using OpenTK.Mathematics;
using Image = SixLabors.ImageSharp.Image;
using SixLabors.ImageSharp.Metadata.Profiles.Exif;
using SixLabors.ImageSharp.Metadata.Profiles.Xmp;
using SixLabors.ImageSharp.Formats;
using SixLabors.ImageSharp.Formats.Jpeg;
using System.Text;
using System.Xml.Linq;

namespace SemiColinGames;

// https://exiftool.org/TagNames/GPS.html
public struct GpsInfo {
  public byte[] VersionId;
  public string Status;
  public string Datestamp;
  public Rational[] Timestamp;
  public Rational[] Latitude;
  public string LatitudeRef;
  public Rational[] Longitude;
  public string LongitudeRef;
  public Rational Altitude;
  public byte AltitudeRef;

  // GpsStatus? DateStamp and TimeStamp?
  public static GpsInfo? ParseExif(ExifProfile exif) {
    GpsInfo gps;

    IExifValue<byte[]>? versionId;
    IExifValue<string>? status;
    IExifValue<string>? datestamp;
    IExifValue<Rational[]>? timestamp;
    IExifValue<Rational[]>? latitude;
    IExifValue<string>? latitudeRef;
    IExifValue<Rational[]>? longitude;
    IExifValue<string>? longitudeRef;
    IExifValue<Rational>? altitude;
    IExifValue<byte>? altitudeRef;

    if (!exif.TryGetValue(ExifTag.GPSVersionID, out versionId)) {
      return null;
    }
    gps.VersionId = versionId.Value ?? throw new NullReferenceException();

    if (!exif.TryGetValue(ExifTag.GPSStatus, out status)) {
      return null;
    }
    gps.Status = status.Value ?? throw new NullReferenceException();

    if (!exif.TryGetValue(ExifTag.GPSDateStamp, out datestamp)) {
      return null;
    }
    gps.Datestamp = datestamp.Value ?? throw new NullReferenceException();

    if (!exif.TryGetValue(ExifTag.GPSTimestamp, out timestamp)) {
      return null;
    }
    gps.Timestamp = timestamp.Value ?? throw new NullReferenceException();

    if (!exif.TryGetValue(ExifTag.GPSLatitude, out latitude)) {
      return null;
    }
    gps.Latitude = latitude.Value ?? throw new NullReferenceException();

    if (!exif.TryGetValue(ExifTag.GPSLatitudeRef, out latitudeRef)) {
      return null;
    }
    gps.LatitudeRef = latitudeRef.Value ?? throw new NullReferenceException();

    if (!exif.TryGetValue(ExifTag.GPSLongitude, out longitude)) {
      return null;
    }
    gps.Longitude = longitude.Value ?? throw new NullReferenceException();

    if (!exif.TryGetValue(ExifTag.GPSLongitudeRef, out longitudeRef)) {
      return null;
    }
    gps.LongitudeRef = longitudeRef.Value ?? throw new NullReferenceException();

    if (!exif.TryGetValue(ExifTag.GPSAltitude, out altitude)) {
      return null;
    }
    gps.Altitude = altitude.Value;

    if (!exif.TryGetValue(ExifTag.GPSAltitudeRef, out altitudeRef)) {
      return null;
    }
    gps.AltitudeRef = altitudeRef.Value;

    return gps;
  }
}

public class Photo {
  public string Filename;
  public bool Loaded = false;
  public long LastTouch = 0;
  public Vector2i Size;
  public DateTime DateTimeOriginal;
  public string CameraModel = "";
  public string LensModel = "";
  public string ShortLensModel = "";
  public string FocalLength = "<unk>";
  public string FNumber = "<unk>";
  public string ExposureTime = "<unk>";
  public string IsoSpeed = "<unk>";
  public int Rating = 0;
  public ushort Orientation = 1;
  public GpsInfo? Gps = null;
  public Rectangle CropRectangle = Rectangle.Empty;

  private static long touchCounter = 0;
  private Texture texture;
  private Texture placeholder;
  private Texture thumbnailTexture;
  private Image<Rgba32>? image = null;
  private Image<Rgba32>? thumbnail = null;

  public Photo(string filename, Texture placeholder) {
    Filename = filename;
    this.placeholder = placeholder;
    texture = placeholder;
    thumbnailTexture = placeholder;

    DateTime creationTime = File.GetCreationTime(filename);  // Local time.
    DateTimeOriginal = creationTime;
    ImageInfo info = Image.Identify(filename);
    Size = new(info.Size.Width, info.Size.Height);
    Rating = ParseRating(info.Metadata.XmpProfile);
    ParseExif(info.Metadata.ExifProfile);
  }

  public async void LoadAsync(Vector2i size) {
    // We don't assign to this.image until Load() is done, because we might
    // edit the image due to rotation (etc) and don't want to try generating
    // a texture for it until that's already happened.
    LastTouch = touchCounter++;
    // FIXME: if we zoom in to more than the display size, actually load the whole image?
    DecoderOptions options = new DecoderOptions {
      TargetSize = new Size(size.X, size.Y),
      SkipMetadata = true
    };
    Image<Rgba32> tmp = await Image.LoadAsync<Rgba32>(options, Filename);
    Util.RotateImageFromExif(tmp, Orientation);
    image = tmp;
  }

  public async void LoadThumbnailAsync(Vector2i size) {
    DecoderOptions options = new DecoderOptions {
      TargetSize = new Size(size.X, size.Y),
      SkipMetadata = true
    };
    Image<Rgba32> tmp = await Image.LoadAsync<Rgba32>(options, Filename);
    Util.RotateImageFromExif(tmp, Orientation);
    thumbnail = tmp;
  }

  public void Unload() {
    Loaded = false;
    if (texture != placeholder) {
      texture.Dispose();
      texture = placeholder;
    }
  }

  public async void SaveAsJpegAsync(string outputRoot, JpegEncoder encoder) {
    // FIXME: if nothing was changed about this image, just copy the file bytes directly, possibly with metadata changed?
    string directory = System.IO.Path.Combine(
        outputRoot,
        String.Format("{0:D4}", DateTimeOriginal.Year),
        String.Format("{0:D2}", DateTimeOriginal.Month),
        String.Format("{0:D2}", DateTimeOriginal.Day));
    Directory.CreateDirectory(directory);
    string filename = System.IO.Path.Combine(directory, System.IO.Path.GetFileName(Filename));
    Console.WriteLine("saving " + filename);
    // FIXME: add comments / captions as ImageDescription?
    // FIXME: warn if the file already exists?
    using (Image<Rgba32> image = await Image.LoadAsync<Rgba32>(Filename)) {
      Util.RotateImageFromExif(image, Orientation);
      if (CropRectangle != Rectangle.Empty) {
        image.Mutate(x => x.Crop(CropRectangle));
      }

      ExifProfile exif = image.Metadata.ExifProfile ?? new();
      exif.SetValue<ushort>(ExifTag.Orientation, 1);
      exif.SetValue<string>(ExifTag.Artist, "Colin McMillen");
      exif.SetValue<string>(ExifTag.Copyright, "Colin McMillen");
      exif.SetValue<string>(ExifTag.Software, "Totte");
      exif.SetValue<ushort>(ExifTag.Rating, (ushort) Rating);
      DateTime now = DateTime.Now;
      string datetime = String.Format(
        "{0:D4}:{1:D2}:{2:D2} {3:D2}:{4:D2}:{5:D2}",
        now.Year, now.Month, now.Day, now.Hour, now.Minute, now.Second);
      exif.SetValue<string>(ExifTag.DateTime, datetime);

      if (Gps != null) {
        GpsInfo gps = (GpsInfo) Gps;
        exif.SetValue<byte[]>(ExifTag.GPSVersionID, gps.VersionId);
        exif.SetValue<string>(ExifTag.GPSStatus, gps.Status);
        exif.SetValue<string>(ExifTag.GPSDateStamp, gps.Datestamp);
        exif.SetValue<Rational[]>(ExifTag.GPSTimestamp, gps.Timestamp);
        exif.SetValue<Rational[]>(ExifTag.GPSLatitude, gps.Latitude);
        exif.SetValue<string>(ExifTag.GPSLatitudeRef, gps.LatitudeRef);
        exif.SetValue<Rational[]>(ExifTag.GPSLongitude, gps.Longitude);
        exif.SetValue<string>(ExifTag.GPSLongitudeRef, gps.LongitudeRef);
        exif.SetValue<Rational>(ExifTag.GPSAltitude, gps.Altitude);
        exif.SetValue<byte>(ExifTag.GPSAltitudeRef, gps.AltitudeRef);
      }

      image.Metadata.XmpProfile = UpdateXmp(image.Metadata.XmpProfile);

      await image.SaveAsync(filename, encoder);
    }
  }

  private XElement? GetXmpRoot(XmpProfile? xmp) {
    if (xmp == null) {
      return null;
    }
    XDocument? doc = xmp.GetDocument();
    if (doc == null) {
      return null;
    }
    return doc.Root;
  }

  private int ParseRating(XmpProfile? xmp) {
    XElement? root = GetXmpRoot(xmp);
    if (root == null) {
      return 0;
    }
    foreach (XElement elt in root.Descendants()) {
      if (elt.Name == "{http://ns.adobe.com/xap/1.0/}Rating") {
        int rating = 0;
        if (int.TryParse(elt.Value, out rating)) {
          return rating;
        }
      }
    }
    return 0;
  }

  private XmpProfile? UpdateXmp(XmpProfile? xmp) {
    if (xmp == null) {
      return null;
    }
    string xmlIn = Encoding.UTF8.GetString(xmp.ToByteArray());
    int index = xmlIn.IndexOf("</xmp:Rating>");
    if (index == -1) {
      return xmp;
    }
    string xmlOut = xmlIn.Substring(0, index - 1) + Rating.ToString() + xmlIn.Substring(index);
    return new XmpProfile(Encoding.UTF8.GetBytes(xmlOut));
  }

  // Exif (and other image metadata) reference, from the now-defunct Metadata Working Group:
  // https://web.archive.org/web/20180919181934/http://www.metadataworkinggroup.org/pdf/mwg_guidance.pdf
  //
  // Specifically:
  //
  // In general, date/time metadata is being used to describe the following scenarios:
  // * Date/time original specifies when a photo was taken
  // * Date/time digitized specifies when an image was digitized
  // * Date/time modified specifies when a file was modified by the user
  //
  // Original Date/Time – Creation date of the intellectual content (e.g. the photograph), rather than the creation date of the content being shown
  // Exif DateTimeOriginal (36867, 0x9003) and SubSecTimeOriginal (37521, 0x9291)
  // IPTC DateCreated (IIM 2:55, 0x0237) and TimeCreated (IIM 2:60, 0x023C)
  // XMP (photoshop:DateCreated)
  //
  // Digitized Date/Time – Creation date of the digital representation
  // Exif DateTimeDigitized (36868, 0x9004) and SubSecTimeDigitized (37522, 0x9292)
  // IPTC DigitalCreationDate (IIM 2:62, 0x023E) and DigitalCreationTime (IIM 2:63, 0x023F)
  // XMP (xmp:CreateDate)
  //
  // Modification Date/Time – Modification date of the digital image file
  // Exif DateTime (306, 0x132) and SubSecTime (37520, 0x9290)
  // XMP (xmp:ModifyDate)
  //
  // See also: https://exiftool.org/TagNames/EXIF.html
  private void ParseExif(ExifProfile? exifs) {
    if (exifs == null) {
      return;
    }

    IExifValue<ushort>? orientation;
    if (exifs.TryGetValue(ExifTag.Orientation, out orientation)) {
      Orientation = orientation.Value;
    }

    IExifValue<string>? model;
    if (exifs.TryGetValue(ExifTag.Model, out model)) {
      CameraModel = model.Value ?? "";
    }

    IExifValue<string>? lensModel;
    if (exifs.TryGetValue(ExifTag.LensModel, out lensModel)) {
      LensModel = lensModel.Value ?? "";
      ShortLensModel = GetShortLensModel(LensModel);
    }

    IExifValue<Rational>? focalLength;
    if (exifs.TryGetValue(ExifTag.FocalLength, out focalLength)) {
      Rational r = focalLength.Value;
      FocalLength = $"{r.Numerator / r.Denominator}mm";
    }

    IExifValue<Rational>? fNumber;
    if (exifs.TryGetValue(ExifTag.FNumber, out fNumber)) {
      Rational r = fNumber.Value;
      if (r.Numerator % r.Denominator == 0) {
        FNumber = $"f/{r.Numerator / r.Denominator}";
      } else {
        int fTimesTen = (int) Math.Round(10f * r.Numerator / r.Denominator);
        FNumber = $"f/{fTimesTen / 10}.{fTimesTen % 10}";
      }
    }

    // FIXME: could also show ExposureBiasValue, ExposureMode, ExposureProgram?
    IExifValue<Rational>? exposureTime;
    if (exifs.TryGetValue(ExifTag.ExposureTime, out exposureTime)) {
      Rational r = exposureTime.Value;
      if (r.Numerator == 1) {
        ExposureTime = $"1/{r.Denominator}";
      } else if (r.Numerator == 10) {
        ExposureTime = $"1/{r.Denominator / 10}";
      } else if (r.Denominator == 1) {
        ExposureTime = $"{r.Numerator }\"";
      } else if (r.Denominator == 10) {
        ExposureTime = $"{r.Numerator / 10}.{r.Numerator % 10}\"";
      } else {
        Console.WriteLine($"*** WARNING: unexpected ExposureTime: {r.Numerator}/{r.Denominator}");
        ExposureTime = r.ToString();
      }
    }

    IExifValue<ushort[]>? isoSpeed;
    if (exifs.TryGetValue(ExifTag.ISOSpeedRatings, out isoSpeed)) {
      ushort[]? iso = isoSpeed.Value;
      if (iso != null) {
        if (iso.Length != 1) {
          Console.WriteLine($"*** WARNING: unexpected ISOSpeedRatings array length: {iso.Length}");
        }
        if (iso.Length >= 1) {
          IsoSpeed = $"ISO {iso[0]}";
        }
      }
    }

    // FIXME: there is also a SubSecTimeOriginal tag we could use to get fractional seconds.
    // FIXME: I think the iPhone stores time in UTC but other cameras report it in local time.
    IExifValue<string>? dateTimeOriginal;
    if (exifs.TryGetValue(ExifTag.DateTimeOriginal, out dateTimeOriginal)) {
      DateTime date;
      if (DateTime.TryParseExact(
          dateTimeOriginal.Value ?? "",
          "yyyy:MM:dd HH:mm:ss",
          System.Globalization.CultureInfo.InvariantCulture,
          System.Globalization.DateTimeStyles.AssumeLocal,
          out date)) {
        DateTimeOriginal = date;
      } else {
        Console.WriteLine($"*** WARNING: unexpected DateTimeOriginal value: {dateTimeOriginal.Value}");
      }
    }

    Gps = GpsInfo.ParseExif(exifs);
  }

  public string GetShortLensModel(string lensModel) {
    // Example Canon RF lens names:
    // RF16mm F2.8 STM
    // RF24-105mm F4-7.1 IS STM
    // RF35mm F1.8 MACRO IS STM
    // RF100-400mm F5.6-8 IS USM
    string[] tokens = lensModel.Split(' ');
    string result = "";
    foreach (string token in tokens) {
      if (token == "STM" || token == "IS" || token == "USM") {
        continue;
      }
      result += token + " ";
    }
    return result.Trim();
  }

  public Texture Texture() {
    LastTouch = touchCounter++;
    if (texture == placeholder && image != null) {
      // The texture needs to be created on the GL thread, so we instantiate
      // it here (since this is called from OnRenderFrame), as long as the
      // image is ready to go.
      texture = new(image);
      image.Dispose();
      image = null;
      Loaded = true;
    }
    return texture != placeholder ? texture : thumbnailTexture;
  }

  public Texture ThumbnailTexture() {
    if (thumbnailTexture == placeholder && thumbnail != null) {
      thumbnailTexture = new(thumbnail);
      thumbnail.Dispose();
      thumbnail = null;
    }
    return thumbnailTexture;
  }

  public string Description() {
    string date = DateTimeOriginal.ToString("yyyy-MM-dd HH:mm:ss");
    return String.Format(
        "{0,6}  {1,-5}  {2,-7} {3,-10} {7,4}x{8,-4} {4}    {5,-20}    {6}",
        FocalLength, FNumber, ExposureTime, IsoSpeed, date, ShortLensModel, Filename, Size.X, Size.Y);
  }
}