package swarm

import "context"

// Tracer is the minimum interface the scheduler needs for distributed
// tracing. A no-op implementation is the default; operators who want
// real OpenTelemetry plug in their own adapter.
//
// This deliberately does NOT import go.opentelemetry.io/otel — keeping
// the dependency footprint small. Bridge code in cmd/pentestswarm can
// wrap an OTel tracer into this shape in a few lines.
type Tracer interface {
	// StartSpan begins a span and returns a ctx carrying it plus an End
	// function. name is the operation name; attrs is a flat list of
	// key-value pairs.
	StartSpan(ctx context.Context, name string, attrs ...Attr) (context.Context, EndSpan)
}

// Attr is a single span attribute. Strings only for simplicity — callers
// that need typed values can serialise themselves.
type Attr struct {
	Key, Value string
}

// EndSpan finishes a span. Call with an error if the operation failed.
type EndSpan func(err error)

// NoopTracer discards all spans. Use as the default so the scheduler
// never crashes on a nil tracer.
type NoopTracer struct{}

// StartSpan implements Tracer with no-op semantics.
func (NoopTracer) StartSpan(ctx context.Context, _ string, _ ...Attr) (context.Context, EndSpan) {
	return ctx, func(error) {}
}