package api

import (
	"net/http"
	"strings"

	"github.com/loyaly/behavision-server/internal/auth"
)

// handleEnrol turns an anonymous install into a known site.
//
// The installer ships with no credentials of any kind, so a leaked build hands
// out nothing at all. An operator types a one-shot code once; the server
// answers with the broker login for exactly one site and marks the code spent.
//
// Deliberately NOT behind a session: the PC doing this has no user signed in
// yet, and requiring one would mean shipping a password to every shop that
// installs the software.
func (s *Server) handleEnrol(w http.ResponseWriter, r *http.Request) {
	var body struct {
		SiteToken string `json:"site_token"`
		Device    string `json:"device"`
	}
	if err := decode(w, r, &body); err != nil {
		badRequest(w, err.Error())
		return
	}
	token := trim(body.SiteToken)
	if token == "" {
		badRequest(w, "site_token is required")
		return
	}
	token = auth.NormalizeCode(token)

	en, err := s.Store.RedeemEnrolment(r.Context(), auth.HashToken(token))
	if err != nil {
		// One message for unknown, expired and already-used. The difference is
		// only useful to somebody guessing codes, and an operator's next step
		// is the same in all three cases: ask for a new one.
		s.logf("enrolment refused: %v", err)
		writeErr(w, http.StatusUnauthorized, "bad_token",
			"That installation code is not valid. Ask for a new one.")
		return
	}
	// Mint the agent's own HTTPS credential now, while we have a proven
	// one-shot token in hand. Separate from the broker password because they
	// authenticate different things, so rotating one must not break the other.
	agentToken, err := auth.NewToken()
	if err != nil {
		s.serverError(w, "mint agent token", err)
		return
	}
	if err := s.Store.SetAgentAPIToken(r.Context(), en.AgentID, agentToken.Hash); err != nil {
		s.serverError(w, "store agent token", err)
		return
	}

	s.Store.Audit(r.Context(), AuditEntry{
		ClientID: en.ClientID, ActorKind: "agent",
		Action: "agent.enrol", Entity: "site", EntityID: en.SiteID,
		Detail: map[string]any{"device": clip(trim(body.Device), 120)},
	})

	models := s.Bootstrap.Models
	if models == nil {
		// An empty list, not null: the agent then falls back to its own built-in
		// download list rather than treating the field as missing.
		models = []ModelRef{}
	}
	writeJSON(w, http.StatusOK, map[string]any{
		"site_id":   en.SiteID,
		"site_name": en.SiteName,
		"site_slug": en.SiteSlug,
		// Derived from the broker username rather than looked up separately,
		// because the agent uses <client>.<site> as its topic prefix and the
		// broker's ACL is written against that exact username. Deriving it
		// makes the two equal by construction; a second lookup could drift.
		"client_slug":   clientSlugOf(en.MQTTUser),
		"topic_prefix":  "bv/" + en.MQTTUser,
		"mqtt_url":      s.Bootstrap.MQTTURL,
		"mqtt_username": en.MQTTUser,
		"mqtt_password": en.MQTTPass,
		// Used for HTTPS calls the PC makes on its own behalf, such as asking
		// for an image upload URL. Shown once and never returned again.
		"agent_token": agentToken.Plain,
		"ca_cert":     s.Bootstrap.CACert,
		"models":      models,
	})
}

// clientSlugOf pulls the tenant out of a broker username of the form
// "<client>.<site>". Split on the FIRST dot only in the sense that a username
// always has exactly one - the same rule contract.ParseTopic enforces on the
// way back in.
func clientSlugOf(brokerUser string) string {
	if i := strings.Index(brokerUser, "."); i > 0 {
		return brokerUser[:i]
	}
	return ""
}