/*
(C) 2015 AARO4130
DO NOT USE PARTS OF, OR THE ENTIRE SCRIPT, AND CLAIM AS YOUR OWN WORK
*/

using System;
using UnityEngine;
using System.Collections;
using System.Collections.Generic;
using System.Globalization;
using System.IO;
using System.Linq;
using System.Text.RegularExpressions;
#if UNITY_EDITOR
using UnityEditor;
#endif

public class OBJLoader
{
    public static bool splitByMaterial = false;
    public static string[] searchPaths = new string[] { "", "%FileName%_Textures" + Path.DirectorySeparatorChar };

    //structures
    struct OBJFace
    {
        public string materialName;
        public string meshName;
        public int[] indexes;
    }

    //functions
#if UNITY_EDITOR
    [MenuItem("GameObject/Import From OBJ")]
    static void ObjLoadMenu()
    {
        string pth = UnityEditor.EditorUtility.OpenFilePanel("Import OBJ", "", "obj");
        if (!string.IsNullOrEmpty(pth))
        {
            System.Diagnostics.Stopwatch s = new System.Diagnostics.Stopwatch();
            s.Start();
            LoadOBJFile(pth);
            Debug.Log("OBJ load took " + s.ElapsedMilliseconds + "ms");
            s.Stop();
        }
    }
#endif

    public static Vector3 ParseVectorFromCMPS(string[] cmps)
    {
        float x = float.Parse(cmps[1]);
        float y = float.Parse(cmps[2]);
        if (cmps.Length == 4)
        {
            float z = float.Parse(cmps[3]);
            return new Vector3(x, y, z);
        }
        return new Vector2(x, y);
    }

    public static Color ParseColorFromCMPS(string[] cmps, float scalar = 1.0f)
    {
        float Kr = float.Parse(cmps[1]) * scalar;
        float Kg = float.Parse(cmps[2]) * scalar;
        float Kb = float.Parse(cmps[3]) * scalar;
        return new Color(Kr, Kg, Kb);
    }

    public static string OBJGetFilePath(string path, string basePath, string fileName)
    {
        foreach (string sp in searchPaths)
        {
            string s = sp.Replace("%FileName%", fileName);
            if (File.Exists(basePath + s + path))
            {
                return basePath + s + path;
            }
            else if (File.Exists(path))
            {
                return path;
            }
        }

        return null;
    }

    public static Material[] LoadMTLFile(string fn)
    {
        Material currentMaterial = null;
        List<Material> matlList = new List<Material>();
        FileInfo mtlFileInfo = new FileInfo(fn);
        string baseFileName = Path.GetFileNameWithoutExtension(fn);
        string mtlFileDirectory = mtlFileInfo.Directory.FullName + Path.DirectorySeparatorChar;
        foreach (string ln in File.ReadAllLines(fn))
        {
            string l = ln.Trim().Replace("  ", " ");
            string[] cmps = l.Split(' ');
            string data = l.Remove(0, l.IndexOf(' ') + 1);

            if (cmps[0] == "newmtl")
            {
                if (currentMaterial != null)
                {
                    matlList.Add(currentMaterial);
                }

                //currentMaterial = new Material(Shader.Find("Standard (Specular setup)"));
                currentMaterial = new Material(Shader.Find("Standard"));
                currentMaterial.name = data;
            }
            else if (cmps[0] == "Kd")
            {
                currentMaterial.SetColor("_Color", ParseColorFromCMPS(cmps));
            }
            else if (cmps[0] == "map_Kd")
            {
                //TEXTURE
                string fpth = OBJGetFilePath(data, mtlFileDirectory, baseFileName);
                if (fpth != null)
                    currentMaterial.SetTexture("_MainTex", TextureLoader.LoadTexture(fpth));
            }
            else if (cmps[0] == "map_Bump")
            {
                //TEXTURE
                string fpth = OBJGetFilePath(data, mtlFileDirectory, baseFileName);
                if (fpth != null)
                {
                    currentMaterial.SetTexture("_BumpMap", TextureLoader.LoadTexture(fpth, true));
                    currentMaterial.EnableKeyword("_NORMALMAP");
                }
            }
            else if (cmps[0] == "Ks")
            {
                currentMaterial.SetColor("_SpecColor", ParseColorFromCMPS(cmps));
            }
            else if (cmps[0] == "Ka")
            {
                currentMaterial.SetColor("_EmissionColor", ParseColorFromCMPS(cmps, 0.05f));
                currentMaterial.EnableKeyword("_EMISSION");
            }
            else if (cmps[0] == "d")
            {
                float visibility = float.Parse(cmps[1]);
                if (visibility < 1)
                {
                    Color temp = currentMaterial.color;

                    temp.a = visibility;
                    currentMaterial.SetColor("_Color", temp);

                    //TRANSPARENCY ENABLER
                    currentMaterial.SetFloat("_Mode", 3);
                    currentMaterial.SetInt("_SrcBlend", (int)UnityEngine.Rendering.BlendMode.SrcAlpha);
                    currentMaterial.SetInt("_DstBlend", (int)UnityEngine.Rendering.BlendMode.OneMinusSrcAlpha);
                    currentMaterial.SetInt("_ZWrite", 0);
                    currentMaterial.DisableKeyword("_ALPHATEST_ON");
                    currentMaterial.EnableKeyword("_ALPHABLEND_ON");
                    currentMaterial.DisableKeyword("_ALPHAPREMULTIPLY_ON");
                    currentMaterial.renderQueue = 3000;
                }

            }
            else if (cmps[0] == "Ns")
            {
                float Ns = float.Parse(cmps[1]);
                Ns = (Ns / 1000);
                currentMaterial.SetFloat("_Glossiness", Ns);

            }
        }
        if (currentMaterial != null)
        {
            matlList.Add(currentMaterial);
        }
        return matlList.ToArray();
    }

    public static GameObject LoadOBJFile(string fn)
    {
        string meshName = Path.GetFileNameWithoutExtension(fn);
        bool hasNormals = false;

        //OBJ LISTS
        List<Vector3> vertices = new List<Vector3>();
        List<Vector3> normals = new List<Vector3>();
        List<Vector2> uvs = new List<Vector2>();

        //UMESH LISTS
        List<Vector3> uvertices = new List<Vector3>();
        List<Vector3> unormals = new List<Vector3>();
        List<Vector2> uuvs = new List<Vector2>();

        //MESH CONSTRUCTION
        List<string> materialNames = new List<string>();
        List<string> objectNames = new List<string>();
        Dictionary<string, int> hashtable = new Dictionary<string, int>();
        List<OBJFace> faceList = new List<OBJFace>();
        string cmaterial = "";
        string cmesh = "default";

        //CACHE
        Material[] materialCache = null;

        //save this info for later
        FileInfo OBJFileInfo = new FileInfo(fn);

        foreach (string ln in File.ReadAllLines(fn))
        {
            if (ln.Length > 0 && ln[0] != '#')
            {
                string l = ln.Trim().Replace("  ", " ");
                string[] cmps = l.Split(' ');
                string data = l.Remove(0, l.IndexOf(' ') + 1);

                if (cmps[0] == "mtllib")
                {
                    //load cache
                    string pth = OBJGetFilePath(data, OBJFileInfo.Directory.FullName + Path.DirectorySeparatorChar, meshName);
                    if (pth != null)
                        materialCache = LoadMTLFile(pth);
                }
                else if ((cmps[0] == "g" || cmps[0] == "o") && splitByMaterial == false)
                {
                    cmesh = data;
                    if (!objectNames.Contains(cmesh))
                    {
                        objectNames.Add(cmesh);
                    }
                }
                else if (cmps[0] == "usemtl")
                {
                    cmaterial = data;
                    if (!materialNames.Contains(cmaterial))
                    {
                        materialNames.Add(cmaterial);
                    }

                    if (splitByMaterial)
                    {
                        if (!objectNames.Contains(cmaterial))
                        {
                            objectNames.Add(cmaterial);
                        }
                    }
                }
                else if (cmps[0] == "v")
                {
                    //VERTEX
                    vertices.Add(ParseVectorFromCMPS(cmps));
                }
                else if (cmps[0] == "vn")
                {
                    //VERTEX NORMAL
                    normals.Add(ParseVectorFromCMPS(cmps));
                }
                else if (cmps[0] == "vt")
                {
                    //VERTEX UV
                    uvs.Add(ParseVectorFromCMPS(cmps));
                }
                else if (cmps[0] == "f")
                {
                    int[] indexes = new int[cmps.Length - 1];
                    for (int i = 1; i < cmps.Length; i++)
                    {
                        string felement = cmps[i];
                        int vertexIndex = -1;
                        int normalIndex = -1;
                        int uvIndex = -1;
                        if (felement.Contains("//"))
                        {
                            //doubleslash, no UVS.
                            string[] elementComps = felement.Split('/');
                            vertexIndex = int.Parse(elementComps[0]) - 1;
                            normalIndex = int.Parse(elementComps[2]) - 1;
                        }
                        else if (felement.Count(x => x == '/') == 2)
                        {
                            //contains everything
                            string[] elementComps = felement.Split('/');
                            vertexIndex = int.Parse(elementComps[0]) - 1;
                            uvIndex = int.Parse(elementComps[1]) - 1;
                            normalIndex = int.Parse(elementComps[2]) - 1;
                        }
                        else if (!felement.Contains("/"))
                        {
                            //just vertex inedx
                            vertexIndex = int.Parse(felement) - 1;
                        }
                        else
                        {
                            //vertex and uv
                            string[] elementComps = felement.Split('/');
                            vertexIndex = int.Parse(elementComps[0]) - 1;
                            uvIndex = int.Parse(elementComps[1]) - 1;
                        }
                        string hashEntry = vertexIndex + "|" + normalIndex + "|" + uvIndex;
                        if (hashtable.ContainsKey(hashEntry))
                        {
                            indexes[i - 1] = hashtable[hashEntry];
                        }
                        else
                        {
                            //create a new hash entry
                            indexes[i - 1] = hashtable.Count;
                            hashtable[hashEntry] = hashtable.Count;
                            uvertices.Add(vertices[vertexIndex]);
                            if (normalIndex < 0 || (normalIndex > (normals.Count - 1)))
                            {
                                unormals.Add(Vector3.zero);
                            }
                            else
                            {
                                hasNormals = true;
                                unormals.Add(normals[normalIndex]);
                            }
                            if (uvIndex < 0 || (uvIndex > (uvs.Count - 1)))
                            {
                                uuvs.Add(Vector2.zero);
                            }
                            else
                            {
                                uuvs.Add(uvs[uvIndex]);
                            }
                        }
                    }
                    if (indexes.Length < 5 && indexes.Length >= 3)
                    {
                        OBJFace f1 = new OBJFace();
                        f1.materialName = cmaterial;
                        f1.indexes = new int[] { indexes[0], indexes[1], indexes[2] };
                        f1.meshName = (splitByMaterial) ? cmaterial : cmesh;
                        faceList.Add(f1);
                        if (indexes.Length > 3)
                        {
                            OBJFace f2 = new OBJFace();
                            f2.materialName = cmaterial;
                            f2.meshName = (splitByMaterial) ? cmaterial : cmesh;
                            f2.indexes = new int[] { indexes[2], indexes[3], indexes[0] };
                            faceList.Add(f2);
                        }
                    }
                }
            }
        }

        if (objectNames.Count == 0)
            objectNames.Add("default");

        //build objects
        GameObject parentObject = new GameObject(meshName);

        foreach (string obj in objectNames)
        {
            GameObject subObject = new GameObject(obj);
            subObject.transform.parent = parentObject.transform;
            subObject.transform.localScale = new Vector3(-1, 1, 1);

            //Create mesh
            Mesh m = new Mesh();
            m.name = obj;

            //LISTS FOR REORDERING
            List<Vector3> processedVertices = new List<Vector3>();
            List<Vector3> processedNormals = new List<Vector3>();
            List<Vector2> processedUVs = new List<Vector2>();
            List<int[]> processedIndexes = new List<int[]>();
            Dictionary<int, int> remapTable = new Dictionary<int, int>();

            //POPULATE MESH
            List<string> meshMaterialNames = new List<string>();

            OBJFace[] ofaces = faceList.Where(x => x.meshName == obj).ToArray();
            foreach (string mn in materialNames)
            {
                OBJFace[] faces = ofaces.Where(x => x.materialName == mn).ToArray();
                if (faces.Length > 0)
                {
                    meshMaterialNames.Add(mn);
                    if (m.subMeshCount != meshMaterialNames.Count)
                        m.subMeshCount = meshMaterialNames.Count;

                    var indexes = faces.SelectMany(f => f.indexes).ToArray();
                    
                    for (int i = 0; i < indexes.Length; i++)
                    {
                        int idx = indexes[i];
                        //build remap table
                        if (remapTable.ContainsKey(idx))
                        {
                            //ezpz
                            indexes[i] = remapTable[idx];
                        }
                        else
                        {
                            processedVertices.Add(uvertices[idx]);
                            processedNormals.Add(unormals[idx]);
                            processedUVs.Add(uuvs[idx]);
                            remapTable[idx] = processedVertices.Count - 1;
                            indexes[i] = remapTable[idx];
                        }
                    }

                    processedIndexes.Add(indexes);
                }
            }

            //apply stuff
            m.vertices = processedVertices.ToArray();
            m.normals = processedNormals.ToArray();
            m.uv = processedUVs.ToArray();

            for (int i = 0; i < processedIndexes.Count; i++)
            {
                m.SetTriangles(processedIndexes[i], i);
            }

            if (!hasNormals)
            {
                m.RecalculateNormals();
            }
            m.RecalculateBounds();

            MeshFilter mf = subObject.AddComponent<MeshFilter>();
            MeshRenderer mr = subObject.AddComponent<MeshRenderer>();

            Material[] processedMaterials = new Material[meshMaterialNames.Count];
            for (int i = 0; i < meshMaterialNames.Count; i++)
            {
                if (materialCache == null)
                {
                    processedMaterials[i] = new Material(Shader.Find("Standard (Specular setup)"));
                }
                else
                {
                    Material mfn = Array.Find(materialCache, x => x.name == meshMaterialNames[i]); ;
                    if (mfn == null)
                    {
                        processedMaterials[i] = new Material(Shader.Find("Standard (Specular setup)"));
                    }
                    else
                    {
                        processedMaterials[i] = mfn;
                    }

                }
                processedMaterials[i].name = meshMaterialNames[i];
            }

            mr.materials = processedMaterials;
            mf.mesh = m;
        }

        return parentObject;
    }
}