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

namespace SQLLinter.Infrastructure.Rules;

public class UserFunctionJoinRule : BaseRuleVisitor
{
    public override string Text => "Запрещено использование пользовательских функций внутри запросов: {0}";

    private bool _inQueryContext;

    // Входим в контекст запроса
    public override void Visit(QuerySpecification node)
    {
        _inQueryContext = true;

        // Проверяем FROM
        if (node.FromClause != null)
        {
            var tables = node.FromClause.TableReferences;

            // Разрешаем ровно одну табличную функцию
            if (!(tables.Count == 1 && tables[0] is SchemaObjectFunctionTableReference ft && IsUserFunction(ft.SchemaObject?.BaseIdentifier?.Value)))
            {
                foreach (var tr in tables)
                    CheckTableReference(tr);
            }
        }

        base.Visit(node);
        _inQueryContext = false;
    }

    // Скалярные функции
    public override void Visit(FunctionCall node)
    {
        if (_inQueryContext && IsUserFunction(node.FunctionName.Value))
        {
            AddViolationFunction(node);
        }

        base.Visit(node);
    }

    // Табличные функции
    public override void Visit(SchemaObjectFunctionTableReference node)
    {
        // Проверка делается в QuerySpecification - здесь ничего не делаем
        base.Visit(node);
    }

    // Подзапросы
    public override void Visit(ScalarSubquery node)
    {
        node.QueryExpression.Accept(this);
        base.Visit(node);
    }

    public override void Visit(QueryDerivedTable node)
    {
        node.QueryExpression.Accept(this);
        base.Visit(node);
    }

    public override void Visit(QualifiedJoin node)
    {
        if (node.SearchCondition != null)
            node.SearchCondition.Accept(this);

        if (node.FirstTableReference != null)
            CheckTableReference(node.FirstTableReference);
        if (node.SecondTableReference != null)
            CheckTableReference(node.SecondTableReference);

        base.Visit(node);
    }

    public override void Visit(UnqualifiedJoin node)
    {
        // Проверяем APPLY
        if (node.UnqualifiedJoinType == UnqualifiedJoinType.CrossApply ||
            node.UnqualifiedJoinType == UnqualifiedJoinType.OuterApply)
        {
            if (node.SecondTableReference is SchemaObjectFunctionTableReference ft &&
                IsUserFunction(ft.SchemaObject?.BaseIdentifier?.Value))
            {
                AddViolation(ft, SQLHelpers.ObjectGetFullName(ft.SchemaObject));
            }
        }

        // Обходим обе стороны
        if (node.FirstTableReference != null)
            CheckTableReference(node.FirstTableReference);
        if (node.SecondTableReference != null)
            CheckTableReference(node.SecondTableReference);

        base.Visit(node);
    }




    // ------------------------
    // Вспомогательные методы
    // ------------------------

    private void AddViolationFunction(FunctionCall func)
    {
        string ident = "";
        if (func.CallTarget is MultiPartIdentifierCallTarget callTarget)
        {
            ident = SQLHelpers.ObjectGetFullName(callTarget.MultiPartIdentifier.Identifiers);
            if (!string.IsNullOrWhiteSpace(ident)) ident += ".";
        }

        ident += "[" + func.FunctionName.Value + "]";
        AddViolation(func, ident);
    }

    private void CheckTableReference(TableReference tr)
    {
        switch (tr)
        {
            case SchemaObjectFunctionTableReference ft:
                if (IsUserFunction(ft.SchemaObject?.BaseIdentifier?.Value))
                    AddViolation(ft, SQLHelpers.ObjectGetFullName(ft.SchemaObject));
                break;

            case QueryDerivedTable qdt:
                qdt.QueryExpression.Accept(this);
                break;

            case QualifiedJoin qj:
                if (qj.FirstTableReference != null)
                    CheckTableReference(qj.FirstTableReference);
                if (qj.SecondTableReference != null)
                    CheckTableReference(qj.SecondTableReference);
                if (qj.SearchCondition != null)
                    qj.SearchCondition.Accept(this);
                break;

            case UnqualifiedJoin aj:
                if (aj.FirstTableReference != null)
                    CheckTableReference(aj.FirstTableReference);
                if (aj.SecondTableReference != null)
                    CheckTableReference(aj.SecondTableReference);
                break;
        }
    }

    private bool IsUserFunction(string? functionName)
    {
        return !string.IsNullOrEmpty(functionName) &&
               !Constants.SystemFunctions.Contains(functionName);
    }
}