// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.

using System.Diagnostics;
using System.Xml;
using System.Xml.XPath;
using System.Xml.Xsl;

namespace MS.Internal.Xml.XPath
{
    internal sealed class NumericExpr : ValueQuery
    {
        private readonly Operator.Op _op;
        private readonly Query _opnd1;
        private readonly Query _opnd2;

        public NumericExpr(Operator.Op op, Query opnd1, Query opnd2)
        {
            Debug.Assert(
                op == Operator.Op.PLUS || op == Operator.Op.MINUS ||
                op == Operator.Op.MUL || op == Operator.Op.DIV ||
                op == Operator.Op.MOD
            );
            Debug.Assert(opnd1 != null && opnd2 != null);
            if (opnd1.StaticType != XPathResultType.Number)
            {
                opnd1 = new NumberFunctions(Function.FunctionType.FuncNumber, opnd1);
            }
            if (opnd2.StaticType != XPathResultType.Number)
            {
                opnd2 = new NumberFunctions(Function.FunctionType.FuncNumber, opnd2);
            }
            _op = op;
            _opnd1 = opnd1;
            _opnd2 = opnd2;
        }
        private NumericExpr(NumericExpr other) : base(other)
        {
            _op = other._op;
            _opnd1 = Clone(other._opnd1);
            _opnd2 = Clone(other._opnd2);
        }

        public override void SetXsltContext(XsltContext context)
        {
            _opnd1.SetXsltContext(context);
            _opnd2.SetXsltContext(context);
        }

        public override object Evaluate(XPathNodeIterator nodeIterator)
        {
            return GetValue(_op,
                XmlConvert.ToXPathDouble(_opnd1.Evaluate(nodeIterator)),
                XmlConvert.ToXPathDouble(_opnd2.Evaluate(nodeIterator))
            );
        }
        private static double GetValue(Operator.Op op, double n1, double n2)
        {
            Debug.Assert(op == Operator.Op.PLUS || op == Operator.Op.MINUS || op == Operator.Op.MOD || op == Operator.Op.DIV || op == Operator.Op.MUL);
            return op switch
            {
                Operator.Op.PLUS => n1 + n2,
                Operator.Op.MINUS => n1 - n2,
                Operator.Op.MOD => n1 % n2,
                Operator.Op.DIV => n1 / n2,
                Operator.Op.MUL => n1 * n2,
                _ => 0,
            };
        }

        public override XPathResultType StaticType { get { return XPathResultType.Number; } }

        public override XPathNodeIterator Clone() { return new NumericExpr(this); }
    }
}