// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
 
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.Options;
 
namespace Microsoft.AspNetCore.HttpOverrides;
 
/// <summary>
/// A middleware for overriding the HTTP method of an incoming POST request.
/// </summary>
public class HttpMethodOverrideMiddleware
{
    private const string xHttpMethodOverride = "X-Http-Method-Override";
    private readonly RequestDelegate _next;
    private readonly HttpMethodOverrideOptions _options;
 
    /// <summary>
    /// Create a new <see cref="HttpMethodOverrideMiddleware"/>.
    /// </summary>
    /// <param name="next">The <see cref="RequestDelegate"/> representing the next middleware in the pipeline.</param>
    /// <param name="options">The <see cref="HttpMethodOverrideOptions"/> for configuring the middleware.</param>
    public HttpMethodOverrideMiddleware(RequestDelegate next, IOptions<HttpMethodOverrideOptions> options)
    {
        ArgumentNullException.ThrowIfNull(next);
        ArgumentNullException.ThrowIfNull(options);
        _next = next;
        _options = options.Value;
    }
 
    /// <summary>
    /// Executes the middleware.
    /// </summary>
    /// <param name="context">The <see cref="HttpContext"/> for the current request.</param>
    public Task Invoke(HttpContext context)
    {
        if (HttpMethods.IsPost(context.Request.Method))
        {
            if (_options.FormFieldName != null)
            {
                if (context.Request.HasFormContentType)
                {
                    return InvokeCore(context);
                }
            }
            else
            {
                var xHttpMethodOverrideValue = context.Request.Headers[xHttpMethodOverride];
                if (!string.IsNullOrEmpty(xHttpMethodOverrideValue))
                {
                    context.Request.Method = xHttpMethodOverrideValue.ToString();
                }
            }
        }
        return _next(context);
    }
 
    private async Task InvokeCore(HttpContext context)
    {
        var form = await context.Request.ReadFormAsync();
        var methodType = form[_options.FormFieldName!];
        if (!string.IsNullOrEmpty(methodType))
        {
            context.Request.Method = methodType.ToString();
        }
        await _next(context);
    }
}