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Artifact 5e108783f7fb14a561e465e1782770e07906678c28f652444d0a27c555db0a6d:

package libfossil

import (
	"context"
)

// Transport delivers sync payloads between peers.
// Implementations handle the network layer (HTTP, NATS, etc.).
// Payloads are opaque zlib-compressed xfer card streams.
type Transport interface {
	RoundTrip(ctx context.Context, payload []byte) ([]byte, error)
}

// FramedTransport is an optional interface a Transport may also implement when
// it can report the framing signal — such as an HTTP Content-Type header — that
// accompanied a reply. Sync uses that signal to select the reply's §4 framing
// instead of assuming the §4.1 compressed container, which matters when the
// peer is a different Fossil-protocol implementation that legitimately replies
// with the uncompressed plain-card framing (e.g. a real Fossil server's clone
// reply).
//
// It is optional in the same way http.Flusher is optional on an
// http.ResponseWriter: a Transport whose framing is fixed by convention (both
// ends always emit the compressed container) need not implement it, and sync
// falls back to assuming the compressed framing for such a Transport. Callers
// type-assert a Transport to FramedTransport and use RoundTripFramed when it is
// available. Reporting the signal as a return value keeps it per-call, with no
// shared mutable state to make a reused Transport unsafe across concurrent
// calls.
type FramedTransport interface {
	Transport
	// RoundTripFramed behaves like RoundTrip but also returns the framing
	// signal (e.g. the reply's Content-Type) the wire carried for this reply,
	// or "" when the transport observed none.
	RoundTripFramed(ctx context.Context, payload []byte) (resp []byte, contentType string, err error)
}

// OriginNamer is an optional interface a Transport may also implement to
// name the peer it addresses. Sync and Clone keep the horizon cursor of
// draft-fossil-horizon-00 §6.2.6 per origin under that name: "A client that
// converged records the cursor of the last reply together with the count of
// its own artifacts at the end of the exchange, per origin", and "A client
// holding a cursor for the origin it addresses sends it on every request,
// and MAY then announce nothing with igot on a pull-only request."
//
// The name must identify the same peer across sessions and must carry no
// credential, since it is written into the repository's config table; the
// HTTP transport uses its URL with any password removed. A Transport that
// does not implement it, or returns "", keeps no cursor, and each of its
// pulls announces the client's whole holding with igot, which §6.2.6 allows.
type OriginNamer interface {
	Transport
	SyncOrigin() string
}

// syncOrigin is the origin t names, or "" when it names none.
func syncOrigin(t Transport) string {
	if o, ok := t.(OriginNamer); ok {
		return o.SyncOrigin()
	}
	return ""
}

// loginCookieTransport is a Transport that can carry a login card in the
// x-f-l-c cookie rather than the body (§6.5), as the HTTP transport can.
type loginCookieTransport interface {
	roundTripLoginCookie(ctx context.Context, payload []byte,
		cookie string) ([]byte, string, error)
}

// MockTransport is a test double that delegates to a handler function.
type MockTransport struct {
	Handler func(req []byte) []byte
}

// RoundTrip calls the Handler function if set, otherwise returns empty bytes.
func (t *MockTransport) RoundTrip(_ context.Context, payload []byte) ([]byte, error) {
	if t.Handler == nil {
		return []byte{}, nil
	}
	return t.Handler(payload), nil
}

// TransportFunc adapts a plain function to the Transport interface.
// This is the Transport equivalent of http.HandlerFunc.
type TransportFunc func(ctx context.Context, payload []byte) ([]byte, error)

// RoundTrip calls the function.
func (f TransportFunc) RoundTrip(ctx context.Context, payload []byte) ([]byte, error) {
	return f(ctx, payload)
}