//***********************************************************
// Filename: Teleport.cs
// Author: Moritz Kolvenbach, Marco Fendrich
// Last changes: Mittwoch, 8. August 2018
// Content: Class for actual positional change of player
//***********************************************************

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

/// <summary>
/// Base class for teleportation
/// </summary>
public class Teleport : MonoBehaviour
{

    /// Origin of SteamVR tracking space
    [Tooltip("Origin of the SteamVR tracking space")]
    public Transform OriginTransform;
    /// Origin of the player's head
    [Tooltip("Transform of the player's head")]
    public Transform HeadTransform;

    /// How long, in seconds, the fade-in/fade-out animation should take
    [Tooltip("Duration of the \"blink\" animation (fading in and out upon teleport) in seconds")]
    public float TeleportFadeDuration = 0.2f;

    /// Indicates the current use of teleportation.
    /// NONE: The player is not using teleportation right now
    /// TELEPORTING: The player has selected a teleport destination and is currently teleporting now (fading in/out)
    private TeleportState currentTeleportState = TeleportState.NONE;

    private bool FadingIn = false; // tracks whether fading in or out
    private float TeleportTimeMarker; // tracks start time of last teleport

    // script to trigger fade in/out effect
    public FadeInOut fadeScript;

    // Spot to be teleported to if called externally
    private Vector3 destinationPoint;
    private float rotation = float.NegativeInfinity;

    // Time to be used as time stamp for teleport event
    private float teleportStartTime;

    /// <summary>
    /// Initiates a teleportation of the player to the given position
    /// </summary>
    /// <param name="destinationPoint">Where the player should be teleported</param>
    public void CallTeleport(Vector3 destinationPoint)
    {
        currentTeleportState = TeleportState.TELEPORTING;
        this.destinationPoint = destinationPoint;
        TeleportTimeMarker = Time.time;
    }

    /// <summary>
    /// Initiates a teleportation including rotation of the player to given position and with given rotation
    /// </summary>
    /// <param name="destinationPoint">Where the player should be teleported</param>
    /// <param name="rotation">Angle in degrees that the player should be rotated</param>
    public void CallTeleport(Vector3 destinationPoint, float rotation)
    {
        currentTeleportState = TeleportState.TELEPORTING;
        this.destinationPoint = destinationPoint;
        TeleportTimeMarker = Time.time;
        this.rotation = rotation;
    }

    /// <summary>
    /// Initiates a teleportation including rotation of the player to given position and with given rotation. Creates an event including timestamps
    /// </summary>
    /// <param name="destinationPoint">Where the player should be teleported</param>
    /// <param name="rotation">Angle in degrees that the player should be rotated</param>
    /// <param name="teleportStartTime">Time at which the teleportbutton was first pressed</param>
    public void CallTeleport(Vector3 destinationPoint, float rotation, float teleportStartTime)
    {
        currentTeleportState = TeleportState.TELEPORTING;
        this.destinationPoint = destinationPoint;
        TeleportTimeMarker = Time.time;
        this.rotation = rotation;
        this.teleportStartTime = teleportStartTime;
    }

    void Update()
    {
        if (currentTeleportState == TeleportState.TELEPORTING)
        {
            // Wait until half of the teleport time has passed before the next event (note: both the switch from fade
            // out to fade in and the switch from fade in to stop the animation is half of the fade duration)
            if (Time.time - TeleportTimeMarker >= TeleportFadeDuration / 2)
            {
                if (FadingIn)
                {
                    // We have finished fading in, reset teleport state
                    currentTeleportState = TeleportState.NONE;
                }
                else
                {
                    // We have finished fading out, get player's transform properties
                    Vector3 startPosition = HeadTransform.position;
                    Vector3 startRotation = HeadTransform.rotation.eulerAngles;

                    // If a rotation was set by teleport method, rotate play area
                    // (player position would change due to this step but this will be compensated for during teleportation)
                    if (rotation > float.NegativeInfinity)
                    {
                        OriginTransform.Rotate(0, rotation, 0);
                        rotation = float.NegativeInfinity; // Reset rotation given by teleport
                    }
                    // Calculate offset between player and play area as play area will be moved but the player position is the one that has been chosen
                    Vector3 offset = OriginTransform.position - HeadTransform.position;
                    offset.y = 0; // Ignore player's height
                    OriginTransform.position = destinationPoint + offset; // Actual teleport

                    // Call teleport event and fire it
                    TeleportEvent teleportEvent = new TeleportEvent
                    {
                        startTeleportTime = teleportStartTime,
                        endTeleportTime = Time.time,
                        startUserPosition = startPosition,
                        endUserPosition = HeadTransform.position,
                        startUserRotation = startRotation,
                        endUserRotation = HeadTransform.rotation.eulerAngles
                    };
                    teleportEvent.FireEvent();
                }
                TeleportTimeMarker = Time.time;
                FadingIn = !FadingIn; 
            }

            // Set alpha value of fadeOut screen for blink effect
            float alpha = Mathf.Clamp01((Time.time - TeleportTimeMarker) / (TeleportFadeDuration / 2));
            if (FadingIn)
                alpha = 1 - alpha;
            fadeScript.setAlphaValue(alpha);
        }
    }
}

/// <summary>
/// Represents the player's current use of the teleport mechanic.
/// </summary>
public enum TeleportState
{
    /// The player is not using teleportation right now
    NONE,
    /// The player has selected a teleport destination and is currently teleporting (fading in/out)
    TELEPORTING,
}