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

namespace NHibernate.SqlCommand
{
	/// <summary>
	/// Helper methods for SqlString.
	/// </summary>
	public static class SqlStringHelper
	{
		public static SqlString Join(SqlString separator, IEnumerable objects)
		{
			SqlStringBuilder buf = new SqlStringBuilder();
			bool first = true;

			foreach (object obj in objects)
			{
				if (!first)
				{
					buf.Add(separator);
				}

				first = false;
				buf.AddObject(obj);
			}

			return buf.ToSqlString();
		}

		internal static SqlString JoinParts(object separator, IList<object> parts)
		{
			if (parts.Count == 0)
				return SqlString.Empty;

			if (parts.Count == 1)
				return parts[0] is SqlString sqlstring
					? sqlstring
					: new SqlString(parts);

			var buf = new SqlStringBuilder();

			buf.AddObject(parts[0]);
			for (var index = 1; index < parts.Count; index++)
			{
				buf.AddObject(separator).AddObject(parts[index]);
			}

			return buf.ToSqlString();
		}

		internal static SqlString Join(string separator, IList<SqlString> strings)
		{
			if (strings.Count == 0)
				return SqlString.Empty;

			if (strings.Count == 1)
				return strings[0];

			var buf = new SqlStringBuilder();

			buf.Add(strings[0]);
			for (var index = 1; index < strings.Count; index++)
			{
				buf.Add(separator).Add(strings[index]);
			}

			return buf.ToSqlString();
		}

		public static SqlString[] Add(SqlString[] x, string sep, SqlString[] y)
		{
			SqlString[] result = new SqlString[x.Length];
			for (int i = 0; i < x.Length; i++)
			{
				result[i] = new SqlString(x[i], sep, y[i]);
			}
			return result;
		}

		/// <summary>
		/// Removes the <c>as someColumnAlias</c> clause from a <c>SqlString</c> representing a column expression.
		/// Consider using <c>CriterionUtil.GetColumn...</c> methods instead.
		/// </summary>
		/// <param name="sql">The <c>SqlString</c> representing a column expression which might be aliased.</param>
		/// <returns><paramref name="sql" /> if it was not aliased, otherwise an un-aliased <c>SqlString</c> representing the column.</returns>
		public static SqlString RemoveAsAliasesFromSql(SqlString sql)
		{
			int index = sql.LastIndexOfCaseInsensitive(" as ");
			if (index < 0) return sql;
			return sql.Substring(0, index);
		}

		public static bool IsNotEmpty(SqlString str)
		{
			return !IsEmpty(str);
		}

		public static bool IsEmpty(SqlString str)
		{
			return str == null || str.Count == 0;
		}

		internal static SqlString ParametersList(List<Parameter> parameters)
		{
			var parametersCount = parameters.Count;
			if (parametersCount == 0)
			{
				return SqlString.Empty;
			}

			if (parametersCount == 1)
			{
				return new SqlString(parameters[0]);
			}

			var builder = new SqlStringBuilder();
			builder.Add("(");

			builder.Add(parameters[0]);

			for (var index = 1; index < parametersCount; index++)
			{
				builder.Add(", ");
				builder.Add(parameters[index]);
			}

			builder.Add(")");

			return builder.ToSqlString();
		}

		internal static SqlString Repeat(SqlString placeholder, int count, string separator, bool wrapInParens)
		{
			if (count == 0)
				return SqlString.Empty;

			if (count == 1)
				return wrapInParens
					? new SqlString("(", placeholder, ")")
					: placeholder;

			var builder = new SqlStringBuilder((placeholder.Count + 1) * count + 1);

			if (wrapInParens)
			{
				builder.Add("(");
			}

			builder.Add(placeholder);

			for (int i = 1; i < count; i++)
			{
				builder.Add(separator).Add(placeholder);
			}

			if (wrapInParens)
			{
				builder.Add(")");
			}

			return builder.ToSqlString();
		}
	}
}