using System;
using System.IO;
using System.Threading;
using System.Threading.Tasks;
using MediaBrowser.Common.Configuration;
using MediaBrowser.Common.Net;
using MediaBrowser.Controller.Configuration;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;

namespace Jellyfin.Plugin.RedditComments.Services;

/// <summary>
/// Injects the plugin's script tag into the Jellyfin web client's index.html at startup,
/// so the player gets the comments button. Re-applies automatically after web client updates.
/// </summary>
public class WebScriptInjector : IHostedService
{
    private const string ScriptMarker = "RedditComments/Static/reddit-comments.js";

    private readonly ILogger<WebScriptInjector> _logger;
    private readonly IApplicationPaths _applicationPaths;
    private readonly IServerConfigurationManager _configurationManager;

    /// <summary>
    /// Initializes a new instance of the <see cref="WebScriptInjector"/> class.
    /// </summary>
    /// <param name="logger">Logger.</param>
    /// <param name="applicationPaths">Application paths.</param>
    /// <param name="configurationManager">Server configuration manager.</param>
    public WebScriptInjector(
        ILogger<WebScriptInjector> logger,
        IApplicationPaths applicationPaths,
        IServerConfigurationManager configurationManager)
    {
        _logger = logger;
        _applicationPaths = applicationPaths;
        _configurationManager = configurationManager;
    }

    /// <inheritdoc />
    public Task StartAsync(CancellationToken cancellationToken)
    {
        try
        {
            InjectScriptTag();
        }
        catch (Exception ex)
        {
            _logger.LogWarning(
                ex,
                "Could not inject the Reddit Comments script into the web client. The API will still work; "
                + "to enable the player button, add this tag to index.html of jellyfin-web manually: {Tag}",
                BuildScriptTag());
        }

        return Task.CompletedTask;
    }

    /// <inheritdoc />
    public Task StopAsync(CancellationToken cancellationToken) => Task.CompletedTask;

    private string BuildScriptTag()
    {
        var baseUrl = string.Empty;
        try
        {
            if (_configurationManager.GetConfiguration("network") is NetworkConfiguration networkConfiguration)
            {
                baseUrl = (networkConfiguration.BaseUrl ?? string.Empty).TrimEnd('/');
            }
        }
        catch (Exception ex)
        {
            _logger.LogDebug(ex, "Could not read the configured base URL, assuming none");
        }

        return string.Format(System.Globalization.CultureInfo.InvariantCulture, "<script src=\"{0}/{1}\" defer></script>", baseUrl, ScriptMarker);
    }

    private void InjectScriptTag()
    {
        var indexPath = Path.Combine(_applicationPaths.WebPath, "index.html");
        if (!File.Exists(indexPath))
        {
            _logger.LogWarning("jellyfin-web index.html not found at {Path}, skipping script injection", indexPath);
            return;
        }

        var contents = File.ReadAllText(indexPath);
        if (contents.Contains(ScriptMarker, StringComparison.Ordinal))
        {
            _logger.LogDebug("Reddit Comments script tag already present in index.html");
            return;
        }

        var tag = BuildScriptTag();
        var bodyIndex = contents.LastIndexOf("</body>", StringComparison.OrdinalIgnoreCase);
        contents = bodyIndex >= 0
            ? contents.Insert(bodyIndex, tag + Environment.NewLine)
            : contents + Environment.NewLine + tag + Environment.NewLine;

        File.WriteAllText(indexPath, contents);
        _logger.LogInformation("Injected Reddit Comments script tag into {Path}", indexPath);
    }
}