPhotoExtractResult ValidateAndNormalizePhoto(string raw, out string photoBase64)
        {
            photoBase64 = null;
            if (string.IsNullOrWhiteSpace(raw))
            {
                return NedoPhotoExtractResult.Missing;
            }

            raw = raw.Trim();
            if (raw.StartsWith("data:", StringComparison.OrdinalIgnoreCase))
            {
                int comma = raw.IndexOf(',');
                if (comma >= 0)
                {
                    raw = raw.Substring(comma + 1);
                }
            }

            raw = raw.Replace("\r", "").Replace("\n", "").Trim();
            if (!IsValidJpegBase64(raw))
            {
                return NedoPhotoExtractResult.Invalid;
            }

            try
            {
                byte[] decoded = Convert.FromBase64String(raw);
                if (!NedoPhotoPreprocessor.IsCompleteJpeg(decoded))
                {
                    return NedoPhotoExtractResult.Invalid;
                }
            }
            catch
            {
                return NedoPhotoExtractResult.Invalid;
            }

            photoBase64 = raw;
            return NedoPhotoExtractResult.Found;
        }

        public static bool IsValidJpegBase64(string base64)
        {
            if (string.IsNullOrWhiteSpace(base64))
            {
                return false;
            }

            try
            {
                byte[] decoded = Convert.FromBase64String(base64);
                return decoded.Length >= 3
                    && decoded[0] == 0xFF
                    && decoded[1] == 0xD8
                    && decoded[2] == 0xFF;
            }
            catch
            {
                return false;
            }
        }

        public static int GetDecodedJpegByteLength(string base64)
        {
            if (string.IsNullOrWhiteSpace(base64))
            {
                return 0;
            }

            try
            {
                return Convert.FromBase64String(base64).Length;
            }
            catch
            {
                return 0;
            }
        }

        public static bool UsesFaceField(DbToDeviceUploadPlan plan)
        {
            return plan != null
                && string.Equals(plan.PushMode, "face", StringComparison.OrdinalIgnoreCase);
        }

        public static bool UsesRecordField(DbToDeviceUploadPlan plan)
        {
            return plan != null
                && string.Equals(plan.PushMode, "record", StringComparison.OrdinalIgnoreCase);
        }
    }
}