using System;
using UnityEngine;
using UnityEngine.EventSystems;
using UnityEngine.UI;

namespace Vanguard.UI
{
    /// <summary>Переключение фокуса между полями по Tab / Shift+Tab.</summary>
    public static class TabFocus
    {
        public static void Move(
            InputField first,
            InputField second,
            bool reverse,
            EventSystem events = null)
        {
            if (first == null || second == null)
                return;

            events = events != null ? events : EventSystem.current;
            if (events == null)
                return;

            var selected = events.currentSelectedGameObject;
            InputField target;

            if (selected == first.gameObject)
                target = reverse ? first : second;
            else if (selected == second.gameObject)
                target = first;
            else
                target = first;

            events.SetSelectedGameObject(target.gameObject);
            target.ActivateInputField();
            target.caretPosition = target.text.Length;
        }

        public static bool TabPressed(out bool reverse)
        {
            reverse = false;
#if ENABLE_INPUT_SYSTEM
            var keyboard = UnityEngine.InputSystem.Keyboard.current;
            if (keyboard != null && keyboard.tabKey.wasPressedThisFrame)
            {
                reverse = keyboard.shiftKey.isPressed;
                return true;
            }
            return false;
#elif ENABLE_LEGACY_INPUT_MANAGER
            if (Input.GetKeyDown(KeyCode.Tab))
            {
                reverse = Input.GetKey(KeyCode.LeftShift) || Input.GetKey(KeyCode.RightShift);
                return true;
            }
            return false;
#else
            return false;
#endif
        }

        /// <summary>Enter или Enter на цифровой клавиатуре.</summary>
        public static bool EnterPressed()
        {
#if ENABLE_INPUT_SYSTEM
            var keyboard = UnityEngine.InputSystem.Keyboard.current;
            return keyboard != null
                && (keyboard.enterKey.wasPressedThisFrame
                    || keyboard.numpadEnterKey.wasPressedThisFrame);
#elif ENABLE_LEGACY_INPUT_MANAGER
            return Input.GetKeyDown(KeyCode.Return) || Input.GetKeyDown(KeyCode.KeypadEnter);
#else
            return false;
#endif
        }

        public static bool EscapePressed()
        {
#if ENABLE_INPUT_SYSTEM
            var keyboard = UnityEngine.InputSystem.Keyboard.current;
            return keyboard != null && keyboard.escapeKey.wasPressedThisFrame;
#elif ENABLE_LEGACY_INPUT_MANAGER
            return Input.GetKeyDown(KeyCode.Escape);
#else
            return false;
#endif
        }
    }

    /// <summary>
    /// Ставится на корень экрана: связывает поля по Tab, отправляет форму по Enter
    /// и закрывает меню по Esc.
    /// </summary>
    public sealed class TabFocusDriver : MonoBehaviour
    {
        public InputField First;
        public InputField Second;
        public Action Submit;
        public Action Cancel;

        private void Update()
        {
            if (TabFocus.TabPressed(out var reverse))
                TabFocus.Move(First, Second, reverse);

            Handle(TabFocus.EnterPressed(), TabFocus.EscapePressed());
        }

        /// <summary>Выполняет действия клавиш; вынесено для EditMode-теста.</summary>
        public void Handle(bool submit, bool cancel)
        {
            if (submit)
                Submit?.Invoke();

            if (cancel)
                Cancel?.Invoke();
        }
    }
}