/*
  ==============================================================================

   This file is part of the JUCE library.
   Copyright (c) 2017 - ROLI Ltd.

   JUCE is an open source library subject to commercial or open-source
   licensing.

   By using JUCE, you agree to the terms of both the JUCE 5 End-User License
   Agreement and JUCE 5 Privacy Policy (both updated and effective as of the
   27th April 2017).

   End User License Agreement: www.juce.com/juce-5-licence
   Privacy Policy: www.juce.com/juce-5-privacy-policy

   Or: You may also use this code under the terms of the GPL v3 (see
   www.gnu.org/licenses).

   JUCE IS PROVIDED "AS IS" WITHOUT ANY WARRANTY, AND ALL WARRANTIES, WHETHER
   EXPRESSED OR IMPLIED, INCLUDING MERCHANTABILITY AND FITNESS FOR PURPOSE, ARE
   DISCLAIMED.

  ==============================================================================
*/

#include <map>


//==============================================================================
/**
    This is a quick-and-dirty parser for the 3D OBJ file format.

    Just call load() and if there aren't any errors, the 'shapes' array should
    be filled with all the shape objects that were loaded from the file.
*/
class WavefrontObjFile
{
public:
    WavefrontObjFile() {}

    Result load (const String& objFileContent)
    {
        shapes.clear();
        return parseObjFile (StringArray::fromLines (objFileContent));
    }

    Result load (const File& file)
    {
        sourceFile = file;
        return load (file.loadFileAsString());
    }

    //==============================================================================
    typedef juce::uint32 Index;

    struct Vertex        { float x, y, z; };
    struct TextureCoord  { float x, y;    };

    struct Mesh
    {
        Array<Vertex> vertices, normals;
        Array<TextureCoord> textureCoords;
        Array<Index> indices;
    };

    struct Material
    {
        Material() noexcept  : shininess (1.0f), refractiveIndex (0.0f)
        {
            zerostruct (ambient);
            zerostruct (diffuse);
            zerostruct (specular);
            zerostruct (transmittance);
            zerostruct (emission);
        }

        String name;

        Vertex ambient, diffuse, specular, transmittance, emission;
        float shininess, refractiveIndex;

        String ambientTextureName, diffuseTextureName,
               specularTextureName, normalTextureName;

        StringPairArray parameters;
    };

    struct Shape
    {
        String name;
        Mesh mesh;
        Material material;
    };

    OwnedArray<Shape> shapes;

private:
    //==============================================================================
    File sourceFile;

    struct TripleIndex
    {
        TripleIndex() noexcept : vertexIndex (-1), textureIndex (-1), normalIndex (-1) {}

        bool operator< (const TripleIndex& other) const noexcept
        {
            if (this == &other)
                return false;

            if (vertexIndex != other.vertexIndex)
                return vertexIndex < other.vertexIndex;

            if (textureIndex != other.textureIndex)
                return textureIndex < other.textureIndex;

            return normalIndex < other.normalIndex;
        }

        int vertexIndex, textureIndex, normalIndex;
    };

    struct IndexMap
    {
        std::map<TripleIndex, Index> map;

        Index getIndexFor (TripleIndex i, Mesh& newMesh, const Mesh& srcMesh)
        {
            const std::map<TripleIndex, Index>::iterator it (map.find (i));

            if (it != map.end())
                return it->second;

            const Index index = (Index) newMesh.vertices.size();

            if (isPositiveAndBelow (i.vertexIndex, srcMesh.vertices.size()))
                newMesh.vertices.add (srcMesh.vertices.getReference (i.vertexIndex));

            if (isPositiveAndBelow (i.normalIndex, srcMesh.normals.size()))
                newMesh.normals.add (srcMesh.normals.getReference (i.normalIndex));

            if (isPositiveAndBelow (i.textureIndex, srcMesh.textureCoords.size()))
                newMesh.textureCoords.add (srcMesh.textureCoords.getReference (i.textureIndex));

            map[i] = index;
            return index;
        }
    };

    static float parseFloat (String::CharPointerType& t)
    {
        t = t.findEndOfWhitespace();
        return (float) CharacterFunctions::readDoubleValue (t);
    }

    static Vertex parseVertex (String::CharPointerType t)
    {
        Vertex v;
        v.x = parseFloat (t);
        v.y = parseFloat (t);
        v.z = parseFloat (t);
        return v;
    }

    static TextureCoord parseTextureCoord (String::CharPointerType t)
    {
        TextureCoord tc;
        tc.x = parseFloat (t);
        tc.y = parseFloat (t);
        return tc;
    }

    static bool matchToken (String::CharPointerType& t, const char* token)
    {
        const int len = (int) strlen (token);

        if (CharacterFunctions::compareUpTo (CharPointer_ASCII (token), t, len) == 0)
        {
            String::CharPointerType end = t + len;

            if (end.isEmpty() || end.isWhitespace())
            {
                t = end.findEndOfWhitespace();
                return true;
            }
        }

        return false;
    }

    struct Face
    {
        Face (String::CharPointerType t)
        {
            while (! t.isEmpty())
                triples.add (parseTriple (t));
        }

        Array<TripleIndex> triples;

        void addIndices (Mesh& newMesh, const Mesh& srcMesh, IndexMap& indexMap)
        {
            TripleIndex i0 (triples[0]), i1, i2 (triples[1]);

            for (int i = 2; i < triples.size(); ++i)
            {
                i1 = i2;
                i2 = triples.getReference (i);

                newMesh.indices.add (indexMap.getIndexFor (i0, newMesh, srcMesh));
                newMesh.indices.add (indexMap.getIndexFor (i1, newMesh, srcMesh));
                newMesh.indices.add (indexMap.getIndexFor (i2, newMesh, srcMesh));
            }
        }

        static TripleIndex parseTriple (String::CharPointerType& t)
        {
            TripleIndex i;

            t = t.findEndOfWhitespace();
            i.vertexIndex = t.getIntValue32() - 1;
            t = findEndOfFaceToken (t);

            if (t.isEmpty() || t.getAndAdvance() != '/')
                return i;

            if (*t == '/')
            {
                ++t;
            }
            else
            {
                i.textureIndex = t.getIntValue32() - 1;
                t = findEndOfFaceToken (t);

                if (t.isEmpty() || t.getAndAdvance() != '/')
                    return i;
            }

            i.normalIndex = t.getIntValue32() - 1;
            t = findEndOfFaceToken (t);
            return i;
        }

        static String::CharPointerType findEndOfFaceToken (String::CharPointerType t) noexcept
        {
            return CharacterFunctions::findEndOfToken (t, CharPointer_ASCII ("/ \t"), String().getCharPointer());
        }
    };

    static Shape* parseFaceGroup (const Mesh& srcMesh,
                                  const Array<Face>& faceGroup,
                                  const Material& material,
                                  const String& name)
    {
        if (faceGroup.size() == 0)
            return nullptr;

        ScopedPointer<Shape> shape (new Shape());
        shape->name = name;
        shape->material = material;

        IndexMap indexMap;

        for (int i = 0; i < faceGroup.size(); ++i)
            faceGroup.getReference(i).addIndices (shape->mesh, srcMesh, indexMap);

        return shape.release();
    }

    Result parseObjFile (const StringArray& lines)
    {
        Mesh mesh;
        Array<Face> faceGroup;

        Array<Material> knownMaterials;
        Material lastMaterial;
        String lastName;

        for (int lineNum = 0; lineNum < lines.size(); ++lineNum)
        {
            String::CharPointerType l = lines[lineNum].getCharPointer().findEndOfWhitespace();

            if (matchToken (l, "v"))    { mesh.vertices.add (parseVertex (l));            continue; }
            if (matchToken (l, "vn"))   { mesh.normals.add (parseVertex (l));             continue; }
            if (matchToken (l, "vt"))   { mesh.textureCoords.add (parseTextureCoord (l)); continue; }
            if (matchToken (l, "f"))    { faceGroup.add (Face (l));                       continue; }

            if (matchToken (l, "usemtl"))
            {
                const String name (String (l).trim());

                for (int i = knownMaterials.size(); --i >= 0;)
                {
                    if (knownMaterials.getReference(i).name == name)
                    {
                        lastMaterial = knownMaterials.getReference(i);
                        break;
                    }
                }

                continue;
            }

            if (matchToken (l, "mtllib"))
            {
                Result r = parseMaterial (knownMaterials, String (l).trim());
                continue;
            }

            if (matchToken (l, "g") || matchToken (l, "o"))
            {
                if (Shape* shape = parseFaceGroup (mesh, faceGroup, lastMaterial, lastName))
                    shapes.add (shape);

                faceGroup.clear();
                lastName = StringArray::fromTokens (l, " \t", "")[0];
                continue;
            }
        }

        if (Shape* shape = parseFaceGroup (mesh, faceGroup, lastMaterial, lastName))
            shapes.add (shape);

        return Result::ok();
    }

    Result parseMaterial (Array<Material>& materials, const String& filename)
    {
        jassert (sourceFile.exists());
        File f (sourceFile.getSiblingFile (filename));

        if (! f.exists())
            return Result::fail ("Cannot open file: " + filename);

        StringArray lines;
        lines.addLines (f.loadFileAsString());

        materials.clear();
        Material material;

        for (int i = 0; i < lines.size(); ++i)
        {
            String::CharPointerType l (lines[i].getCharPointer().findEndOfWhitespace());

            if (matchToken (l, "newmtl"))   { materials.add (material); material.name = String (l).trim(); continue; }

            if (matchToken (l, "Ka"))       { material.ambient         = parseVertex (l); continue; }
            if (matchToken (l, "Kd"))       { material.diffuse         = parseVertex (l); continue; }
            if (matchToken (l, "Ks"))       { material.specular        = parseVertex (l); continue; }
            if (matchToken (l, "Kt"))       { material.transmittance   = parseVertex (l); continue; }
            if (matchToken (l, "Ke"))       { material.emission        = parseVertex (l); continue; }
            if (matchToken (l, "Ni"))       { material.refractiveIndex = parseFloat (l);  continue; }
            if (matchToken (l, "Ns"))       { material.shininess       = parseFloat (l);  continue; }

            if (matchToken (l, "map_Ka"))   { material.ambientTextureName  = String (l).trim(); continue; }
            if (matchToken (l, "map_Kd"))   { material.diffuseTextureName  = String (l).trim(); continue; }
            if (matchToken (l, "map_Ks"))   { material.specularTextureName = String (l).trim(); continue; }
            if (matchToken (l, "map_Ns"))   { material.normalTextureName   = String (l).trim(); continue; }

            StringArray tokens;
            tokens.addTokens (l, " \t", "");

            if (tokens.size() >= 2)
                material.parameters.set (tokens[0].trim(), tokens[1].trim());
        }

        materials.add (material);
        return Result::ok();
    }

    JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (WavefrontObjFile)
};