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

namespace SQLLinter.Infrastructure.Rules;

public class CrossDatabaseTransactionRule : BaseRuleVisitor, IRule
{

    public override string Text => "Межбазовые вставки или обновления, включенные в транзакцию, могут привести к повреждению данных.";

    public override void Visit(TSqlBatch node)
    {
        var childTransactionVisitor = new ChildTransactionVisitor();
        node.Accept(childTransactionVisitor);
        foreach (var transaction in childTransactionVisitor.TransactionLists)
        {
            var childInsertUpdateQueryVisitor = new ChildInsertUpdateQueryVisitor(transaction);
            node.Accept(childInsertUpdateQueryVisitor);
            if (childInsertUpdateQueryVisitor.DatabasesUpdated.Count > 1)
            {
                AddViolation(
                    Name,
                    Text,
                    GetLineNumber(transaction.Begin),
                    GetColumnNumber(transaction.Begin));
            }
        }
    }

    public class TrackedTransaction
    {
        public BeginTransactionStatement Begin { get; set; }

        public CommitTransactionStatement Commit { get; set; }
    }

    public class ChildTransactionVisitor : TSqlFragmentVisitor
    {
        public List<TrackedTransaction> TransactionLists { get; } = new List<TrackedTransaction>();

        public override void Visit(BeginTransactionStatement node)
        {
            TransactionLists.Add(new TrackedTransaction { Begin = node });
        }

        public override void Visit(CommitTransactionStatement node)
        {
            var firstUncomitted = TransactionLists.LastOrDefault(x => x.Commit == null);
            if (firstUncomitted != null)
            {
                firstUncomitted.Commit = node;
            }
        }
    }

    public class ChildInsertUpdateQueryVisitor : TSqlFragmentVisitor
    {
        private readonly TrackedTransaction transaction;

        private readonly ChildDatabaseNameVisitor childDatabaseNameVisitor = new ChildDatabaseNameVisitor();

        public ChildInsertUpdateQueryVisitor(TrackedTransaction transaction)
        {
            this.transaction = transaction;
        }

        public HashSet<string> DatabasesUpdated { get; } = new HashSet<string>();

        public override void Visit(InsertStatement node)
        {
            GetDatabasesUpdated(node);
        }

        public override void Visit(UpdateStatement node)
        {
            GetDatabasesUpdated(node);
        }

        private void GetDatabasesUpdated(TSqlFragment node)
        {
            if (IsWithinTransaction(node))
            {
                node.Accept(childDatabaseNameVisitor);
                DatabasesUpdated.UnionWith(childDatabaseNameVisitor.DatabasesUpdated);
            }
        }

        private bool IsWithinTransaction(TSqlFragment node)
        {
            if (node.StartLine == transaction.Begin?.StartLine &&
                node.StartColumn < transaction.Begin?.StartColumn)
            {
                return false;
            }

            if (node.StartLine == transaction.Commit?.StartLine &&
                node.StartColumn > transaction.Commit?.StartColumn)
            {
                return false;
            }

            return node.StartLine >= transaction.Begin?.StartLine && node.StartLine <= transaction.Commit?.StartLine;
        }
    }

    public class ChildDatabaseNameVisitor : TSqlFragmentVisitor
    {
        public HashSet<string> DatabasesUpdated { get; } = new HashSet<string>();

        public override void Visit(NamedTableReference node)
        {
            if (node.SchemaObject.DatabaseIdentifier != null)
            {
                DatabasesUpdated.Add(node.SchemaObject.DatabaseIdentifier.Value);
            }
        }
    }
}