github.com/storacha/go-ucanto@v0.7.2/core/ipld/view.go

package ipld

import (
	"iter"
)

// View represents a materialized IPLD DAG View, which provides a generic
// traversal API. It is useful for encoding (potentially partial) IPLD DAGs
// into content archives (e.g. CARs).
type View interface {
	// Root is the root block of the IPLD DAG this is the view of. This is the
	// block from which all other blocks are linked directly or transitively.
	Root() Block
	// Blocks returns an iterator of all the IPLD blocks that are included in
	// this view.
	//
	// It is RECOMMENDED that implementations return blocks in bottom up order
	// (i.e. leaf blocks first, root block last).
	//
	// Iterator MUST include the root block otherwise it will lead encoders into
	// omitting it when encoding the view into a CAR archive.
	Blocks() iter.Seq2[Block, error]
}

// ViewBuilder represents a materializable IPLD DAG View. It is a useful
// abstraction that can be used to defer actual IPLD encoding.
//
// Note that represented DAG could be partial implying that some of the blocks
// may not be included. This by design allowing a user to include whatever
// blocks they want to include.
type ViewBuilder[V View] interface {
	// BuildIPLDView encodes all the blocks and creates a new IPLDView instance over them.
	BuildIPLDView() V
}