using Microsoft.SqlServer.TransactSql.ScriptDom;
using SQLLinter.Common;

namespace SQLLinter.Infrastructure.Rules;

public class UpperLowerRule : BaseRuleVisitor, IRule
{

    public override string Text => "Использование функций UPPER или LOWER при выполнении сравнений в операторах SELECT не требуется при запуске базы данных в режиме без учета регистра.";

    public override void Visit(SelectStatement node)
    {
        var visitor = new ChildQueryComparisonVisitor();
        node.Accept(visitor);
        if (visitor.QueryExpressionUpperLowerFunctionFound)
        {
            AddViolation(node);
        }
    }

    public class ChildQueryComparisonVisitor : TSqlFragmentVisitor
    {
        public bool QueryExpressionUpperLowerFunctionFound { get; private set; }

        public override void Visit(QueryExpression node)
        {
            var visitor = new ChildBooleanComparisonVisitor();
            node.Accept(visitor);
            if (visitor.UpperLowerFunctionCallInComparison)
            {
                QueryExpressionUpperLowerFunctionFound = true;
            }
        }
    }

    public class ChildBooleanComparisonVisitor : TSqlFragmentVisitor
    {
        public bool UpperLowerFunctionCallInComparison { get; private set; }

        public override void Visit(BooleanComparisonExpression node)
        {
            var visitor = new ChildFunctionCallVisitor();
            node.Accept(visitor);
            if (visitor.UpperLowerFound)
            {
                UpperLowerFunctionCallInComparison = true;
            }
        }
    }

    public class ChildFunctionCallVisitor : TSqlFragmentVisitor
    {
        public bool UpperLowerFound { get; private set; }

        public override void Visit(FunctionCall node)
        {
            if (node.FunctionName.Value.Equals("UPPER", StringComparison.OrdinalIgnoreCase) ||
                node.FunctionName.Value.Equals("LOWER", StringComparison.OrdinalIgnoreCase))
            {
                UpperLowerFound = true;
            }
        }
    }
}