// Copyright (c) 2025 TerraByte Inc.
//
// This script creates a custom Unity Editor window called "Arbitrator" to compare 
// local Git changes with the tracked remote branch using the LibGit2Sharp library.
//
// HOW TO USE:
// 1. Ensure you have manually installed the LibGit2Sharp v0.27.0 package.
// 2. Create an "Editor" folder in your Assets directory if you don't have one.
// 3. Save this script as "Arbitrator.cs" inside the "Editor" folder.
// 4. In Unity, open the window from the top menu: Terra > Arbitrator.
// 5. Click the "Compare with Cloud" button. Results will appear in the console.

using System;
using System.IO;
using UnityEngine;
using UnityEditor;
using LibGit2Sharp;

namespace Terra.Arbitrator
{
    public class Arbitrator : EditorWindow
    {
        // Creates a menu item in the Unity Editor to open this window.
        [MenuItem("Terra/Arbitrator")]
        public static void ShowWindow()
        {
            // Get an existing open window or if none, make a new one.
            GetWindow<Arbitrator>("Arbitrator");
        }

        // This method is called to draw the contents of the editor window.
        private void OnGUI()
        {   
            // Add some descriptive text to the window.
            EditorGUILayout.LabelField("Compare local changes against the cloud.", EditorStyles.boldLabel);
            EditorGUILayout.HelpBox("This tool will fetch the latest state from the remote repository and show you which files have been added, modified, or deleted locally.", MessageType.Info);

            // Render a button. If the user clicks it, call our main logic function.
            if (GUILayout.Button("Compare with Cloud", GUILayout.Height(40)))
            {
                CompareLocalToRemote();
            }
        }

        /// <summary>
        /// The core function that performs the fetch and diff operations.
        /// </summary>
        private static void CompareLocalToRemote()
        {
            // The project root is one level above the "Assets" directory.
            var projectRoot = Directory.GetParent(Application.dataPath)?.FullName;

            try
            {
                // Use a 'using' statement to ensure the repository object is properly disposed of.
                // This opens the repository at the root of your Unity project.
                using var repo = new Repository(projectRoot);
                Debug.Log("Repository opened successfully.");

                // --- Step 1: Fetch the latest state from the remote ---
                // Get the primary remote, which is typically named "origin".
                var remote = repo.Network.Remotes["origin"];
                if (remote == null)
                {
                    Debug.LogError("No remote named 'origin' was found. Please configure a remote for your repository.");
                    return;
                }

                // IMPORTANT: For private repositories, you'll need to provide credentials.
                // This is a more advanced topic involving Personal Access Tokens (PATs).
                var fetchOptions = new FetchOptions();
                    
                Debug.Log($"Fetching latest changes from '{remote.Name}' at {remote.Url}...");
                Commands.Fetch(repo, remote.Name, Array.Empty<string>(), fetchOptions, null);
                Debug.Log("Fetch complete.");

                // --- Step 2: Identify branches to compare ---
                var currentBranch = repo.Head;
                var remoteBranch = currentBranch.TrackedBranch;

                if (remoteBranch == null || !remoteBranch.IsRemote)
                {
                    Debug.LogError($"The current branch '{currentBranch.FriendlyName}' is not tracking a remote branch. Set the upstream branch using 'git branch --set-upstream-to=origin/{currentBranch.FriendlyName}'.");
                    return;
                }
                    
                Debug.Log($"Comparing local '{currentBranch.FriendlyName}' against remote '{remoteBranch.FriendlyName}'.");

                // --- Step 3: Perform the Diff ---
                // We compare the tree from the latest commit on the remote branch
                // against the files currently in your working directory.
                var remoteTree = remoteBranch.Tip.Tree;

                var changes = repo.Diff.Compare<TreeChanges>(remoteTree, DiffTargets.Index | DiffTargets.WorkingDirectory);

                // --- Step 4: Log the Results ---
                if (changes.Count == 0)
                {
                    Debug.Log("--- STATUS: You are up to date! No differences found with the remote branch. ---");
                }
                else
                {
                    Debug.Log($"--- STATUS: Found {changes.Count} changes. ---");
                    foreach (var change in changes)
                    {
                        // Log the status (Added, Deleted, Modified) and the file path.
                        // The color-coding helps to quickly see the status.
                        switch (change.Status)
                        {
                            case ChangeKind.Added:
                                Debug.Log($"<color=green>ADDED: {change.Path}</color>");
                                break;
                            case ChangeKind.Deleted:
                                Debug.Log($"<color=red>DELETED: {change.Path}</color>");
                                break;
                            case ChangeKind.Modified:
                                Debug.Log($"<color=orange>MODIFIED: {change.Path}</color>");
                                break;
                            case ChangeKind.Unmodified:
                            case ChangeKind.Renamed:
                            case ChangeKind.Copied:
                            case ChangeKind.Ignored:
                            case ChangeKind.Untracked:
                            case ChangeKind.TypeChanged:
                            case ChangeKind.Unreadable:
                            case ChangeKind.Conflicted:
                            default:
                                Debug.Log($"{change.Status.ToString().ToUpper()}: {change.Path}");
                                break;
                        }
                    }
                    Debug.Log("--- End of Report ---");
                }
            }
            catch (RepositoryNotFoundException)
            {
                Debug.LogError("Error: This project is not a Git repository or the .git folder is missing. Please initialize a repository first.");
            }
            catch (Exception ex)
            {
                // Catch any other exceptions that might occur (e.g., network issues during fetch).
                Debug.LogError($"An unexpected error occurred: {ex.Message}");
                Debug.LogException(ex);
            }
        }
    }
}