prs/prs.mobile.new/PRS.Mobile/Components/DigitalForms/Editor/Views/DigitalFormSignature.cs

using System;
using System.IO;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using InABox.Core;
using InABox.Mobile;
using Syncfusion.XForms.SignaturePad;
using Xamarin.Forms;

namespace PRS.Mobile
{
    public class DigitalFormSignature : MobileCard, IDigitalFormField<DFLayoutSignaturePad, DFLayoutSignaturePadProperties, byte[]>
    {

        private readonly Grid _grid;
        private readonly SfSignaturePad _pad;
        private readonly Image _image;
        private readonly MobileButton _save;
        private readonly MobileButton _apply;
        private readonly MobileButton _clear;
        
        private DFLayoutSignaturePad _definition;
        public DFLayoutSignaturePad Definition
        {
            get => _definition;
            set
            {
                _definition = value;
                Initialize(value ??  new DFLayoutSignaturePad());
            } 
        }

        private Guid _id;
        
        private byte[] _value;
        public byte[] Value
        {
            get => _value;
            set
            {
                _value = value;
                UpdateValue();
            }
        }

        public bool IsEmpty => Value?.Any() != true;
        
        private bool _readOnly;
        public bool ReadOnly
        {
            get => _readOnly;
            set
            {
                _readOnly = value;
                UpdateStatus();
            }
        }
        
        public void Deserialize(string serialized)
        {
            if (String.IsNullOrWhiteSpace(serialized))
                return;
            if (Guid.TryParse(serialized, out _id) && (_id != Guid.Empty))
                DigitalFormDocumentFactory.LoadDocument(_id,
                    v => Device.BeginInvokeOnMainThread(() => Value = v));
            else if (serialized.IsBase64String())
                Value = Convert.FromBase64String(serialized);
        }

        public string Serialize()
        {
            if ((_id == Guid.Empty) && Value?.Any() == true)
                _id = DigitalFormDocumentFactory.SaveDocument(Value);
            return _id.ToString();
        }

        public event DigitalFormViewChangedHandler ValueChanged;

        public DigitalFormSignature()
        {
            Padding = 5;
            _grid = new Grid();
            _grid.ColumnDefinitions.Add(new ColumnDefinition() { Width = GridLength.Star });
            _grid.ColumnDefinitions.Add(new ColumnDefinition() { Width = GridLength.Star });
            _grid.ColumnDefinitions.Add(new ColumnDefinition() { Width = GridLength.Star });

            _grid.RowDefinitions.Add(new RowDefinition() { Height= GridLength.Star });
            _grid.RowDefinitions.Add(new RowDefinition() { Height= GridLength.Auto });
            
            _save = AddButton("Save New", SaveSignature, 0, false);
            _apply = AddButton("Apply Saved", ApplySignature, 1, App.Data.Me.Signature?.Any() == true);
            _clear = AddButton("Clear", ClearSignature, 2, false);
            
            _pad = new SfSignaturePad()
            {
                MinimumStrokeWidth = 0.2,
                MaximumStrokeWidth = 17,
                BackgroundColor = Color.Transparent
            };
            _pad.StrokeCompleted += (sender, args) =>
            {
                _save.IsEnabled = true;
                _clear.IsEnabled = true;
            };
            _pad.SetValue(Grid.ColumnProperty,0);
            _pad.SetValue(Grid.ColumnSpanProperty,3);
            _pad.SetValue(Grid.RowProperty,0);
            _grid.Children.Add(_pad);

            _image = new Image
            {
                IsVisible = false
            };
            _image.SetValue(Grid.ColumnProperty,0);
            _image.SetValue(Grid.ColumnSpanProperty,3);
            _image.SetValue(Grid.RowProperty,0);
            _grid.Children.Add(_image);



            Content = _grid;
        }
        
        private MobileButton AddButton(String text, Action clicked, int column, bool enabled)
        {
            var result = new MobileButton() { Text = text };
            result.SetValue(Grid.RowProperty,1);
            result.SetValue(Grid.ColumnProperty,column);
            result.Clicked += (sender, args) => clicked();
            result.IsEnabled = enabled;
            _grid.Children.Add(result);
            return result;
        }
        
        private void SaveSignature()
        {
            _pad.Save();
            _value = GetSignature(_pad.ImageSource);
            App.Data.Me.Signature = _value;
            App.Data.Me.Save("Updated Signature");
            _save.IsEnabled = false;
            _apply.IsEnabled = App.Data.Me.Signature?.Any() == true;
            UpdateValue();
        }
        
        private void ApplySignature()
        {
            _value = App.Data.Me.Signature;
            _save.IsEnabled = false;
            UpdateValue();
        }
        
        private void ClearSignature()
        {
            _pad.Clear();
            _pad.Save();
            _value = null;
            _save.IsEnabled = false;
            _clear.IsEnabled = false;
            UpdateValue();
        }
        
        private byte[] GetSignature(ImageSource source)
        {
            try
            {
                StreamImageSource streamImageSource = (StreamImageSource)source;
                CancellationToken cancellationToken = CancellationToken.None;
                Task<Stream> task = streamImageSource.Stream(cancellationToken);
                Stream stream = task.Result;
                byte[] bytes = new byte[stream.Length];
                _ = stream.Read(bytes, 0, bytes.Length);
                return bytes;
            }
            catch (Exception e)
            {
                InABox.Mobile.MobileLogging.Log(e,"GetSignature");
                return new byte[] { };
            }
        }

        
        private void Initialize(DFLayoutSignaturePad definition)
        {
            UpdateStatus();
        }

        private void UpdateStatus()
        {
            bool enabled = !_readOnly && !Definition.Properties.Secure;
            _pad.IsEnabled = enabled;
            _save.IsEnabled = enabled && (Value?.Any() == true);
            _apply.IsEnabled = enabled && (App.Data.Me.Signature?.Any() == true);
            _clear.IsEnabled = enabled && (Value?.Any() == true);
            
            var colors = DigitalFormUtils.GetColors(!enabled, Definition.Properties.Required, false);
            BackgroundColor = colors.Background;
            BorderColor = colors.Border;
        }
        
        private void UpdateValue()
        {
            if (_value == null)
            {
                _pad.Clear();
                _pad.IsVisible = true;
                _image.IsVisible = false;
            }
            else
            {
                _pad.IsVisible = false;
                _image.Source = ImageSource.FromStream(() => new MemoryStream(_value));
                _image.IsVisible = true;
            }
            UpdateStatus();
        }
        
    }
}