feat: initial commit

vendor/sourcery.dny.nu/pana/processor.go

@@ -0,0 +1,115 @@
+package pana
+
+import (
+	"fmt"
+	"log/slog"
+
+	ld "sourcery.dny.nu/longdistance"
+	"sourcery.dny.nu/pana/internal/json"
+	"sourcery.dny.nu/pana/internal/loader"
+	"sourcery.dny.nu/pana/vocab/schema"
+	as "sourcery.dny.nu/pana/vocab/w3/activitystreams"
+)
+
+// Processor is used to process incoming messages and prepare outgoing messages.
+//
+// Your application only needs a single processor instance.
+type Processor struct {
+	ldproc *ld.Processor
+	l      *loader.Builtin
+}
+
+// NewProcessor initialised a new [Processor] suitable for dealing with
+// ActivityStreams messages.
+//
+// It uses [loader.Builtin] to retrieve contexts and does not retrieve them over
+// the network.
+func NewProcessor(
+	logger *slog.Logger,
+) *Processor {
+	if logger == nil {
+		logger = slog.New(slog.DiscardHandler)
+	}
+
+	loader := loader.New()
+	return &Processor{
+		l: loader,
+		ldproc: ld.NewProcessor(
+			ld.WithLogger(logger),
+			ld.WithCompactArrays(true),
+			ld.WithCompactToRelative(false), // Avoids compacting to relative IRIs
+			ld.With10Processing(false),      // Misskey seems to do some JSON-LD 1.1
+			ld.WithRemoteContextLoader(loader.Get),
+			ld.WithExcludeIRIsFromCompaction(as.PublicCollection),
+			ld.WithRemapPrefixIRIs("http://schema.org#", schema.Namespace),
+		),
+	}
+}
+
+// Marshal takes an [Activity] and returns JSON-LD in compacted document form.
+//
+// This is the shape of JSON you want to exchange with other servers and
+// clients.
+//
+// The compaction context is a JSON document representing the JSON-LD context
+// that should be used for compaction.
+func (p *Processor) Marshal(
+	compactionContext json.RawMessage,
+	activity Activity,
+) (json.RawMessage, error) {
+	if compactionContext[0] == '{' {
+		ctx, err := json.GetContextDocument(compactionContext)
+		if err != nil {
+			return nil, err
+		}
+		compactionContext = ctx
+	}
+
+	return p.ldproc.Compact(
+		compactionContext,
+		[]ld.Node{ld.Node(activity)},
+		"",
+	)
+}
+
+// Unmarshal takes a JSON document and returns an [Activity] that represents it
+// using JSON-LD expanded document form.
+//
+// In JSON-LD the result of expanding a document is always a list. But in the
+// case of ActivityPub we only ever send out a single document at a time, so it
+// returns [Activity]. If the result happens to have more than one object an
+// error is raised so it doesn't go unnoticed.
+func (p *Processor) Unmarshal(
+	document json.RawMessage,
+) (*Activity, error) {
+	res, err := p.ldproc.Expand(document, "")
+	if err != nil {
+		return nil, err
+	}
+
+	if lres := len(res); lres != 1 {
+		return nil, fmt.Errorf("expected a single document, got: %d", lres)
+	}
+
+	return (*Activity)(&res[0]), nil
+}
+
+// RegisterContextURL adds or overrides a context document for the specified
+// remote context URL in the loader.
+func (p *Processor) RegisterContextURL(
+	url string,
+	doc json.RawMessage,
+) error {
+	return p.l.RegisterContextURL(url, doc)
+}
+
+// RegisterContextPath adds or overrides a context document for the specified
+// remote path in the loader.
+//
+// Paths are always matches as URL suffixes.
+func (p *Processor) RegisterContextPath(
+	path string,
+	doc json.RawMessage,
+) error {
+	return p.l.RegisterContextPath(path, doc)
+}