/* jslint node: true */
'use strict';

//  ENiGMA½
const Config            = require('./config.js').get;
const Errors            = require('./enig_error.js').Errors;
const sortAreasOrConfs  = require('./conf_area_util.js').sortAreasOrConfs;
const FileEntry         = require('./file_entry.js');
const FileDb            = require('./database.js').dbs.file;
const ArchiveUtil       = require('./archive_util.js');
const CRC32             = require('./crc.js').CRC32;
const Log               = require('./logger.js').log;
const resolveMimeType   = require('./mime_util.js').resolveMimeType;
const stringFormat      = require('./string_format.js');
const wordWrapText      = require('./word_wrap.js').wordWrapText;
const StatLog           = require('./stat_log.js');
const UserProps         = require('./user_property.js');
const SysProps          = require('./system_property.js');

//  deps
const _             = require('lodash');
const async         = require('async');
const fs            = require('graceful-fs');
const crypto        = require('crypto');
const paths         = require('path');
const temptmp       = require('temptmp').createTrackedSession('file_area');
const iconv         = require('iconv-lite');
const execFile      = require('child_process').execFile;
const moment        = require('moment');

exports.startup                         = startup;
exports.isInternalArea                  = isInternalArea;
exports.getAvailableFileAreas           = getAvailableFileAreas;
exports.getAvailableFileAreaTags        = getAvailableFileAreaTags;
exports.getSortedAvailableFileAreas     = getSortedAvailableFileAreas;
exports.isValidStorageTag               = isValidStorageTag;
exports.getAreaStorageDirectoryByTag    = getAreaStorageDirectoryByTag;
exports.getAreaDefaultStorageDirectory  = getAreaDefaultStorageDirectory;
exports.getAreaStorageLocations         = getAreaStorageLocations;
exports.getDefaultFileAreaTag           = getDefaultFileAreaTag;
exports.getFileAreaByTag                = getFileAreaByTag;
exports.getFileEntryPath                = getFileEntryPath;
exports.changeFileAreaWithOptions       = changeFileAreaWithOptions;
exports.scanFile                        = scanFile;
exports.scanFileAreaForChanges          = scanFileAreaForChanges;
exports.getDescFromFileName             = getDescFromFileName;
exports.getAreaStats                    = getAreaStats;
exports.cleanUpTempSessionItems         = cleanUpTempSessionItems;

//  for scheduler:
exports.updateAreaStatsScheduledEvent   = updateAreaStatsScheduledEvent;

const WellKnownAreaTags                 = exports.WellKnownAreaTags = {
    Invalid             : '',
    MessageAreaAttach   : 'system_message_attachment',
    TempDownloads       : 'system_temporary_download',
};

function startup(cb) {
    async.series(
        [
            (callback) => {
                return cleanUpTempSessionItems(callback);
            },
            (callback) => {
                getAreaStats( (err, stats) => {
                    if(!err) {
                        StatLog.setNonPersistentSystemStat(SysProps.FileBaseAreaStats, stats);
                    }

                    return callback(null);
                });
            }
        ],
        err => {
            return cb(err);
        }
    );
}

function isInternalArea(areaTag) {
    return [ WellKnownAreaTags.MessageAreaAttach, WellKnownAreaTags.TempDownloads ].includes(areaTag);
}

function getAvailableFileAreas(client, options) {
    options = options || { };

    //  perform ACS check per conf & omit internal if desired
    const allAreas = _.map(Config().fileBase.areas, (areaInfo, areaTag) => Object.assign(areaInfo, { areaTag : areaTag } ));

    return _.omitBy(allAreas, areaInfo => {
        if(!options.includeSystemInternal && isInternalArea(areaInfo.areaTag)) {
            return true;
        }

        if(options.skipAcsCheck) {
            return false;   //  no ACS checks (below)
        }

        if(options.writeAcs && !client.acs.hasFileAreaWrite(areaInfo)) {
            return true;    //  omit
        }

        return !client.acs.hasFileAreaRead(areaInfo);
    });
}

function getAvailableFileAreaTags(client, options) {
    return _.map(getAvailableFileAreas(client, options), area => area.areaTag);
}

function getSortedAvailableFileAreas(client, options) {
    const areas = _.map(getAvailableFileAreas(client, options), v => v);
    sortAreasOrConfs(areas);
    return areas;
}

function getDefaultFileAreaTag(client, disableAcsCheck) {
    const config = Config();
    let defaultArea = _.findKey(config.fileBase, o => o.default);
    if(defaultArea) {
        const area = config.fileBase.areas[defaultArea];
        if(true === disableAcsCheck || client.acs.hasFileAreaRead(area)) {
            return defaultArea;
        }
    }

    //  just use anything we can
    defaultArea = _.findKey(config.fileBase.areas, (area, areaTag) => {
        return WellKnownAreaTags.MessageAreaAttach !== areaTag && (true === disableAcsCheck || client.acs.hasFileAreaRead(area));
    });

    return defaultArea;
}

function getFileAreaByTag(areaTag) {
    const areaInfo = Config().fileBase.areas[areaTag];
    if(areaInfo) {
        areaInfo.areaTag    = areaTag;  //  convienence!
        areaInfo.storage    = getAreaStorageLocations(areaInfo);
        return areaInfo;
    }
}

function changeFileAreaWithOptions(client, areaTag, options, cb) {
    async.waterfall(
        [
            function getArea(callback) {
                const area = getFileAreaByTag(areaTag);
                return callback(area ? null : Errors.Invalid('Invalid file areaTag'), area);
            },
            function validateAccess(area, callback) {
                if(!client.acs.hasFileAreaRead(area)) {
                    return callback(Errors.AccessDenied('No access to this area'));
                }
            },
            function changeArea(area, callback) {
                if(true === options.persist) {
                    client.user.persistProperty(UserProps.FileAreaTag, areaTag, err => {
                        return callback(err, area);
                    });
                } else {
                    client.user.properties[UserProps.FileAreaTag] = areaTag;
                    return callback(null, area);
                }
            }
        ],
        (err, area) => {
            if(!err) {
                client.log.info( { areaTag : areaTag, area : area }, 'Current file area changed');
            } else {
                client.log.warn( { areaTag : areaTag, area : area, error : err.message }, 'Could not change file area');
            }

            return cb(err);
        }
    );
}

function isValidStorageTag(storageTag) {
    return storageTag in Config().fileBase.storageTags;
}

function getAreaStorageDirectoryByTag(storageTag) {
    const config = Config();
    const storageLocation = (storageTag && config.fileBase.storageTags[storageTag]);

    return paths.resolve(config.fileBase.areaStoragePrefix, storageLocation || '');
}

function getAreaDefaultStorageDirectory(areaInfo) {
    return getAreaStorageDirectoryByTag(areaInfo.storageTags[0]);
}

function getAreaStorageLocations(areaInfo) {

    const storageTags = Array.isArray(areaInfo.storageTags) ?
        areaInfo.storageTags :
        [ areaInfo.storageTags || '' ];

    const avail = Config().fileBase.storageTags;

    return _.compact(storageTags.map(storageTag => {
        if(avail[storageTag]) {
            return {
                storageTag  : storageTag,
                dir         : getAreaStorageDirectoryByTag(storageTag),
            };
        }
    }));
}

function getFileEntryPath(fileEntry) {
    const areaInfo = getFileAreaByTag(fileEntry.areaTag);
    if(areaInfo) {
        return paths.join(areaInfo.storageDirectory, fileEntry.fileName);
    }
}

function getExistingFileEntriesBySha256(sha256, cb) {
    const entries = [];

    FileDb.each(
        `SELECT file_id, area_tag
        FROM file
        WHERE file_sha256=?;`,
        [ sha256 ],
        (err, fileRow) => {
            if(fileRow) {
                entries.push({
                    fileId  : fileRow.file_id,
                    areaTag : fileRow.area_tag,
                });
            }
        },
        err => {
            return cb(err, entries);
        }
    );
}

//  :TODO: This is bascially sliceAtEOF() from art.js .... DRY!
function sliceAtSauceMarker(data) {
    let eof         = data.length;
    const stopPos   = Math.max(data.length - (256), 0); //  256 = 2 * sizeof(SAUCE)

    for(let i = eof - 1; i > stopPos; i--) {
        if(0x1a === data[i]) {
            eof = i;
            break;
        }
    }
    return data.slice(0, eof);
}

function attemptSetEstimatedReleaseDate(fileEntry) {
    //  :TODO: yearEstPatterns RegExp's should be cached - we can do this @ Config (re)load time
    const patterns  = Config().fileBase.yearEstPatterns.map( p => new RegExp(p, 'gmi'));

    function getMatch(input) {
        if(input) {
            let m;
            for(let i = 0; i < patterns.length; ++i) {
                m = patterns[i].exec(input);
                if(m) {
                    return m;
                }
            }
        }
    }

    //
    //  We attempt detection in short -> long order
    //
    //  Throw out anything that is current_year + 2 (we give some leway)
    //  with the assumption that must be wrong.
    //
    const maxYear = moment().add(2, 'year').year();
    const match = getMatch(fileEntry.desc) || getMatch(fileEntry.descLong);

    if(match && match[1]) {
        let year;
        if(2 === match[1].length) {
            year = parseInt(match[1]);
            if(year) {
                if(year > 70) {
                    year += 1900;
                } else {
                    year += 2000;
                }
            }
        } else {
            year = parseInt(match[1]);
        }

        if(year && year <= maxYear) {
            fileEntry.meta.est_release_year = year;
        }
    }
}

//  a simple log proxy for when we call from oputil.js
const maybeLog = (obj, msg, level) => {
    if(Log) {
        Log[level](obj, msg);
    } else if ('error' === level) {
        console.error(`${msg}: ${JSON.stringify(obj)}`);    //  eslint-disable-line no-console
    }
};

const logDebug = (obj, msg) => maybeLog(obj, msg, 'debug');
const logTrace = (obj, msg) => maybeLog(obj, msg, 'trace');
const logError = (obj, msg) => maybeLog(obj, msg, 'error');

function extractAndProcessDescFiles(fileEntry, filePath, archiveEntries, cb) {
    async.waterfall(
        [
            function extractDescFiles(callback) {
                //  :TODO: would be nice if these RegExp's were cached
                //  :TODO: this is long winded...
                const config = Config();
                const extractList = [];

                const shortDescFile = archiveEntries.find( e => {
                    return config.fileBase.fileNamePatterns.desc.find( pat => new RegExp(pat, 'i').test(e.fileName) );
                });

                if(shortDescFile) {
                    extractList.push(shortDescFile.fileName);
                }

                const longDescFile = archiveEntries.find( e => {
                    return config.fileBase.fileNamePatterns.descLong.find( pat => new RegExp(pat, 'i').test(e.fileName) );
                });

                if(longDescFile) {
                    extractList.push(longDescFile.fileName);
                }

                if(0 === extractList.length) {
                    return callback(null, [] );
                }

                temptmp.mkdir( { prefix : 'enigextract-' }, (err, tempDir) => {
                    if(err) {
                        return callback(err);
                    }

                    const archiveUtil = ArchiveUtil.getInstance();
                    archiveUtil.extractTo(filePath, tempDir, fileEntry.meta.archive_type, extractList, err => {
                        if(err) {
                            return callback(err);
                        }

                        const descFiles = {
                            desc        : shortDescFile ? paths.join(tempDir, shortDescFile.fileName) : null,
                            descLong    : longDescFile ? paths.join(tempDir, longDescFile.fileName) : null,
                        };

                        return callback(null, descFiles);
                    });
                });
            },
            function readDescFiles(descFiles, callback) {
                const config = Config();
                async.each(Object.keys(descFiles), (descType, next) => {
                    const path = descFiles[descType];
                    if(!path) {
                        return next(null);
                    }

                    fs.stat(path, (err, stats) => {
                        if(err) {
                            return next(null);
                        }

                        //  skip entries that are too large
                        const maxFileSizeKey = `max${_.upperFirst(descType)}FileByteSize`;
                        if(config.fileBase[maxFileSizeKey] && stats.size > config.fileBase[maxFileSizeKey]) {
                            logDebug( { byteSize : stats.size, maxByteSize : config.fileBase[maxFileSizeKey] }, `Skipping "${descType}"; Too large` );
                            return next(null);
                        }

                        fs.readFile(path, (err, data) => {
                            if(err || !data) {
                                return next(null);
                            }

                            //
                            //  Assume FILE_ID.DIZ, NFO files, etc. are CP437.
                            //
                            //  :TODO: This isn't really always the case - how to handle this? We could do a quick detection...
                            fileEntry[descType]         = iconv.decode(sliceAtSauceMarker(data, 0x1a), 'cp437');
                            fileEntry[`${descType}Src`] = 'descFile';
                            return next(null);
                        });
                    });
                }, () => {
                    //  cleanup but don't wait
                    temptmp.cleanup( paths => {
                        //  note: don't use client logger here - may not be avail
                        logTrace( { paths : paths, sessionId : temptmp.sessionId }, 'Cleaned up temporary files' );
                    });
                    return callback(null);
                });
            },
        ],
        err => {
            return cb(err);
        }
    );
}

function extractAndProcessSingleArchiveEntry(fileEntry, filePath, archiveEntries, cb) {

    async.waterfall(
        [
            function extractToTemp(callback) {
                //  :TODO: we may want to skip this if the compressed file is too large...
                temptmp.mkdir( { prefix : 'enigextract-' }, (err, tempDir) => {
                    if(err) {
                        return callback(err);
                    }

                    const archiveUtil = ArchiveUtil.getInstance();

                    //  ensure we only extract one - there should only be one anyway -- we also just need the fileName
                    const extractList = archiveEntries.slice(0, 1).map(entry => entry.fileName);

                    archiveUtil.extractTo(filePath, tempDir, fileEntry.meta.archive_type, extractList, err => {
                        if(err) {
                            return callback(err);
                        }

                        return callback(null, paths.join(tempDir, extractList[0]));
                    });
                });
            },
            function processSingleExtractedFile(extractedFile, callback) {
                populateFileEntryInfoFromFile(fileEntry, extractedFile, err => {
                    if(!fileEntry.desc) {
                        fileEntry.desc      = getDescFromFileName(filePath);
                        fileEntry.descSrc   = 'fileName';
                    }
                    return callback(err);
                });
            }
        ],
        err => {
            return cb(err);
        }
    );
}

function populateFileEntryWithArchive(fileEntry, filePath, stepInfo, iterator, cb) {
    const archiveUtil   = ArchiveUtil.getInstance();
    const archiveType   = fileEntry.meta.archive_type;  //  we set this previous to populateFileEntryWithArchive()

    async.waterfall(
        [
            function getArchiveFileList(callback) {
                stepInfo.step = 'archive_list_start';

                iterator(err => {
                    if(err) {
                        return callback(err);
                    }

                    archiveUtil.listEntries(filePath, archiveType, (err, entries) => {
                        if(err) {
                            stepInfo.step = 'archive_list_failed';
                        } else {
                            stepInfo.step = 'archive_list_finish';
                            stepInfo.archiveEntries = entries || [];
                        }

                        iterator(iterErr => {
                            return callback( iterErr, entries || [] );  //  ignore original |err| here
                        });
                    });
                });
            },
            function processDescFilesStart(entries, callback) {
                stepInfo.step = 'desc_files_start';
                iterator(err => {
                    return callback(err, entries);
                });
            },
            function extractDescFromArchive(entries, callback) {
                //
                //  If we have a -single- entry in the archive, extract that file
                //  and try retrieving info in the non-archive manor. This should
                //  work for things like zipped up .pdf files.
                //
                //  Otherwise, try to find particular desc files such as FILE_ID.DIZ
                //  and README.1ST
                //
                const archDescHandler = (1 === entries.length) ? extractAndProcessSingleArchiveEntry : extractAndProcessDescFiles;
                archDescHandler(fileEntry, filePath, entries, err => {
                    return callback(err);
                });
            },
            function attemptReleaseYearEstimation(callback) {
                attemptSetEstimatedReleaseDate(fileEntry);
                return callback(null);
            },
            function processDescFilesFinish(callback) {
                stepInfo.step = 'desc_files_finish';
                return iterator(callback);
            },
        ],
        err => {
            return cb(err);
        }
    );
}

function getInfoExtractUtilForDesc(mimeType, filePath, descType) {
    const config = Config();
    let fileType = _.get(config, [ 'fileTypes', mimeType ] );

    if(Array.isArray(fileType)) {
        //  further refine by extention
        fileType = fileType.find(ft => paths.extname(filePath) === ft.ext);
    }

    if(!_.isObject(fileType)) {
        return;
    }

    let util = _.get(fileType, `${descType}DescUtil`);
    if(!_.isString(util)) {
        return;
    }

    util = _.get(config, [ 'infoExtractUtils', util ]);
    if(!util || !_.isString(util.cmd)) {
        return;
    }

    return util;
}

function populateFileEntryInfoFromFile(fileEntry, filePath, cb) {
    const mimeType = resolveMimeType(filePath);
    if(!mimeType) {
        return cb(null);
    }

    async.eachSeries( [ 'short', 'long' ], (descType, nextDesc) => {
        const util = getInfoExtractUtilForDesc(mimeType, filePath, descType);
        if(!util) {
            return nextDesc(null);
        }

        const args = (util.args || [ '{filePath}'] ).map( arg => stringFormat(arg, { filePath : filePath } ) );

        execFile(util.cmd, args, { timeout : 1000 * 30 }, (err, stdout) => {
            if(err || !stdout) {
                const reason = err ? err.message : 'No description produced';
                logDebug(
                    { reason : reason, cmd : util.cmd, args : args },
                    `${_.upperFirst(descType)} description command failed`
                );
            } else {
                stdout = (stdout || '').trim();
                if(stdout.length > 0) {
                    const key = 'short' === descType ? 'desc' : 'descLong';
                    if('desc' === key) {
                        //
                        //  Word wrap short descriptions to FILE_ID.DIZ spec
                        //
                        //  "...no more than 45 characters long"
                        //
                        //  See http://www.textfiles.com/computers/fileid.txt
                        //
                        stdout = (wordWrapText( stdout, { width : 45 } ).wrapped || []).join('\n');
                    }

                    fileEntry[key]          = stdout;
                    fileEntry[`${key}Src`]  = 'infoTool';
                }
            }

            return nextDesc(null);
        });
    }, () => {
        return cb(null);
    });
}

function populateFileEntryNonArchive(fileEntry, filePath, stepInfo, iterator, cb) {

    async.series(
        [
            function processDescFilesStart(callback) {
                stepInfo.step = 'desc_files_start';
                return iterator(callback);
            },
            function getDescriptions(callback) {
                populateFileEntryInfoFromFile(fileEntry, filePath, err => {
                    if(!fileEntry.desc) {
                        fileEntry.desc      = getDescFromFileName(filePath);
                        fileEntry.descSrc   = 'fileName';
                    }
                    return callback(err);
                });
            },
            function processDescFilesFinish(callback) {
                stepInfo.step = 'desc_files_finish';
                return iterator(callback);
            },
        ],
        err => {
            return cb(err);
        }
    );
}

function addNewFileEntry(fileEntry, filePath, cb) {
    //  :TODO: Use detectTypeWithBuf() once avail - we *just* read some file data

    async.series(
        [
            function addNewDbRecord(callback) {
                return fileEntry.persist(callback);
            }
        ],
        err => {
            return cb(err);
        }
    );
}

const HASH_NAMES =  [ 'sha1', 'sha256', 'md5', 'crc32' ];

function scanFile(filePath, options, iterator, cb) {

    if(3 === arguments.length && _.isFunction(iterator)) {
        cb          = iterator;
        iterator    = null;
    } else if(2 === arguments.length && _.isFunction(options)) {
        cb          = options;
        iterator    = null;
        options     = {};
    }

    const fileEntry = new FileEntry({
        areaTag     : options.areaTag,
        meta        : options.meta,
        hashTags    : options.hashTags, //  Set() or Array
        fileName    : paths.basename(filePath),
        storageTag  : options.storageTag,
        fileSha256  : options.sha256,   //  caller may know this already
    });

    const stepInfo = {
        filePath    : filePath,
        fileName    : paths.basename(filePath),
    };

    const callIter = (next) => {
        return iterator ? iterator(stepInfo, next) : next(null);
    };

    const readErrorCallIter = (origError, next) => {
        stepInfo.step   = 'read_error';
        stepInfo.error  = origError.message;

        callIter( () => {
            return next(origError);
        });
    };

    let lastCalcHashPercent;

    //  don't re-calc hashes for any we already have in |options|
    const hashesToCalc = HASH_NAMES.filter(hn =>  {
        if('sha256' === hn && fileEntry.fileSha256) {
            return false;
        }

        if(`file_${hn}` in fileEntry.meta) {
            return false;
        }

        return true;
    });

    async.waterfall(
        [
            function startScan(callback) {
                fs.stat(filePath, (err, stats) => {
                    if(err) {
                        return readErrorCallIter(err, callback);
                    }

                    stepInfo.step       = 'start';
                    stepInfo.byteSize   = fileEntry.meta.byte_size = stats.size;

                    return callIter(callback);
                });
            },
            function processPhysicalFileGeneric(callback) {
                stepInfo.bytesProcessed = 0;

                const hashes = {};
                hashesToCalc.forEach(hashName => {
                    if('crc32' === hashName) {
                        hashes.crc32 = new CRC32;
                    } else {
                        hashes[hashName] = crypto.createHash(hashName);
                    }
                });

                const updateHashes = (data) => {
                    for(let i = 0; i < hashesToCalc.length; ++i) {
                        hashes[hashesToCalc[i]].update(data);
                    }
                };

                //
                //  Note that we are not using fs.createReadStream() here:
                //  While convenient, it is quite a bit slower -- which adds
                //  up to many seconds in time for larger files.
                //
                const chunkSize = 1024 * 64;
                const buffer = Buffer.allocUnsafe(chunkSize);

                fs.open(filePath, 'r', (err, fd) => {
                    if(err) {
                        return readErrorCallIter(err, callback);
                    }

                    const nextChunk = () => {
                        fs.read(fd, buffer, 0, chunkSize, null, (err, bytesRead) => {
                            if(err) {
                                return fs.close(fd, closeErr => {
                                    if(closeErr) {
                                        logError( { filePath, error : err.message }, 'Failed to close file');
                                    }
                                    return readErrorCallIter(err, callback);
                                });
                            }

                            if(0 === bytesRead) {
                                //  done - finalize
                                fileEntry.meta.byte_size = stepInfo.bytesProcessed;

                                for(let i = 0; i < hashesToCalc.length; ++i) {
                                    const hashName = hashesToCalc[i];
                                    if('sha256' === hashName) {
                                        stepInfo.sha256 = fileEntry.fileSha256 = hashes.sha256.digest('hex');
                                    } else if('sha1' === hashName || 'md5' === hashName) {
                                        stepInfo[hashName] = fileEntry.meta[`file_${hashName}`] = hashes[hashName].digest('hex');
                                    } else if('crc32' === hashName) {
                                        stepInfo.crc32 = fileEntry.meta.file_crc32 = hashes.crc32.finalize().toString(16);
                                    }
                                }

                                stepInfo.step = 'hash_finish';
                                return fs.close(fd, closeErr => {
                                    if(closeErr) {
                                        logError( { filePath, error : err.message }, 'Failed to close file');
                                    }
                                    return callIter(callback);
                                });
                            }

                            stepInfo.bytesProcessed     += bytesRead;
                            stepInfo.calcHashPercent    = Math.round(((stepInfo.bytesProcessed / stepInfo.byteSize) * 100));

                            //
                            //  Only send 'hash_update' step update if we have a noticable percentage change in progress
                            //
                            const data = bytesRead < chunkSize ? buffer.slice(0, bytesRead) : buffer;
                            if(!iterator || stepInfo.calcHashPercent === lastCalcHashPercent) {
                                updateHashes(data);
                                return nextChunk();
                            } else {
                                lastCalcHashPercent = stepInfo.calcHashPercent;
                                stepInfo.step       = 'hash_update';

                                callIter(err => {
                                    if(err) {
                                        return callback(err);
                                    }

                                    updateHashes(data);
                                    return nextChunk();
                                });
                            }
                        });
                    };

                    nextChunk();
                });
            },
            function processPhysicalFileByType(callback) {
                const archiveUtil = ArchiveUtil.getInstance();

                archiveUtil.detectType(filePath, (err, archiveType) => {
                    if(archiveType) {
                        //  save this off
                        fileEntry.meta.archive_type = archiveType;

                        populateFileEntryWithArchive(fileEntry, filePath, stepInfo, callIter, err => {
                            if(err) {
                                populateFileEntryNonArchive(fileEntry, filePath, stepInfo, callIter, err => {
                                    if(err) {
                                        logDebug( { error : err.message }, 'Non-archive file entry population failed');
                                    }
                                    return callback(null);  //  ignore err
                                });
                            } else {
                                return callback(null);
                            }
                        });
                    } else {
                        populateFileEntryNonArchive(fileEntry, filePath, stepInfo, callIter, err => {
                            if(err) {
                                logDebug( { error : err.message }, 'Non-archive file entry population failed');
                            }
                            return callback(null);  //  ignore err
                        });
                    }
                });
            },
            function fetchExistingEntry(callback) {
                getExistingFileEntriesBySha256(fileEntry.fileSha256, (err, dupeEntries) => {
                    return callback(err, dupeEntries);
                });
            },
            function finished(dupeEntries, callback) {
                stepInfo.step = 'finished';
                callIter( () => {
                    return callback(null, dupeEntries);
                });
            }
        ],
        (err, dupeEntries) => {
            if(err) {
                return cb(err);
            }

            return cb(null, fileEntry, dupeEntries);
        }
    );
}

function scanFileAreaForChanges(areaInfo, options, iterator, cb) {
    if(3 === arguments.length && _.isFunction(iterator)) {
        cb          = iterator;
        iterator    = null;
    } else if(2 === arguments.length && _.isFunction(options)) {
        cb          = options;
        iterator    = null;
        options     = {};
    }

    const storageLocations = getAreaStorageLocations(areaInfo);

    async.eachSeries(storageLocations, (storageLoc, nextLocation) => {
        async.series(
            [
                function scanPhysFiles(callback) {
                    const physDir = storageLoc.dir;

                    fs.readdir(physDir, (err, files) => {
                        if(err) {
                            return callback(err);
                        }

                        async.eachSeries(files, (fileName, nextFile) => {
                            const fullPath = paths.join(physDir, fileName);

                            fs.stat(fullPath, (err, stats) => {
                                if(err) {
                                    //  :TODO: Log me!
                                    return nextFile(null);  //  always try next file
                                }

                                if(!stats.isFile()) {
                                    return nextFile(null);
                                }

                                scanFile(
                                    fullPath,
                                    {
                                        areaTag     : areaInfo.areaTag,
                                        storageTag  : storageLoc.storageTag
                                    },
                                    iterator,
                                    (err, fileEntry, dupeEntries) => {
                                        if(err) {
                                            //  :TODO: Log me!!!
                                            return nextFile(null);  //  try next anyway
                                        }

                                        if(dupeEntries.length > 0) {
                                            //  :TODO: Handle duplidates -- what to do here???
                                        } else {
                                            if(Array.isArray(options.tags)) {
                                                options.tags.forEach(tag => {
                                                    fileEntry.hashTags.add(tag);
                                                });
                                            }
                                            addNewFileEntry(fileEntry, fullPath, err => {
                                                //  pass along error; we failed to insert a record in our DB or something else bad
                                                return nextFile(err);
                                            });
                                        }
                                    }
                                );
                            });
                        }, err => {
                            return callback(err);
                        });
                    });
                },
                function scanDbEntries(callback) {
                    //  :TODO: Look @ db entries for area that were *not* processed above
                    return callback(null);
                }
            ],
            err => {
                return nextLocation(err);
            }
        );
    },
    err => {
        return cb(err);
    });
}

function getDescFromFileName(fileName) {
    //
    //  Example filenames:
    //
    //  input                                                               desired output
    //  -----------------------------------------------------------------------------------------
    //  Nintendo_Power_Issue_011_March-April_1990.cbr                       Nintendo Power Issue 011 March-April 1990
    //  Atari User Issue 3 (July 1985).pdf                                  Atari User Issue 3 (July 1985)
    //  Out_Of_The_Shadows_010__1953_.cbz                                   Out Of The Shadows 010 1953
    //  ABC A Basic Compiler 1.03 [pro].atr                                 ABC A Basic Compiler 1.03 [pro]
    //  221B Baker Street v1.0 (1987)(Datasoft)(Side B)[cr The Bounty].zip  221B Baker Street v1.0 (1987)(Datasoft)(Side B)[cr the Bounty]
    //
    //  See also:
    //  * https://scenerules.org/
    //

    const ext       = paths.extname(fileName);
    const name      = paths.basename(fileName, ext);
    const asIsRe    = /([vV]?(?:[0-9]{1,4})(?:\.[0-9]{1,4})+[-+]?(?:[a-z]{1,4})?)|(Incl\.)|(READ\.NFO)/g;

    const normalize = (s) => {
        return _.upperFirst(s.replace(/[-_.+]/g, ' ').replace(/\s+/g, ' '));
    };

    let out = '';
    let m;
    let pos;
    do {
        pos = asIsRe.lastIndex;
        m = asIsRe.exec(name);
        if(m) {
            if(m.index > pos) {
                out += normalize(name.slice(pos, m.index));
            }
            out += m[0];    //  as-is
        }
    } while(0 != asIsRe.lastIndex);

    if(pos < name.length) {
        out += normalize(name.slice(pos));
    }

    return out;
}

//
//  Return an object of stats about an area(s)
//
//  {
//
//      totalFiles : <totalFileCount>,
//      totalBytes : <totalByteSize>,
//      areas : {
//          <areaTag> : {
//              files : <fileCount>,
//              bytes : <byteSize>
//          }
//      }
//  }
//
function getAreaStats(cb) {
    FileDb.all(
        `SELECT DISTINCT f.area_tag, COUNT(f.file_id) AS total_files, SUM(m.meta_value) AS total_byte_size
        FROM file f, file_meta m
        WHERE f.file_id = m.file_id AND m.meta_name='byte_size'
        GROUP BY f.area_tag;`,
        (err, statRows) => {
            if(err) {
                return cb(err);
            }

            if(!statRows || 0 === statRows.length) {
                return cb(Errors.DoesNotExist('No file areas to acquire stats from'));
            }

            return cb(
                null,
                statRows.reduce( (stats, v) => {
                    stats.totalFiles = (stats.totalFiles || 0) + v.total_files;
                    stats.totalBytes = (stats.totalBytes || 0) + v.total_byte_size;

                    stats.areas = stats.areas || {};

                    stats.areas[v.area_tag] = {
                        files   : v.total_files,
                        bytes   : v.total_byte_size,
                    };
                    return stats;
                }, {})
            );
        }
    );
}

//  method exposed for event scheduler
function updateAreaStatsScheduledEvent(args, cb) {
    getAreaStats( (err, stats) => {
        if(!err) {
            StatLog.setNonPersistentSystemStat(SysProps.FileBaseAreaStats, stats);
        }

        return cb(err);
    });
}

function cleanUpTempSessionItems(cb) {
    //  find (old) temporary session items and nuke 'em
    const filter = {
        areaTag     : WellKnownAreaTags.TempDownloads,
        metaPairs   : [
            {
                name    : 'session_temp_dl',
                value   : 1
            }
        ]
    };

    FileEntry.findFiles(filter, (err, fileIds) => {
        if(err) {
            return cb(err);
        }

        async.each(fileIds, (fileId, nextFileId) => {
            const fileEntry = new FileEntry();
            fileEntry.load(fileId, err => {
                if(err) {
                    Log.warn( { fileId }, 'Failed loading temporary session download item for cleanup');
                    return nextFileId(null);
                }

                FileEntry.removeEntry(fileEntry, { removePhysFile : true }, err => {
                    if(err) {
                        Log.warn( { fileId : fileEntry.fileId, filePath : fileEntry.filePath }, 'Failed to clean up temporary session download item');
                    }
                    return nextFileId(null);
                });
            });
        }, () => {
            return cb(null);
        });
    });
}