CreateParser.cs

using Waher.Runtime.Collections;
using Waher.Script.Model;
 
namespace Waher.Script.Persistence.SQL.Parsers
{
    public class CreateParser : IKeyWord
    {
        public CreateParser()
        {
        }
 
        public string KeyWord => "CREATE";
 
        public string[] Aliases => null;
 
        public string[] InternalKeywords => new string[] 
        { 
            "INDEX", 
            "ON" 
        };
 
        public bool TryParse(ScriptParser Parser, out ScriptNode Result)
        {
            Result = null;
 
            string s = Parser.NextToken().ToUpper();
            if (s != "INDEX")
                return false;
 
            ScriptNode Name = Parser.ParseNoWhiteSpace();
 
            s = Parser.NextToken().ToUpper();
            if (s != "ON")
                return false;
 
            if (!SelectParser.TryParseSources(Parser, out SourceDefinition Source))
                return false;
 
            s = Parser.NextToken();
            if (s != "(")
                return false;
 
            this.ParseList(Parser, out ScriptNode[] Columns, out bool[] Ascending);
 
            if (Columns.Length == 0)
                return false;
 
            if (Parser.NextToken() != ")")
                return false;
 
            Result = new CreateIndex(Name, Source, Columns, Ascending, Parser.Start, Parser.Length, Parser.Expression);
 
            return true;
        }
 
        internal void ParseList(ScriptParser Parser, out ScriptNode[] Columns, out bool[] Ascending)
        {
            ChunkedList<ScriptNode> ColumnList = new ChunkedList<ScriptNode>();
            ChunkedList<bool> AscendingList = new ChunkedList<bool>();
            string s;
 
            do
            {
                ScriptNode Node = Parser.ParseIf();
 
                switch (s = Parser.PeekNextToken().ToUpper())
                {
                    case "ASC":
                        Parser.NextToken();
                        ColumnList.Add(Node);
                        AscendingList.Add(true);
                        s = Parser.PeekNextToken();
                        break;
 
                    case "DESC":
                        Parser.NextToken();
                        ColumnList.Add(Node);
                        AscendingList.Add(false);
                        s = Parser.PeekNextToken();
                        break;
 
                    case ",":
                        Parser.NextToken();
                        ColumnList.Add(Node);
                        AscendingList.Add(true);
                        break;
 
                    default:
                        ColumnList.Add(Node);
                        AscendingList.Add(true);
                        break;
                }
            }
            while (s == ",");
 
            Columns = ColumnList.ToArray();
            Ascending = AscendingList.ToArray();
        }
 
    }
}