using System;
using System.Collections.Generic;
using System.Linq;

using UnityEditor.Localization;
using UnityEngine;

using Crowdin.Plugin.Models.Settings;
using Crowdin.Plugin.Server_API.Helpers;

namespace Crowdin.Editor
{
    public class TableSelector : IDisposable
    {
        public bool AllTablesSelected => currentIndex is 0;
        
        private int currentIndex;
        private Vector2 scrollPosition;
        private readonly Dictionary<string, bool> tableStates = new();
        private readonly TablesSelection rawSettings;
        private readonly List<string> allTableNames;

        private TableSelector(
            TablesSelection settings,
            IEnumerable<string> allTableNames)
        {
            rawSettings = settings;
            this.allTableNames = allTableNames.ToList();

            currentIndex = settings.allSelected ? 0 : 1;

            var existingTableNames = new HashSet<string>(this.allTableNames);

            foreach (string selectedTable in settings.selectedTables)
            {
                // A table saved in "Selected tables" may have since been renamed or removed from the
                // project. Skip it so it can't linger as an unchecked, un-removable selection that
                // later operations still try to resolve against a now-missing table.
                if (existingTableNames.Contains(selectedTable))
                {
                    tableStates[selectedTable] = true;
                }
            }
        }
        
        public static TableSelector CreateForStringTables()
        {
            return new TableSelector(
                SettingsHelper.GetStringTablesSelection(),
                LocalizationEditorSettings
                    .GetStringTableCollections()
                    .Select(collection => collection.TableCollectionName));
        }
        
        public static TableSelector CreateForAssetTables()
        {
            return new TableSelector(
                SettingsHelper.GetAssetTablesSelection(),
                LocalizationEditorSettings
                    .GetAssetTableCollections()
                    .Select(collection => collection.TableCollectionName));
        }

        public void DrawLayout()
        {
            const int WidthForText = 60;
            const int MaxElementsNoScrolling = 10;
            
            GUILayout.Space(10);
            
            currentIndex = GUILayout.SelectionGrid(currentIndex, new[]
            {
                " All tables",
                " Selected tables"
            }, 1, "radio");

            if (currentIndex is 1)
            {
                if (allTableNames.Count > MaxElementsNoScrolling)
                {
                    scrollPosition = GUILayout.BeginScrollView(scrollPosition);
                }

                foreach (string tableName in allTableNames)
                {
                    bool currentState = tableStates.TryGetValue(tableName, out bool state) && state;

                    GUILayout.BeginHorizontal();
                    GUILayout.Space(23);
                    
                    tableStates[tableName] = GUILayout.Toggle(currentState, LimitString(tableName, WidthForText));
                    GUILayout.EndHorizontal();
                }

                if (allTableNames.Count > MaxElementsNoScrolling)
                {
                    GUILayout.EndScrollView();
                }
            }
                
            GUILayout.Space(10);
        }

        private static string LimitString(string text, int limit)
        {
            if (text.Length <= limit) return text;
            return text[..limit] + "...";
        }

        public IEnumerable<string> GetSelectedTables()
        {
            return tableStates
                .Where(kvPair => kvPair.Value)
                .Select(kvPair => kvPair.Key);
        }

        /// The concrete list of table names an operation should act on: every known table when
        /// "All tables" is selected, otherwise just the checked ones. Filtered against
        /// allTableNames so a selection saved before a table was renamed or removed can't resolve
        /// to a table that no longer exists.
        public IReadOnlyList<string> ResolveTables()
        {
            IEnumerable<string> tables = AllTablesSelected ? allTableNames : GetSelectedTables();
            return tables.Where(allTableNames.Contains).ToList();
        }

        public void SaveSettings()
        {
            rawSettings.allSelected = AllTablesSelected;
            rawSettings.selectedTables = GetSelectedTables().ToList();
        }

        public void Dispose()
        {
            SaveSettings();
        }
    }
}