ColumnChecker.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;

using Deveel.Data;
using Deveel.Data.Sql.Expressions;
using Deveel.Data.Sql.Query;
using Deveel.Data.Sql.Tables;

namespace Deveel.Data.Sql.Statements {
    abstract class ColumnChecker {
        public string StripTableName(string tableDomain, string column) {
            var index = column.IndexOf('.');

            if (index != -1) {
                var columnPrefix = column.Substring(0, index);
                if (!columnPrefix.Equals(tableDomain))
                    throw new InvalidOperationException(String.Format("Column '{0}' is not within the expected table'{1}'", 
                        column, tableDomain));

                column = column.Substring(index + 1);
            }

            return column;
        }

        public IEnumerable<string> StripColumnList(string tableDomain, IEnumerable<string> columnList) {
            return columnList.Select(x => StripTableName(tableDomain, x));
        }

        public abstract string ResolveColumnName(string columnName);

        public SqlExpression CheckExpression(SqlExpression expression) {
            var expChecker = new ExpressionChecker(this);
            return expChecker.Visit(expression);
        }

        public IEnumerable<string> CheckColumns(IEnumerable<string> columnNames) {
            var result = new List<string>();

            foreach (var columnName in columnNames) {
                var resolved = ResolveColumnName(columnName);
                if (resolved == null)
                    throw new InvalidOperationException(String.Format("Column '{0}' not found in table.", columnName));

                result.Add(resolved);
            }

            return result.ToArray();
        }

        public static ColumnChecker Default(IRequest context, ObjectName tableName) {
            var table = context.Query.GetTable(tableName);
            if (table == null)
                throw new InvalidOperationException(String.Format("Table '{0}' not found in the context.", tableName));

            var tableInfo = table.TableInfo;
            var ignoreCase = context.Query.IgnoreIdentifiersCase();

            return new DefaultChecker(tableInfo, ignoreCase);
        }

        #region DefaultChecker

        class DefaultChecker : ColumnChecker {
            private readonly TableInfo tableInfo;
            private readonly bool ignoreCase;

            public DefaultChecker(TableInfo tableInfo, bool ignoreCase) {
                this.tableInfo = tableInfo;
                this.ignoreCase = ignoreCase;
            }

            public override string ResolveColumnName(string columnName) {
                var comparison = ignoreCase ? StringComparison.OrdinalIgnoreCase : StringComparison.Ordinal;
                string foundColumn = null;

                foreach (var columnInfo in tableInfo) {
                    if (foundColumn != null)
                        throw new InvalidOperationException(String.Format("Column name '{0}' caused an ambiguous match in table.", columnName));

                    if (String.Equals(columnInfo.ColumnName, columnName, comparison))
                        foundColumn = columnInfo.ColumnName;
                }

                return foundColumn;
            }
        }

        #endregion

        #region ExpressionChecker

        class ExpressionChecker : SqlExpressionVisitor {
            private readonly ColumnChecker checker;

            public ExpressionChecker(ColumnChecker checker) {
                this.checker = checker;
            }

            public override SqlExpression VisitReference(SqlReferenceExpression reference) {
                var refName = reference.ReferenceName;
                var origColumn = refName.Name;
                var resolvedColumn = checker.ResolveColumnName(origColumn);
                if (resolvedColumn == null)
                    throw new InvalidOperationException(String.Format("Column '{0} not found in table.", origColumn));

                if (!origColumn.Equals(resolvedColumn))
                    refName = new ObjectName(refName.Parent, resolvedColumn);

                return SqlExpression.Reference(refName);
            }

            public override SqlExpression VisitQuery(SqlQueryExpression query) {
                throw new InvalidOperationException("Sub-queries are not permitted in a CHECK expression.");
            }
        }

        #endregion
    }
}