using UnityEngine;

public class CameraFollow : MonoBehaviour
{
    [Header("拖动控制")]
    public float keyboardDragSpeed = 10f; // WASD拖动速度（模拟手指拖动屏幕）
    public float mouseDragSpeed = 0.5f; // 鼠标拖动速度
    public float touchDragSpeed = 0.5f; // 触摸拖动速度
    
    [Header("缩放控制（正交相机用orthographicSize，透视相机用fieldOfView）")]
    public float zoomSpeed = 5f; // 缩放速度
    public float minOrthographicSize = 5f; // 正交相机最小size
    public float maxOrthographicSize = 20f; // 正交相机最大size
    public float minFieldOfView = 30f; // 透视相机最小FOV
    public float maxFieldOfView = 90f; // 透视相机最大FOV
    
    [Header("边界限制")]
    public bool enableBounds = true;
    public float minX = -6f;
    public float maxX = 6f;
    public float minZ = -30f;
    public float maxZ = 91f;

    private Vector3 lastMousePosition;
    private bool isDragging = false;
    private Camera cam;

    private void Start()
    {
        cam = GetComponent<Camera>();
        if (cam == null)
        {
            Debug.LogError("CameraFollow需要挂载在Camera组件上");
        }
    }

    private void Update()
    {
        HandleKeyboardDrag();
        HandleMouseDrag();
        HandleKeyboardZoom();
    }

    private void HandleKeyboardDrag()
    {
        float horizontal = 0f;
        float vertical = 0f;

        if (Input.GetKey(KeyCode.W)) vertical = 1f;
        if (Input.GetKey(KeyCode.S)) vertical = -1f;
        if (Input.GetKey(KeyCode.A)) horizontal = -1f;
        if (Input.GetKey(KeyCode.D)) horizontal = 1f;

        if (horizontal != 0f || vertical != 0f)
        {
            Vector3 movement = new Vector3(horizontal, 0, vertical) * keyboardDragSpeed * Time.deltaTime;
            MoveCameraWithBounds(movement);
        }
    }

    private void HandleMouseDrag()
    {
        // 鼠标拖动
        if (Input.GetMouseButtonDown(0))
        {
            lastMousePosition = Input.mousePosition;
            isDragging = true;
        }
        else if (Input.GetMouseButton(0) && isDragging)
        {
            Vector3 delta = Input.mousePosition - lastMousePosition;
            Vector3 movement = new Vector3(-delta.x, 0, -delta.y) * mouseDragSpeed * Time.deltaTime;
            MoveCameraWithBounds(movement);
            lastMousePosition = Input.mousePosition;
        }
        else if (Input.GetMouseButtonUp(0))
        {
            isDragging = false;
        }

        // 触摸拖动（移动设备）
        if (Input.touchCount == 1 && Input.GetTouch(0).phase == TouchPhase.Moved)
        {
            Vector2 touchDelta = Input.GetTouch(0).deltaPosition;
            Vector3 movement = new Vector3(-touchDelta.x, 0, -touchDelta.y) * touchDragSpeed * Time.deltaTime;
            MoveCameraWithBounds(movement);
        }
    }

    private void HandleKeyboardZoom()
    {
        if (cam == null) return;

        float zoomDelta = 0f;

        // 上下键控制缩放
        if (Input.GetKey(KeyCode.UpArrow)) zoomDelta = -1f; // 缩小（拉近）
        if (Input.GetKey(KeyCode.DownArrow)) zoomDelta = 1f; // 放大（拉远）

        // 触摸双指缩放
        if (Input.touchCount == 2)
        {
            Touch touch0 = Input.GetTouch(0);
            Touch touch1 = Input.GetTouch(1);

            Vector2 touch0PrevPos = touch0.position - touch0.deltaPosition;
            Vector2 touch1PrevPos = touch1.position - touch1.deltaPosition;

            float prevMagnitude = (touch0PrevPos - touch1PrevPos).magnitude;
            float currentMagnitude = (touch0.position - touch1.position).magnitude;

            float difference = currentMagnitude - prevMagnitude;
            zoomDelta = -difference * 0.01f; // 负号：手指分开=拉近，手指合拢=拉远
        }

        if (zoomDelta != 0f)
        {
            if (cam.orthographic)
            {
                // 正交相机：调整 orthographicSize
                float newSize = cam.orthographicSize + zoomDelta * zoomSpeed * Time.deltaTime;
                cam.orthographicSize = Mathf.Clamp(newSize, minOrthographicSize, maxOrthographicSize);
            }
            else
            {
                // 透视相机：调整 fieldOfView
                float newFov = cam.fieldOfView + zoomDelta * zoomSpeed * Time.deltaTime;
                cam.fieldOfView = Mathf.Clamp(newFov, minFieldOfView, maxFieldOfView);
            }
        }
    }

    private void MoveCameraWithBounds(Vector3 movement)
    {
        Vector3 newPosition = transform.position + movement;

        if (enableBounds)
        {
            newPosition.x = Mathf.Clamp(newPosition.x, minX, maxX);
            newPosition.z = Mathf.Clamp(newPosition.z, minZ, maxZ);
        }

        transform.position = newPosition;
    }
}