// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
 
using System.ComponentModel.DataAnnotations;
using System.Reflection;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Options;
 
namespace Microsoft.AspNetCore.Http.Validation;
 
internal static class ValidationEndpointFilterFactory
{
    public static EndpointFilterDelegate Create(EndpointFilterFactoryContext context, EndpointFilterDelegate next)
    {
        var parameters = context.MethodInfo.GetParameters();
        var options = context.ApplicationServices.GetService<IOptions<ValidationOptions>>()?.Value;
        if (options is null || options.Resolvers.Count == 0)
        {
            return next;
        }
 
        var parameterCount = parameters.Length;
        var validatableParameters = new IValidatableInfo[parameterCount];
        var parameterDisplayNames = new string[parameterCount];
        var hasValidatableParameters = false;
 
        for (var i = 0; i < parameterCount; i++)
        {
            if (options.TryGetValidatableParameterInfo(parameters[i], out var validatableParameter))
            {
                validatableParameters[i] = validatableParameter;
                parameterDisplayNames[i] = GetDisplayName(parameters[i]);
                hasValidatableParameters = true;
            }
        }
 
        if (!hasValidatableParameters)
        {
            return next;
        }
 
        return async (context) =>
        {
            var validatableContext = new ValidateContext { ValidationOptions = options };
 
            for (var i = 0; i < context.Arguments.Count; i++)
            {
                var validatableParameter = validatableParameters[i];
                var displayName = parameterDisplayNames[i];
 
                var argument = context.Arguments[i];
                if (argument is null || validatableParameter is null)
                {
                    continue;
                }
 
                var validationContext = new ValidationContext(argument, displayName, context.HttpContext.RequestServices, items: null);
                validatableContext.ValidationContext = validationContext;
                await validatableParameter.ValidateAsync(argument, validatableContext, context.HttpContext.RequestAborted);
            }
 
            if (validatableContext.ValidationErrors is { Count: > 0 })
            {
                context.HttpContext.Response.StatusCode = StatusCodes.Status400BadRequest;
                context.HttpContext.Response.ContentType = "application/problem+json";
                return await ValueTask.FromResult(new HttpValidationProblemDetails(validatableContext.ValidationErrors));
            }
 
            return await next(context);
        };
    }
 
    private static string GetDisplayName(ParameterInfo parameterInfo)
    {
        var displayAttribute = parameterInfo.GetCustomAttribute<DisplayAttribute>();
        if (displayAttribute != null)
        {
            return displayAttribute.Name ?? parameterInfo.Name!;
        }
 
        return parameterInfo.Name!;
    }
}