using System;
using System.Collections.Generic;
using TMPro;
using UnityEngine;
using UnityEngine.UI;

namespace Ashwild.Settings
{
    /// <summary>
    /// A "◄ value ►" control that cycles a list of preset values. Pure UI: it knows nothing about
    /// which setting it drives. The hosting panel calls <see cref="Init"/> once with the presets
    /// (each a value plus its display label) and the action to run when the user steps; afterwards
    /// the panel pushes the current value through <see cref="SetValue"/>. Because each preset
    /// carries its own label, a value like -1 can read as "Unlimited" rather than a number.
    /// </summary>
    [DisallowMultipleComponent]
    public class SettingStepperWidget : MonoBehaviour
    {
        #region Serialized Fields

        [Header("References")]
        [SerializeField] private Button previousButton;
        [SerializeField] private Button nextButton;
        [SerializeField] private TMP_Text valueLabel;

        #endregion

        #region State

        private IReadOnlyList<(int value, string label)> presets;
        private Action<int> onChanged;
        private bool wrap;
        private int currentIndex;

        #endregion

        #region Public API

        /// <summary>
        /// Configures the stepper with its presets and wrap behaviour, and registers the action to
        /// run when the user steps. Call once (the action is not invoked by <see cref="SetValue"/>).
        /// </summary>
        public void Init(IReadOnlyList<(int value, string label)> presets, bool wrap, Action<int> onChanged)
        {
            if (presets == null || presets.Count == 0)
            {
                Debug.LogError($"[SettingStepperWidget] '{name}' was initialized with no presets.", this);
                return;
            }

            this.presets = presets;
            this.wrap = wrap;
            this.onChanged = onChanged;

            if (previousButton != null)
            {
                previousButton.onClick.RemoveListener(StepDown);
                previousButton.onClick.AddListener(StepDown);
            }
            if (nextButton != null)
            {
                nextButton.onClick.RemoveListener(StepUp);
                nextButton.onClick.AddListener(StepUp);
            }
        }

        /// <summary>
        /// Selects the preset matching the given value (falling back to the first) and shows its
        /// label, without invoking the apply action.
        /// </summary>
        public void SetValue(int value)
        {
            if (presets == null) return;
            currentIndex = IndexOfValue(value);
            UpdateLabel();
        }

        #endregion

        #region Event Handlers

        private void StepDown() => Step(-1);
        private void StepUp() => Step(+1);

        #endregion

        #region Internal Helpers

        /// <summary>
        /// Moves the selection by one step (clamped or wrapped), shows it and runs the apply action.
        /// </summary>
        private void Step(int direction)
        {
            if (presets == null || presets.Count == 0) return;

            int count = presets.Count;
            int next = currentIndex + direction;
            if (wrap)
                next = (next % count + count) % count;
            else
                next = Mathf.Clamp(next, 0, count - 1);

            if (next == currentIndex) return;

            currentIndex = next;
            UpdateLabel();
            onChanged?.Invoke(presets[currentIndex].value);
        }

        /// <summary>
        /// Returns the preset index whose value equals the given one, or 0 when none matches.
        /// </summary>
        private int IndexOfValue(int value)
        {
            for (int i = 0; i < presets.Count; i++)
                if (presets[i].value == value) return i;
            return 0;
        }

        /// <summary>
        /// Shows the current preset's label and disables arrows that would do nothing.
        /// </summary>
        private void UpdateLabel()
        {
            if (valueLabel != null) valueLabel.text = presets[currentIndex].label;

            if (!wrap)
            {
                if (previousButton != null) previousButton.interactable = currentIndex > 0;
                if (nextButton != null) nextButton.interactable = currentIndex < presets.Count - 1;
            }
        }

        #endregion
    }
}