package utils import ( "bytes" "errors" canonicalJson "github.com/gibson042/canonicaljson-go" "github.com/ipfs/go-cid" "github.com/ipld/go-ipld-prime/codec/dagcbor" "github.com/ipld/go-ipld-prime/codec/dagjson" "github.com/ipld/go-ipld-prime/linking" cidlink "github.com/ipld/go-ipld-prime/linking/cid" "github.com/ipld/go-ipld-prime/multicodec" basicnode "github.com/ipld/go-ipld-prime/node/basic" "github.com/ipld/go-ipld-prime/storage/memstore" ) var store = memstore.Store{} func init() { multicodec.RegisterEncoder(0x71, dagcbor.Encode) multicodec.RegisterDecoder(0x71, dagcbor.Decode) } // GenerateHash returns the hash of the canonicalized JSON input. func GenerateHash(json map[string]interface{}) (string, []byte, error) { content, err := canonicalJson.Marshal(json) if err != nil { return "", nil, err } cidString, err := CIDFromJSONBytes(content) if err != nil { return "", nil, err } return cidString, content, nil } // GetAttributeAsString returns a map attribute as string, if possible. func GetAttributeAsString(obj map[string]interface{}, attr string) (string, error) { if value, ok := obj[attr]; ok { if valueStr, ok := value.(string); ok { return valueStr, nil } return "", errors.New("attribute not of string type") } return "", errors.New("attribute not found") } // CIDFromJSONBytes returns CID (dagcbor) for json (as bytes). // This is combination of samples for unmarshalling and linking // see: https://pkg.go.dev/github.com/ipld/go-ipld-prime func CIDFromJSONBytes(content []byte) (string, error) { if len(content) == 0 { return "", nil } np := basicnode.Prototype.Any // Pick a stle for the in-memory data. nb := np.NewBuilder() // Create a builder. err := dagjson.Decode(nb, bytes.NewReader(content)) // Hand the builder to decoding -- decoding will fill it in! if err != nil { return "", err } n := nb.Build() // Call 'Build' to get the resulting Node. (It's immutable!) lsys := cidlink.DefaultLinkSystem() // We want to store the serialized data somewhere. // We'll use an in-memory store for this. (It's a package scoped variable.) // You can use any kind of storage system here; // or if you need even more control, you could also write a function that conforms to the linking.BlockWriteOpener interface. lsys.SetWriteStorage(&store) // To create any links, first we need a LinkPrototype. // This gathers together any parameters that might be needed when making a link. // (For CIDs, the version, the codec, and the multihash type are all parameters we'll need.) // Often, you can probably make this a constant for your whole application. lp := cidlink.LinkPrototype{Prefix: cid.Prefix{ //nolint:golint Version: 1, // Usually '1'. Codec: 0x71, // 0x71 means "dag-cbor" -- See the multicodecs table: https://github.com/multiformats/multicodec/ MhType: 0x12, // 0x12 means "sha2-256" -- See the multicodecs table: https://github.com/multiformats/multicodec/ MhLength: 32, // sha2-256 hash has a 32-byte sum. }} // Now: time to apply the LinkSystem, and do the actual store operation! lnk, err := lsys.Store( linking.LinkContext{}, // The zero value is fine. Configure it it you want cancellability or other features. lp, // The LinkPrototype says what codec and hashing to use. n, // And here's our data. ) if err != nil { return "", err } return lnk.String(), nil }