UpdateParser.cs

using System;
using System.Collections.Generic;
using Waher.Script.Model;
using Waher.Script.Operators;
using Waher.Script.Operators.Assignments;
using Waher.Script.Operators.Comparisons;
 
namespace Waher.Script.Persistence.SQL.Parsers
{
    public class UpdateParser : IKeyWord
    {
        public UpdateParser()
        {
        }
 
        public string KeyWord => "UPDATE";
 
        public string[] Aliases => null;
 
        public string[] InternalKeywords => new string[] 
        { 
            "LAZY", 
            "SET", 
            "WHERE" 
        };
 
        public bool TryParse(ScriptParser Parser, out ScriptNode Result)
        {
            Result = null;
 
            string s = Parser.PeekNextToken().ToUpper();
            bool Lazy = s == "LAZY";
 
            if (Lazy)
                Parser.NextToken();
 
            if (!SelectParser.TryParseSources(Parser, out SourceDefinition Source))
                return false;
 
            s = Parser.NextToken().ToUpper();
            if (s != "SET")
                return false;
 
            List<Assignment> SetOperations = new List<Assignment>();
            ScriptNode Node = Parser.ParseList();
 
            if (!(Node is ElementList List))
                List = new ElementList(new ScriptNode[] { Node }, Node.Start, Node.Length, Node.Expression);
 
            foreach (ScriptNode Operation in List.Elements)
            {
                if (Operation is EqualTo EqualTo)
                {
                    if (EqualTo.LeftOperand is VariableReference Ref)
                        SetOperations.Add(new Assignment(Ref.VariableName, EqualTo.RightOperand, EqualTo.Start, EqualTo.Length, EqualTo.Expression));
                    else
                        return false;
                }
                else if (Operation is Assignment Assignment)
                    SetOperations.Add(Assignment);
                else
                    return false;
            }
 
            ScriptNode Where = null;
 
            s = Parser.PeekNextToken().ToUpper();
            if (s == "WHERE")
            {
                Parser.NextToken();
                Where = Parser.ParseOrs();
            }
 
            Result = new Update(Source, SetOperations.ToArray(), Where, Lazy, Parser.Start, Parser.Length, Parser.Expression);
 
            return true;
        }
 
    }
}