// Copyright (c) 2025 TerraByte Inc.
//
// A modal editor window for displaying text differences (diffs) and
// confirming an action with the user.

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

namespace Terra.Arbitrator.GUI
{
    public class DiffWindow : EditorWindow
    {
        private string _filePath;
        private string _diffContent;
        private Action<bool> _onCloseCallback;
        private Vector2 _scrollPosition;
        private bool _callbackInvoked;
        private GUIStyle _diffStyle;

        /// <summary>
        /// Shows a modal window to display the diff and get user confirmation.
        /// </summary>
        /// <param name="filePath">The path of the file being diffed.</param>
        /// <param name="diffContent">The diff text to display.</param>
        /// <param name="onCloseCallback">A callback that returns true if the user confirmed, otherwise false.</param>
        public static void ShowWindow(string filePath, string diffContent, Action<bool> onCloseCallback)
        {
            var window = GetWindow<DiffWindow>(true, "Diff Viewer", true);
            window.titleContent = new GUIContent($"Diff: {Path.GetFileName(filePath)}");
            window.minSize = new Vector2(700, 500);
            window._filePath = filePath;
            window._diffContent = diffContent;
            window._onCloseCallback = onCloseCallback;
            window._callbackInvoked = false;
            window.ShowModalUtility(); // Show as a blocking modal window
        }

        private void OnEnable()
        {
            // Initialize the style here to avoid doing it every OnGUI call.
            _diffStyle = new GUIStyle(EditorStyles.label)
            {
                richText = true,
                wordWrap = false,
                alignment = TextAnchor.UpperLeft
            };
        }

        private void OnGUI()
        {
            EditorGUILayout.LabelField(_filePath, EditorStyles.boldLabel);

            _scrollPosition = EditorGUILayout.BeginScrollView(_scrollPosition, EditorStyles.helpBox);
            
            var coloredText = GetColoredDiff(_diffContent);
            var content = new GUIContent(coloredText);
            
            // Calculate the required height based on the window's width, accounting for scrollbar and padding.
            var viewWidth = EditorGUIUtility.currentViewWidth - 30; // Approximate width inside scroll view
            var requiredHeight = _diffStyle.CalcHeight(content, viewWidth);
            
            // Use GUILayout.Label with an explicit height to ensure the ScrollView's content area is sized correctly.
            EditorGUILayout.SelectableLabel(coloredText, _diffStyle, GUILayout.MinHeight(requiredHeight));

            EditorGUILayout.EndScrollView();

            EditorGUILayout.Space();
            EditorGUILayout.HelpBox("Review the changes above. Green lines are additions, red lines are deletions. Reverting will permanently discard these changes.", MessageType.Warning);

            EditorGUILayout.BeginHorizontal();
            GUILayout.FlexibleSpace();
            if (GUILayout.Button("Revert Changes", GUILayout.Height(30), GUILayout.Width(150)))
            {
                _callbackInvoked = true;
                _onCloseCallback?.Invoke(true);
                Close();
            }
            if (GUILayout.Button("Cancel", GUILayout.Height(30), GUILayout.Width(120)))
            {
                Close();
            }
            EditorGUILayout.EndHorizontal();
        }

        private static string GetColoredDiff(string rawDiff)
        {
            var coloredDiff = "";
            var lines = rawDiff.Split(new[] { '\r', '\n' }, StringSplitOptions.RemoveEmptyEntries);
            foreach (var line in lines)
            {
                if (line.StartsWith("+"))
                {
                    coloredDiff += $"<color=green>{line}</color>\n";
                }
                else if (line.StartsWith("-"))
                {
                    coloredDiff += $"<color=red>{line}</color>\n";
                }
                else if (line.StartsWith("@@"))
                {
                     coloredDiff += $"<color=cyan>{line}</color>\n";
                }
                else
                {
                    coloredDiff += $"{line}\n";
                }
            }
            return coloredDiff + "\n";
        }

        private void OnDestroy()
        {
            // This is called when the window is closed by any means.
            // If the callback hasn't been invoked yet (i.e., user clicked 'X' or 'Cancel'),
            // we invoke it with 'false' to signify cancellation.
            if (!_callbackInvoked)
            {
                _onCloseCallback?.Invoke(false);
            }
        }
    }
}