LayerMetadata.sketchplugin

// Converts JSON string to JavaScript Object.
function jsonToObject(json) {
    var str=[[NSString alloc] initWithString:json];
    return [NSJSONSerialization JSONObjectWithData:str.dataUsingEncoding(NSUTF8StringEncoding) options:0 error:nil];
}

// Converts JavaScript Object to JSON string.
function objectToJson(obj,prettyPrint) {
    var prettyPrint = prettyPrint || false;

    var error=MOPointer.alloc().init();
    var jsonData = [NSJSONSerialization dataWithJSONObject:obj options:((prettyPrint) ? NSJSONWritingPrettyPrinted : 0) error:error];

    if (!jsonData) {
        // print(error.value());
        return null;
    } else {
        return [[NSString alloc] initWithData:jsonData encoding:NSUTF8StringEncoding];
    }
}


function ModelStorage(obj,useNameStorage) {
    return {
        set: function(key,value,remove) {
            var remove = remove || false;

            if(!useNameStorage) {
                if (obj.cache() === null) {
                    return this;
                }

                [[obj cache] setObject:value forKey:key];
            } else {
                var name = obj.name();
                if(this.nameContainsData(name)) {
                    var parts=this.extractDataParts(name);
                    if(parts[1].length>0) {
                        var data=jsonToObject(parts[1]);
                        if(data===null) return null;

                        var newData={};
                        for(var objKey in data) {
                            if(objKey!=key) {
                                newData[objKey]=data[objKey];
                            }
                        }

                        if(!remove) { newData[key]=value; }

                        obj.setName(parts[0]+"[!$#]"+objectToJson(newData)+"[!$#]"+parts[2]);
                    }

                } else {
                    if(!remove) {
                        var data={};
                        data[key]=value;
                        obj.setName(name+"\n"+"[!$#]"+objectToJson(data)+"[!$#]");
                    }
                }

            }

            return this;
        },
        get: function(key) {
            if(!useNameStorage) {
                if(obj.cache()===null || obj.cache()===undefined) {
                    return null;
                }

                return obj.cache().objectForKey(key);
            } else {
                var parts=this.extractDataParts(obj.name());
                if(parts.length<2) return null;

                if(parts[1].length>0) {
                    var data=jsonToObject(parts[1]);
                    if(data===null) return null;

                    return data[key];
                }

                return null;
            }
        },

        nameContainsData: function(str) {
            return str.split("[!$#]").length>1;
        },

        extractDataParts: function(str) {
            return str.split("[!$#]");
        },

        normalized: function(str) {
            var parts=str.split("[!$#]");
            if(parts.length>2) {
                return (parts[0]+parts[2]).replace(/\n/g, '');
            }

            return str;
        },

        normalizeName: function() {
            obj.setName(this.normalized(obj.name()));
        },

        remove: function(key) {
            if(useNameStorage) {
                this.set(key,undefined,true);
            } else {
                // TO-DO: The Finest Code Goes here! :)
            }

            return this;
        }
    };
};

// Entry-Point.
(function(){

    var layer=selection.firstObject();
    if(layer) {

        print("Layer's name before:");
        print(layer.name())
        print(" ");

        var pluginAMetaID="com.turbobabr.annotation-kit";
        var pluginBMetaID="com.SomeAwesomeCompany.ReallyUsefulPlugin";

        // Plugin A sets its metadata.
        ModelStorage(layer,true).set(pluginAMetaID,{
            toolType: "Annotation.Arrow",
            scale: 5,
            description: "This is a very informative description..."
        });

        // Plugin B sets its metadata.
        ModelStorage(layer,true).set(pluginBMetaID,{
            id: "EFA3F9E9-FB79-4DB6-B250-56ABF908BD65",
            status: "Really tired... :("
        });


        // Plugin A accesses its metadata.
        var dataA=ModelStorage(layer,true).get(pluginAMetaID);
        if(dataA!=null) {
            print("Plugin A metadata:")
            print("Tool Type: "+dataA.toolType);
            print("Scale Factor: "+dataA.scale);
            print("Description: "+dataA.description);
            print(" ");
        }

        // Plugin B accesses its metadata.
        var dataB=ModelStorage(layer,true).get(pluginBMetaID);
        if(dataB!=null) {
            print("Plugin B metadata:")
            print("ID: "+dataB.id);
            print("Status: "+dataB.status);
            print(" ");
        }

        print("Layer's name after:");
        print(layer.name())
        print(" ");
    }

})();