µ on-chain metadata utils

Features:

1. on-chain base-64 encoding for any content type
2. on-chain json builder (supports arrays, nested content).
3. re-exports openzeppelin strings support

this is the spiritual successor of https://github.com/ourzora/nft-editions/blob/main/contracts/IPublicSharedMetadata.sol the public shared metadata renderer libraries within nft-editions.

This project may be exported and deployed on-chain as a registry, but for now is being offered in library form.

API:

1. MetadataBuilder: Main class for metadata methods
   1. generateJSON(MetadataBuilder.JSONItem[] items): Takes a list of items and makes a key value json object from them. Objects with empty values will be removed.
   2. generateEncodedJSON(MetadataBuilder.JSONItem[] items): Same as above but returns a data-uri instead of the raw JSON string.
   3. generateSVG(string contents, string viewBox, string width, string height): Generates a SVG tag and content for an SVG image.
   4. generateEncodedSVG(string contents, string viewBox, string width, string height): Same as above but generates a data-uri instead of the raw SVG.
   5. generateJSONArray(MetadataBuilder.JSONItem[] itemsArray): Takes an array of items and using the value and quote flags generates a JSON array. Ignores the key value of the object and empty values will be removed from the array generated.
   6. encodeURI(string contentType, string content): Encodes the given content string as a base-64 data-uri with the given contentType.
2. MetadataMIMETypes: List of common metadata mime type constants
   1. mimeJSON = "application/json"
   2. mimeSVG = "image/svg+xml"
   3. mimeTextPlain = "text/plain"
3. MetadataJSONKeys: List of common NFT Metadata JSON keys
   1. keyName = "name"
   2. keyDescription = "description"
   3. keyImage = "image"
   4. keyAnimationURL = "animation_url"
   5. keyAttributes = "attributes"
   6. keyProperties = "properties";

• All methods are views returning strings unless otherwise noted.

import {MetadataBuilder} from "micro-onchain-metadata-utils/MetadataBuilder.sol";
import {MetadataJSONKeys} from "micro-onchain-metadata-utils/MetadataJSONKeys.sol";

contract NFTObject {
  function contractURI() external view returns (string memory) {
    // Build JSON object
    MetadataBuilder.JSONItem[] memory items = new MetadataBuilder.JSONItem[](2);
    items[0].key = MetadataJSONKeys.keyName;
    items[0].value = "Contract Name";
    items[0].quote = true;
    items[1].key = MetadataJSONKeys.keyImage;
    // Build Embedded SVG
    items[1].value = MetadataBuilder.generateEncodedSVG({
      contents: "<rect width='10' height='10' style='fill: red' />",
      viewBox: '0 0 10 10',
      width: '10',
      height: '10',
    });
    items[1].quote = true;

    // Build JSON Array
    MetadataBuilder.JSONItem[] memory randomNumbersArray = MetadataBuilder.JSONItem[](2);
    properties[0].value = '2';
    properties[0].quote = false;
    properties[1].value = '42';
    properties[1].quote = false;
    
    items[2].key = 'randomNumbers';
    items[2].quote = false;
    items[2].value = MetadataBuilder.generateJSON(properties);

    return MetadataBuilder.generateEncodedJSON(items);
  }
}