using UnityEngine;
#if UNITY_EDITOR
using UnityEditor;
#endif
using System.Collections;
using System.Collections.Generic;

[RequireComponent(typeof(MeshFilter))]
public class SoftNormalsToVertexColor:MonoBehaviour {

    public enum Method { Simple, AngularDeviation };

    public Method method = Method.AngularDeviation;
    public bool generateOnAwake = false;
    public bool generateNow = false;

    void OnDrawGizmos() {
        if(generateNow) {
            generateNow = false;
            TryGenerate();
        }
    }

    void Awake() {
        if(generateOnAwake)
            TryGenerate();
    }

    void TryGenerate() {
        MeshFilter mf = GetComponent<MeshFilter>();
        if(mf == null) {
            Debug.LogError("MeshFilter missing on the vertex color generator", gameObject);
            return;
        }
        if(mf.sharedMesh == null) {
            Debug.LogError("Assign a mesh to the MeshFilter before generating vertex colors", gameObject);
            return;
        }
        Generate(mf.sharedMesh);
        Debug.Log("Vertex colors generated", gameObject);
    }

    void Generate(Mesh m) {

        Vector3[] n = m.normals;
        Vector3[] v = m.vertices;
        Color[] colors = new Color[n.Length];
        List<List<int>> groups = new List<List<int>>();

        for(int i = 0; i < v.Length; i++) {     // Group verts at the same location
            bool added = false;
            foreach(List<int> group in groups) {    // Add to exsisting group if possible
                if(v[group[0]] == v[i]) {
                    group.Add(i);
                    added = true;
                    break;
                }
            }
            if(!added) {                            // Create new group if necessary
                List<int> newList = new List<int>();
                newList.Add(i);
                groups.Add(newList);
            }
        }

        foreach(List<int> group in groups) { // Calculate soft normals
            Vector3 avgNrm = Vector3.zero;
            foreach(int i in group) { // TODO: This can actually be improved. Averaging will not give the best outline.
                avgNrm += n[i];
            }
            avgNrm.Normalize(); // Average normal done
            if(method == Method.AngularDeviation) {
                float avgDot = 0f; // Calculate deviation to alter length
                foreach(int i in group) {
                    avgDot += Vector3.Dot(n[i], avgNrm);
                }
                avgDot /= group.Count;
                float angDeviation = Mathf.Acos(avgDot) * Mathf.Rad2Deg;
                float aAng = 180f - angDeviation - 90;
                float lMult = 0.5f / Mathf.Sin(aAng * Mathf.Deg2Rad);  // 0.5f looks better empirically, but mathematically it should be 1f
                avgNrm *= lMult;
            }

            foreach(int i in group) {

                //colors[i] = new Color(avgNrm.x, avgNrm.y, avgNrm.z); // Save normals as colors
                Vector3 remappedNormal = ((avgNrm.normalized + Vector3.one) / 2f); //[-1, 1] -> [0,1]; Loses precision, but fbx exporter seems to clamp colors [0,1] so our normals get messed up
                colors[i] = new Color(remappedNormal.x, remappedNormal.y, remappedNormal.z);
            }
        }

        m.colors = colors; // Assign as vertex colors
        Debug.Log("v: " + m.vertices.Length + " : vc: " + colors.Length);
#if UNITY_EDITOR
        EditorUtility.SetDirty(this);
        SceneView.RepaintAll();
#endif

    }


}