'use strict';

const Promise = require("bluebird");
const promiseWhile = require("promise-while-loop");

const parseVolumeDescriptor = require("../parse/volume-descriptor");

module.exports = function readVolumeDescriptors(image) {
    return Promise.try(() => {
        let encounteredTerminator = false;
        let currentSector = 16;

        return promiseWhile(() => encounteredTerminator === false, (lastResult) => {
            return Promise.try(() => {
                let offset = currentSector * 2048; // Always assume a sector size of 2048 for volume descriptors

                return image.readRange(offset, offset + 2047);
            }).then((buffer) => {
                let descriptor = parseVolumeDescriptor(buffer);

                if (descriptor.type === "terminator") {
                    encounteredTerminator = true;
                }

                currentSector += 1;
                return descriptor;
            });
        });
    }).map((volumeDescriptor, i) => {
        return Object.assign({
            volumeDescriptorIndex: i
        }, volumeDescriptor);
    });
};