// Copyright (c) Microsoft Corporation. All rights reserved.
// Licensed under the MIT License. See LICENSE in the project root for license information.

using UnityEngine;
using System.Collections.Generic;

namespace HoloToolkit.Unity.InputModule
{
    /// <summary>
    /// Input source supporting basic touchscreen input:
    /// * taps
    /// * holds
    /// Note that a hold-started is raised as soon as a contact exceeds the Epsilon value;
    /// if the contact subsequently qualifies as a tap then a hold-cancelled is also raised.
    /// </summary>
    public class TouchscreenInputSource : BaseInputSource
    {
        const float kContactEpsilon = 2.0f/60.0f;

        [SerializeField]
        [Tooltip("Time in seconds to determine if the contact registers as a tap or a hold")]
        protected float MaxTapContactTime = 0.5f;

        private List<PersistentTouch> ActiveTouches = new List<PersistentTouch>(0);

        private class PersistentTouch
        {
            public Touch touchData;
            public Ray screenpointRay;
            public float lifetime;
            public PersistentTouch(Touch touch, Ray ray)
            {
                touchData = touch;
                this.screenpointRay = ray;
                lifetime = 0.0f;
            }
        }

        #region Unity methods

        protected virtual void Start()
        {
            // Disable the inputsource if not supported by the device
            if (!Input.touchSupported)
            {
                this.enabled = false;
            }
        }

        protected virtual void Update()
        {
            foreach (Touch touch in Input.touches)
            {
                // Construct a ray from the current touch coordinates
                Ray ray = CameraCache.Main.ScreenPointToRay(touch.position);

                switch (touch.phase)
                {
                    case TouchPhase.Began:
                    case TouchPhase.Moved:
                    case TouchPhase.Stationary:
                        UpdateTouch(touch, ray);
                        break;

                    case TouchPhase.Ended:
                    case TouchPhase.Canceled:
                        RemoveTouch(touch);
                        break;
                }
            }
        }

        #endregion // Unity methods

        #region Event generation logic

        public bool UpdateTouch(Touch touch, Ray ray)
        {
            PersistentTouch knownTouch = GetPersistentTouch(touch.fingerId);
            if (knownTouch != null)
            {
                knownTouch.lifetime += Time.deltaTime;

                return true;
            }
            else
            {
                ActiveTouches.Add(new PersistentTouch(touch, ray));
                OnHoldStartedEvent(touch.fingerId);
                return false;
            }
        }

        public void RemoveTouch(Touch touch)
        {
            PersistentTouch knownTouch = GetPersistentTouch(touch.fingerId);
            if (knownTouch != null)
            {
                if (touch.phase == TouchPhase.Ended)
                {
                    if (knownTouch.lifetime < kContactEpsilon)
                    {
                        OnHoldCanceledEvent(touch.fingerId);
                    }
                    else if (knownTouch.lifetime < MaxTapContactTime)
                    {
                        OnHoldCanceledEvent(touch.fingerId);
                        OnTappedEvent(touch.fingerId, touch.tapCount);
                    }
                    else
                    {
                        OnHoldCompletedEvent(touch.fingerId);
                    }
                }
                else
                {
                    OnHoldCanceledEvent(touch.fingerId);
                }
                ActiveTouches.Remove(knownTouch);
            }
        }

        #endregion // Event generation logic

        private PersistentTouch GetPersistentTouch(int id)
        {
            for (int i = 0; i < ActiveTouches.Count; ++i)
            {
                if (ActiveTouches[i].touchData.fingerId == id)
                {
                    return ActiveTouches[i];
                }
            }
            return null;
        }

        private Touch? GetTouch(int id)
        {
            PersistentTouch knownTouch = GetPersistentTouch(id);
            if (knownTouch != null)
            {
                return knownTouch.touchData;
            }
            else
            {
                return null;
            }
        }

        protected void OnTappedEvent(int id, int tapCount)
        {
            InputManager.Instance.RaiseInputClicked(this, (uint)id, InteractionSourcePressInfo.Select, tapCount);
        }

        protected void OnHoldStartedEvent(int id)
        {
            InputManager.Instance.RaiseHoldStarted(this, (uint)id);
        }

        protected void OnHoldCanceledEvent(int id)
        {
            InputManager.Instance.RaiseHoldCanceled(this, (uint)id);
        }

        protected void OnHoldCompletedEvent(int id)
        {
            InputManager.Instance.RaiseHoldCompleted(this, (uint)id);
        }


        #region Base Input Source Methods

        public override bool TryGetSourceKind(uint sourceId, out InteractionSourceInfo sourceKind)
        {
            sourceKind = InteractionSourceInfo.Hand;
            return true;
        }

        public override bool TryGetPointerPosition(uint sourceId, out Vector3 position)
        {
            Touch? knownTouch = GetTouch((int)sourceId);
            position = (knownTouch.HasValue) ? (Vector3)knownTouch.Value.position : Vector3.zero;
            return knownTouch.HasValue;
        }

        public override bool TryGetPointerRotation(uint sourceId, out Quaternion rotation)
        {
            rotation = Quaternion.identity;
            return false;
        }

        public override bool TryGetPointingRay(uint sourceId, out Ray pointingRay)
        {
            PersistentTouch knownTouch = GetPersistentTouch((int)sourceId);
            if (knownTouch != null)
            {
                pointingRay = knownTouch.screenpointRay;
                return true;
            }
            pointingRay = default(Ray);
            return false;
        }

        public override bool TryGetGripPosition(uint sourceId, out Vector3 position)
        {
            position = Vector3.zero;
            return false;
        }

        public override bool TryGetGripRotation(uint sourceId, out Quaternion rotation)
        {
            rotation = Quaternion.identity;
            return false;
        }

        public override SupportedInputInfo GetSupportedInputInfo(uint sourceId)
        {
            return SupportedInputInfo.Position | SupportedInputInfo.Pointing;
        }

        public override bool TryGetThumbstick(uint sourceId, out bool isPressed, out Vector2 position)
        {
            isPressed = false;
            position = Vector2.zero;
            return false;
        }

        public override bool TryGetTouchpad(uint sourceId, out bool isPressed, out bool isTouched, out Vector2 position)
        {
            isPressed = false;
            isTouched = false;
            position = Vector2.zero;
            return false;
        }

        public override bool TryGetSelect(uint sourceId, out bool isPressed, out double pressedAmount)
        {
            isPressed = false;
            pressedAmount = 0.0;
            return false;
        }

        public override bool TryGetGrasp(uint sourceId, out bool isPressed)
        {
            isPressed = false;
            return false;
        }

        public override bool TryGetMenu(uint sourceId, out bool isPressed)
        {
            isPressed = false;
            return false;
        }

        #endregion // Base Input Source Methods

    }
}