LINQ for paging missing episodes

Marr.Data/QGen/SqlitePagingQueryDecorator.cs

@@ -0,0 +1,90 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using Marr.Data.Mapping;
+using Marr.Data.QGen.Dialects;
+
+namespace Marr.Data.QGen
+{
+    /// <summary>
+    /// Decorates the SelectQuery by wrapping it in a paging query.
+    /// </summary>
+    public class SqlitePagingQueryDecorator : IQuery
+    {
+        private SelectQuery _innerQuery;
+        private int _skip;
+        private int _take;
+
+        public SqlitePagingQueryDecorator(SelectQuery innerQuery, int skip, int take)
+        {
+            if (string.IsNullOrEmpty(innerQuery.OrderBy.ToString()))
+            {
+                throw new DataMappingException("A paged query must specify an order by clause.");
+            }
+
+            _innerQuery = innerQuery;
+            _skip = skip;
+            _take = take;
+        }
+
+        public string Generate()
+        {
+            StringBuilder sql = new StringBuilder();
+
+            _innerQuery.BuildSelectClause(sql);
+            _innerQuery.BuildFromClause(sql);
+            _innerQuery.BuildJoinClauses(sql);
+            _innerQuery.BuildWhereClause(sql);
+            _innerQuery.BuildOrderClause(sql);
+            sql.AppendLine(String.Format(" LIMIT {0},{1}", _skip, _take));
+
+            return sql.ToString();
+        }
+
+        public void BuildSelectClause(StringBuilder sql)
+        {
+            List<string> appended = new List<string>();
+
+            sql.Append("SELECT ");
+
+            int startIndex = sql.Length;
+
+            // COLUMNS
+            foreach (Table join in _innerQuery.Tables)
+            {
+                for (int i = 0; i < join.Columns.Count; i++)
+                {
+                    var c = join.Columns[i];
+
+                    if (sql.Length > startIndex && sql[sql.Length - 1] != ',')
+                        sql.Append(",");
+
+                    if (join is View)
+                    {
+                        string token = _innerQuery.Dialect.CreateToken(string.Concat(join.Alias, ".", _innerQuery.NameOrAltName(c.ColumnInfo)));
+                        if (appended.Contains(token))
+                            continue;
+
+                        sql.Append(token);
+                        appended.Add(token);
+                    }
+                    else
+                    {
+                        string token = string.Concat(join.Alias, ".", c.ColumnInfo.Name);
+                        if (appended.Contains(token))
+                            continue;
+
+                        sql.Append(_innerQuery.Dialect.CreateToken(token));
+
+                        if (_innerQuery.UseAltName && c.ColumnInfo.AltName != null && c.ColumnInfo.AltName != c.ColumnInfo.Name)
+                        {
+                            string altName = c.ColumnInfo.AltName;
+                            sql.AppendFormat(" AS {0}", altName);
+                        }
+                    }
+                }
+            }
+        }
+    }
+}