using System;
using System.IO;
using MediaBrowser.Common.Configuration;
using Microsoft.Extensions.Logging;

namespace Jellyfin.Plugin.JellyLMS.Services;

/// <summary>
/// Injects (or removes) a script tag in the web client's <c>index.html</c>
/// that adds a floating button linking to the JellyLMS remote control page.
/// This follows the pattern used by other Jellyfin plugins (e.g. Intro Skipper)
/// since there is no official plugin hook for adding buttons to the web client.
/// </summary>
public static class WebClientPatchService
{
    private const string Marker = "<!-- jellylms-remote-button -->";
    private const string ScriptTag = "<script defer src=\"/JellyLms/RemoteControl/ClientScript\"></script>";
    private const string Injected = ScriptTag + Marker + "\n</body>";

    /// <summary>
    /// Ensures the web client's index.html either has or does not have the
    /// JellyLMS remote button script injected, matching <paramref name="enableButton"/>.
    /// </summary>
    /// <param name="applicationPaths">The Jellyfin application paths.</param>
    /// <param name="enableButton">Whether the remote button script should be present.</param>
    /// <param name="logger">The logger.</param>
    public static void Apply(IApplicationPaths applicationPaths, bool enableButton, ILogger logger)
    {
        var indexPath = Path.Combine(applicationPaths.WebPath, "index.html");

        try
        {
            if (!File.Exists(indexPath))
            {
                logger.LogDebug("JellyLMS: web client index.html not found at {Path}", indexPath);
                return;
            }

            var html = File.ReadAllText(indexPath);
            var hasMarker = html.Contains(Marker, StringComparison.Ordinal);

            if (enableButton && !hasMarker)
            {
                var patched = ReplaceLast(html, "</body>", Injected);
                File.WriteAllText(indexPath, patched);
                logger.LogInformation("JellyLMS: injected remote control button into {Path}", indexPath);
            }
            else if (!enableButton && hasMarker)
            {
                var patched = html.Replace(ScriptTag + Marker + "\n", string.Empty, StringComparison.Ordinal)
                    .Replace(ScriptTag + Marker, string.Empty, StringComparison.Ordinal);
                File.WriteAllText(indexPath, patched);
                logger.LogInformation("JellyLMS: removed remote control button from {Path}", indexPath);
            }
        }
        catch (Exception ex) when (ex is IOException or UnauthorizedAccessException)
        {
            logger.LogWarning(ex, "JellyLMS: failed to patch web client index.html at {Path}", indexPath);
        }
    }

    private static string ReplaceLast(string source, string find, string replace)
    {
        var index = source.LastIndexOf(find, StringComparison.Ordinal);
        if (index < 0)
        {
            return source;
        }

        return source[..index] + replace + source[(index + find.Length)..];
    }
}