package console

import (
	"context"
	"sort"
)

// instanceChoices lists, under their names, the regions an EXPLICIT
// request for this same socket-backed instance would pass right now (codex
// plan-R4 2): the manifest's allow-list as the door reads it (each code
// normalized through homeRegionIn first), the armed gate's reachable and
// hosting bars, and R9's refusal. These are the explicit door's rules, not
// automatic eligibility. except, the region just refused, is left out.
//
// The home joins the list only when CONSOLE_HOME_REGION names it: an
// unnamed home has no name a caller could pass. The bars are
// explicitGate.refusal, the same predicate the app-region doors use, so no
// door lists a region another would refuse.
func (s *Server) instanceChoices(ctx context.Context, allowed []string, cands []regionCandidate, except string) []string {
	g := explicitGate{cands: cands}
	g.caps, g.published = placements(ctx, s.cfg.Releases)
	codes := map[string]bool{}
	if s.cfg.HomeRegion != "" {
		codes[""] = true
	}
	for c := range g.caps {
		if code := s.homeRegionIn(c); code != "" {
			codes[code] = true
		}
	}
	for _, c := range allowed {
		if code := s.homeRegionIn(c); code != "" {
			codes[code] = true
		}
	}
	var out []string
	for code := range codes {
		if code == except || !instanceRegionAllowed(allowed, code) || g.refusal(code) != "" {
			continue
		}
		out = append(out, s.homeRegionOut(code))
	}
	sort.Strings(out)
	return out
}