using System;
using System.Threading.Tasks;
using Xamarin.Forms;
using System.IO;
using Syncfusion.XForms.SignaturePad;

namespace PRS.Mobile
{
    public delegate void NameAdded(string s);
    public delegate void NameRemoved(string s);
    class SignaturePad : Frame
    {
        private SfSignaturePad Pad = new SfSignaturePad();
        public string Name = "";
        public string Data = "";
        public bool StrokeAdded = false;
        public event NameAdded OnNameAdded;
        public event NameRemoved OnNameRemoved;
        private Entry entry = new Entry();
        Grid SignatureGrid = new Grid() { Margin = 0, Padding = 0 };
        EmbeddedImageCapture hiddenEmbeddedImageCapture = new EmbeddedImageCapture() { HeightRequest = 180, IsVisible = false, IsEnabled = false };
        public SignaturePad()
        {
            Padding = 4;

            Pad = new SfSignaturePad();
            Pad.BackgroundColor = Color.White;
            Pad.MinimumHeightRequest = 200;
            Pad.MinimumStrokeWidth = 0.2;
            Pad.MaximumStrokeWidth = 17;
            Pad.StrokeCompleted += Pad_StrokeCompleted;

            entry = new Entry
            {
                Placeholder = "Add Name",
                HorizontalOptions = LayoutOptions.FillAndExpand,
                Margin = new Thickness(1, 1, 0, 1),
                BackgroundColor = Color.White,
                VerticalOptions = LayoutOptions.Center
            };

            entry.TextChanged += (object sender, TextChangedEventArgs e) =>
            {
                entry.Text = entry.Text.ToUpper().Trim();
                Name = entry.Text;
            };

            Button lookupButton = new Button()
            {
                Text = "...",
                VerticalOptions = LayoutOptions.Center,
                FontAttributes = FontAttributes.Bold,
                CornerRadius = 5,
                Padding = 1,
                Margin = new Thickness(0, 1, 0, 1),
            };
            lookupButton.Clicked += (object sender, EventArgs e) =>
            {
                EmployeeSelectionPage page = new EmployeeSelectionPage(
                    (employee) =>
                    {
                        entry.Text = employee.Name.ToUpper();
                        OnNameAdded?.Invoke(entry.Text);
                    });
                Navigation.PushAsync(page);
            };

            Button clearButton = new Button()
            {
                Text = "Clear",
                HorizontalOptions = LayoutOptions.FillAndExpand,
                VerticalOptions = LayoutOptions.End,
                Margin = new Thickness(0, 1, 1, 1),
                BackgroundColor = Color.FromHex("#15C7C1"),
                FontAttributes = FontAttributes.Bold,
                TextColor = Color.White,
                CornerRadius = 5,
                Padding = 1
            };
            clearButton.Clicked += (object sender, EventArgs e) =>
            {
                Pad.Clear();
                hiddenEmbeddedImageCapture.ClearItems();
                hiddenEmbeddedImageCapture.IsVisible = false;
                Pad.IsVisible = true;
                ClearName();
                Data = "";
                StrokeAdded = false;
            };

            Grid.SetColumn(entry, 0);
            Grid.SetColumn(lookupButton, 1);
            Grid.SetColumn(clearButton, 2);
            Grid buttonsGrid = new Grid { Margin = 0, Padding = 0, VerticalOptions = LayoutOptions.End };

            buttonsGrid.ColumnDefinitions.Add(new ColumnDefinition { Width = new GridLength(2, GridUnitType.Star) });
            buttonsGrid.ColumnDefinitions.Add(new ColumnDefinition { Width = new GridLength(35, GridUnitType.Absolute) });
            buttonsGrid.ColumnDefinitions.Add(new ColumnDefinition { Width = new GridLength(1, GridUnitType.Star) });

            buttonsGrid.Children.Add(entry);
            buttonsGrid.Children.Add(lookupButton);
            buttonsGrid.Children.Add(clearButton);
                        
            SignatureGrid.RowDefinitions.Add(new RowDefinition { Height = new GridLength(200, GridUnitType.Absolute) });
            Grid.SetRow(Pad, 0);
            Grid.SetRow(hiddenEmbeddedImageCapture, 0);

            SignatureGrid.Children.Add(hiddenEmbeddedImageCapture);
            SignatureGrid.Children.Add(Pad);
            SignatureGrid.Children.Add(buttonsGrid);

            CornerRadius = 10;
            BorderColor = Color.FromHex("#15C7C1");
            Content = SignatureGrid;
        }

        private void Pad_StrokeCompleted(object sender, EventArgs e)
        {
            StrokeAdded = true;
        }

        public void ClearName()
        {
            OnNameRemoved?.Invoke(entry.Text);
            entry.Text = "";            
        }

        public void SaveSignature()
        {
            if (Data == null || string.IsNullOrWhiteSpace(Data))
            {
                Pad.Save();
                if (Pad.ImageSource != null)
                {
                    Data = ImageSourceToBase64(Pad.ImageSource);
                }
            }           
        }

        public void PopulateSignature(byte[] data)
        {
            Pad.IsVisible = false;
            hiddenEmbeddedImageCapture.IsVisible = true;
            hiddenEmbeddedImageCapture.DataToImage(data);
            ImageSource src = ImageSource.FromStream(() => new MemoryStream(data));
            Data = ImageSourceToBase64(src);
            StrokeAdded = true;
        }

        public void PopulateName(string s)
        {
            entry.Text = s;
        }

        private string ImageSourceToBase64(ImageSource source)
        {
            StreamImageSource streamImageSource = (StreamImageSource)source;
            System.Threading.CancellationToken cancellationToken = System.Threading.CancellationToken.None;
            Task<Stream> task = streamImageSource.Stream(cancellationToken);
            Stream stream = task.Result;
            byte[] bytes = new byte[stream.Length];
            stream.Read(bytes, 0, bytes.Length);
            string s = Convert.ToBase64String(bytes, Base64FormattingOptions.InsertLineBreaks);
            return s;
        }

    }
}