CursorManager.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 System.Collections.Generic;
using System.Linq;

namespace Deveel.Data.Sql.Cursors {
    public sealed class CursorManager : IObjectManager {
        private List<Cursor> cursors;

        public CursorManager(ICursorScope scope) {
            if (scope == null)
                throw new ArgumentNullException("scope");

            Scope = scope;
            cursors = new List<Cursor>();
        }

        ~CursorManager() {
            Dispose(false);
        }

        public ICursorScope Scope { get; private set; }

        public void Dispose() {
            Dispose(true);
            GC.SuppressFinalize(this);
        }

        private void Dispose(bool disposing) {
            if (disposing) {
                if (cursors != null) {
                    foreach (var cursor in cursors) {
                        cursor.Dispose();
                    }

                    cursors.Clear();
                }
            }

            cursors = null;
            Scope = null;
        }

        DbObjectType IObjectManager.ObjectType {
            get { return DbObjectType.Cursor; }
        }

        void IObjectManager.Create() {
        }

        void IObjectManager.CreateObject(IObjectInfo objInfo) {
            DeclareCursor((CursorInfo)objInfo);
        }

        bool IObjectManager.RealObjectExists(ObjectName objName) {
            return CursorExists(objName.Name);
        }

        bool IObjectManager.ObjectExists(ObjectName objName) {
            return CursorExists(objName.Name);
        }

        IDbObject IObjectManager.GetObject(ObjectName objName) {
            return GetCursor(objName.Name);
        }

        bool IObjectManager.AlterObject(IObjectInfo objInfo) {
            throw new NotSupportedException("Cannot alter a cursor");
        }

        bool IObjectManager.DropObject(ObjectName objName) {
            return DropCursor(objName.Name);
        }

        public ObjectName ResolveName(ObjectName objName, bool ignoreCase) {
            var ojectName = objName.Name;
            var comparison = ignoreCase ? StringComparison.OrdinalIgnoreCase : StringComparison.Ordinal;
            foreach (var cursor in cursors) {
                var cursorName = cursor.CursorInfo.CursorName;
                if (cursorName.Equals(ojectName, comparison))
                    return new ObjectName(cursorName);
            }

            return null;
        }

        public void DeclareCursor(CursorInfo cursorInfo) {
            if (cursorInfo == null)
                throw new ArgumentNullException("cursorInfo");


            lock (this) {
                var cursorName = cursorInfo.CursorName;
                if (cursors.Any(x => x.CursorInfo.CursorName.Equals(cursorName, StringComparison.OrdinalIgnoreCase)))
                    throw new ArgumentException(String.Format("Cursor '{0}' was already declared.", cursorName));

                var cursor = new Cursor(cursorInfo);
                cursors.Add(cursor);
            }
        }

        public bool CursorExists(string cursorName) {
            var ignoreCase = Scope.IgnoreCase;
            var comparison = ignoreCase ? StringComparison.OrdinalIgnoreCase : StringComparison.Ordinal;
            return cursors.Any(x => x.CursorInfo.CursorName.Equals(cursorName, comparison));
        }

        public Cursor GetCursor(string cursorName) {
            var ignoreCase = Scope.IgnoreCase;
            var comparison = ignoreCase ? StringComparison.OrdinalIgnoreCase : StringComparison.Ordinal;
            return cursors.FirstOrDefault(x => x.CursorInfo.CursorName.Equals(cursorName, comparison));
        }

        internal void DisposeCursor(Cursor cursor) {
            var name = cursor.CursorInfo.CursorName;
            for (int i = cursors.Count - 1; i >= 0; i--) {
                var cursorName = cursors[i].CursorInfo.CursorName;
                if (cursorName.Equals(name, StringComparison.OrdinalIgnoreCase))
                    cursors.RemoveAt(i);
            }
        }

        public bool DropCursor(string cursorName) {
            var ignoreCase = Scope.IgnoreCase;
            var comparison = ignoreCase ? StringComparison.OrdinalIgnoreCase : StringComparison.Ordinal;
            for (int i = cursors.Count - 1; i >= 0; i--) {
                var cursor = cursors[i];
                if (cursor.CursorInfo.CursorName.Equals(cursorName, comparison)) {
                    cursors.RemoveAt(i);
                    cursor.Dispose();
                    return true;
                }
            }

            return false;
        }
    }
}