/**
 * @license node-stream-zip | (c) 2015 Antelle | https://github.com/antelle/node-stream-zip/blob/master/MIT-LICENSE.txt
 * Portions copyright https://github.com/cthackers/adm-zip | https://raw.githubusercontent.com/cthackers/adm-zip/master/MIT-LICENSE.txt
 */

// region Deps

var
    util = require('util'),
    fs = require('fs'),
    path = require('path'),
    events = require('events'),
    zlib = require('zlib'),
    stream = require('stream');

// endregion

// region Constants

var consts = {
    /* The local file header */
    LOCHDR           : 30, // LOC header size
    LOCSIG           : 0x04034b50, // "PK\003\004"
    LOCVER           : 4, // version needed to extract
    LOCFLG           : 6, // general purpose bit flag
    LOCHOW           : 8, // compression method
    LOCTIM           : 10, // modification time (2 bytes time, 2 bytes date)
    LOCCRC           : 14, // uncompressed file crc-32 value
    LOCSIZ           : 18, // compressed size
    LOCLEN           : 22, // uncompressed size
    LOCNAM           : 26, // filename length
    LOCEXT           : 28, // extra field length

    /* The Data descriptor */
    EXTSIG           : 0x08074b50, // "PK\007\008"
    EXTHDR           : 16, // EXT header size
    EXTCRC           : 4, // uncompressed file crc-32 value
    EXTSIZ           : 8, // compressed size
    EXTLEN           : 12, // uncompressed size

    /* The central directory file header */
    CENHDR           : 46, // CEN header size
    CENSIG           : 0x02014b50, // "PK\001\002"
    CENVEM           : 4, // version made by
    CENVER           : 6, // version needed to extract
    CENFLG           : 8, // encrypt, decrypt flags
    CENHOW           : 10, // compression method
    CENTIM           : 12, // modification time (2 bytes time, 2 bytes date)
    CENCRC           : 16, // uncompressed file crc-32 value
    CENSIZ           : 20, // compressed size
    CENLEN           : 24, // uncompressed size
    CENNAM           : 28, // filename length
    CENEXT           : 30, // extra field length
    CENCOM           : 32, // file comment length
    CENDSK           : 34, // volume number start
    CENATT           : 36, // internal file attributes
    CENATX           : 38, // external file attributes (host system dependent)
    CENOFF           : 42, // LOC header offset

    /* The entries in the end of central directory */
    ENDHDR           : 22, // END header size
    ENDSIG           : 0x06054b50, // "PK\005\006"
    ENDSUB           : 8, // number of entries on this disk
    ENDTOT           : 10, // total number of entries
    ENDSIZ           : 12, // central directory size in bytes
    ENDOFF           : 16, // offset of first CEN header
    ENDCOM           : 20, // zip file comment length
    MAXFILECOMMENT   : 0xFFFF,

    /* Compression methods */
    STORED           : 0, // no compression
    SHRUNK           : 1, // shrunk
    REDUCED1         : 2, // reduced with compression factor 1
    REDUCED2         : 3, // reduced with compression factor 2
    REDUCED3         : 4, // reduced with compression factor 3
    REDUCED4         : 5, // reduced with compression factor 4
    IMPLODED         : 6, // imploded
    // 7 reserved
    DEFLATED         : 8, // deflated
    ENHANCED_DEFLATED: 9, // enhanced deflated
    PKWARE           : 10,// PKWare DCL imploded
    // 11 reserved
    BZIP2            : 12, //  compressed using BZIP2
    // 13 reserved
    LZMA             : 14, // LZMA
    // 15-17 reserved
    IBM_TERSE        : 18, // compressed using IBM TERSE
    IBM_LZ77         : 19, //IBM LZ77 z

    /* General purpose bit flag */
    FLG_ENC          : 0,  // encrypted file
    FLG_COMP1        : 1,  // compression option
    FLG_COMP2        : 2,  // compression option
    FLG_DESC         : 4,  // data descriptor
    FLG_ENH          : 8,  // enhanced deflation
    FLG_STR          : 16, // strong encryption
    FLG_LNG          : 1024, // language encoding
    FLG_MSK          : 4096, // mask header values
    FLG_ENTRY_ENC    : 1,

    /* 4.5 Extensible data fields */
    EF_ID            : 0,
    EF_SIZE          : 2,

    /* Header IDs */
    ID_ZIP64         : 0x0001,
    ID_AVINFO        : 0x0007,
    ID_PFS           : 0x0008,
    ID_OS2           : 0x0009,
    ID_NTFS          : 0x000a,
    ID_OPENVMS       : 0x000c,
    ID_UNIX          : 0x000d,
    ID_FORK          : 0x000e,
    ID_PATCH         : 0x000f,
    ID_X509_PKCS7    : 0x0014,
    ID_X509_CERTID_F : 0x0015,
    ID_X509_CERTID_C : 0x0016,
    ID_STRONGENC     : 0x0017,
    ID_RECORD_MGT    : 0x0018,
    ID_X509_PKCS7_RL : 0x0019,
    ID_IBM1          : 0x0065,
    ID_IBM2          : 0x0066,
    ID_POSZIP        : 0x4690,

    EF_ZIP64_OR_32   : 0xffffffff,
    EF_ZIP64_OR_16   : 0xffff,
    EF_ZIP64_SUNCOMP : 0,
    EF_ZIP64_SCOMP   : 8,
    EF_ZIP64_RHO     : 16,
    EF_ZIP64_DSN     : 24
};

// endregion

// region StreamZip

var StreamZip = function(config) {
    var
        fd,
        fileSize,
        chunkSize,
        ready = false,
        that = this,
        op,
        centralDirectory,

        entries = config.storeEntries !== false ? {} : null,
        fileName = config.file;

    open();

    function open() {
        fs.open(fileName, 'r', function(err, f) {
            if (err)
                return that.emit('error', err);
            fd = f;
            fs.fstat(fd, function(err, stat) {
                if (err)
                    return that.emit('error', err);
                fileSize = stat.size;
                chunkSize = config.chunkSize || Math.round(fileSize / 1000);
                chunkSize = Math.max(Math.min(chunkSize, Math.min(128*1024, fileSize)), Math.min(1024, fileSize));
                readCentralDirectory();
            });
        });
    }

    function readCentralDirectory() {
        var totalReadLength = Math.min(consts.ENDHDR + consts.MAXFILECOMMENT, fileSize);
        op = {
            win: new FileWindowBuffer(fd),
            totalReadLength: totalReadLength,
            minPos: fileSize - totalReadLength,
            lastPos: fileSize,
            chunkSize: 1024
        };
        op.win.read(fileSize - op.chunkSize, op.chunkSize, readCentralDirectoryCallback);
    }

    function readCentralDirectoryCallback(err, bytesRead) {
        if (err || !bytesRead)
            return that.emit('error', err || 'Archive read error');
        var
            buffer = op.win.buffer,
            pos = op.lastPos,
            bufferPosition = pos - op.win.position,
            minPos = Math.max(op.minPos, bufferPosition);
        while (--pos >= minPos && --bufferPosition >= 0) {
            if (buffer[bufferPosition] === 0x50) { // quick check that the byte is 'P'
                if (buffer.readUInt32LE(bufferPosition) === consts.ENDSIG) { // "PK\005\006"
                    op = {};
                    try {
                        centralDirectory = new CentralDirectoryHeader();
                        centralDirectory.read(buffer.slice(bufferPosition, bufferPosition + consts.ENDHDR));
                        centralDirectory.headerOffset = pos;
                        if (centralDirectory.commentLength)
                            that.comment = buffer.slice(bufferPosition + consts.ENDHDR,
                                bufferPosition + consts.ENDHDR + centralDirectory.commentLength).toString();
                        else
                            that.comment = null;
                        that.entriesCount = centralDirectory.volumeEntries;
                        that.centralDirectory = centralDirectory;
                        readEntries();
                    } catch (err) {
                        that.emit('error', err);
                    }
                    return;
                }
            }
        }
        if (pos === minPos) {
            return that.emit('error', 'Bad archive format');
        }
        op.lastPos = pos + 1;
        op.chunkSize *= 2;
        if (pos <= minPos)
            return that.emit('error', 'Bad archive');
        var expandLength = Math.min(op.chunkSize, pos - minPos);
        op.win.expandLeft(expandLength, readCentralDirectoryCallback);
    }

    function readEntries() {
        op = {
            win: new FileWindowBuffer(fd),
            pos: centralDirectory.offset,
            chunkSize: chunkSize,
            entriesLeft: centralDirectory.volumeEntries
        };
        op.win.read(op.pos, Math.min(chunkSize, fileSize - op.pos), readEntriesCallback);
    }

    function readEntriesCallback(err, bytesRead) {
        if (err || !bytesRead)
            return that.emit('error', err || 'Entries read error');
        var
            buffer = op.win.buffer,
            bufferPos = op.pos - op.win.position,
            bufferLength = buffer.length,
            entry = op.entry;
        try {
            while (op.entriesLeft > 0) {
                if (!entry) {
                    entry = new ZipEntry();
                    entry.readHeader(buffer, bufferPos);
                    entry.headerOffset = op.pos;
                    op.entry = entry;
                    op.pos += consts.CENHDR;
                    bufferPos += consts.CENHDR;
                }
                var entryHeaderSize = entry.fnameLen + entry.extraLen + entry.comLen;
                var advanceBytes = entryHeaderSize + (op.entriesLeft > 1 ? consts.CENHDR : 0);
                if (bufferLength - bufferPos < advanceBytes) {
                    op.win.moveRight(chunkSize, readEntriesCallback, bufferPos);
                    op.move = true;
                    return;
                }
                entry.read(buffer, bufferPos);
                if (entries)
                    entries[entry.name] = entry;
                that.emit('entry', entry);
                op.entry = entry = null;
                op.entriesLeft--;
                op.pos += entryHeaderSize;
                bufferPos += entryHeaderSize;
            }
            that.emit('ready');
        } catch (err) {
            that.emit('error', err);
        }
    }

    function checkEntriesExist() {
        if (!entries)
            throw 'storeEntries disabled';
    }

    Object.defineProperty(this, 'ready', { get: function() { return ready; } });

    this.entry = function(name) {
        checkEntriesExist();
        return entries[name];
    };

    this.entries = function() {
        checkEntriesExist();
        return entries;
    };

    this.stream = function(entry, callback) {
        return openEntry(entry, function(err, entry) {
            if (err)
                return callback(err);
            var offset = dataOffset(entry);
            var entryStream = new EntryDataReaderStream(fd, offset, entry.compressedSize);
            if (entry.method === consts.STORED) {
            } else if (entry.method === consts.DEFLATED || entry.method === consts.ENHANCED_DEFLATED) {
                entryStream = entryStream.pipe(zlib.createInflateRaw());
            } else {
                return callback('Unknown compression method: ' + entry.method);
            }
            if (canVerifyCrc(entry))
                entryStream = entryStream.pipe(new EntryVerifyStream(entryStream, entry.crc, entry.size));
            callback(null, entryStream);
        }, false);
    };

    this.entryDataSync = function(entry) {
        var err = null;
        openEntry(entry, function(e, en) {
            err = e;
            entry = en;
        }, true);
        if (err)
            throw err;
        var
            data = new Buffer(entry.compressedSize),
            bytesRead;
        new FsRead(fd, data, 0, entry.compressedSize, dataOffset(entry), function(e, br) {
            err = e;
            bytesRead = br;
        }).read(true);
        if (err)
            throw err;
        if (entry.method === consts.STORED) {
        } else if (entry.method === consts.DEFLATED || entry.method === consts.ENHANCED_DEFLATED) {
            data = zlib.inflateRawSync(data);
        } else {
            throw 'Unknown compression method: ' + entry.method;
        }
        if (data.length !== entry.size)
            throw 'Invalid size';
        if (canVerifyCrc(entry)) {
            var verify = new CrcVerify(entry.crc, entry.size);
            verify.data(data);
        }
        return data;
    };

    function openEntry(entry, callback, sync) {
        if (typeof entry === 'string') {
            checkEntriesExist();
            entry = entries[entry];
            if (!entry)
                return callback('Entry not found');
        }
        if (!entry.isFile)
            return callback('Entry is not file');
        if (!fd)
            return callback('Archive closed');
        var buffer = new Buffer(consts.LOCHDR);
        new FsRead(fd, buffer, 0, buffer.length, entry.offset, function(err) {
            if (err)
                return callback(err);
            try {
                entry.readDataHeader(buffer);
                if (entry.encrypted) {
                    return callback('Entry encrypted');
                }
                callback(null, entry);
            } catch (ex) {
                callback(ex);
            }
        }).read(sync);
    }

    function dataOffset(entry) {
        return entry.offset + consts.LOCHDR + entry.fnameLen + entry.extraLen;
    }

    function canVerifyCrc(entry) {
        // if bit 3 (0x08) of the general-purpose flags field is set, then the CRC-32 and file sizes are not known when the header is written
        return (entry.flags & 0x8) != 0x8
    }

    function extract(entry, outPath, callback) {
        that.stream(entry, function (err, stm) {
            if (err) {
                callback(err);
            } else {
                var fsStm, errThrown;
                stm.on('error', function(err) {
                    errThrown = err;
                    if (fsStm) {
                        stm.unpipe(fsStm);
                        fsStm.close(function () {
                            callback(err);
                        });
                    }
                });
                fs.open(outPath, 'w', function(err, fdFile) {
                    if (err)
                        return callback(err || errThrown);
                    if (errThrown) {
                        fs.close(fd, function() {
                            callback(errThrown);
                        });
                        return;
                    }
                    fsStm = fs.createWriteStream(outPath, { fd: fdFile });
                    fsStm.on('finish', function() {
                        that.emit('extract', entry, outPath);
                        if (!errThrown)
                            callback();
                    });
                    stm.pipe(fsStm);
                });
            }
        });
    }

    function createDirectories(baseDir, dirs, callback) {
        if (!dirs.length)
            return callback();
        var dir = dirs.shift();
        dir = path.join(baseDir, path.join.apply(path, dir));
        fs.mkdir(dir, function(err) {
            if (err && err.code !== 'EEXIST')
                return callback(err);
            createDirectories(baseDir, dirs, callback);
        });
    }

    function extractFiles(baseDir, baseRelPath, files, callback, extractedCount) {
        if (!files.length)
            return callback(null, extractedCount);
        var file = files.shift();
        var targetPath = path.join(baseDir, file.name.replace(baseRelPath, ''));
        extract(file, targetPath, function (err) {
            if (err)
                return callback(err, extractedCount);
            extractFiles(baseDir, baseRelPath, files, callback, extractedCount + 1);
        });
    }

    this.extract = function(entry, outPath, callback) {
        var entryName = entry || '';
        if (typeof entry === 'string') {
            entry = this.entry(entry);
            if (entry) {
                entryName = entry.name;
            } else {
                if (entryName.length && entryName[entryName.length - 1] !== '/')
                    entryName += '/';
            }
        }
        if (!entry || entry.isDirectory) {
            var files = [], dirs = [], allDirs = {};
            for (var e in entries) {
                if (Object.prototype.hasOwnProperty.call(entries, e) && e.lastIndexOf(entryName, 0) === 0) {
                    var relPath = e.replace(entryName, '');
                    var childEntry = entries[e];
                    if (childEntry.isFile) {
                        files.push(childEntry);
                        relPath = path.dirname(relPath);
                    }
                    if (relPath && !allDirs[relPath] && relPath[0] !== '.') {
                        allDirs[relPath] = true;
                        var parts = relPath.split('/').filter(function (f) { return f; });
                        if (parts.length)
                            dirs.push(parts);
                    }
                }
            }
            dirs.sort(function(x, y) { return x.length - y.length; });
            if (dirs.length) {
                createDirectories(outPath, dirs, function (err) {
                    if (err)
                        callback(err);
                    else
                        extractFiles(outPath, entryName, files, callback, 0);
                });
            } else {
                extractFiles(outPath, entryName, files, callback, 0);
            }
        } else {
            fs.stat(outPath, function(err, stat) {
                if (stat && stat.isDirectory())
                    extract(entry, path.join(outPath, path.basename(entry.name)), callback);
                else
                    extract(entry, outPath, callback);
            });
        }
    };

    this.close = function() {
        if (fd) {
            fs.close(fd, function() {
                fd = null;
            });
        }
    };
};

util.inherits(StreamZip, events.EventEmitter);

// endregion

// region CentralDirectoryHeader

var CentralDirectoryHeader = function() {
};

CentralDirectoryHeader.prototype.read = function(data) {
    if (data.length != consts.ENDHDR || data.readUInt32LE(0) != consts.ENDSIG)
        throw 'Invalid central directoty';
    // number of entries on this volume
    this.volumeEntries = data.readUInt16LE(consts.ENDSUB);
    // total number of entries
    this.totalEntries = data.readUInt16LE(consts.ENDTOT);
    // central directory size in bytes
    this.size = data.readUInt32LE(consts.ENDSIZ);
    // offset of first CEN header
    this.offset = data.readUInt32LE(consts.ENDOFF);
    // zip file comment length
    this.commentLength = data.readUInt16LE(consts.ENDCOM);
};

// endregion

// region ZipEntry

var ZipEntry = function() {
};

ZipEntry.prototype.readHeader = function(data, offset) {
    // data should be 46 bytes and start with "PK 01 02"
    if (data.length < offset + consts.CENHDR || data.readUInt32LE(offset) != consts.CENSIG) {
        throw 'Invalid entry header';
    }
    // version made by
    this.verMade = data.readUInt16LE(offset + consts.CENVEM);
    // version needed to extract
    this.version = data.readUInt16LE(offset + consts.CENVER);
    // encrypt, decrypt flags
    this.flags = data.readUInt16LE(offset + consts.CENFLG);
    // compression method
    this.method = data.readUInt16LE(offset + consts.CENHOW);
    // modification time (2 bytes time, 2 bytes date)
    this.time = data.readUInt32LE(offset + consts.CENTIM);
    // uncompressed file crc-32 value
    this.crc = data.readUInt32LE(offset + consts.CENCRC);
    // compressed size
    this.compressedSize = data.readUInt32LE(offset + consts.CENSIZ);
    // uncompressed size
    this.size = data.readUInt32LE(offset + consts.CENLEN);
    // filename length
    this.fnameLen = data.readUInt16LE(offset + consts.CENNAM);
    // extra field length
    this.extraLen = data.readUInt16LE(offset + consts.CENEXT);
    // file comment length
    this.comLen = data.readUInt16LE(offset + consts.CENCOM);
    // volume number start
    this.diskStart = data.readUInt16LE(offset + consts.CENDSK);
    // internal file attributes
    this.inattr = data.readUInt16LE(offset + consts.CENATT);
    // external file attributes
    this.attr = data.readUInt32LE(offset + consts.CENATX);
    // LOC header offset
    this.offset = data.readUInt32LE(offset + consts.CENOFF);
};

ZipEntry.prototype.readDataHeader = function(data) {
    // 30 bytes and should start with "PK\003\004"
    if (data.readUInt32LE(0) != consts.LOCSIG) {
        throw 'Invalid local header';
    }
    // version needed to extract
    this.version = data.readUInt16LE(consts.LOCVER);
    // general purpose bit flag
    this.flags = data.readUInt16LE(consts.LOCFLG);
    // compression method
    this.method = data.readUInt16LE(consts.LOCHOW);
    // modification time (2 bytes time ; 2 bytes date)
    this.time = data.readUInt32LE(consts.LOCTIM);
    // uncompressed file crc-32 value
    this.crc = data.readUInt32LE(consts.LOCCRC) || this.crc;
    // compressed size
    this.compressedSize = data.readUInt32LE(consts.LOCSIZ) || this.compressedSize;
    // uncompressed size
    this.size = data.readUInt32LE(consts.LOCLEN) || this.size;
    // filename length
    this.fnameLen = data.readUInt16LE(consts.LOCNAM);
    // extra field length
    this.extraLen = data.readUInt16LE(consts.LOCEXT);
};

ZipEntry.prototype.read = function(data, offset) {
    this.name = data.slice(offset, offset += this.fnameLen).toString();
    var lastChar = data[offset - 1];
    this.isDirectory = (lastChar == 47) || (lastChar == 92);

    if (this.extraLen) {
        this.readExtra(data, offset);
        offset += this.extraLen;
    }
    this.comment = this.comLen ? data.slice(offset, offset + this.comLen).toString() : null;
};

ZipEntry.prototype.readExtra = function(data, offset) {
    var signature, size, maxPos = offset + this.extraLen;
    while (offset < maxPos) {
        signature = data.readUInt16LE(offset);
        offset += 2;
        size = data.readUInt16LE(offset);
        offset += 2;
        if (consts.ID_ZIP64 === signature) {
            this.parseZip64Extra(data, offset, size);
        }
        offset += size;
    }
};

ZipEntry.prototype.parseZip64Extra = function(data, offset, length) {
    if (length >= consts.EF_ZIP64_SCOMP && this.size === consts.EF_ZIP64_OR_32)
        this.size = this.readUInt64LE(data, offset + consts.EF_ZIP64_SUNCOMP);
    if (length >= consts.EF_ZIP64_RHO && this.compressedSize === consts.EF_ZIP64_OR_32)
        this.compressedSize = this.readUInt64LE(data, offset + consts.EF_ZIP64_SCOMP);
    if (length >= consts.EF_ZIP64_DSN && this.offset === consts.EF_ZIP64_OR_32)
        this.offset = this.readUInt64LE(data, offset + consts.EF_ZIP64_RHO);
    if (length >= consts.EF_ZIP64_DSN + 4 && this.diskStart === consts.EF_ZIP64_OR_16)
        this.diskStart = data.readUInt32LE(consts.EF_ZIP64_DSN);
};

ZipEntry.prototype.readUInt64LE = function(buffer, offset) {
    return (buffer.readUInt32LE(offset + 4) << 4) + buffer.readUInt32LE(offset);
};

Object.defineProperty(ZipEntry.prototype, 'encrypted', {
    get: function() { return (this.flags & consts.FLG_ENTRY_ENC) == consts.FLG_ENTRY_ENC; }
});

Object.defineProperty(ZipEntry.prototype, 'isFile', {
    get: function() { return !this.isDirectory; }
});

// endregion

// region FsRead

var FsRead = function(fd, buffer, offset, length, position, callback) {
    this.fd = fd;
    this.buffer = buffer;
    this.offset = offset;
    this.length = length;
    this.position = position;
    this.callback = callback;
    this.bytesRead = 0;
    this.waiting = false;
};

FsRead.prototype.read = function(sync) {
    //console.log('read', this.position, this.bytesRead, this.length, this.offset);
    this.waiting = true;
    if (sync) {
        try {
            var bytesRead = fs.readSync(this.fd, this.buffer, this.offset + this.bytesRead,
                this.length - this.bytesRead, this.position + this.bytesRead);
            this.readCallback(sync, null, bytesRead);
        } catch (err) {
            this.readCallback(sync, err, null);
        }
    } else {
        fs.read(this.fd, this.buffer, this.offset + this.bytesRead,
            this.length - this.bytesRead, this.position + this.bytesRead,
            this.readCallback.bind(this, sync));
    }
};

FsRead.prototype.readCallback = function(sync, err, bytesRead) {
    if (typeof bytesRead === 'number')
        this.bytesRead += bytesRead;
    if (err || !bytesRead || this.bytesRead === this.length) {
        this.waiting = false;
        return this.callback(err, this.bytesRead);
    } else {
        this.read(sync);
    }
};

// endregion

// region FileWindowBuffer

var FileWindowBuffer = function(fd) {
    this.position = 0;
    this.buffer = new Buffer(0);

    var fsOp = null;

    this.checkOp = function() {
        if (fsOp && fsOp.waiting)
            throw 'Operation in progress';
    };

    this.read = function(pos, length, callback) {
        this.checkOp();
        if (this.buffer.length < length)
            this.buffer = new Buffer(length);
        this.position = pos;
        fsOp = new FsRead(fd, this.buffer, 0, length, this.position, callback).read();
    };

    this.expandLeft = function(length, callback) {
        this.checkOp();
        this.buffer = Buffer.concat([new Buffer(length), this.buffer]);
        this.position -= length;
        if (this.position < 0)
            this.position = 0;
        fsOp = new FsRead(fd, this.buffer, 0, length, this.position, callback).read();
    };

    this.expandRight = function(length, callback) {
        this.checkOp();
        var offset = this.buffer.length;
        this.buffer = Buffer.concat([this.buffer, new Buffer(length)]);
        fsOp = new FsRead(fd, this.buffer, offset, length, this.position + offset, callback).read();
    };

    this.moveRight = function(length, callback, shift) {
        this.checkOp();
        if (shift) {
            this.buffer.copy(this.buffer, 0, shift);
        } else {
            shift = 0;
        }
        this.position += shift;
        fsOp = new FsRead(fd, this.buffer, this.buffer.length - shift, shift, this.position + this.buffer.length - shift, callback).read();
    };
};

// endregion

// region EntryDataReaderStream

var EntryDataReaderStream = function(fd, offset, length) {
    stream.Readable.prototype.constructor.call(this);
    this.fd = fd;
    this.offset = offset;
    this.length = length;
    this.pos = 0;
    this.readCallback = this.readCallback.bind(this);
};

util.inherits(EntryDataReaderStream, stream.Readable);

EntryDataReaderStream.prototype._read = function(n) {
    var buffer = new Buffer(Math.min(n, this.length - this.pos));
    if (buffer.length) {
        fs.read(this.fd, buffer, 0, buffer.length, this.offset + this.pos, this.readCallback);
    } else {
        this.push(null);
    }
};

EntryDataReaderStream.prototype.readCallback = function(err, bytesRead, buffer) {
    this.pos += bytesRead;
    if (err) {
        this.emit('error', err);
        this.push(null);
    } else if (!bytesRead) {
        this.push(null);
    } else {
        if (bytesRead !== buffer.length)
            buffer = buffer.slice(0, bytesRead);
        this.push(buffer);
    }
};

// endregion

// region EntryVerifyStream

var EntryVerifyStream = function(baseStm, crc, size) {
    stream.Transform.prototype.constructor.call(this);
    this.verify = new CrcVerify(crc, size);
    var that = this;
    baseStm.on('error', function(e) {
        that.emit('error', e);
    });
};

util.inherits(EntryVerifyStream, stream.Transform);

EntryVerifyStream.prototype._transform = function(data, encoding, callback) {
    try {
        this.verify.data(data);
        callback(null, data);
    } catch (err) {
        callback(err, data);
    }
};

// endregion

// region CrcVerify

var CrcVerify = function(crc, size) {
    this.crc = crc;
    this.size = size;
    this.state = {
        crc: ~0,
        size: 0
    };
};

CrcVerify.prototype.data = function(data) {
    var crcTable = CrcVerify.getCrcTable();
    var crc = this.state.crc, off = 0, len = data.length;
    while (--len >= 0)
        crc = crcTable[(crc ^ data[off++]) & 0xff] ^ (crc >>> 8);
    this.state.crc = crc;
    this.state.size += data.length;
    if (this.state.size >= this.size) {
        var buf = new Buffer(4);
        buf.writeInt32LE(~this.state.crc & 0xffffffff, 0);
        crc = buf.readUInt32LE(0);
        if (crc !== this.crc)
            throw 'Invalid CRC';
        if (this.state.size !== this.size)
            throw 'Invalid size';
    }
};

CrcVerify.getCrcTable = function() {
    var crcTable = CrcVerify.crcTable;
    if (!crcTable) {
        CrcVerify.crcTable = crcTable = [];
        var b = new Buffer(4);
        for (var n = 0; n < 256; n++) {
            var c = n;
            for (var k = 8; --k >= 0; )
                if ((c & 1) != 0)  { c = 0xedb88320 ^ (c >>> 1); } else { c = c >>> 1; }
            if (c < 0) {
                b.writeInt32LE(c, 0);
                c = b.readUInt32LE(0);
            }
            crcTable[n] = c;
        }
    }
    return crcTable;
};

// endregion

// region exports

module.exports = StreamZip;

// endregion