public Expression <Action <StringBuilder, T, Y> > Generate <T, Y>(ExpressContext expressContext, ScriptBlockStatement scriptBlockStatement)
{
ParameterExpression StringBuilderParmeter = Expression.Parameter(typeof(StringBuilder));
ParameterExpression inputParameter = Expression.Parameter(typeof(T), "Model");
ParameterExpression libraryParameter = Expression.Parameter(typeof(Y), "Library");
ParameterFinder parameterFinder = new ParameterFinder();
parameterFinder.AddParameter(libraryParameter);
parameterFinder.AddParameter(inputParameter);
var blockExpression = GetStatementExpression(expressContext, StringBuilderParmeter, scriptBlockStatement, parameterFinder);
return(Expression.Lambda <Action <StringBuilder, T, Y> >(blockExpression, StringBuilderParmeter, inputParameter, libraryParameter));
}
public ExpressContext <T, L> GetExpressContext <T>(string templateText)
{
Func <string, ExpressContext <T, L> > CompileTemplate = _ =>
{
ExpressContext <T, L> expressContext = new ExpressContext <T, L>();
logger.LogInformation("Compiling {templateText} for {type}", templateText, typeof(T));
try
{
var template = Template.Parse(templateText, null, null, null);
expressContext.Messages.AddRange(template.Messages);
if (template.HasErrors)
{
logger.LogError("Scriban Parsing Failed on {templateText} for {type}", templateText, typeof(T));
expressContext.CompiledTemplate = (sb, target, library) => { };
return(expressContext);
}
else
{
logger.LogInformation("Scriban Parsing Succeded on {templateText} for {type}", templateText, typeof(T));
}
var expression = statementGenerator.Generate <T, L>(expressContext, template.Page.Body);
expressContext.CompiledTemplate = expression.Compile();
return(expressContext);
}
catch (Exception ex)
{
// effectively swallow exceptions here,
// as compilation could take a long time and we don't want to overload the server with repeated failing compiles
logger.LogError(ex, "Compilation Failed on {templateText} for {type}", templateText, typeof(T));
Action <StringBuilder, T, L> emptyAction = (sb, target, library) => { };
expressContext.CompiledTemplate = emptyAction;
return(expressContext);
}
};
string cacheKey = typeof(T) + templateText;
var compiltedTemplate = functionary.GetOrAdd(cacheKey, CompileTemplate) as ExpressContext <T, L>;
return(compiltedTemplate);
}
public Expression GetStatementExpression(ExpressContext expressContext, ParameterExpression stringBuilderParameter, ScriptStatement scriptStatement, ParameterFinder parameterFinder)
{
var appendMethodInfo = typeof(StringBuilder).GetMethod("Append", new[] { typeof(string) });
switch (scriptStatement)
{
case ScriptRawStatement scriptRawStatement:
var constant = Expression.Constant(scriptRawStatement.ToString());
var methodCall = Expression.Call(stringBuilderParameter, appendMethodInfo, constant);
return(methodCall);
case ScriptExpressionStatement scriptExpressionStatement:
var expressionBody = expressionGenerator.GetExpressionBody(scriptExpressionStatement.Expression, parameterFinder, null);
expressionBody = AddToString(expressionBody);
var scriptmethodCall = Expression.Call(stringBuilderParameter, appendMethodInfo, expressionBody);
return(scriptmethodCall);
case ScriptIfStatement scriptIfStatement:
var predicateExpression = expressionGenerator.GetExpressionBody(scriptIfStatement.Condition, parameterFinder, null);
var trueStatementBlock = GetStatementExpression(expressContext, stringBuilderParameter, scriptIfStatement.Then, parameterFinder);
if (scriptIfStatement.Else != null)
{
var elseStatment = GetStatementExpression(expressContext, stringBuilderParameter, scriptIfStatement.Else, parameterFinder);
ConditionalExpression ifThenElseExpr = Expression.IfThenElse(predicateExpression, trueStatementBlock, elseStatment);
return(ifThenElseExpr);
}
else
{
ConditionalExpression ifThenExpr = Expression.IfThen(predicateExpression, trueStatementBlock);
return(ifThenExpr);
}
case ScriptElseStatement scriptElseStatement:
var elseStatmentExpression = GetStatementExpression(expressContext, stringBuilderParameter, scriptElseStatement.Body, parameterFinder);
return(elseStatmentExpression);
case ScriptBlockStatement scriptBlockStatement:
List <Expression> statements = new List <Expression>();
foreach (var statement in scriptBlockStatement.Statements)
{
try
{
statements.Add(GetStatementExpression(expressContext, stringBuilderParameter, statement, parameterFinder));
}
catch (SpanException ex)
{
logger.LogError(ex, "Failed to build: {statement}", statement);
expressContext.Messages.Add(new LogMessage(ParserMessageType.Error, ex.Span, ex.Message));
}
catch (Exception ex)
{
logger.LogError(ex, "Statement Failed to build: {statement}", statement);
expressContext.Messages.Add(new LogMessage(ParserMessageType.Error, scriptBlockStatement.Span, $"Statement Failed to build: {statement?.GetType()}"));
}
}
var blockExpression = Expression.Block(statements);
return(blockExpression);
case ScriptForStatement scriptForStatement:
// foreach(item in items)
var itemsExpression = expressionGenerator.GetExpressionBody(scriptForStatement.Iterator, parameterFinder, null);
var itemVariableName = (scriptForStatement.Variable as ScriptVariableGlobal).Name;
var itemType = itemsExpression.Type.GenericTypeArguments[0];
ParameterExpression itemVariable = Expression.Parameter(itemType, itemVariableName);
using (var scopedParameterFinder = parameterFinder.CreateScope())
{
scopedParameterFinder.AddLocalVariable(itemVariable);
var body = GetStatementExpression(expressContext, stringBuilderParameter, scriptForStatement.Body, scopedParameterFinder);
var foreachExpression = ExpressionHelpers.ForEach(itemsExpression, itemVariable, body);
return(foreachExpression);
}
default:
throw new NotImplementedException("Unknown ScriptStatement");
}
}
public string Render <T>(ExpressContext <T, L> expressContext, T value)
{
return(MapFunction(expressContext.CompiledTemplate, standardLibrary)
(value));
}
