SelectFragment.cs

using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using NHibernate.Util;

namespace NHibernate.SqlCommand
{
	/// <summary>
	/// Represents part of an SQL <c>SELECT</c> clause
	/// </summary>
	public class SelectFragment
	{
		private string suffix;
		private readonly List<string> columns = new List<string>();
		private readonly List<string> columnAliases = new List<string>();
		private Dialect.Dialect dialect;
		private string[] usedAliases;
		private string extraSelectList;
		private string[] _extraAliases;
		private bool _useAliasesAsColumns;
		private string _renderedText; // 6.0 TODO: Remove

		public SelectFragment(Dialect.Dialect d)
		{
			this.dialect = d;
		}

		internal List<string> Columns => columns;

		// 6.0 TODO: Remove
		internal SelectFragment(Dialect.Dialect d, string renderedText, List<string> columnAliases)
		{
			dialect = d;
			_renderedText = renderedText.TrimStart(' ', ',');
			this.columnAliases = columnAliases;
		}

		public SelectFragment SetUsedAliases(string[] usedAliases)
		{
			this.usedAliases = usedAliases;
			return this;
		}

		public SelectFragment SetSuffix(string suffix)
		{
			this.suffix = suffix;
			return this;
		}

		public SelectFragment AddColumn(string columnName)
		{
			AddColumn(null, columnName);
			return this;
		}

		public SelectFragment AddColumns(string[] columnNames)
		{
			for (int i = 0; i < columnNames.Length; i++)
			{
				AddColumn(columnNames[i]);
			}
			return this;
		}

		public SelectFragment AddColumn(string tableAlias, string columnName)
		{
			return AddColumn(tableAlias, columnName, null);
		}

		public SelectFragment AddColumn(string tableAlias, string columnName, string columnAlias)
		{
			if (string.IsNullOrEmpty(tableAlias))
			{
				columns.Add(columnName);
			}
			else
			{
				columns.Add(tableAlias + StringHelper.Dot + columnName);
			}

			columnAliases.Add(columnAlias);
			return this;
		}

		public SelectFragment AddColumns(string tableAlias, string[] columnNames)
		{
			for (int i = 0; i < columnNames.Length; i++)
			{
				if (columnNames[i] != null)
					AddColumn(tableAlias, columnNames[i]);
			}
			return this;
		}

		internal SelectFragment AddColumns(IEnumerable<string> columnNames)
		{
			foreach (var columnName in columnNames)
			{
				if (columnName != null)
				{
					AddColumn(columnName);
				}
			}

			return this;
		}

		public SelectFragment AddColumns(string tableAlias, string[] columnNames, string[] columnAliases)
		{
			for (int i = 0; i < columnNames.Length; i++)
			{
				if (columnNames[i] != null)
					AddColumn(tableAlias, columnNames[i], columnAliases[i]);
			}
			return this;
		}

		public SelectFragment AddFormulas(string tableAlias, string[] formulas, string[] formulaAliases)
		{
			for (int i = 0; i < formulas.Length; i++)
			{
				if (formulas[i] != null)
					AddFormula(tableAlias, formulas[i], formulaAliases[i]);
			}

			return this;
		}

		public SelectFragment AddFormula(string tableAlias, string formula, string formulaAlias)
		{
			AddColumn(
				null,
				Template.ReplacePlaceholder(formula, tableAlias),
				formulaAlias);

			return this;
		}

		/// <summary>
		/// Equivalent to ToSqlStringFragment.
		/// </summary>
		/// <returns></returns>
		/// <remarks>
		/// In H3, it is called ToFragmentString(). It appears to be 
		/// functionally equivalent as ToSqlStringFragment() here.
		/// </remarks>
		public string ToFragmentString()
		{
			return ToSqlStringFragment();
		}

		public string ToSqlStringFragment()
		{
			// this preserves the way this existing method works now.
			return ToSqlStringFragment(true);
		}

		public string ToSqlStringFragment(bool includeLeadingComma)
		{
			if (!string.IsNullOrEmpty(_renderedText))
			{
				return includeLeadingComma ? $"{StringHelper.CommaSpace}{_renderedText}" : _renderedText;
			}

			StringBuilder buf = new StringBuilder(columns.Count * 10);
			HashSet<string> columnsUnique =
				usedAliases != null ? new HashSet<string>(usedAliases) : new HashSet<string>();

			bool found = false;
			for (int i = 0; i < columns.Count; i++)
			{
				string col = columns[i];
				string columnAlias = columnAliases[i];

				if (columnsUnique.Add(columnAlias ?? col))
				{
					if (found || includeLeadingComma)
					{
						buf.Append(StringHelper.CommaSpace);
					}

					if (_useAliasesAsColumns)
					{
						col = col.Split(StringHelper.Dot)[0] + StringHelper.Dot + columnAlias;
						buf.Append(new Alias(suffix).ToAliasString(col, dialect));
					}
					else if (columnAlias == null)
					{
						buf.Append(col);
					}
					else
					{
						buf.Append(col)
						   .Append(" as ")
						   .Append(new Alias(suffix).ToAliasString(columnAlias, dialect));
					}

					// Set the flag for the next time
					found = true;
				}
			}

			if (extraSelectList != null)
			{
				if (found || includeLeadingComma)
				{
					buf.Append(StringHelper.CommaSpace);
				}

				buf.Append(extraSelectList);
			}

			return buf.ToString();
		}

		// Since v5.4
		[Obsolete("This method has no more usage in NHibernate and will be removed in a future version.")]
		public SelectFragment SetExtraSelectList(string extraSelectList)
		{
			this.extraSelectList = extraSelectList;
			return this;
		}

		public SelectFragment SetExtraSelectList(CaseFragment caseFragment, string fragmentAlias)
		{
			extraSelectList = caseFragment.SetReturnColumnName(fragmentAlias, suffix).ToSqlStringFragment();
			_extraAliases = new[] {caseFragment.returnColumnName};
			return this;
		}

		internal IEnumerable<string> GetColumnAliases()
		{
			return columnAliases.Select((o, i) => new Alias(suffix).ToAliasString(o ?? columns[i], dialect))
			                    .Union(_extraAliases ?? Enumerable.Empty<string>());
		}

		internal SelectFragment UseAliasesAsColumns(bool value)
		{
			_useAliasesAsColumns = value;
			return this;
		}
	}
}