package agent

import (
	"context"
	"os"
	"runtime"
	"time"

	"gitea.mynodes.xyz/ilker/llmgw/internal/release"

	llmgwv1 "gitea.mynodes.xyz/ilker/llmgw/api/gen/llmgw/v1"
)

// upgradeExit is the exit status after an upgrade: non-zero, so systemd's
// Restart=on-failure starts the new binary, and distinct, so the journal says
// why the agent went.
const upgradeExit = 75

// exitForUpgrade ends the process; a variable so a test can see it called
// rather than have its own process end.
var exitForUpgrade = func() { os.Exit(upgradeExit) }

// upgradeTarget is the binary an upgrade replaces; a variable so a test
// replaces a file of its own rather than the test binary running it.
var upgradeTarget = os.Executable

// upgrade replaces this agent's binary with a release and restarts into it.
//
// Engines are not touched: an agent restart leaves them running and adopts
// them again, which is what makes upgrading a node something that can be done
// while it serves.
func (a *Agent) upgrade(ctx context.Context, m *llmgwv1.UpgradeAgent, out chan<- *llmgwv1.AgentMessage) {
	reply := &llmgwv1.UpgradeReply{RequestId: m.GetRequestId(), Version: m.GetVersion()}
	send := func() {
		select {
		case out <- &llmgwv1.AgentMessage{Msg: &llmgwv1.AgentMessage_Upgrade{Upgrade: reply}}:
		case <-ctx.Done():
		}
	}
	a.log.Info("upgrading", "to", m.GetVersion(), "from", a.cfg.Version)
	self, err := upgradeTarget()
	if err == nil {
		dctx, cancel := context.WithTimeout(ctx, 10*time.Minute)
		_, err = release.Install(dctx, nil, m.GetReleases(), m.GetVersion(), runtime.GOOS, runtime.GOARCH, self)
		cancel()
	}
	if err != nil {
		reply.Error = err.Error()
		a.log.Error("upgrade failed; still running the old version", "to", m.GetVersion(), "err", err)
		send()
		return
	}
	send()
	a.log.Info("upgraded; restarting into the new version", "to", m.GetVersion())
	// A moment for the reply to leave before the stream goes.
	time.Sleep(500 * time.Millisecond)
	exitForUpgrade()
}