Hedera NFT Utilities

Introduction
Package: HIP412 metadata validator
Package: Local metadata validator
Package: Risk score calculation
Package: Rarity score calculation
Questions, contact us, or improvement proposals?

Introduction

// What is this?

HIP412 Validator

How to use this validator package

Install the package:

npm i -s @michielmulders/hip412-validator

Import the package into your project. You can import the validator function and the default schema version for HIP412 with defaultVersion.

const { validator, defaultVersion } = require('@michielmulders/hip412-validator');

You can use the validator like below.

The first parameter is the stringified JSON object you want to verify against a JSON schema
The second parameter is the version of HIP412 metadata schema against which you want to validate your metadata instance. The default value is 1.0.0. In the future, new HIP412 schema versions might be added depending on community needs.

const metadata = {
    attributes: [
        { trait_type: "Background", value: "Yellow" }
    ],
    creator: "NFT artist",
};
const version = '1.0.0';

const issues = validator(JSON.stringify(metadata), version);

Issues format

The interface for issues contains of errors and warnings.

{
    "errors": [
        {
            "type": "Indicates which validator created the error. Possible values: schema, attribute, localization, and SHA256.",
            "msg": "Indicates the specific error explanation to be displayed to the user",
            "path": "Indicates the path of the property for which the error is returned"
        }
    ],
    "warning": [
        {
            "type": "schema",
            "msg": "is not allowed to have the additional property 'someAdditionalProperty'",
            "path": "Indicates the path of the property for which the error is returned"
        }
    ]
}

Here's an example:

{
    "errors": [
        {
            "type": "attribute",
            "msg": "Trait stamina of type 'percentage' must be between [0-100], found 157",
            "path": "instance.attributes[0]"
        }
    ],
    "warnings": [
        {
            "type": "schema",
            "msg": "is not allowed to have the additional property 'imagePreview'",
            "path": "instance"
        }
    ]
}

Add custom schema versions

You can add custom JSON schemas to the /schemas folder.

You can then add the version to the schemaMap in /schema/index.js using the following code:

const HIP412_1_0_0 = require("./HIP412@1.0.0.json");
const myCustomSchema = require("./myschema.json"); // import your schema

const schemaMap = new Map();
schemaMap.set('1.0.0', HIP412_1_0_0);
schemaMap.set('<version>', myCustomSchema); // Add your schema to the map

When you've added your schema to the map, you can validate against your schema version by passing your version to the validator() function.

Add custom validation rules

Set custom validation rules by importing new validators from the /validators folder into the index.js file. You can then add them to the validator() function. Make sure to stick to the issues format of errors and warnings (see section "Issues format" for the detailed description).

const { myCustomValidator, schemaValidator } = require("./validators");

const validator = (instance, schemaVersion = defaultVersion) => {
    let errors = [];
    let warnings = [];

    const schema = getSchema(schemaVersion)

    // When errors against the schema are found, you don't want to continue verifying the NFT
    // Warnings don't matter because they only contain "additional property" warnings that don't break the other validators
    const schemaProblems = schemaValidator(instance, schema);
    warnings.push(...schemaProblems.warnings);
    if (schemaProblems.errors.length > 0) {
        errors.push(...schemaProblems.errors);

        return {
            errors,
            warnings
        }
    }

    const customErrors = myCustomValidator(instance);
    errors.push(...customErrors);

    return {
        errors,
        warnings
    };
}

Who is this for

Anyone who wants to build NFT tooling on Hedera Hashgraph and needs to verify NFT metadata for validatiy against the HIP412 metadata standard.

Local validator

Risk score calculation

Rarity score calculation

Questions or Improvement Proposals

Please create an issue or PR on this repository. Make sure to join the Hedera Discord server to ask questions or discuss improvement suggestions.

michielmulders/hip412-validator