This package has multiple functions that read a metadata object, denormalizes it, and builds other structures needed for different processes
npm install @pezkuwi/metadata-buildersThis package has multiple functions that read a metadata object, denormalizes it, and builds other structures needed for different processes
##Â getLookupFn
``ts
interface MetadataLookup {
(id: number): LookupEntry
metadata: V14 | V15
}
function getLookupFn(metadata: Metadata): MetadataLookup
`
Given the a metadata, returns a function that will give the LookupEntry for an id along. The function also has access to the original metadata, as it's usually needed to work with the actual lookup.
The LookupEntry is a denormalized data structure for one entry in the metadata. It also "shortcuts" type references when those are pointers (composites or tuples of length 1). Essentially, it's a union of each of the different types that can be found in the lookup, mostly equivalent to something like:
`ts
type TerminalVar =
| PrimitiveVar // u8, str, char, i128, etc.
| CompactVar
| BitSequenceVar
| AccountId32
type ComposedVar =
| TupleVar
| StructVar
| SequenceVar
| ArrayVar
| OptionVar
| ResultVar
| EnumVar
type LookupEntry = TerminalVar | ComposedVar
`
Where, for instance, a StructVar is of the shape
`ts`
type StructVar = {
type: "struct"
value: Record
}
It's useful to get types referenced by storage calls, etc.
`ts`
function getDynamicBuilder(metadataLookup: MetadataLookup): {
buildDefinition: (id: number) => Codec
buildConstant: (pallet: string, name: string) => Codec
buildEvent: (pallet: string, name: string) => VariantEntry
buildError: (pallet: string, name: string) => VariantEntry
buildCall: (pallet: string, name: string) => VariantEntry
buildStorage: (pallet: string, entry: string) => StorageEntry
buildRuntimeCall: (api: string, method: string) => RuntimeEntry
}
Generates all the codecs needed to SCALE encode or decode the data for any interaction with the chain.
buildDefinition returns the codec for the type identified by the parameter id
buildConstant returns the codec for the requested constant (equivalent as calling buildDefinition with the type id of that constant)
buildEvent, buildError and buildCall return an object with the codec, and the indices of the pallet and entry within the metadata:
`ts`
interface VariantEntry {
location: [number, number] // [palletIdx, entryIdx],
codec: Codec
}
buildStorage creates all the encoders/decoders needed to encode a storage call and decode its result:
`ts`
interface StorageEntry {
// Encodes the arguments of the storage call.
enc: (...args: any[]) => string
// Decodes the result from the storage call.
dec: (value: string) => any
// Decodes the arguments of the storage call
keyDecoder: (value: string) => any[]
// Expected number of arguments
len: number
// Decoded fallback value as defined in the metadata entry
fallback: unknown
}
Similarly, buildRuntimeCall returns the codecs for both encoding the arguments of the runtime call, and the codec for decoding the result
`ts`
interface RuntimeEntry {
args: Codec
value: Codec
}
`ts`
function getChecksumBuilder(metadataLookup: MetadataLookup): {
buildDefinition: (id: number) => string | null
buildRuntimeCall: (api: string, method: string) => string | null
buildStorage: (pallet: string, entry: string) => string | null
buildCall: (pallet: string, name: string) => string | null
buildEvent: (pallet: string, name: string) => string | null
buildError: (pallet: string, name: string) => string | null
buildConstant: (pallet: string, constantName: string) => string | null
}
Generates the checksums for the different components defined in the metadata.
buildDefinition` builds the checksum of one of the types in the lookup. The rest of the methods build the checksum for each of the interfaces of the chain.