package host

import (
	"strings"

	"github.com/carlosframework/platform/internal/release"
	"github.com/carlosframework/platform/internal/status"
)

// systemChannelEnv is the box's platform channel: canary or stable. Set in
// host.env, read through the getenv seam like every other CARLOS_* value;
// the ROOT apply reads it from its own unit environment, never from the
// agent's request (spec §6 step 2).
const systemChannelEnv = "CARLOS_SYSTEM_CHANNEL"

// A value that is not a channel at all — a typo, a shell that expanded to
// nothing useful, a name with a slash too many — falls back to stable
// rather than travelling into a bucket key and an on-box state file to ask
// for a pointer nobody publishes. It comes back as invalid so the caller
// can say so ONCE: this is read per tick, and a line per tick is a line
// nobody reads.
func systemChannel(getenv func(string) string) (channel, invalid string) {
	c := strings.TrimSpace(getenv(systemChannelEnv))
	switch {
	case c == "":
		return "stable", ""
	case !release.ValidChannel(c):
		return "stable", c
	}
	return c, ""
}

// boxSystemChannel is systemChannel for the caller that has nowhere to log:
// the status tick, which publishes this every five minutes.
func boxSystemChannel(getenv func(string) string) string {
	c, _ := systemChannel(getenv)
	return c
}

// systemStateProbe is root's result.json as the heartbeat carries it, or nil
// when this box has never been asked to update.
func systemStateProbe(optDir string) *status.SystemState {
	r, err := readSystemResult(optDir)
	if err != nil || r == nil {
		return nil
	}
	return &status.SystemState{Channel: r.Channel, Version: r.Version, PromotedAt: r.PromotedAt, Outcome: r.Outcome, Reason: r.Reason, At: r.At}
}