using HyperBooru.ApiModels;
using System.Reflection;
using System.Text.Json;
using System.Text.Json.Serialization;
using System.Text.Json.Serialization.Metadata;

namespace HyperBooru;

// Middleware class to intercept API controller exceptions and
// return said exceptions to API clients as serialized JSON objects
public sealed class ExceptionMiddleware {
    private RequestDelegate next;

    public ExceptionMiddleware(RequestDelegate next) =>
        this.next = next;

    public async Task Invoke(HttpContext context) {
        try {
            await next(context);
        } catch(HBException e) {
            context.Response.ContentType = "application/json";
            context.Response.StatusCode  =
                e.GetType().GetCustomAttribute<ExceptionStatusCodeAttribute>()?.StatusCode ??
                StatusCodes.Status500InternalServerError;

            context.Response.Clear();

            await context.Response.WriteAsJsonAsync(e);
        } catch(Exception) {
            context.Response.StatusCode = StatusCodes.Status500InternalServerError;
            context.Response.ContentType = "application/json";

            context.Response.Clear();

            await context.Response.WriteAsJsonAsync(new ServerException());
        }
    }
}

// This class is needed as the JSON serializer often fails to serialize
// members of the native 'Exception' class
public sealed class ExceptionJsonResolver : DefaultJsonTypeInfoResolver {
    public override JsonTypeInfo GetTypeInfo(Type type, JsonSerializerOptions options) {
        var info = base.GetTypeInfo(type, options);

        if(!typeof(Exception).IsAssignableFrom(type))
            return info;

        string[] excludedProps = [
            "data",
            "hResult",
            "helpLink",
            "innerException",
            "source",
            "stackTrace",
            "targetSite"
        ];

        foreach(var p in info.Properties.Where(p => excludedProps.Contains(p.Name)))
            p.ShouldSerialize = (_, _) => false;

        return info;
    }
}