using System.Collections;
using UnityEngine;

[RequireComponent(typeof(AudioSource))]
public class IntroBGMController : MonoBehaviour
{
    [Header("Audio Source")]
    [SerializeField] private AudioSource audioSource;

    [Header("Start Timing")]
    [SerializeField] private bool playOnStart = true;
    [SerializeField] private float startDelay = 0.5f;

    [Header("Fade In")]
    [SerializeField] private bool useFadeIn = true;
    [SerializeField] private float fadeInDuration = 2.0f;
    [Range(0f, 1f)]
    [SerializeField] private float targetVolume = 0.55f;

    [Header("Loop")]
    [SerializeField] private bool loop = true;

    private Coroutine bgmRoutine;

    private void Awake()
    {
        if (audioSource == null)
        {
            audioSource = GetComponent<AudioSource>();
        }

        audioSource.playOnAwake = false;
        audioSource.loop = loop;
        audioSource.volume = 0f;
        audioSource.spatialBlend = 0f;
    }

    private void Start()
    {
        if (playOnStart)
        {
            PlayBGM();
        }
    }

    public void PlayBGM()
    {
        if (audioSource == null || audioSource.clip == null)
        {
            Debug.LogWarning("[IntroBGMController] AudioSource 또는 AudioClip이 없습니다.");
            return;
        }

        if (bgmRoutine != null)
        {
            StopCoroutine(bgmRoutine);
        }

        bgmRoutine = StartCoroutine(PlayBGMRoutine());
    }

    private IEnumerator PlayBGMRoutine()
    {
        if (startDelay > 0f)
        {
            yield return new WaitForSeconds(startDelay);
        }

        audioSource.volume = useFadeIn ? 0f : targetVolume;
        audioSource.loop = loop;
        audioSource.Play();

        if (useFadeIn)
        {
            float elapsed = 0f;

            while (elapsed < fadeInDuration)
            {
                elapsed += Time.deltaTime;
                float t = Mathf.Clamp01(elapsed / fadeInDuration);
                float easedT = EaseOutCubic(t);

                audioSource.volume = Mathf.Lerp(0f, targetVolume, easedT);

                yield return null;
            }

            audioSource.volume = targetVolume;
        }

        bgmRoutine = null;
    }

    public void StopBGM(float fadeOutDuration = 1.0f)
    {
        if (audioSource == null)
            return;

        if (bgmRoutine != null)
        {
            StopCoroutine(bgmRoutine);
        }

        bgmRoutine = StartCoroutine(StopBGMRoutine(fadeOutDuration));
    }

    private IEnumerator StopBGMRoutine(float fadeOutDuration)
    {
        float startVolume = audioSource.volume;
        float elapsed = 0f;

        while (elapsed < fadeOutDuration)
        {
            elapsed += Time.deltaTime;
            float t = Mathf.Clamp01(elapsed / fadeOutDuration);
            float easedT = EaseOutCubic(t);

            audioSource.volume = Mathf.Lerp(startVolume, 0f, easedT);

            yield return null;
        }

        audioSource.volume = 0f;
        audioSource.Stop();

        bgmRoutine = null;
    }

    private float EaseOutCubic(float t)
    {
        return 1f - Mathf.Pow(1f - t, 3f);
    }
}