deployment/Deployment/ConfigurationBootstrapper.cs

using System;
using System.Dynamic;
using System.Reflection;
using System.Runtime.CompilerServices;
using Newtonsoft.Json;

[assembly: InternalsVisibleTo("deployment.tests")]
namespace greyn.Deployment
{
    public static class ConfigurationBootstrapper
    {
        private const string confpath = "appsettings.json";

        public static T Load<T>() where T : new()
        {
            if (File.Exists("appsettings.json"))
            {
                /* "aaaahhh this is the most abstract and reflective thing in the goddamn world aaaahhhhh next you'll make an ECS on a dynamic aaaahhh"
                 * Ok, yes. I share these fears. but.
                 * this way we can read a *very* arbitrary configuration file.
                 * some random external file's configuration values is a good reason to aim for very high flexibility, imo
                 * if the configuration expects new values we write them in, 
                 * if you left other junk for whatever reason, we don't delete them.
                 */
                var actualConfig = JsonConvert.DeserializeObject<ExpandoObject>(File.ReadAllText(confpath)) ?? new ExpandoObject();
                var toReturn = new T();
                PopulateExpando(toReturn, ref actualConfig);
                File.WriteAllText(confpath, JsonConvert.SerializeObject(actualConfig, Formatting.Indented));

                readFromExpando(ref toReturn, actualConfig);

                return toReturn;
            }
            else
            {
                var toReturn = new T();
                File.WriteAllText(confpath, JsonConvert.SerializeObject(toReturn));
                return toReturn;
            }
        }

        //TODO: make private but get tests to cooperate... I think that's a c# limitation
        internal static void PopulateExpando<T>(T config, ref ExpandoObject fromFile)
        {
            if (config == null) return;
            if (fromFile == null)
            {
                fromFile = new ExpandoObject();
            }
            var dictionaryFromExpandoFromFile = (IDictionary<string, object?>)fromFile;
            
            foreach (var memberInfo in config.GetType().GetMembers())
            {   
                if(memberInfo.DeclaringType == typeof(System.Object))
                {
                    continue;
                }
                if(memberInfo.MemberType != MemberTypes.Field && memberInfo.MemberType != MemberTypes.Property)
                {
                    continue;
                }
                
                if (dictionaryFromExpandoFromFile.TryGetValue(memberInfo.Name, out object? valueFromDict))
                {
                    if (valueFromDict != null)
                    {
                        switch (memberInfo.MemberType)
                        {
                            case MemberTypes.Field:
                                var asField = (FieldInfo)memberInfo;
                                if (dictionaryFromExpandoFromFile[asField.Name] is ExpandoObject childMemberField)
                                {
                                    PopulateExpando(asField.GetValue(config), ref childMemberField);
                                }
                                break;
                            case MemberTypes.Property:
                                var asProperty = (PropertyInfo)memberInfo;
                                if (dictionaryFromExpandoFromFile[asProperty.Name] is ExpandoObject childMemberProperty)
                                {
                                    PopulateExpando(asProperty.GetValue(config), ref childMemberProperty);
                                }
                                break;
                            default:
                                break;
                        }

                    }
                }
                else
                {
                    switch (memberInfo.MemberType)
                    {
                        case MemberTypes.Field:
                            fromFile.TryAdd(memberInfo.Name, ((FieldInfo)memberInfo).GetValue(config));
                            break;
                        case MemberTypes.Property:
                            fromFile.TryAdd(memberInfo.Name, ((PropertyInfo)memberInfo).GetValue(config));
                            break;
                        default:
                            break;
                    }
                    
                }
            }
        }
        internal static void readFromExpando<T>(ref T config, ExpandoObject readFromFile)
        {
            //TODO: read from Expando
        }

        // private static T sync<T>(ref T config, ref ExpandoObject readFromFile)
        // {
        //     var fieldsFoundThisLevel = new List<string>();

        //     if(config == null)
        //     {
        //         //TODO: it's entirely possible this is null.
        //         throw new ArgumentNullException();
        //     }
        //     if(readFromFile == null)
        //     {
        //         //TODO: it's entirely possible this is null.
        //         throw new ArgumentNullException();
        //     }
        //     var readUnExpandoed = (IDictionary<string, object?>)readFromFile;
        //     //if it's present on what was read
        //     //set it on Config
        //     //if it's not found on what was read, or type is different

        //     foreach (var prop in config.GetType().GetProperties())
        //     {
        //         fieldsFoundThisLevel.Add(prop.Name);
        //         if(readUnExpandoed.TryGetValue(prop.Name, out object? valueFromFile)) //so a configuration file can *set* a value *to null*
        //         {
        //             if(valueFromFile != null)
        //             {
        //                 var defaultConfigValue = prop.GetValue(config);
        //                 if (defaultConfigValue != null)
        //                 {
        //                     //expandofy, since we objectified it.
        //                     var expandoFromFile = new ExpandoObject();
        //                     var dictionaryFromExpandoFromFile = (IDictionary<string, object?>)expandoFromFile;
        //                     foreach (var property in valueFromFile.GetType().GetProperties())
        //                         dictionaryFromExpandoFromFile.Add(property.Name, property.GetValue(valueFromFile));
        //                     expandoFromFile = (ExpandoObject)dictionaryFromExpandoFromFile;
        //                     //dive in, repeat
        //                     sync(ref defaultConfigValue, ref expandoFromFile);
        //                     //we've now Sync'd expandoFromFile and defaultConfigValue
        //                     prop.SetValue(readFromFile, expandoFromFile);
        //                     prop.SetValue(config, expandoFromFile);
        //                 }

        //             }
        //         }
        //         else
        //         {
        //             readFromFile.TryAdd(prop.Name, prop.GetValue(config));
        //         }
        //     }
        // }
    }
}