public static XDoc WebLink(
            [DekiScriptParam("link uri")] string uri,
            [DekiScriptParam("link contents; can be text, an image, or another document (default: link uri)", true)] object text,
            [DekiScriptParam("link hover title (default: none)", true)] string title,
            [DekiScriptParam("link target (default: none)", true)] string target
            )
        {
            // check __settings.nofollow if links should be followed or not
            bool         nofollow = true;
            DreamContext context  = DreamContext.CurrentOrNull;

            if (context != null)
            {
                DekiScriptEnv env = context.GetState <DekiScriptEnv>();
                if (env != null)
                {
                    // TODO (steveb): this should be stored in the runtime instead!
                    DekiScriptBool setting = env.Vars.GetAt(new[] { DekiScriptEnv.SETTINGS, "nofollow" }) as DekiScriptBool;
                    if (setting != null)
                    {
                        nofollow = setting.AsBool() ?? true;
                    }
                }
            }

            XDoc result = DekiScriptLiteral.FromNativeValue(text ?? uri).AsEmbeddableXml(true);
            XDoc body   = result["body[not(@target)]"];

            result.Start("body").Start("a");
            if (nofollow)
            {
                result.Attr("rel", "custom nofollow");
            }
            else
            {
                result.Attr("rel", "custom");
            }
            result.Attr("href", WebCheckUri(uri)).Attr("title", title).Attr("target", target).AddNodes(body).End().End();
            body.Remove();
            return(result);
        }
        public DekiScriptLiteral Visit(DekiScriptUnary expr, DekiScriptEnv env)
        {
            switch (expr.OpCode)
            {
            case DekiScriptUnary.Op.Negate:
                return(DekiScriptNumber.New(-expr.Value.VisitWith(this, env).AsNumber()));

            case DekiScriptUnary.Op.LogicalNot:
                return(DekiScriptBool.New(expr.Value.VisitWith(this, env).IsNilFalseZero));

            case DekiScriptUnary.Op.TypeOf:
                return(DekiScriptString.New(expr.Value.VisitWith(this, env).ScriptTypeName));

            case DekiScriptUnary.Op.Length: {
                DekiScriptLiteral value = expr.Value.VisitWith(this, env);
                switch (value.ScriptType)
                {
                case DekiScriptType.NIL:
                    return(DekiScriptNumber.New(0));

                case DekiScriptType.LIST:
                    return(DekiScriptNumber.New(((DekiScriptList)value).Value.Count));

                case DekiScriptType.STR:
                    return(DekiScriptNumber.New(((DekiScriptString)value).Value.Length));

                case DekiScriptType.MAP:
                    return(DekiScriptNumber.New(((DekiScriptMap)value).Value.Count));

                case DekiScriptType.XML:
                    return(DekiScriptNumber.New(((DekiScriptXml)value).Value.ListLength));

                default:
                    return(DekiScriptNil.Value);
                }
            }
            }
            throw new InvalidOperationException("invalid op code:" + expr.OpCode);
        }
 public DekiScriptExpression Visit(DekiScriptBool expr, DekiScriptExpressionEvaluationState state)
 {
     return(expr);
 }
 public DekiScriptOutputBuffer.Range Visit(DekiScriptBool expr, DekiScriptExpressionEvaluationState state)
 {
     return(state.Push(expr));
 }
 public DekiScriptExpression Visit(DekiScriptBool expr, DekiScriptOptimizerState state)
 {
     return(expr);
 }
        public DekiScriptLiteral Visit(DekiScriptBinary expr, DekiScriptEnv env)
        {
            DekiScriptExpression Left  = expr.Left;
            DekiScriptExpression Right = expr.Right;

            switch (expr.OpCode)
            {
            case DekiScriptBinary.Op.LeftValue:
                return(Left.VisitWith(this, env));

            case DekiScriptBinary.Op.IdentityEqual: {
                DekiScriptLiteral left  = Left.VisitWith(this, env);
                DekiScriptLiteral right = Right.VisitWith(this, env);
                return(DekiScriptBinary.IdentityEqual(left, right));
            }

            case DekiScriptBinary.Op.IdentityNotEqual: {
                DekiScriptLiteral left  = Left.VisitWith(this, env);
                DekiScriptLiteral right = Right.VisitWith(this, env);
                return(DekiScriptBinary.IdentityNotEqual(left, right));
            }

            case DekiScriptBinary.Op.IsType: {
                DekiScriptLiteral left = Left.VisitWith(this, env);
                string            type = ((DekiScriptString)Right).Value;
                return(DekiScriptBool.New(StringUtil.EqualsInvariantIgnoreCase(type, "any") || StringUtil.EqualsInvariantIgnoreCase(left.ScriptTypeName, type)));
            }

            case DekiScriptBinary.Op.Equal: {
                DekiScriptLiteral left  = Left.VisitWith(this, env);
                DekiScriptLiteral right = Right.VisitWith(this, env);
                return(DekiScriptBinary.Equal(left, right));
            }

            case DekiScriptBinary.Op.NotEqual: {
                DekiScriptLiteral left  = Left.VisitWith(this, env);
                DekiScriptLiteral right = Right.VisitWith(this, env);
                return(DekiScriptBinary.NotEqual(left, right));
            }

            case DekiScriptBinary.Op.GreaterOrEqual: {
                DekiScriptLiteral left  = Left.VisitWith(this, env);
                DekiScriptLiteral right = Right.VisitWith(this, env);
                if (DekiScriptLiteral.CoerceValuesToSameType(ref left, ref right))
                {
                    switch (left.ScriptType)
                    {
                    case DekiScriptType.BOOL:
                    case DekiScriptType.NUM:
                        return(DekiScriptBool.New(left.AsNumber() >= right.AsNumber()));

                    case DekiScriptType.STR:
                        return(DekiScriptBool.New(StringUtil.CompareInvariant(left.AsString(), right.AsString()) >= 0));

                    default:
                        return(DekiScriptNil.Value);
                    }
                }
                else
                {
                    return(DekiScriptNil.Value);
                }
            }

            case DekiScriptBinary.Op.GreaterThan: {
                DekiScriptLiteral left  = Left.VisitWith(this, env);
                DekiScriptLiteral right = Right.VisitWith(this, env);
                if (DekiScriptLiteral.CoerceValuesToSameType(ref left, ref right))
                {
                    switch (left.ScriptType)
                    {
                    case DekiScriptType.BOOL:
                    case DekiScriptType.NUM:
                        return(DekiScriptBool.New(left.AsNumber() > right.AsNumber()));

                    case DekiScriptType.STR:
                        return(DekiScriptBool.New(StringUtil.CompareInvariant(left.AsString(), right.AsString()) > 0));

                    default:
                        return(DekiScriptNil.Value);
                    }
                }
                else
                {
                    return(DekiScriptNil.Value);
                }
            }

            case DekiScriptBinary.Op.LessOrEqual: {
                DekiScriptLiteral left  = Left.VisitWith(this, env);
                DekiScriptLiteral right = Right.VisitWith(this, env);
                if (DekiScriptLiteral.CoerceValuesToSameType(ref left, ref right))
                {
                    switch (left.ScriptType)
                    {
                    case DekiScriptType.BOOL:
                    case DekiScriptType.NUM:
                        return(DekiScriptBool.New(left.AsNumber() <= right.AsNumber()));

                    case DekiScriptType.STR:
                        return(DekiScriptBool.New(StringUtil.CompareInvariant(left.AsString(), right.AsString()) <= 0));

                    default:
                        return(DekiScriptNil.Value);
                    }
                }
                else
                {
                    return(DekiScriptNil.Value);
                }
            }

            case DekiScriptBinary.Op.LessThan: {
                DekiScriptLiteral left  = Left.VisitWith(this, env);
                DekiScriptLiteral right = Right.VisitWith(this, env);
                if (DekiScriptLiteral.CoerceValuesToSameType(ref left, ref right))
                {
                    switch (left.ScriptType)
                    {
                    case DekiScriptType.BOOL:
                    case DekiScriptType.NUM:
                        return(DekiScriptBool.New(left.AsNumber() < right.AsNumber()));

                    case DekiScriptType.STR:
                        return(DekiScriptBool.New(StringUtil.CompareInvariant(left.AsString(), right.AsString()) < 0));

                    default:
                        return(DekiScriptNil.Value);
                    }
                }
                else
                {
                    return(DekiScriptNil.Value);
                }
            }

            case DekiScriptBinary.Op.LogicalAnd: {
                DekiScriptLiteral result = Left.VisitWith(this, env);
                if (!result.IsNilFalseZero)
                {
                    result = Right.VisitWith(this, env);
                }
                return(result);
            }

            case DekiScriptBinary.Op.LogicalOr: {
                DekiScriptLiteral result = Left.VisitWith(this, env);
                if (result.IsNilFalseZero)
                {
                    result = Right.VisitWith(this, env);
                }
                return(result);
            }

            case DekiScriptBinary.Op.Addition:
                return(DekiScriptNumber.New(Left.VisitWith(this, env).AsNumber() + Right.VisitWith(this, env).AsNumber()));

            case DekiScriptBinary.Op.Division:
                return(DekiScriptNumber.New(Left.VisitWith(this, env).AsNumber() / Right.VisitWith(this, env).AsNumber()));

            case DekiScriptBinary.Op.Modulo: {
                DekiScriptLiteral left  = Left.VisitWith(this, env);
                DekiScriptLiteral right = Right.VisitWith(this, env);
                if ((left is DekiScriptString) && ((right is DekiScriptMap) || (right is DekiScriptList)))
                {
                    // NOTE (steveb): string.format shorthand notation: "abc = $abc" % { abc: 123 } -OR- "0 = $0" % [ 123 ]
                    return(DekiScriptLiteral.FromNativeValue(DekiScriptLibrary.StringFormat(((DekiScriptString)left).Value, right.NativeValue)));
                }
                else
                {
                    return(DekiScriptNumber.New(left.AsNumber() % right.AsNumber()));
                }
            }

            case DekiScriptBinary.Op.Multiplication:
                return(DekiScriptNumber.New(Left.VisitWith(this, env).AsNumber() * Right.VisitWith(this, env).AsNumber()));

            case DekiScriptBinary.Op.Subtraction:
                return(DekiScriptNumber.New(Left.VisitWith(this, env).AsNumber() - Right.VisitWith(this, env).AsNumber()));

            case DekiScriptBinary.Op.NullCoalesce: {
                DekiScriptLiteral result = Left.VisitWith(this, env);
                if (result.IsNil)
                {
                    result = Right.VisitWith(this, env);
                }
                return(result);
            }

            case DekiScriptBinary.Op.Concat: {
                DekiScriptLiteral left  = Left.VisitWith(this, env);
                DekiScriptLiteral right = Right.VisitWith(this, env);
                if (left is DekiScriptNil)
                {
                    return(right);
                }
                else if (right is DekiScriptNil)
                {
                    return(left);
                }
                else if ((left is DekiScriptMap) && (right is DekiScriptMap))
                {
                    // left and right expressions are maps, merge them
                    DekiScriptMap result = new DekiScriptMap();
                    result.AddRange((DekiScriptMap)left);
                    result.AddRange((DekiScriptMap)right);
                    return(result);
                }
                else if ((left is DekiScriptList) && (right is DekiScriptList))
                {
                    // left and right expressions are lists, concatenate them
                    DekiScriptList result = new DekiScriptList();
                    result.AddRange((DekiScriptList)left);
                    result.AddRange((DekiScriptList)right);
                    return(result);
                }
                else
                {
                    // treat left and right expressions as strings
                    string leftText  = left.AsString();
                    string rightText = right.AsString();
                    if ((leftText != null) && (rightText != null))
                    {
                        return(DekiScriptString.New(leftText + rightText));
                    }
                    else if (leftText != null)
                    {
                        return(DekiScriptString.New(leftText));
                    }
                    else if (rightText != null)
                    {
                        return(DekiScriptString.New(rightText));
                    }
                    else
                    {
                        return(DekiScriptNil.Value);
                    }
                }
            }

            case DekiScriptBinary.Op.UriAppend: {
                // TODO (steveb): we should throw an exception when the LHS is not a valid string or uri

                XUri   left   = XUri.TryParse(Left.VisitWith(this, env).AsString());
                string result = null;
                if (left != null)
                {
                    DekiScriptLiteral right = Right.VisitWith(this, env);
                    if (right is DekiScriptString)
                    {
                        result = DekiScriptLibrary.UriBuild(left, right.AsString(), null);
                    }
                    else if (right is DekiScriptMap)
                    {
                        result = DekiScriptLibrary.UriBuild(left, null, (Hashtable)right.NativeValue);
                    }
                    else
                    {
                        result = left.ToString();
                    }
                }
                return(DekiScriptLiteral.FromNativeValue(result));
            }

            case DekiScriptBinary.Op.InCollection: {
                DekiScriptLiteral left  = Left.VisitWith(this, env);
                DekiScriptLiteral right = Right.VisitWith(this, env);
                if (right is DekiScriptList)
                {
                    foreach (DekiScriptLiteral item in ((DekiScriptList)right).Value)
                    {
                        if (!DekiScriptBinary.Equal(left, item).IsNilFalseZero)
                        {
                            return(DekiScriptBool.True);
                        }
                    }
                    return(DekiScriptBool.False);
                }
                else if (right is DekiScriptMap)
                {
                    foreach (DekiScriptLiteral item in ((DekiScriptMap)right).Value.Values)
                    {
                        if (!DekiScriptBinary.Equal(left, item).IsNilFalseZero)
                        {
                            return(DekiScriptBool.True);
                        }
                    }
                    return(DekiScriptBool.False);
                }
                else
                {
                    return(DekiScriptBool.False);
                }
            }
            }
            throw new InvalidOperationException("invalid op code:" + expr.OpCode);
        }
 public DekiScriptLiteral Visit(DekiScriptBool expr, DekiScriptEnv env)
 {
     return(expr);
 }