ModelBuilder.cs

/*
Creates TypeScript models from CSharp models
- TypeScript model is set by config key TsModelsPath
- CSharp models namespace is set by config key ModelNamespace

1) Add to your Program.cs:
if (ModelBuilder.Build(args))
{
    return;
}

2) Call with: "dotnet run -- build-models"
*/
using System.Reflection;
using System.Text;

namespace MyNamespace.Scripts;

public static class ModelBuilder
{
    private static bool IsNullable(this Type type) => type == typeof(string) || type.IsClass
                ? true
                : type.IsGenericType && type.GetGenericTypeDefinition() == typeof(Nullable<>);
    private static bool IsDict(this Type type) => type.IsGenericType && type.GetGenericTypeDefinition() == typeof(Dictionary<,>);
    private static bool IsList(this Type type) => type.IsGenericType && type.GetGenericTypeDefinition() == typeof(List<>);
    private static string ToTsType(this Type? type) => type switch
    {
        Type t when t == typeof(string) => "string",
        Type t when t == typeof(List<string>) => "string[]",
        Type t when t == typeof(int) || t == typeof(int?) => "number",
        Type t when t == typeof(bool) || t == typeof(bool?) => "boolean",
        Type t when t.IsList() => $"I{t.GenericTypeArguments?.FirstOrDefault()?.ToTsType()}[]",
        Type t when t.IsDict() => $"Record<{t.GenericTypeArguments?.FirstOrDefault()?.ToTsType()}, {t.GenericTypeArguments?.LastOrDefault()?.ToTsType()}>",
        Type t when t.IsClass => $"I{t.Name}",
        _ => "any"
    };

    public static bool Build(string[] args)
    {
        if (!(args.Length == 1 && args[0] == "build-models"))
        {
            return false;
        }

        var config = new ConfigurationBuilder()
            .AddJsonFile("appsettings.json", false, false)
            .AddJsonFile("appsettings.Development.json", false, false)
            .Build();

        var filePath = config.GetValue<string>("TsModelsPath");
        if (filePath is null)
        {
            Console.WriteLine("ERROR: ConfigModelsPath is not set.");
            return true;
        }
        var modelNamespace = config.GetValue<string>("ModelNamespace");
        if (filePath is null)
        {
            Console.WriteLine("ERROR: ModelNamespace is not set.");
            return true;
        }

        StringBuilder sb = new();
        sb.AppendLine("/*auto generated*/");

        foreach (var modelClass in Assembly.Load(modelNamespace?.Split('.')[0] ?? "")
            .GetTypes()
            .Where(t => string.Equals(t.Namespace, modelNamespace, StringComparison.Ordinal)) ?? Enumerable.Empty<Type>())
        {
            sb.AppendLine();
            sb.AppendLine($"interface I{modelClass.Name} {{");

            foreach (var prop in modelClass.GetProperties())
            {
                var type = prop.PropertyType.ToTsType();
                var nullable = prop.PropertyType.IsNullable();
                var name = string.Concat(prop.Name[0].ToString().ToLower(), prop.Name[1..]);
                sb.AppendLine($"    {name}{(nullable ? "?" : "")}: {type};");
            }
            sb.AppendLine("}");
        }

        File.WriteAllText(filePath, sb.ToString());
        Console.WriteLine($"{filePath} written successfully");
        return true;
    }
}