/*
 * StandaloneInputModule : 
 *     PointerInputModule : 
 *         BaseInputModule
 */

using System;
using UnityEngine;
using UnityEngine.Serialization;

namespace UnityEngine.EventSystems
{
    [AddComponentMenu("Event/Standalone Input Module")]
    public class StandaloneInputModule : PointerInputModule
    {
        private float m_PrevActionTime;
        private Vector2 m_LastMoveVector;
        private int m_ConsecutiveMoveCount = 0;

				// 上一个鼠标位置和当前鼠标位置，每帧更新
        private Vector2 m_LastMousePosition;
        private Vector2 m_MousePosition;

        private GameObject m_CurrentFocusedGameObject;

        protected StandaloneInputModule()
        {
        }

        [Obsolete("Mode is no longer needed on input module as it handles both mouse and keyboard simultaneously.", false)]
        public enum InputMode
        {
            Mouse,
            Buttons
        }

        [Obsolete("Mode is no longer needed on input module as it handles both mouse and keyboard simultaneously.", false)]
        public InputMode inputMode
        {
            get { return InputMode.Mouse; }
        }

        [SerializeField]
        private string m_HorizontalAxis = "Horizontal";

        /// <summary>
        /// Name of the vertical axis for movement (if axis events are used).
        /// </summary>
        [SerializeField]
        private string m_VerticalAxis = "Vertical";

        /// <summary>
        /// Name of the submit button.
        /// </summary>
        [SerializeField]
        private string m_SubmitButton = "Submit";

        /// <summary>
        /// Name of the submit button.
        /// </summary>
        [SerializeField]
        private string m_CancelButton = "Cancel";

        [SerializeField]
        private float m_InputActionsPerSecond = 10;

        [SerializeField]
        private float m_RepeatDelay = 0.5f;

        [SerializeField]
        [FormerlySerializedAs("m_AllowActivationOnMobileDevice")]
        private bool m_ForceModuleActive;

        [Obsolete("allowActivationOnMobileDevice has been deprecated. Use forceModuleActive instead (UnityUpgradable) -> forceModuleActive")]
        public bool allowActivationOnMobileDevice
        {
            get { return m_ForceModuleActive; }
            set { m_ForceModuleActive = value; }
        }

        public bool forceModuleActive
        {
            get { return m_ForceModuleActive; }
            set { m_ForceModuleActive = value; }
        }

        public float inputActionsPerSecond
        {
            get { return m_InputActionsPerSecond; }
            set { m_InputActionsPerSecond = value; }
        }

        public float repeatDelay
        {
            get { return m_RepeatDelay; }
            set { m_RepeatDelay = value; }
        }

        /// <summary>
        /// Name of the horizontal axis for movement (if axis events are used).
        /// </summary>
        public string horizontalAxis
        {
            get { return m_HorizontalAxis; }
            set { m_HorizontalAxis = value; }
        }

        /// <summary>
        /// Name of the vertical axis for movement (if axis events are used).
        /// </summary>
        public string verticalAxis
        {
            get { return m_VerticalAxis; }
            set { m_VerticalAxis = value; }
        }

        public string submitButton
        {
            get { return m_SubmitButton; }
            set { m_SubmitButton = value; }
        }

        public string cancelButton
        {
            get { return m_CancelButton; }
            set { m_CancelButton = value; }
        }

        private bool ShouldIgnoreEventsOnNoFocus()
        {
            switch (SystemInfo.operatingSystemFamily)
            {
                case OperatingSystemFamily.Windows:
                case OperatingSystemFamily.Linux:
                case OperatingSystemFamily.MacOSX:
#if UNITY_EDITOR
                    if (UnityEditor.EditorApplication.isRemoteConnected)
                        return false;
#endif
                    return true;
                default:
                    return false;
            }
        }

        //c! 这里只更新鼠标位置
        public override void UpdateModule()
        {
			// 如果没有获取焦点，且忽略没有焦点时的事件，返回（除非开启远程连接，否则会这样）
            if (!eventSystem.isFocused && ShouldIgnoreEventsOnNoFocus())
                return;

		    // 更新鼠标位置
            m_LastMousePosition = m_MousePosition;
            m_MousePosition = input.mousePosition;
        }

        public override bool IsModuleSupported()
        {
            return m_ForceModuleActive || input.mousePresent || input.touchSupported;
        }

        public override bool ShouldActivateModule()
        {
            if (!base.ShouldActivateModule())
                return false;

            var shouldActivate = m_ForceModuleActive;
            shouldActivate |= input.GetButtonDown(m_SubmitButton);
            shouldActivate |= input.GetButtonDown(m_CancelButton);
            shouldActivate |= !Mathf.Approximately(input.GetAxisRaw(m_HorizontalAxis), 0.0f);
            shouldActivate |= !Mathf.Approximately(input.GetAxisRaw(m_VerticalAxis), 0.0f);
            shouldActivate |= (m_MousePosition - m_LastMousePosition).sqrMagnitude > 0.0f;
            shouldActivate |= input.GetMouseButtonDown(0);

            if (input.touchCount > 0)
                shouldActivate = true;

            return shouldActivate;
        }

        public override void ActivateModule()
        {
            if (!eventSystem.isFocused && ShouldIgnoreEventsOnNoFocus())
                return;

            base.ActivateModule();
            m_MousePosition = input.mousePosition;
            m_LastMousePosition = input.mousePosition;

            var toSelect = eventSystem.currentSelectedGameObject;
            if (toSelect == null)
                toSelect = eventSystem.firstSelectedGameObject;

            eventSystem.SetSelectedGameObject(toSelect, GetBaseEventData());
        }

        public override void DeactivateModule()
        {
            base.DeactivateModule();
            ClearSelection();
        }
        
        //c! input module事件处理主入口，每帧更新
        public override void Process()
        {
            // 如果没有获取焦点，不需要处理
            if (!eventSystem.isFocused && ShouldIgnoreEventsOnNoFocus()) 
                return;

            //event 给选中的对象发布更新事件
            bool usedEvent = SendUpdateEventToSelectedObject();

            // 如果勾上了Send Navigation Events，发送move , submit, cancel事件
            if (eventSystem.sendNavigationEvents)
            {
                if (!usedEvent)
                    usedEvent |= SendMoveEventToSelectedObject(); //event 键盘方向键移动时给eventSystem选中的对象发布IMoveHandler事件

                if (!usedEvent)
                    SendSubmitEventToSelectedObject(); //event 如果按了相应按键，发布submit或者cancel事件
            }

            // 模拟触摸或鼠标输入
            // touch needs to take precedence because of the mouse emulation layer
            usedEvent = ProcessTouchEvents(); //event 检测屏幕触摸，PC上没有

            if(!usedEvent && input.mousePresent)
                ProcessMouseEvent(); // 处理鼠标事件
        }

        //c 触摸事件
        private bool ProcessTouchEvents()
        {
            for (int i = 0; i < input.touchCount; ++i)  //多点触控
            {
                Debug.Log("Touch");

                Touch touch = input.GetTouch(i);

                if (touch.type == TouchType.Indirect)
                    continue;

                bool released; // 这是一个手指抬起操作
                bool pressed; // 这是一个手指放下操作
                //
                PointerEventData pointer = GetTouchPointerEventData(touch, out pressed, out released); // 射线检测并保存检测结果

                // 处理触摸或抬起反馈，已经准备好了被触摸的物体
                ProcessTouchPress(pointer, pressed, released);

                if (!released)
                {
                    ProcessMove(pointer);
                    ProcessDrag(pointer);
                }
                else
                    RemovePointerData(pointer);
            }
            return input.touchCount > 0;
        }

        //c 处理触摸\抬起
        protected void ProcessTouchPress(PointerEventData pointerEvent, bool pressed, bool released)
        {
            var currentOverGo = pointerEvent.pointerCurrentRaycast.gameObject;

            // 触摸反馈
            // PointerDown notification
            if (pressed)
            {
                pointerEvent.eligibleForClick = true;
                pointerEvent.delta = Vector2.zero;
                pointerEvent.dragging = false;
                pointerEvent.useDragThreshold = true;
                pointerEvent.pressPosition = pointerEvent.position;
                pointerEvent.pointerPressRaycast = pointerEvent.pointerCurrentRaycast;

                DeselectIfSelectionChanged(currentOverGo, pointerEvent);

                if (pointerEvent.pointerEnter != currentOverGo)
                {
                    // send a pointer enter to the touched element if it isn't the one to select...
                    HandlePointerExitAndEnter(pointerEvent, currentOverGo);
                    pointerEvent.pointerEnter = currentOverGo;
                }

                //event IPointerDownHandler 
                // search for the control that will receive the press
                // if we can't find a press handler set the press
                // handler to be what would receive a click.
                var newPressed = ExecuteEvents.ExecuteHierarchy(currentOverGo, pointerEvent, ExecuteEvents.pointerDownHandler);

                // didnt find a press handler... search for a click handler
                if (newPressed == null)
                    newPressed = ExecuteEvents.GetEventHandler<IPointerClickHandler>(currentOverGo);

                // Debug.Log("Pressed: " + newPressed);

                float time = Time.unscaledTime;

                if (newPressed == pointerEvent.lastPress)
                {
                    var diffTime = time - pointerEvent.clickTime;
                    if (diffTime < 0.3f)
                        ++pointerEvent.clickCount;
                    else
                        pointerEvent.clickCount = 1;

                    pointerEvent.clickTime = time;
                }
                else
                {
                    pointerEvent.clickCount = 1;
                }

                pointerEvent.pointerPress = newPressed;
                pointerEvent.rawPointerPress = currentOverGo;

                pointerEvent.clickTime = time;

                // Save the drag handler as well
                pointerEvent.pointerDrag = ExecuteEvents.GetEventHandler<IDragHandler>(currentOverGo);

                if (pointerEvent.pointerDrag != null)
                    ExecuteEvents.Execute(pointerEvent.pointerDrag, pointerEvent, ExecuteEvents.initializePotentialDrag);
            }

            // 抬起反馈
            // PointerUp notification
            if (released)
            {
                // Debug.Log("Executing pressup on: " + pointer.pointerPress);
                ExecuteEvents.Execute(pointerEvent.pointerPress, pointerEvent, ExecuteEvents.pointerUpHandler);

                // Debug.Log("KeyCode: " + pointer.eventData.keyCode);

                // see if we mouse up on the same element that we clicked on...
                var pointerUpHandler = ExecuteEvents.GetEventHandler<IPointerClickHandler>(currentOverGo); // 从这个对象开始往上找，直到一个挂了继承了IPointerClickHandler的组件

                // PointerClick and Drop events
                if (pointerEvent.pointerPress == pointerUpHandler && pointerEvent.eligibleForClick) //只有在pointerPress == pointerUpHandler时才会触发click事件
                {
                    ExecuteEvents.Execute(pointerEvent.pointerPress, pointerEvent, ExecuteEvents.pointerClickHandler);
                }
                else if (pointerEvent.pointerDrag != null && pointerEvent.dragging) // 如果两者不相等，触发drop事件
                {
                    ExecuteEvents.ExecuteHierarchy(currentOverGo, pointerEvent, ExecuteEvents.dropHandler);
                }

                pointerEvent.eligibleForClick = false;
                pointerEvent.pointerPress = null;
                pointerEvent.rawPointerPress = null;

                if (pointerEvent.pointerDrag != null && pointerEvent.dragging)
                    ExecuteEvents.Execute(pointerEvent.pointerDrag, pointerEvent, ExecuteEvents.endDragHandler);

                pointerEvent.dragging = false;
                pointerEvent.pointerDrag = null;

                // send exit events as we need to simulate this on touch up on touch device
                ExecuteEvents.ExecuteHierarchy(pointerEvent.pointerEnter, pointerEvent, ExecuteEvents.pointerExitHandler);
                pointerEvent.pointerEnter = null;
            }
        }

        /// <summary>
        /// Process submit keys.
        /// </summary>
        protected bool SendSubmitEventToSelectedObject()
        {
            if (eventSystem.currentSelectedGameObject == null)
                return false;

            // 发布submit事件或者cancel事件

            var data = GetBaseEventData();
            if (input.GetButtonDown(m_SubmitButton)) // 这里是Project>Input里面配置的
                ExecuteEvents.Execute(eventSystem.currentSelectedGameObject, data, ExecuteEvents.submitHandler);

            if (input.GetButtonDown(m_CancelButton))
                ExecuteEvents.Execute(eventSystem.currentSelectedGameObject, data, ExecuteEvents.cancelHandler);
            return data.used;
        }

        private Vector2 GetRawMoveVector()
        {
            Vector2 move = Vector2.zero;
            move.x = input.GetAxisRaw(m_HorizontalAxis);
            move.y = input.GetAxisRaw(m_VerticalAxis);

            if (input.GetButtonDown(m_HorizontalAxis))
            {
                if (move.x < 0)
                    move.x = -1f;
                if (move.x > 0)
                    move.x = 1f;
            }
            if (input.GetButtonDown(m_VerticalAxis))
            {
                if (move.y < 0)
                    move.y = -1f;
                if (move.y > 0)
                    move.y = 1f;
            }
            return move;
        }

        /// <summary>
        /// Process keyboard events.
        /// </summary>
        protected bool SendMoveEventToSelectedObject()
        {
            float time = Time.unscaledTime;

            Vector2 movement = GetRawMoveVector();
            if (Mathf.Approximately(movement.x, 0f) && Mathf.Approximately(movement.y, 0f)) // 如果键盘方向键没动，返回
            {
                m_ConsecutiveMoveCount = 0;
                return false;
            }

            //allow即是否允许发布事件
            // If user pressed key again, always allow event
            bool allow = input.GetButtonDown(m_HorizontalAxis) || input.GetButtonDown(m_VerticalAxis);
            bool similarDir = (Vector2.Dot(movement, m_LastMoveVector) > 0); // 和之前的方向是否夹角在90°以内，如果是的话说明很接近
            if (!allow)
            {
                // Otherwise, user held down key or axis.
                // If direction didn't change at least 90 degrees, wait for delay before allowing consequtive event.
                if (similarDir && m_ConsecutiveMoveCount == 1)
                    allow = (time > m_PrevActionTime + m_RepeatDelay);
                // If direction changed at least 90 degree, or we already had the delay, repeat at repeat rate.
                else
                    allow = (time > m_PrevActionTime + 1f / m_InputActionsPerSecond);
            }
            if (!allow)
                return false;

            // 发布IMoveHandler事件

            // Debug.Log(m_ProcessingEvent.rawType + " axis:" + m_AllowAxisEvents + " value:" + "(" + x + "," + y + ")");
            var axisEventData = GetAxisEventData(movement.x, movement.y, 0.6f);

            if (axisEventData.moveDir != MoveDirection.None)
            {
                ExecuteEvents.Execute(eventSystem.currentSelectedGameObject, axisEventData, ExecuteEvents.moveHandler); // IMoveHandler.OnMove
                if (!similarDir)
                    m_ConsecutiveMoveCount = 0;
                m_ConsecutiveMoveCount++;

                m_PrevActionTime = time;
                m_LastMoveVector = movement;
            }
            else
            {
                m_ConsecutiveMoveCount = 0;
            }

            return axisEventData.used;
        }

        protected void ProcessMouseEvent()
        {
            ProcessMouseEvent(0);
        }

        [Obsolete("This method is no longer checked, overriding it with return true does nothing!")]
        protected virtual bool ForceAutoSelect()
        {
            return false;
        }

        /// <summary>
        /// Process all mouse events.
        /// </summary>
        protected void ProcessMouseEvent(int id)
        {
            var mouseData = GetMousePointerEventData(id);
            var leftButtonData = mouseData.GetButtonState(PointerEventData.InputButton.Left).eventData;

            m_CurrentFocusedGameObject = leftButtonData.buttonData.pointerCurrentRaycast.gameObject;

            // Process the first mouse button fully
            ProcessMousePress(leftButtonData);
            ProcessMove(leftButtonData.buttonData);
            ProcessDrag(leftButtonData.buttonData);

            // Now process right / middle clicks
            ProcessMousePress(mouseData.GetButtonState(PointerEventData.InputButton.Right).eventData);
            ProcessDrag(mouseData.GetButtonState(PointerEventData.InputButton.Right).eventData.buttonData);
            ProcessMousePress(mouseData.GetButtonState(PointerEventData.InputButton.Middle).eventData);
            ProcessDrag(mouseData.GetButtonState(PointerEventData.InputButton.Middle).eventData.buttonData);

            if (!Mathf.Approximately(leftButtonData.buttonData.scrollDelta.sqrMagnitude, 0.0f))
            {
                var scrollHandler = ExecuteEvents.GetEventHandler<IScrollHandler>(leftButtonData.buttonData.pointerCurrentRaycast.gameObject);
                ExecuteEvents.ExecuteHierarchy(scrollHandler, leftButtonData.buttonData, ExecuteEvents.scrollHandler);
            }
        }

        // 每帧发送一个OnUpdateSelected事件
        protected bool SendUpdateEventToSelectedObject()
        {
            if (eventSystem.currentSelectedGameObject == null)
                return false;

            var data = GetBaseEventData();
            //event 向eventSystem当前选中的gameobject发布一个更新事件IUpdateSelectedHandler，比如inputfield
            ExecuteEvents.Execute(eventSystem.currentSelectedGameObject, data, ExecuteEvents.updateSelectedHandler);
            return data.used;
        }

        // 处理鼠标按下事件，发送消息，调用回调
        /// <summary>
        /// Process the current mouse press.
        /// </summary>
        protected void ProcessMousePress(MouseButtonEventData data)
        {
            var pointerEvent = data.buttonData;
            var currentOverGo = pointerEvent.pointerCurrentRaycast.gameObject;

            // PointerDown notification
            if (data.PressedThisFrame())
            {
                pointerEvent.eligibleForClick = true;
                pointerEvent.delta = Vector2.zero;
                pointerEvent.dragging = false;
                pointerEvent.useDragThreshold = true;
                pointerEvent.pressPosition = pointerEvent.position;
                pointerEvent.pointerPressRaycast = pointerEvent.pointerCurrentRaycast;

                DeselectIfSelectionChanged(currentOverGo, pointerEvent);

                // search for the control that will receive the press
                // if we can't find a press handler set the press
                // handler to be what would receive a click.
                var newPressed = ExecuteEvents.ExecuteHierarchy(currentOverGo, pointerEvent, ExecuteEvents.pointerDownHandler);

                // didnt find a press handler... search for a click handler
                if (newPressed == null)
                    newPressed = ExecuteEvents.GetEventHandler<IPointerClickHandler>(currentOverGo);

                // Debug.Log("Pressed: " + newPressed);

                float time = Time.unscaledTime;

                if (newPressed == pointerEvent.lastPress)
                {
                    var diffTime = time - pointerEvent.clickTime;
                    if (diffTime < 0.3f)
                        ++pointerEvent.clickCount;
                    else
                        pointerEvent.clickCount = 1;

                    pointerEvent.clickTime = time;
                }
                else
                {
                    pointerEvent.clickCount = 1;
                }

                pointerEvent.pointerPress = newPressed;
                pointerEvent.rawPointerPress = currentOverGo;

                pointerEvent.clickTime = time;

                // Save the drag handler as well
                pointerEvent.pointerDrag = ExecuteEvents.GetEventHandler<IDragHandler>(currentOverGo);

                if (pointerEvent.pointerDrag != null)
                    ExecuteEvents.Execute(pointerEvent.pointerDrag, pointerEvent, ExecuteEvents.initializePotentialDrag);
            }

            // PointerUp notification
            if (data.ReleasedThisFrame())
            {
                // Debug.Log("Executing pressup on: " + pointer.pointerPress);
                ExecuteEvents.Execute(pointerEvent.pointerPress, pointerEvent, ExecuteEvents.pointerUpHandler);

                // Debug.Log("KeyCode: " + pointer.eventData.keyCode);

                // see if we mouse up on the same element that we clicked on...
                var pointerUpHandler = ExecuteEvents.GetEventHandler<IPointerClickHandler>(currentOverGo);

                // PointerClick and Drop events
                if (pointerEvent.pointerPress == pointerUpHandler && pointerEvent.eligibleForClick)
                {
                    ExecuteEvents.Execute(pointerEvent.pointerPress, pointerEvent, ExecuteEvents.pointerClickHandler);
                }
                else if (pointerEvent.pointerDrag != null && pointerEvent.dragging)
                {
                    ExecuteEvents.ExecuteHierarchy(currentOverGo, pointerEvent, ExecuteEvents.dropHandler);
                }

                pointerEvent.eligibleForClick = false;
                pointerEvent.pointerPress = null;
                pointerEvent.rawPointerPress = null;

                if (pointerEvent.pointerDrag != null && pointerEvent.dragging)
                    ExecuteEvents.Execute(pointerEvent.pointerDrag, pointerEvent, ExecuteEvents.endDragHandler);

                pointerEvent.dragging = false;
                pointerEvent.pointerDrag = null;

                // redo pointer enter / exit to refresh state
                // so that if we moused over somethign that ignored it before
                // due to having pressed on something else
                // it now gets it.
                if (currentOverGo != pointerEvent.pointerEnter)
                {
                    HandlePointerExitAndEnter(pointerEvent, null);
                    HandlePointerExitAndEnter(pointerEvent, currentOverGo);
                }
            }
        }

        protected GameObject GetCurrentFocusedGameObject()
        {
            return m_CurrentFocusedGameObject;
        }
    }
}