CssxToCss.cs

using System;
using System.IO;
using System.Text;
using System.Threading.Tasks;
using SkiaSharp;
using Waher.Content;
using Waher.Content.Html.Css;
using Waher.IoTGateway.ScriptExtensions.Constants;
using Waher.IoTGateway.Setup;
using Waher.Runtime.Inventory;
using Waher.Script;
 
namespace Waher.IoTGateway.Cssx
{
    public class CssxToCss : IContentConverter
    {
        public CssxToCss()
        {
        }
 
        public string[] FromContentTypes => new string[] { "text/x-cssx" };
 
        public string[] ToContentTypes => new string[] { CssCodec.ContentType };
 
        public Grade ConversionGrade => Grade.Perfect;
 
        public async Task<bool> ConvertAsync(ConversionState State)
        {
            string Cssx;
 
            using (StreamReader rd = new StreamReader(State.From))
            {
                Cssx = await rd.ReadToEndAsync();
            }
 
            string Css = await Convert(Cssx, State.Session, State.FromFileName);
 
            byte[] Data = Utf8WithBOM.GetBytes(Css);
            await State.To.WriteAsync(Data, 0, Data.Length);
            State.ToContentType += "; charset=utf-8";
 
            return false;
        }
 
        public static Task<string> Convert(string Cssx, Variables Session, string FileName)
        {
            return Convert(Cssx, Session, FileName, true);
        }
 
        internal static async Task<string> Convert(string Cssx, Variables Session, string FileName, bool LockSession)
        {
            bool Pushed = false;
 
            if (Session is null)
                throw new ArgumentNullException("No session defined.", nameof(Session));
 
            if (LockSession)
                await Session.LockAsync();
            try
            {
                if (LockSession)
                {
                    Session.Push();
                    Pushed = true;
                }
 
                ThemeDefinition Def = Theme.GetCurrentTheme(Session);
                Def?.Prepare(Session);
 
                StringBuilder Result = new StringBuilder();
                Expression Exp;
                int i = 0;
                int c = Cssx.Length;
                int j, k;
                string Script;
                object Value;
 
                while (i < c)
                {
                    j = Cssx.IndexOf('¤', i);
                    if (j < 0)
                        break;
 
                    if (j > i)
                        Result.Append(Cssx.Substring(i, j - i));
 
                    k = Cssx.IndexOf('¤', j + 1);
                    if (k < 0)
                        break;
 
                    Script = Cssx.Substring(j + 1, k - j - 1);
                    Exp = new Expression(Script, FileName);
                    Value = await Exp.EvaluateAsync(Session);
 
                    if (Value is SKColor Color)
                    {
                        if (Color.Alpha == 255)
                        {
                            Result.Append('#');
                            Result.Append(Color.Red.ToString("X2"));
                            Result.Append(Color.Green.ToString("X2"));
                            Result.Append(Color.Blue.ToString("X2"));
                        }
                        else
                        {
                            Result.Append("rgba(");
                            Result.Append(Color.Red.ToString());
                            Result.Append(',');
                            Result.Append(Color.Green.ToString());
                            Result.Append(',');
                            Result.Append(Color.Blue.ToString());
                            Result.Append(',');
                            Result.Append(Expression.ToString(Color.Alpha / 255.0));
                            Result.Append(')');
                        }
                    }
                    else if (Value is string s)
                        Result.Append(s);
                    else
                        Result.Append(Expression.ToString(Value));
 
                    i = k + 1;
                }
 
                if (i < c)
                    Result.Append(Cssx.Substring(i));
 
                return Result.ToString();
            }
            finally
            {
                if (LockSession)
                {
                    if (Pushed)
                        Session.Pop();
 
                    Session.Release();
                }
            }
        }
 
        internal static readonly System.Text.Encoding Utf8WithBOM = new UTF8Encoding(true);
 
    }
}