//====================================================================================
//
// Purpose: To generate a bezier curve between at least 4 points in space and draw
// a number of spheres across the generated curve
//
// This script is heavily based on the tutorial at: 
// http://catlikecoding.com/unity/tutorials/curves-and-splines/
//
//====================================================================================

using UnityEngine;
using System.Collections;
using System;

public static class Bezier
{

    public static Vector3 GetPoint(Vector3 p0, Vector3 p1, Vector3 p2, float t)
    {
        t = Mathf.Clamp01(t);
        float oneMinusT = 1f - t;
        return
            oneMinusT * oneMinusT * p0 +
            2f * oneMinusT * t * p1 +
            t * t * p2;
    }

    public static Vector3 GetFirstDerivative(Vector3 p0, Vector3 p1, Vector3 p2, float t)
    {
        return
            2f * (1f - t) * (p1 - p0) +
            2f * t * (p2 - p1);
    }

    public static Vector3 GetPoint(Vector3 p0, Vector3 p1, Vector3 p2, Vector3 p3, float t)
    {
        t = Mathf.Clamp01(t);
        float OneMinusT = 1f - t;
        return
            OneMinusT * OneMinusT * OneMinusT * p0 +
            3f * OneMinusT * OneMinusT * t * p1 +
            3f * OneMinusT * t * t * p2 +
            t * t * t * p3;
    }

    public static Vector3 GetFirstDerivative(Vector3 p0, Vector3 p1, Vector3 p2, Vector3 p3, float t)
    {
        t = Mathf.Clamp01(t);
        float oneMinusT = 1f - t;
        return
            3f * oneMinusT * oneMinusT * (p1 - p0) +
            6f * oneMinusT * t * (p2 - p1) +
            3f * t * t * (p3 - p2);
    }
}

public class CurveGenerator : MonoBehaviour
{
    private enum BezierControlPointMode
    {
        Free,
        Aligned,
        Mirrored
    }

    private Vector3[] points;
    private GameObject[] items;
    private BezierControlPointMode[] modes;
    private bool loop;
    private int frequency;
    private bool customTracer;

    public void Create(int setFrequency, float radius, GameObject tracer)
    {
        float circleSize = radius / 8;

        frequency = setFrequency;
        items = new GameObject[frequency];
        for (int f = 0; f < items.Length; f++)
        {
            customTracer = true;
            items[f] = (tracer ? Instantiate(tracer) : CreateSphere());
            items[f].transform.parent = this.transform;
            items[f].layer = 2;
            items[f].transform.localScale = new Vector3(circleSize, circleSize, circleSize);
        }
    }

    public void SetPoints(Vector3[] controlPoints, Material material)
    {
        points = controlPoints;
        modes = new BezierControlPointMode[] {
            BezierControlPointMode.Free,
            BezierControlPointMode.Free
        };

        SetObjects(material);
    }

    public void TogglePoints(bool state)
    {
        this.gameObject.SetActive(state);
    }

    private GameObject CreateSphere()
    {
        customTracer = false;
        GameObject item = GameObject.CreatePrimitive(PrimitiveType.Sphere);
        Destroy(item.GetComponent<SphereCollider>());
        item.GetComponent<MeshRenderer>().shadowCastingMode = UnityEngine.Rendering.ShadowCastingMode.Off;
        item.GetComponent<MeshRenderer>().receiveShadows = false;

        return item;
    }

    private bool Loop
    {
        get
        {
            return loop;
        }
        set
        {
            loop = value;
            if (value == true)
            {
                modes[modes.Length - 1] = modes[0];
                SetControlPoint(0, points[0]);
            }
        }
    }

    private int ControlPointCount
    {
        get
        {
            return points.Length;
        }
    }

    private Vector3 GetControlPoint(int index)
    {
        return points[index];
    }

    private void SetControlPoint(int index, Vector3 point)
    {
        if (index % 3 == 0)
        {
            Vector3 delta = point - points[index];
            if (loop)
            {
                if (index == 0)
                {
                    points[1] += delta;
                    points[points.Length - 2] += delta;
                    points[points.Length - 1] = point;
                }
                else if (index == points.Length - 1)
                {
                    points[0] = point;
                    points[1] += delta;
                    points[index - 1] += delta;
                }
                else
                {
                    points[index - 1] += delta;
                    points[index + 1] += delta;
                }
            }
            else
            {
                if (index > 0)
                {
                    points[index - 1] += delta;
                }
                if (index + 1 < points.Length)
                {
                    points[index + 1] += delta;
                }
            }
        }
        points[index] = point;
        EnforceMode(index);
    }

    private void EnforceMode(int index)
    {
        int modeIndex = (index + 1) / 3;
        BezierControlPointMode mode = modes[modeIndex];
        if (mode == BezierControlPointMode.Free || !loop && (modeIndex == 0 || modeIndex == modes.Length - 1))
        {
            return;
        }

        int middleIndex = modeIndex * 3;
        int fixedIndex, enforcedIndex;
        if (index <= middleIndex)
        {
            fixedIndex = middleIndex - 1;
            if (fixedIndex < 0)
            {
                fixedIndex = points.Length - 2;
            }
            enforcedIndex = middleIndex + 1;
            if (enforcedIndex >= points.Length)
            {
                enforcedIndex = 1;
            }
        }
        else
        {
            fixedIndex = middleIndex + 1;
            if (fixedIndex >= points.Length)
            {
                fixedIndex = 1;
            }
            enforcedIndex = middleIndex - 1;
            if (enforcedIndex < 0)
            {
                enforcedIndex = points.Length - 2;
            }
        }

        Vector3 middle = points[middleIndex];
        Vector3 enforcedTangent = middle - points[fixedIndex];
        if (mode == BezierControlPointMode.Aligned)
        {
            enforcedTangent = enforcedTangent.normalized * Vector3.Distance(middle, points[enforcedIndex]);
        }
        points[enforcedIndex] = middle + enforcedTangent;
    }

    private int CurveCount
    {
        get
        {
            return (points.Length - 1) / 3;
        }
    }

    private Vector3 GetPoint(float t)
    {
        int i;
        if (t >= 1f)
        {
            t = 1f;
            i = points.Length - 4;
        }
        else
        {
            t = Mathf.Clamp01(t) * CurveCount;
            i = (int)t;
            t -= i;
            i *= 3;
        }
        return transform.TransformPoint(Bezier.GetPoint(points[i], points[i + 1], points[i + 2], points[i + 3], t));
    }

    private void SetObjects(Material material)
    {
        float stepSize = frequency * 1;
        if (this.Loop || stepSize == 1)
        {
            stepSize = 1f / stepSize;
        }
        else
        {
            stepSize = 1f / (stepSize - 1);
        }

        for (int f = 0; f < frequency; f++)
        {
            if (customTracer && (f == 0 || f == (frequency - 1)))
            {
                items[f].SetActive(false);
                continue;
            }
            setMeshMaterial(items[f], material);
            setSkinnedMeshMaterial(items[f], material);

            Vector3 position = this.GetPoint(f * stepSize);
            items[f].transform.position = position;

            Vector3 nextPosition = this.GetPoint((f + 1) * stepSize);
            Vector3 lookPosition = (nextPosition - position).normalized;
            if (lookPosition != Vector3.zero)
            {
                items[f].transform.rotation = Quaternion.LookRotation(lookPosition);
            }
        }
    }

    private void setMeshMaterial(GameObject item, Material material)
    {
        if (item.GetComponent<MeshRenderer>())
        {
            item.GetComponent<MeshRenderer>().material = material;
        }

        foreach (MeshRenderer mr in item.GetComponentsInChildren<MeshRenderer>())
        {
            mr.material = material;
        }
    }

    private void setSkinnedMeshMaterial(GameObject item, Material material)
    {
        if (item.GetComponent<SkinnedMeshRenderer>())
        {
            item.GetComponent<SkinnedMeshRenderer>().material = material;
        }

        foreach (SkinnedMeshRenderer mr in item.GetComponentsInChildren<SkinnedMeshRenderer>())
        {
            mr.material = material;
        }
    }
}