// 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.Http;
using Microsoft.AspNetCore.Http.Extensions;
 
namespace Microsoft.AspNetCore.Rewrite.UrlActions;
 
internal sealed class RewriteAction : UrlAction
{
    public RuleResult Result { get; }
    public bool QueryStringAppend { get; }
    public bool QueryStringDelete { get; }
    public bool EscapeBackReferences { get; }
 
    public RewriteAction(
        RuleResult result,
        Pattern pattern,
        bool queryStringAppend,
        bool queryStringDelete,
        bool escapeBackReferences)
    {
        // For the replacement, we must have at least
        // one segment (cannot have an empty replacement)
        Result = result;
        Url = pattern;
        QueryStringAppend = queryStringAppend;
        QueryStringDelete = queryStringDelete;
        EscapeBackReferences = escapeBackReferences;
    }
 
    public RewriteAction(
        RuleResult result,
        Pattern pattern,
        bool queryStringAppend) :
        this(result,
            pattern,
            queryStringAppend,
            queryStringDelete: false,
            escapeBackReferences: false)
    {
 
    }
 
    public override void ApplyAction(RewriteContext context, BackReferenceCollection? ruleBackReferences, BackReferenceCollection? conditionBackReferences)
    {
        var pattern = Url!.Evaluate(context, ruleBackReferences, conditionBackReferences);
        var request = context.HttpContext.Request;
 
        if (string.IsNullOrEmpty(pattern))
        {
            pattern = "/";
        }
 
        if (EscapeBackReferences)
        {
            // because escapebackreferences will be encapsulated by the pattern, just escape the pattern
            pattern = Uri.EscapeDataString(pattern);
        }
 
        // Defense in depth: this rule does not emit a Location header itself, but the rewritten value is
        // assigned to Request.Path below and a downstream component (or a later rule) may issue a redirect
        // from it. PathString does not reject a leading '//' or '/\', so neutralize the scheme-relative
        // shape here rather than auditing every downstream consumer.
        pattern = UrlNormalizer.CollapseLeadingSlashes(pattern);
 
        // TODO PERF, substrings, object creation, etc.
        if (pattern.Contains(Uri.SchemeDelimiter, StringComparison.Ordinal))
        {
            string scheme;
            HostString host;
            PathString path;
            QueryString query;
            UriHelper.FromAbsolute(pattern, out scheme, out host, out path, out query, out _);
 
            if (query.HasValue)
            {
                if (QueryStringAppend)
                {
                    request.QueryString = request.QueryString.Add(query);
                }
                else
                {
                    request.QueryString = query;
                }
            }
            else if (QueryStringDelete)
            {
                request.QueryString = QueryString.Empty;
            }
 
            request.Scheme = scheme;
            request.Host = host;
            request.Path = path;
        }
        else
        {
            var split = pattern.IndexOf('?');
            if (split >= 0)
            {
                var path = pattern.Substring(0, split);
                if (path[0] == '/')
                {
                    request.Path = PathString.FromUriComponent(path);
                }
                else
                {
                    request.Path = PathString.FromUriComponent('/' + path);
                }
 
                if (QueryStringAppend)
                {
                    request.QueryString = request.QueryString.Add(
                        QueryString.FromUriComponent(
                            pattern.Substring(split)));
                }
                else
                {
                    request.QueryString = QueryString.FromUriComponent(
                        pattern.Substring(split));
                }
            }
            else
            {
                if (pattern[0] == '/')
                {
                    request.Path = PathString.FromUriComponent(pattern);
                }
                else
                {
                    request.Path = PathString.FromUriComponent('/' + pattern);
                }
 
                if (QueryStringDelete)
                {
                    request.QueryString = QueryString.Empty;
                }
            }
        }
        context.Result = Result;
    }
}