package gateway

import "git.yeij.top/AskaEth/Cyrene_v2/internal/runtime/model"

// This file owns the conversation-tail helpers of the session orchestrator
// (design/15 §2.2/§4): the bounded window that continuation resumes from and the
// emptiness check that keeps a vacuous turn from marking a session busy. They are
// pure functions over []model.Message, kept apart from the state machine so the
// orchestrator file stays small.

// boundedTail returns a fresh copy of the last maxTail messages, so continuation
// stays incremental and bounded (design/15 §2.2, §4) and never aliases the input
// slice or another state's tail.
func (o *Orchestrator) boundedTail(msgs []model.Message) []model.Message {
	if len(msgs) <= o.maxTail {
		return append([]model.Message(nil), msgs...)
	}
	out := make([]model.Message, o.maxTail)
	copy(out, msgs[len(msgs)-o.maxTail:])
	return out
}

// messagesEmpty reports whether a turn carries no usable text or image, so the
// orchestrator does not mark a session busy on a vacuous message.
func (o *Orchestrator) messagesEmpty(msgs []model.Message) bool {
	for _, m := range msgs {
		for _, c := range m.Content {
			if c.Type == model.ContentTypeText && c.Text != "" {
				return false
			}
			if c.Type == model.ContentTypeImage && c.ImageURL != "" {
				return false
			}
		}
	}
	return true
}

// concatMessages returns a new slice combining a and b (never reusing a or b
// backing arrays) so the continuation tail is safe to hand to a concurrent run.
func concatMessages(a []model.Message, b ...model.Message) []model.Message {
	out := make([]model.Message, 0, len(a)+len(b))
	out = append(out, a...)
	out = append(out, b...)
	return out
}