CssxToCss.cs

using SkiaSharp;
using System;
using System.IO;
using System.Text;
using System.Threading.Tasks;
using Waher.Content;
using Waher.Content.Html.Css;
using Waher.IoTGateway.ScriptExtensions.Constants;
using Waher.IoTGateway.Setup;
using Waher.Networking.HTTP;
using Waher.Runtime.Inventory;
using Waher.Runtime.IO;
using Waher.Script;
 
namespace Waher.IoTGateway.Cssx
{
    public class CssxToCss : IContentConverter
    {
        public CssxToCss()
        {
        }
 
        public string[] FromContentTypes => new string[] { CssxDecoder.DefaultContentType };
 
        public string[] ToContentTypes => new string[] { CssCodec.DefaultContentType };
 
        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, State.FromFileName);
            if (State.HasError)
                return false;
 
            byte[] Data = Strings.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, ConversionState State, string FileName)
        {
            return Convert(Cssx, State, State.Session, FileName, true);
        }
 
        public static Task<string> Convert(string Cssx, Variables Session, string FileName)
        {
            return Convert(Cssx, null, Session, FileName, true);
        }
 
        internal static Task<string> Convert(string Cssx, ConversionState State, Variables Session, string FileName, bool LockSession)
        {
            return Convert(Cssx, "¤", "¤", State, Session, FileName, LockSession);
        }
 
        internal static async Task<string> Convert(string WebContent, string StartDelimiter, string StopDelimiter, ConversionState State, 
            Variables Session, string FileName, bool PreserveVariables)
        {
            if (Session is null)
            {
                Exception ex = new ArgumentNullException("No session defined.", nameof(Session));
 
                if (State is null)
                    throw ex;
                else
                {
                    State.Error = ex;
                    return null;
                }
            }
 
            if (PreserveVariables)
                Session.Push();
            try
            {
                ThemeDefinition Def = Theme.GetCurrentTheme(Session as SessionVariables);
                Def?.Prepare(Session);
 
                StringBuilder Result = new StringBuilder();
                Expression Exp;
                int i = 0;
                int c = WebContent.Length;
                int j, k;
                string Script;
                object Value;
 
                while (i < c)
                {
                    j = WebContent.IndexOf(StartDelimiter, i);
                    if (j < 0)
                        break;
 
                    if (j > i)
                        Result.Append(WebContent[i..j]);
 
                    k = WebContent.IndexOf(StopDelimiter, j + 1);
                    if (k < 0)
                        break;
 
                    Script = WebContent.Substring(j + 1, k - j - 1);
                    Exp = new Expression(Script, FileName);
                    Value = await Exp.EvaluateAsync(Session);
 
                    if (Value is SKColor Color)
                        ColorToCss(Result, Color);
                    else if (Value is string s)
                        Result.Append(s);
                    else
                        Result.Append(Expression.ToExpressionString(Value));
 
                    i = k + 1;
                }
 
                if (i < c)
                    Result.Append(WebContent[i..]);
 
                return Result.ToString();
            }
            finally
            {
                if (PreserveVariables)
                    Session.Pop();
            }
        }
 
        public static string ColorToCss(SKColor Color)
        {
            StringBuilder sb = new StringBuilder();
            ColorToCss(sb, Color);
            return sb.ToString();
        }
 
        public static void ColorToCss(StringBuilder Result, 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(')');
            }
        }
 
    }
}