Samisdat/not-fs

'use strict';

var Permission = function(mode) {

    if (undefined === mode){
        mode = '0000';
    }

    mode = '' + mode;

    this.setMode(mode);
};


Permission.prototype._validate = function(mode){

    /*
     * 4 = read
     * 2 = write
     * 1 = execute
     * 0 = no permission
     *
     * 3 = w+x
     * 5 = r+x
     * 6 = r+w
     * 7 = r+w+x
     */
    var regEx = /^0{0,1}[01234567]{3}$/;
    return regEx.test(mode);

};

Permission.prototype._normalise = function(mode){

    if (3 === mode.length){
        mode = '0' + mode;
    }

    return mode;

};

Permission.prototype.getMode = function(){

    return this.mode;

};

Permission.prototype.setMode = function(mode){

    if (false === this._validate(mode)){
        throw new Error(mode + ' is not a valid permission');
    }

    this.mode = this._normalise(mode);

};

Permission.prototype._getPart = function(isOwner, isOwnerGroupMember){

    // other part
    var part = this.mode[3];
    if (true === isOwner){
        part = this.mode[1];
    }
    else if (true === isOwnerGroupMember){
        part = this.mode[2];
    }

    return part;
};

Permission.prototype.isReadable = function(isOwner, isOwnerGroupMember){

    var part = this._getPart(isOwner, isOwnerGroupMember);

    if ('7' === part){
        return true;
    }

    if ('6' === part){
        return true;
    }

    if ('5' === part){
        return true;
    }

    if ('4' === part){
        return true;
    }

    return false;
};

Permission.prototype.isWritable = function(isOwner, isOwnerGroupMember){

    var part = this._getPart(isOwner, isOwnerGroupMember);

    if ('7' === part){
        return true;
    }

    if ('6' === part){
        return true;
    }

    if ('3' === part){
        return true;
    }

    if ('2' === part){
        return true;
    }

    return false;
};

Permission.prototype.isExecutable = function(isOwner, isOwnerGroupMember){

    var part = this._getPart(isOwner, isOwnerGroupMember);

    if ('7' === part){
        return true;
    }

    if ('5' === part){
        return true;
    }

    if ('3' === part){
        return true;
    }

    if ('1' === part){
        return true;
    }

    return false;
};


module.exports = Permission;