µ on-chain metadata utils

$3

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.

$3

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: "",
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);
}
}
``