using System.Collections.Generic;
using UnityEngine;
#if ENABLE_INPUT_SYSTEM
using UnityEngine.InputSystem;
using UnityEngine.InputSystem.EnhancedTouch;
using ETouch = UnityEngine.InputSystem.EnhancedTouch.Touch;
#endif

/// <summary>
/// Mobile touch dispatcher for the five gameplay tracks.
/// PC builds disable this component immediately and use keyboard input only.
/// </summary>
public class TrackTouchInput : MonoBehaviour
{
    [SerializeField] private Camera gameplayCamera;
    [SerializeField] private bool enableMouseFallback = false;
    [Tooltip("推荐：给 5 个 TrackTouchZone 物体单独设一个 layer(比如 layer 10 TouchZone)，这里只勾该 layer，避免音符/背景碰撞体挤爆缓冲导致间歇漏点")]
    [SerializeField] private LayerMask hitLayers = ~0;
    [SerializeField] private float trackPlaneWorldZ = 0f;
    [SerializeField] private bool forceOrthographicMode = false;

    private readonly Dictionary<int, int> activeTouches = new Dictionary<int, int>();
    private int mouseHeldTrack = -1;

    // 缓冲从 16 扩到 64：密集音符流量下防止 TrackTouchZone 被挤出 OverlapPoint 结果
    private static readonly Collider2D[] overlapResults = new Collider2D[64];
    private ContactFilter2D overlapFilter;
    private bool filterReady;

    private Camera Cam
    {
        get
        {
            if (gameplayCamera == null)
                gameplayCamera = Camera.main;
            return gameplayCamera;
        }
    }

    private static bool ShouldProcessTouchInput()
    {
#if UNITY_ANDROID || UNITY_IOS
        return true;
#else
        return false;
#endif
    }

    private void Awake()
    {
        if (!ShouldProcessTouchInput())
            enabled = false;
    }

#if ENABLE_INPUT_SYSTEM
    private void OnEnable()
    {
        if (!ShouldProcessTouchInput())
            return;

        EnhancedTouchSupport.Enable();
    }
#endif

    private void Update()
    {
        if (!ShouldProcessTouchInput())
            return;

        InputManager inputManager = InputManager.Instance;
        Camera cam = Cam;
        if (inputManager == null || cam == null)
            return;

        int touchCount = ProcessTouches(inputManager, cam);
        if (enableMouseFallback && touchCount == 0)
        {
            ProcessMouse(inputManager, cam);
        }
    }

    private int ProcessTouches(InputManager inputManager, Camera cam)
    {
#if ENABLE_INPUT_SYSTEM
        var touches = ETouch.activeTouches;
        int count = touches.Count;
        for (int i = 0; i < count; i++)
        {
            ETouch touch = touches[i];
            switch (touch.phase)
            {
                case UnityEngine.InputSystem.TouchPhase.Began:
                    HandleTouchBegan(inputManager, cam, touch.touchId, touch.screenPosition);
                    break;
                case UnityEngine.InputSystem.TouchPhase.Ended:
                case UnityEngine.InputSystem.TouchPhase.Canceled:
                    HandleTouchEnded(inputManager, touch.touchId);
                    break;
            }
        }
        return count;
#else
        int count = Input.touchCount;
        for (int i = 0; i < count; i++)
        {
            Touch touch = Input.GetTouch(i);
            switch (touch.phase)
            {
                case TouchPhase.Began:
                    HandleTouchBegan(inputManager, cam, touch.fingerId, touch.position);
                    break;
                case TouchPhase.Ended:
                case TouchPhase.Canceled:
                    HandleTouchEnded(inputManager, touch.fingerId);
                    break;
            }
        }
        return count;
#endif
    }

    private void HandleTouchBegan(InputManager inputManager, Camera cam, int touchId, Vector2 screenPosition)
    {
        int track = ResolveTrack(cam, screenPosition);
        if (track < 0)
            return;

        activeTouches[touchId] = track;
        inputManager.PressTrack(track);
    }

    private void HandleTouchEnded(InputManager inputManager, int touchId)
    {
        if (!activeTouches.TryGetValue(touchId, out int track))
            return;

        activeTouches.Remove(touchId);
        inputManager.ReleaseTrack(track);
    }

    private void ProcessMouse(InputManager inputManager, Camera cam)
    {
#if ENABLE_INPUT_SYSTEM
        Mouse mouse = Mouse.current;
        if (mouse == null)
            return;

        if (mouse.leftButton.wasPressedThisFrame)
        {
            int track = ResolveTrack(cam, mouse.position.ReadValue());
            if (track >= 0)
            {
                mouseHeldTrack = track;
                inputManager.PressTrack(track);
            }
        }
        else if (mouse.leftButton.wasReleasedThisFrame && mouseHeldTrack >= 0)
        {
            inputManager.ReleaseTrack(mouseHeldTrack);
            mouseHeldTrack = -1;
        }
#else
        if (Input.GetMouseButtonDown(0))
        {
            int track = ResolveTrack(cam, Input.mousePosition);
            if (track >= 0)
            {
                mouseHeldTrack = track;
                inputManager.PressTrack(track);
            }
        }
        else if (Input.GetMouseButtonUp(0) && mouseHeldTrack >= 0)
        {
            inputManager.ReleaseTrack(mouseHeldTrack);
            mouseHeldTrack = -1;
        }
#endif
    }

    private int ResolveTrack(Camera cam, Vector2 screenPosition)
    {
        EnsureOverlapFilter();

        Vector2 worldPoint;
        if (forceOrthographicMode || cam.orthographic)
        {
            Vector3 world = cam.ScreenToWorldPoint(screenPosition);
            worldPoint = new Vector2(world.x, world.y);
        }
        else
        {
            Ray ray = cam.ScreenPointToRay(screenPosition);
            float denom = ray.direction.z;
            if (Mathf.Abs(denom) < 1e-6f)
                return -1;

            float t = (trackPlaneWorldZ - ray.origin.z) / denom;
            if (t < 0f)
                return -1;

            Vector3 world = ray.origin + ray.direction * t;
            worldPoint = new Vector2(world.x, world.y);
        }

        int count = Physics2D.OverlapPoint(worldPoint, overlapFilter, overlapResults);
        for (int i = 0; i < count; i++)
        {
            Collider2D hit = overlapResults[i];
            if (hit == null)
                continue;

            TrackTouchZone zone = hit.GetComponent<TrackTouchZone>();
            if (zone == null)
                zone = hit.GetComponentInParent<TrackTouchZone>();
            if (zone != null)
                return zone.trackIndex;
        }

        return ResolveNearestZone(worldPoint);
    }

    private int ResolveNearestZone(Vector2 worldPoint)
    {
        IReadOnlyList<TrackTouchZone> zones = TrackTouchZone.All;
        int bestTrack = -1;
        float bestDistance = float.MaxValue;

        for (int i = 0; i < zones.Count; i++)
        {
            TrackTouchZone zone = zones[i];
            if (zone == null || zone.Collider == null)
                continue;

            Bounds bounds = zone.Collider.bounds;
            if (worldPoint.y < bounds.min.y - 0.1f || worldPoint.y > bounds.max.y + 0.1f)
                continue;

            float distance = Mathf.Abs(worldPoint.x - bounds.center.x);
            if (distance < bestDistance)
            {
                bestDistance = distance;
                bestTrack = zone.trackIndex;
            }
        }

        return bestTrack;
    }

    private void EnsureOverlapFilter()
    {
        if (filterReady)
            return;

        overlapFilter = new ContactFilter2D();
        overlapFilter.useLayerMask = true;
        overlapFilter.SetLayerMask(hitLayers);
        overlapFilter.useTriggers = true;
        filterReady = true;
    }

    private void OnDisable()
    {
        if (!ShouldProcessTouchInput())
            return;

        InputManager inputManager = InputManager.Instance;
        if (inputManager != null)
        {
            foreach (KeyValuePair<int, int> touch in activeTouches)
            {
                inputManager.ReleaseTrack(touch.Value);
            }

            if (mouseHeldTrack >= 0)
                inputManager.ReleaseTrack(mouseHeldTrack);
        }

        activeTouches.Clear();
        mouseHeldTrack = -1;

#if ENABLE_INPUT_SYSTEM
        EnhancedTouchSupport.Disable();
#endif
    }
}