import getAccessorByteStride from './getAccessorByteStride.js'
import getComponentReader from './getComponentReader.js'
import numberOfComponentsForType from './numberOfComponentsForType.js'
import arrayFill from '../../Core/arrayFill.js'
import ComponentDatatype from '../../Core/ComponentDatatype.js'
import defined from '../../Core/defined.js'

    /**
     * Returns the accessor data in a contiguous array.
     *
     * @param {Object} gltf A javascript object containing a glTF asset.
     * @param {Object} accessor The accessor.
     * @returns {Array} The accessor values in a contiguous array.
     *
     * @private
     */
    function readAccessorPacked(gltf, accessor) {
        var byteStride = getAccessorByteStride(gltf, accessor);
        var componentTypeByteLength = ComponentDatatype.getSizeInBytes(accessor.componentType);
        var numberOfComponents = numberOfComponentsForType(accessor.type);
        var count = accessor.count;
        var values = new Array(numberOfComponents * count);

        if (!defined(accessor.bufferView)) {
            arrayFill(values, 0);
            return values;
        }

        var bufferView = gltf.bufferViews[accessor.bufferView];
        var source = gltf.buffers[bufferView.buffer].extras._pipeline.source;
        var byteOffset = accessor.byteOffset + bufferView.byteOffset + source.byteOffset;

        var dataView = new DataView(source.buffer);
        var components = new Array(numberOfComponents);
        var componentReader = getComponentReader(accessor.componentType);

        for (var i = 0; i < count; ++i) {
            componentReader(dataView, byteOffset, numberOfComponents, componentTypeByteLength, components);
            for (var j = 0; j < numberOfComponents; ++j) {
                values[i * numberOfComponents + j] = components[j];
            }
            byteOffset += byteStride;
        }
        return values;
    }

    export default readAccessorPacked;