package console

import (
	"net/http"
	"sort"
)

// The armed-regions endpoint (issue #346): one authoritative answer to
// "which regions can serve right now", for consumer pickers — titogo's
// signup picker and move doors consume it through a 60s cache and hide
// themselves when it is unreachable, so it is never in a request path.
//
//	GET /api/cli/apps/{account}/{app}/regions
//	{"regions":[{"code":"ie","armed":true},{"code":"uk","armed":true}],
//	 "default":"ie"}
//
// Codes are CARLOS placement codes, never AWS region strings. armed is
// EXACTLY the create door's predicate (#329's armedPlacements — a picker
// built on this can never offer what create would refuse): a box publishes
// the code, has a dial address, and can host (#110 — see armedPlacements
// for why reachability alone advertised five regions that served 502).
// The home region appears under its NAME
// (Config.HomeRegion) with armed true — create accepts it by normalizing
// the name to the record's "" — and is also the default. A deployment with
// no named home and no placement-publishing boxes answers empty lists, and
// consumers hide their pickers.
//
// Nearest-region additions (§9.3): each entry may carry aws_region and
// name, and the answer carries app_default (regiondefault.go). regions and
// default are unchanged for every older reader.
//
// The instance family's gate, deliberately: the answer is deployment
// topology (which regions exist), the same information the create door's
// refusal message already hands the same bearer.
func (s *Server) handleAPIRegions(w http.ResponseWriter, r *http.Request) {
	_, acct, app, ok := s.instanceGate(w, r)
	if !ok {
		return
	}
	type region struct {
		Code      string `json:"code"`
		Armed     bool   `json:"armed"`
		AWSRegion string `json:"aws_region,omitempty"`
		Name      string `json:"name,omitempty"`
	}
	set, _ := armedPlacements(r.Context(), s.cfg.Releases)
	cands := s.candsOrHome(r.Context())
	named := func(code string) region {
		c, _ := findCandidate(cands, s.homeRegionIn(code))
		return region{Code: code, AWSRegion: c.AWSRegion, Name: s.placeOf(s.homeRegionIn(code), cands)}
	}
	out := make([]region, 0, len(set)+1)
	if s.cfg.HomeRegion != "" {
		h := named(s.cfg.HomeRegion)
		h.Armed = true
		out = append(out, h)
		// A box that publishes the home's code explicitly (a future coded
		// home) must not appear twice.
		delete(set, s.cfg.HomeRegion)
	}
	for code, armed := range set {
		e := named(code)
		e.Armed = armed
		out = append(out, e)
	}
	sort.Slice(out, func(i, j int) bool { return out[i].Code < out[j].Code })
	// regions and default are what older clients and titogo read; they stay
	// as they were. app_default is the nearest-region addition (§9.3).
	writeJSON(w, http.StatusOK, map[string]any{
		"regions": out, "default": s.cfg.HomeRegion,
		"app_default": s.appDefault(r.Context(), acct, app),
	})
}