'use strict';

const Promise = require("bluebird");

const parseDirectoryRecord = require("../parse/directory-record");

module.exports = function readDirectoryExtent(image, sector, length, encoding) {
    return Promise.try(() => {
        return image.getSectorSize();
    }).then((sectorSize) => {
        const roundToNextSector = require("../round-to-next-sector")(sectorSize);

        function splitRecordBuffers(buffer) {
            let pos = 0;
            let recordBuffers = [];

            while (pos < buffer.length) {
                let recordLength = buffer.readUInt8(pos);

                if (recordLength === 0) {
                    /* We ran out of records for this sector, skip to the next. */
                    pos = roundToNextSector(pos);
                } else {
                    let directoryRecord = buffer.slice(pos, pos + recordLength);
                    recordBuffers.push(directoryRecord);
                    pos += recordLength;
                }
            }

            return recordBuffers;
        }

        return Promise.try(() => {
            let sectorOffset = sector * sectorSize;
            return image.readRange(sectorOffset, sectorOffset + length - 1);
        }).then((buffer) => {
            let recordBuffers = splitRecordBuffers(buffer);
        })
    })
};