ModChecker.cs

using System.Collections.Generic;
using System.Linq;
using BepInEx.Bootstrap;

namespace ModSync
{
    internal static class ModChecker
    {
        /// <summary>
        /// Returns a serialized list of all loaded plugins as "GUID|Version" entries.
        /// ModSync itself is excluded so clients aren't flagged for version differences in the sync tool.
        /// </summary>
        internal static string[] GetLocalModList()
        {
            return Chainloader.PluginInfos
                .Where(kvp => kvp.Key != MyPluginInfo.PLUGIN_GUID)
                .Select(kvp => $"{kvp.Key}|{kvp.Value.Metadata.Version}")
                .OrderBy(s => s)
                .ToArray();
        }

        /// <summary>
        /// Compares a remote mod list against the local one and returns a MismatchReport.
        /// </summary>
        internal static MismatchReport Compare(string[] localMods, string[] remoteMods)
        {
            var localSet = new HashSet<string>(localMods);
            var remoteSet = new HashSet<string>(remoteMods);

            var missingFromLocal = remoteSet.Except(localSet).ToArray();   // host has, we don't
            var missingFromRemote = localSet.Except(remoteSet).ToArray();  // we have, host doesn't

            return new MismatchReport(missingFromLocal, missingFromRemote);
        }
    }

    internal class MismatchReport
    {
        internal string[] MissingFromLocal { get; }   // present on host, absent locally
        internal string[] MissingFromRemote { get; }  // present locally, absent on host

        internal bool HasMismatches => MissingFromLocal.Length > 0 || MissingFromRemote.Length > 0;

        internal MismatchReport(string[] missingFromLocal, string[] missingFromRemote)
        {
            MissingFromLocal = missingFromLocal;
            MissingFromRemote = missingFromRemote;
        }

        internal string FormatForDisplay()
        {
            var lines = new List<string>();

            if (MissingFromLocal.Length > 0)
            {
                lines.Add("[ModSync] Mods you're missing:");
                foreach (var entry in MissingFromLocal)
                    lines.Add($"  - {FormatEntry(entry)}");
            }

            if (MissingFromRemote.Length > 0)
            {
                lines.Add("[ModSync] Mods the host doesn't have:");
                foreach (var entry in MissingFromRemote)
                    lines.Add($"  + {FormatEntry(entry)}");
            }

            return string.Join("\n", lines);
        }

        private static string FormatEntry(string entry)
        {
            var parts = entry.Split('|');
            return parts.Length == 2 ? $"{parts[0]} (v{parts[1]})" : entry;
        }
    }
}