dsa/FireBase/Offline/Internals/MemberAccessVisitor.cs


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using System.Collections.Generic;
using System.Linq.Expressions;
using System.Reflection;
using Newtonsoft.Json;

namespace Firebase.Database.Offline.Internals {
    public class MemberAccessVisitor : ExpressionVisitor {
        private readonly IList<string> propertyNames = new List<string>();

        private bool wasDictionaryAccess;

        public IEnumerable<string> PropertyNames => propertyNames;

        public override Expression Visit(Expression expr) {
            if (expr?.NodeType == ExpressionType.MemberAccess) {
                if (wasDictionaryAccess) {
                    wasDictionaryAccess = false;
                }
                else {
                    var memberExpr = (MemberExpression) expr;
                    var jsonAttr = memberExpr.Member.GetCustomAttribute<JsonPropertyAttribute>();

                    propertyNames.Add(jsonAttr?.PropertyName ?? memberExpr.Member.Name);
                }
            }
            else if (expr?.NodeType == ExpressionType.Call) {
                var callExpr = (MethodCallExpression) expr;
                if (callExpr.Method.Name == "get_Item" && callExpr.Arguments.Count == 1) {
                    var e = Expression.Lambda(callExpr.Arguments[0]).Compile();
                    propertyNames.Add(e.DynamicInvoke().ToString());
                    wasDictionaryAccess = callExpr.Arguments[0].NodeType == ExpressionType.MemberAccess;
                }
            }

            return base.Visit(expr);
        }
    }
}