package gateway

import (
	"context"
)

// wsReplayLimit is the number of most-recent messages replayed to a connecting
// client. It is intentionally small so a reconnect is cheap; the frontend pulls
// the full active-session history via REST (design/16 §4.1) and the replay is
// only there to give a brand-new connection immediate context.
const wsReplayLimit = 50

// replayHistory sends the most recent messages for sessionID to a single,
// freshly-registered connection as a ws "history" event. It is best-effort: a
// nil store or a read error skips the replay silently. Thinking is NOT included
// (design/16 §6) so the frame never leaks chain-of-thought to a connection whose
// role the gateway did not restrict on upgrade.
func (h *hub) replayHistory(c *wsConn, sessionID string) {
	if h.history == nil {
		return
	}
	msgs, err := h.history.Recent(context.Background(), sessionID, wsReplayLimit)
	if err != nil {
		h.log.Warn("history replay", "err", err, "session", sessionID)
		return
	}
	out := make([]historyMessage, 0, len(msgs))
	for _, m := range msgs {
		wire := toHistoryMessage(m)
		wire.Thinking = ""
		out = append(out, wire)
	}
	c.enqueueJSON(wsEvent{Type: "history", SessionID: sessionID, Data: map[string]any{"messages": out}})
}