wrote revised library skeleton

post.go

@@ -1 +1,117 @@
 package prism
+
+import (
+	"container/list"
+	"context"
+	"log/slog"
+	"sync"
+	"sync/atomic"
+	"time"
+)
+
+// ----------------------------------------------------------------------------
+// Types
+// ----------------------------------------------------------------------------
+
+// Letters
+
+type LetterID = uint64
+
+type OutboundLetter struct {
+}
+
+type letterRecord struct {
+}
+
+type LetterOutcomeKind int
+
+type LetterOutcome struct {
+}
+
+// Postmaster
+
+type Postmaster struct {
+	couriers map[string]*Courier
+	letters  map[LetterID]letterRecord
+	events   <-chan PoolEvent // Adapter.Subscribe
+	send     PoolSendFunc     // Adapter.Send
+	counter  atomic.Uint64
+
+	ctx    context.Context
+	cancel context.CancelFunc
+	mu     sync.Mutex
+	wg     sync.WaitGroup
+	cfg    postmasterConfig
+	logger *slog.Logger
+}
+
+// Courier
+
+type Courier struct {
+	id     string // peer id
+	master *Postmaster
+	cmd    chan courierCommand
+	send   func(data Envelope) error
+
+	// state
+	queue     list.List
+	connected bool
+	sending   bool
+
+	ctx    context.Context
+	cancel context.CancelFunc
+	wg     sync.WaitGroup
+	logger *slog.Logger
+}
+
+// Commands
+
+type courierCommand interface {
+	apply(c *Courier)
+}
+
+// Options
+
+type PostmasterOption func(*postmasterConfig)
+
+type postmasterConfig struct{}
+
+// ----------------------------------------------------------------------------
+// Postmaster
+// ----------------------------------------------------------------------------
+
+func NewPostmaster(
+	pool *Adapter,
+	send PoolSendFunc,
+	opts ...PostmasterOption,
+) *Postmaster {
+	return nil
+}
+
+func (m *Postmaster) Send(
+	ctx context.Context,
+	peerID string,
+	data Envelope,
+	deadline time.Duration,
+	onOutcome func(LetterOutcome), // should be non-blocking
+) (LetterID, error) {
+	return 0, nil
+}
+
+func (m *Postmaster) Close() {}
+
+// ----------------------------------------------------------------------------
+// Courier
+// ----------------------------------------------------------------------------
+
+func NewCourier() *Courier {
+	return nil
+}
+
+func (c *Courier) Enqueue(letter OutboundLetter) {}
+
+func (c *Courier) Close() {}
+
+// ----------------------------------------------------------------------------
+// Commands
+// ----------------------------------------------------------------------------