ContextExtensions.cs

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// 
//  Copyright 2010-2015 Deveel
// 
//    Licensed under the Apache License, Version 2.0 (the "License");
//    you may not use this file except in compliance with the License.
//    You may obtain a copy of the License at
// 
//        http://www.apache.org/licenses/LICENSE-2.0
// 
//    Unless required by applicable law or agreed to in writing, software
//    distributed under the License is distributed on an "AS IS" BASIS,
//    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
//    See the License for the specific language governing permissions and
//    limitations under the License.
//

using System;

using Deveel.Data.Services;
using Deveel.Data.Sql.Expressions;

namespace Deveel.Data.Sql.Cursors {
    public static class ContextExtensions {
        public static bool DeclareCursor(this IContext context, CursorInfo cursorInfo) {
            if (context.CursorExists(cursorInfo.CursorName))
                throw new InvalidOperationException(String.Format("A cursor named '{0}' was already defined in the context.",
                    cursorInfo.CursorName));

            var currentContext = context;
            while (currentContext != null) {
                if (currentContext is ICursorScope) {
                    var scope = (ICursorScope)currentContext;
                    scope.DeclareCursor(cursorInfo);
                    return true;
                }

                currentContext = currentContext.Parent;
            }

            return false;
        }

        public static void DeclareCursor(this IContext context, string cursorName, SqlQueryExpression query) {
            DeclareCursor(context, cursorName, (CursorFlags)0, query);
        }

        public static void DeclareCursor(this IContext context, string cursorName, CursorFlags flags, SqlQueryExpression query) {
            context.DeclareCursor(new CursorInfo(cursorName, flags, query));
        }

        public static void DeclareInsensitiveCursor(this IContext context, string cursorName, SqlQueryExpression query) {
            DeclareInsensitiveCursor(context, cursorName, query, false);
        }

        public static void DeclareInsensitiveCursor(this IContext context, string cursorName, SqlQueryExpression query, bool withScroll) {
            var flags = CursorFlags.Insensitive;
            if (withScroll)
                flags |= CursorFlags.Scroll;

            context.DeclareCursor(cursorName, flags, query);
        }


        public static bool CursorExists(this IContext context, string cursorName) {
            var currentContext = context;
            while (currentContext != null) {
                if (currentContext is ICursorScope) {
                    var scope = (ICursorScope) currentContext;
                    if (scope.CursorExists(cursorName))
                        return true;
                }

                currentContext = currentContext.Parent;
            }

            return false;
        }

        public static Cursor FindCursor(this IContext context, string cursorName) {
            var currentContext = context;
            while (currentContext != null) {
                if (currentContext is ICursorScope) {
                    var scope = (ICursorScope)currentContext;
                    var cursor = scope.GetCursor(cursorName);
                    if (cursor != null)
                        return cursor;
                }

                currentContext = currentContext.Parent;
            }

            return null;
        }

        public static bool DropCursor(this IContext context, string cursorName) {
            var currentContext = context;
            while (currentContext != null) {
                if (currentContext is ICursorScope) {
                    var scope = (ICursorScope)currentContext;
                    if (scope.CursorExists(cursorName))
                        return scope.DropCursor(cursorName);
                }

                currentContext = currentContext.Parent;
            }

            return false;
        }

        public static bool CloseCursor(this IContext context, string cursorName) {
            var cursor = context.FindCursor(cursorName);
            if (cursor == null)
                return false;

            cursor.Close();
            return true;
        }

        public static bool OpenCursor(this IContext context, IRequest request, string cursorName, params  SqlExpression[] args) {
            var cursor = context.FindCursor(cursorName);
            if (cursor == null)
                return false;

            // TODO: support the evaluate in context (and not just IQueryContext)
            throw new NotImplementedException();
        }
    }
}