// 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.Rewrite.PatternSegments;
using Microsoft.Net.Http.Headers;
 
namespace Microsoft.AspNetCore.Rewrite.IISUrlRewrite;
 
internal static class ServerVariables
{
    /// <summary>
    /// Returns the matching <see cref="PatternSegment"/> for the given <paramref name="serverVariable"/>
    /// </summary>
    /// <param name="serverVariable">The server variable</param>
    /// <param name="context">The parser context which is utilized when an exception is thrown</param>
    /// <param name="uriMatchPart">Indicates whether the full URI or the path should be evaluated for URL segments</param>
    /// <param name="alwaysUseManagedServerVariables">Determines whether server variables are sourced from the managed server</param>
    /// <exception cref="FormatException">Thrown when the server variable is unknown</exception>
    /// <returns>The matching <see cref="PatternSegment"/></returns>
    public static PatternSegment FindServerVariable(string serverVariable, ParserContext context, UriMatchPart uriMatchPart, bool alwaysUseManagedServerVariables)
    {
        Func<PatternSegment>? managedVariableThunk = default;
 
        switch (serverVariable)
        {
            // TODO Add all server variables here.
            case "ALL_RAW":
                managedVariableThunk = () => throw new NotSupportedException(Resources.FormatError_UnsupportedServerVariable(serverVariable));
                break;
            case "APP_POOL_ID":
                managedVariableThunk = () => throw new NotSupportedException(Resources.FormatError_UnsupportedServerVariable(serverVariable));
                break;
            case "CONTENT_LENGTH":
                managedVariableThunk = () => new HeaderSegment(HeaderNames.ContentLength);
                break;
            case "CONTENT_TYPE":
                managedVariableThunk = () => new HeaderSegment(HeaderNames.ContentType);
                break;
            case "HTTP_ACCEPT":
                managedVariableThunk = () => new HeaderSegment(HeaderNames.Accept);
                break;
            case "HTTP_COOKIE":
                managedVariableThunk = () => new HeaderSegment(HeaderNames.Cookie);
                break;
            case "HTTP_HOST":
                managedVariableThunk = () => new HeaderSegment(HeaderNames.Host);
                break;
            case "HTTP_REFERER":
                managedVariableThunk = () => new HeaderSegment(HeaderNames.Referer);
                break;
            case "HTTP_USER_AGENT":
                managedVariableThunk = () => new HeaderSegment(HeaderNames.UserAgent);
                break;
            case "HTTP_CONNECTION":
                managedVariableThunk = () => new HeaderSegment(HeaderNames.Connection);
                break;
            case "HTTP_URL":
                managedVariableThunk = () => new UrlSegment(uriMatchPart);
                break;
            case "HTTPS":
                managedVariableThunk = () => new IsHttpsUrlSegment();
                break;
            case "LOCAL_ADDR":
                managedVariableThunk = () => new LocalAddressSegment();
                break;
            case "HTTP_PROXY_CONNECTION":
                managedVariableThunk = () => throw new NotSupportedException(Resources.FormatError_UnsupportedServerVariable(serverVariable));
                break;
            case "QUERY_STRING":
                managedVariableThunk = () => new QueryStringSegment();
                break;
            case "REMOTE_ADDR":
                managedVariableThunk = () => new RemoteAddressSegment();
                break;
            case "REMOTE_HOST":
                managedVariableThunk = () => throw new NotSupportedException(Resources.FormatError_UnsupportedServerVariable(serverVariable));
                break;
            case "REMOTE_PORT":
                managedVariableThunk = () => new RemotePortSegment();
                break;
            case "REQUEST_FILENAME":
                managedVariableThunk = () => new RequestFileNameSegment();
                break;
            case "REQUEST_METHOD":
                managedVariableThunk = () => new RequestMethodSegment();
                break;
            case "REQUEST_URI":
                managedVariableThunk = () => new UrlSegment(uriMatchPart);
                break;
            case "SERVER_NAME":
                managedVariableThunk = () => new ServerNameSegment();
                break;
            default:
                throw new FormatException(Resources.FormatError_InputParserUnrecognizedParameter(serverVariable, context.Index));
        }
 
        if (alwaysUseManagedServerVariables)
        {
            return managedVariableThunk();
        }
 
        return new IISServerVariableSegment(serverVariable, managedVariableThunk);
    }
}