OV.ThreeImporter = class extends OV.ImporterBase
{
    constructor ()
    {
        super ();
    }

    CanImportExtension (extension)
    {
        return extension === 'fbx';
    }

    GetKnownFileFormats ()
    {
        return {
            'fbx' : OV.FileFormat.Binary
        };
    }
    
    GetUpDirection ()
    {
        return OV.Direction.Y;
    }    
    
    ClearContent ()
    {
        if (this.loadedScene !== undefined && this.loadedScene !== null) {
            this.loadedScene.traverse ((child) => {
                if (child.isMesh) {
                    child.geometry.dispose ();
                }
            });
            this.loadedScene = null;
        }
    }

    ResetContent ()
    {
        this.loadedScene = null;
    }

    ImportContent (fileContent, onFinish)
    {
        const libraries = this.GetExternalLibraries ();
        if (libraries === null) {
            onFinish ();
            return;
        }
        Promise.all (libraries).then (() => {
            this.LoadModel (fileContent, onFinish);    
        }).catch (() => {
            onFinish ();
        });
    }

    GetExternalLibraries ()
    {
        if (this.extension === 'fbx') {
            return [
                OV.LoadExternalLibrary ('three_loaders/FBXLoader.js'),
                OV.LoadExternalLibrary ('three_loaders/fflate.min.js')
            ];
        }
        return null;
    }

    CreateLoader (manager)
    {
        let loader = null;
        if (this.extension === 'fbx') {
            loader = new THREE.FBXLoader (manager);
        }        
        return loader;
    }

    LoadModel (fileContent, onFinish)
    {
        let loadedScene = null;
        let loadingManager = new THREE.LoadingManager (() => {
            this.OnThreeObjectsLoaded (loadedScene, onFinish);
        });

        const mainFileUrl = OV.CreateObjectUrl (fileContent);
        loadingManager.setURLModifier ((url) => {
            if (url === mainFileUrl) {
                return url;
            }
            if (url.startsWith ('data:')) {
                return url;
            }
            const fileBuffer = this.callbacks.getFileBuffer (url);
            const fileUrl = OV.CreateObjectUrl (fileBuffer);
            return fileUrl;
        });

        const loader = this.CreateLoader (loadingManager);
        if (loader === null) {
            onFinish ();
            return;
        }

        // TODO: error handling
        loader.load (mainFileUrl,
            (object) => {
                loadedScene = object;
            },
            () => {
            },
            (err) => {
                this.SetError ();
                this.SetMessage (err);
                onFinish ();
            }
        );
    }

    OnThreeObjectsLoaded (scene, onFinish)
    {
        this.loadedScene = scene;
        scene.traverse ((child) => {
            if (child.isMesh) {
                // TODO: merge same materials
                // TODO: PBR materials
                console.log (child);
                let material = OV.ConvertThreeMaterialToMaterial (child.material);
                const materialIndex = this.model.AddMaterial (material);
                let mesh = OV.ConvertThreeGeometryToMesh (child.geometry, materialIndex);
                if (child.matrixWorld !== undefined && child.matrixWorld !== null) {
                    const matrix = new OV.Matrix (child.matrixWorld.elements);
                    const transformation = new OV.Transformation (matrix);
                    const determinant = matrix.Determinant ();
                    const mirrorByX = OV.IsNegative (determinant);
                    OV.TransformMesh (mesh, transformation);
                    if (mirrorByX) {
                        OV.FlipMeshTrianglesOrientation (mesh);
                    }
                }
                this.model.AddMesh (mesh);
            }
        });
        onFinish ();
    }
};