package link

import (
	"context"
	"time"
)

// The enrolment conversation, as the host's own words for it.
//
// **Its own seam rather than part of Link**, because almost nothing about it is the same. The
// credential is a one-time secret rather than this node's own; there is no declaration to hear; the
// whole exchange is a single question asked and possibly asked again. And the stakes differ: a node
// that fails here is not in the mesh at all, where a node that fails in Link has merely lost touch
// with one it belongs to.

// Approach is how a node reaches a mesh it does not yet belong to.
//
// The three things a token carries about where to go, and nothing about who is asking: the address,
// the certificate that address must present, and which bus is at the other end. **Every token names
// the bus the mesh runs on today until the rollout** (novox/hq ADR 0116 step 5), so an empty
// Transport is the ordinary case rather than something missing.
type Approach struct {
	Address     string
	Fingerprint string
	Transport   string
}

// Asking is one open enrolment conversation.
type Asking interface {
	// Ask puts the request to the mesh and waits for one answer, or says why none came.
	//
	// Called again, with the same bytes, while the mesh says "try again": the keys this node
	// generated are the ones it keeps, so the same request is the same enrolment and the mesh holds
	// the token for it (novox/hq issue 083).
	Ask(ctx context.Context, request []byte, wait time.Duration) ([]byte, error)

	// Close lets go of the connection made with the token.
	Close()
}

// Present opens an enrolment conversation with the mesh.
//
// The connection is made before anything is sent, and the certificate is checked while it is being
// made — so a node pointed at the wrong bus finds out before its token has left the machine (ADR
// 0004).
func Present(ctx context.Context, to Approach, node, secret string,
	timeout time.Duration) (Asking, error) {

	switch to.Transport {
	case OnNATS:
		return presentNats(ctx, to, node, secret, timeout)
	default:
		return presentCurrent(ctx, to, node, secret, timeout)
	}
}