package main

import (
	"context"
	"encoding/json"
	"errors"
	"flag"
	"fmt"
	"log"
	"os"
	"os/exec"
	"os/signal"
	"strconv"
	"strings"
	"syscall"
	"time"

	"scm.bstein.dev/bstein/hecate/internal/cluster"
	"scm.bstein.dev/bstein/hecate/internal/config"
	"scm.bstein.dev/bstein/hecate/internal/execx"
	"scm.bstein.dev/bstein/hecate/internal/service"
	"scm.bstein.dev/bstein/hecate/internal/state"
	"scm.bstein.dev/bstein/hecate/internal/ups"
)

func main() {
	logger := log.New(os.Stdout, "[hecate] ", log.LstdFlags)
	if len(os.Args) < 2 {
		usage()
		os.Exit(2)
	}

	sub := os.Args[1]
	switch sub {
	case "startup":
		if err := runStartup(logger, os.Args[2:]); err != nil {
			logger.Printf("startup failed: %v", err)
			os.Exit(1)
		}
	case "shutdown":
		if err := runShutdown(logger, os.Args[2:]); err != nil {
			logger.Printf("shutdown failed: %v", err)
			os.Exit(1)
		}
	case "etcd-restore":
		if err := runEtcdRestore(logger, os.Args[2:]); err != nil {
			logger.Printf("etcd-restore failed: %v", err)
			os.Exit(1)
		}
	case "daemon":
		if err := runDaemon(logger, os.Args[2:]); err != nil {
			logger.Printf("daemon failed: %v", err)
			os.Exit(1)
		}
	case "status":
		if err := runStatus(logger, os.Args[2:]); err != nil {
			logger.Printf("status failed: %v", err)
			os.Exit(1)
		}
	case "intent":
		if err := runIntent(logger, os.Args[2:]); err != nil {
			logger.Printf("intent failed: %v", err)
			os.Exit(1)
		}
	case "help", "-h", "--help":
		usage()
	default:
		logger.Printf("unknown command: %s", sub)
		usage()
		os.Exit(2)
	}
}

func runStartup(logger *log.Logger, args []string) error {
	fs := flag.NewFlagSet("startup", flag.ExitOnError)
	configPath := fs.String("config", "/etc/hecate/hecate.yaml", "Path to config file")
	execute := fs.Bool("execute", false, "Actually execute changes (default dry-run)")
	forceBranch := fs.String("force-flux-branch", "", "Patch Flux source branch before resume")
	skipLocalBootstrap := fs.Bool("skip-local-bootstrap", false, "Skip local fallback bootstrap applies")
	allowPeerStartup := fs.Bool("allow-peer-startup", false, "Allow startup to run on a peer instance")
	autoPeerFailover := fs.Bool("auto-peer-failover", false, "On peer role, try coordinator bootstrap handoff first and only run local startup as fallback")
	peerWaitSeconds := fs.Int("peer-wait-seconds", 180, "How long auto peer failover waits for coordinator handoff before local fallback startup")
	allowOnBattery := fs.Bool("allow-on-battery", false, "Allow startup when UPS reports on-battery")
	reason := fs.String("reason", "manual-startup", "Startup reason for run history")
	_ = fs.Parse(args)

	cfg, orch, err := buildOrchestrator(logger, *configPath, !*execute)
	if err != nil {
		return err
	}
	allowPeer := *allowPeerStartup
	if *execute {
		if cfg.Coordination.Role == "peer" && !allowPeer {
			if *autoPeerFailover {
				handoffCtx, cancel := context.WithTimeout(context.Background(), time.Duration(maxInt(*peerWaitSeconds, 1))*time.Second)
				defer cancel()
				handoff, handoffErr := tryPeerBootstrapHandoff(handoffCtx, cfg, logger)
				if handoffErr != nil {
					logger.Printf("warning: peer bootstrap handoff failed: %v", handoffErr)
				}
				if handoff {
					logger.Printf("peer startup handoff complete; skipping local startup")
					return nil
				}
				guardCtx, guardCancel := context.WithTimeout(context.Background(), time.Duration(maxInt(cfg.Coordination.CommandTimeoutSeconds, 15))*time.Second)
				defer guardCancel()
				allowed, guardReason, guardErr := coordinatorAllowsPeerFallbackStartup(guardCtx, cfg, logger)
				if guardErr != nil {
					return fmt.Errorf("startup blocked: unable to evaluate coordinator startup guard: %w", guardErr)
				}
				if !allowed {
					return fmt.Errorf("startup blocked: coordinator guard disallowed peer fallback (%s)", guardReason)
				}
				logger.Printf("peer startup handoff unavailable; proceeding with local peer startup fallback")
				allowPeer = true
			} else {
				return fmt.Errorf("startup blocked: this instance is configured as role=peer (use --allow-peer-startup to override)")
			}
		}
		if cfg.UPS.Enabled && !cfg.Coordination.AllowStartupOnBattery && !*allowOnBattery {
			targets, targetErr := buildUPSTargets(cfg)
			if targetErr != nil {
				return targetErr
			}
			checkCtx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
			defer cancel()
			if err := ensureStartupPowerSafe(checkCtx, targets); err != nil {
				return err
			}
		}
	}
	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()

	return orch.Startup(ctx, cluster.StartupOptions{
		ForceFluxBranch:    *forceBranch,
		SkipLocalBootstrap: *skipLocalBootstrap,
		Reason:             *reason,
	})
}

func runShutdown(logger *log.Logger, args []string) error {
	fs := flag.NewFlagSet("shutdown", flag.ExitOnError)
	configPath := fs.String("config", "/etc/hecate/hecate.yaml", "Path to config file")
	execute := fs.Bool("execute", false, "Actually execute changes (default dry-run)")
	skipEtcd := fs.Bool("skip-etcd-snapshot", false, "Skip etcd snapshot")
	skipDrain := fs.Bool("skip-drain", false, "Skip worker drain")
	reason := fs.String("reason", "manual-shutdown", "Shutdown reason for run history")
	_ = fs.Parse(args)

	_, orch, err := buildOrchestrator(logger, *configPath, !*execute)
	if err != nil {
		return err
	}
	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()

	return orch.Shutdown(ctx, cluster.ShutdownOptions{
		SkipEtcdSnapshot: *skipEtcd,
		SkipDrain:        *skipDrain,
		Reason:           *reason,
	})
}

func runDaemon(logger *log.Logger, args []string) error {
	fs := flag.NewFlagSet("daemon", flag.ExitOnError)
	configPath := fs.String("config", "/etc/hecate/hecate.yaml", "Path to config file")
	dryRunActions := fs.Bool("dry-run-actions", false, "Log planned actions without executing")
	_ = fs.Parse(args)

	cfg, orch, err := buildOrchestrator(logger, *configPath, *dryRunActions)
	if err != nil {
		return err
	}
	if !cfg.UPS.Enabled {
		return fmt.Errorf("UPS monitoring is disabled in config")
	}
	targets, err := buildUPSTargets(cfg)
	if err != nil {
		return err
	}

	d := service.NewDaemon(cfg, orch, targets, logger)
	ctx, stop := signal.NotifyContext(context.Background(), os.Interrupt, syscall.SIGTERM)
	defer stop()
	if err := d.Run(ctx); err != nil && !errors.Is(err, context.Canceled) {
		return err
	}
	return nil
}

func runEtcdRestore(logger *log.Logger, args []string) error {
	fs := flag.NewFlagSet("etcd-restore", flag.ExitOnError)
	configPath := fs.String("config", "/etc/hecate/hecate.yaml", "Path to config file")
	execute := fs.Bool("execute", false, "Actually execute restore (default dry-run)")
	controlPlane := fs.String("control-plane", "", "Control plane to run restore on (defaults to startup.etcd_restore_control_plane)")
	snapshotPath := fs.String("snapshot", "", "Explicit snapshot path (defaults to latest on selected control plane)")
	_ = fs.Parse(args)

	_, orch, err := buildOrchestrator(logger, *configPath, !*execute)
	if err != nil {
		return err
	}
	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()
	return orch.EtcdRestore(ctx, cluster.EtcdRestoreOptions{
		ControlPlane: *controlPlane,
		SnapshotPath: *snapshotPath,
	})
}

func runStatus(logger *log.Logger, args []string) error {
	fs := flag.NewFlagSet("status", flag.ExitOnError)
	configPath := fs.String("config", "/etc/hecate/hecate.yaml", "Path to config file")
	_ = fs.Parse(args)

	cfg, orch, err := buildOrchestrator(logger, *configPath, true)
	if err != nil {
		return err
	}
	recs, err := state.New(cfg.State.RunHistoryPath).Load()
	if err != nil {
		return err
	}
	last := "none"
	if len(recs) > 0 {
		r := recs[len(recs)-1]
		last = fmt.Sprintf("%s success=%t duration=%ds at=%s", r.Action, r.Success, r.DurationSeconds, r.EndedAt.Format(time.RFC3339))
	}
	logger.Printf("expected_flux_branch=%s", cfg.ExpectedFluxBranch)
	logger.Printf("control_planes=%v", cfg.ControlPlanes)
	logger.Printf("estimated_shutdown_budget_seconds=%d", orch.EstimatedShutdownSeconds())
	intent, intentErr := state.ReadIntent(cfg.State.IntentPath)
	if intentErr != nil {
		logger.Printf("intent_read_error=%v", intentErr)
	} else if intent.State == "" {
		logger.Printf("intent=none")
	} else {
		logger.Printf("intent=%s reason=%q source=%s updated_at=%s",
			intent.State, intent.Reason, intent.Source, intent.UpdatedAt.Format(time.RFC3339))
	}
	logger.Printf("last_run=%s", last)
	return nil
}

func runIntent(logger *log.Logger, args []string) error {
	fs := flag.NewFlagSet("intent", flag.ExitOnError)
	configPath := fs.String("config", "/etc/hecate/hecate.yaml", "Path to config file")
	setState := fs.String("set", "", "Set intent state (normal|startup_in_progress|shutting_down|shutdown_complete)")
	reason := fs.String("reason", "manual-intent", "Intent reason (used with --set)")
	source := fs.String("source", "manual", "Intent source (used with --set)")
	execute := fs.Bool("execute", false, "Actually write intent state (default read-only)")
	_ = fs.Parse(args)

	cfg, err := config.Load(*configPath)
	if err != nil {
		return err
	}
	if strings.TrimSpace(*setState) == "" {
		in, readErr := state.ReadIntent(cfg.State.IntentPath)
		if readErr != nil {
			return readErr
		}
		if in.State == "" {
			logger.Printf("intent=none")
			return nil
		}
		logger.Printf("intent=%s reason=%q source=%s updated_at=%s",
			in.State, in.Reason, in.Source, in.UpdatedAt.Format(time.RFC3339))
		return nil
	}
	if !*execute {
		return fmt.Errorf("refusing to write intent without --execute")
	}
	stateValue := strings.TrimSpace(*setState)
	if err := state.MustWriteIntent(cfg.State.IntentPath, stateValue, *reason, *source); err != nil {
		return err
	}
	logger.Printf("intent updated: state=%s reason=%q source=%s", stateValue, *reason, *source)
	return nil
}

func buildUPSTargets(cfg config.Config) ([]service.Target, error) {
	targets := make([]service.Target, 0, len(cfg.UPS.Targets)+1)
	switch cfg.UPS.Provider {
	case "nut":
		if len(cfg.UPS.Targets) == 0 {
			target := cfg.UPS.Target
			if target == "" {
				return nil, fmt.Errorf("ups target must be set")
			}
			targets = append(targets, service.Target{
				Name:     "primary",
				Target:   target,
				Provider: ups.NewNUTProvider(target),
			})
		} else {
			for idx, t := range cfg.UPS.Targets {
				name := t.Name
				if name == "" {
					name = fmt.Sprintf("target-%d", idx+1)
				}
				targets = append(targets, service.Target{
					Name:     name,
					Target:   t.Target,
					Provider: ups.NewNUTProvider(t.Target),
				})
			}
		}
	default:
		return nil, fmt.Errorf("unsupported UPS provider: %s", cfg.UPS.Provider)
	}
	return targets, nil
}

func ensureStartupPowerSafe(ctx context.Context, targets []service.Target) error {
	type targetState struct {
		seenGood bool
		lastErr  error
	}
	states := make(map[string]*targetState, len(targets))
	for _, t := range targets {
		key := t.Name + "|" + t.Target
		states[key] = &targetState{}
	}
	const pollInterval = 3 * time.Second
	for {
		onBatteryTargets := []string{}
		allSeen := true
		for _, t := range targets {
			key := t.Name + "|" + t.Target
			st := states[key]
			sample, err := t.Provider.Read(ctx)
			if err != nil {
				st.lastErr = err
				if !st.seenGood {
					allSeen = false
				}
				continue
			}
			st.seenGood = true
			st.lastErr = nil
			if sample.OnBattery {
				onBatteryTargets = append(onBatteryTargets, fmt.Sprintf("%s(status=%s runtime_s=%d)", t.Name, sample.RawStatus, sample.RuntimeSeconds))
			}
		}
		if len(onBatteryTargets) > 0 {
			return fmt.Errorf("startup blocked: UPS is on battery for %s", strings.Join(onBatteryTargets, ", "))
		}
		if allSeen {
			return nil
		}
		select {
		case <-ctx.Done():
			unverified := make([]string, 0, len(targets))
			for _, t := range targets {
				key := t.Name + "|" + t.Target
				st := states[key]
				if st.seenGood {
					continue
				}
				if st.lastErr != nil {
					unverified = append(unverified, fmt.Sprintf("%s(%s): %v", t.Name, t.Target, st.lastErr))
				} else {
					unverified = append(unverified, fmt.Sprintf("%s(%s): no telemetry sample yet", t.Name, t.Target))
				}
			}
			return fmt.Errorf("startup blocked: unable to verify UPS telemetry before timeout: %s", strings.Join(unverified, " | "))
		case <-time.After(pollInterval):
		}
	}
}

func buildOrchestrator(logger *log.Logger, cfgPath string, dryRun bool) (config.Config, *cluster.Orchestrator, error) {
	cfg, err := config.Load(cfgPath)
	if err != nil {
		return config.Config{}, nil, err
	}
	if err := state.EnsureDir(cfg.State.Dir); err != nil {
		return config.Config{}, nil, err
	}
	runner := &execx.Runner{
		DryRun:     dryRun,
		Kubeconfig: cfg.Kubeconfig,
		Logger:     logger,
	}
	store := state.New(cfg.State.RunHistoryPath)
	orch := cluster.New(cfg, runner, store, logger)
	return cfg, orch, nil
}

func usage() {
	fmt.Print(`hecate: staged startup/shutdown + UPS-triggered protection

Usage:
  hecate <command> [flags]

Commands:
  startup   Perform staged cluster startup
  shutdown  Perform graceful cluster shutdown
  etcd-restore  Restore etcd from snapshot on a control plane
  daemon    Monitor UPS and auto-trigger shutdown
  status    Print current hecate status and estimates
  intent    Read or manually set intent state

Examples:
  hecate startup --config /etc/hecate/hecate.yaml --execute --force-flux-branch main
  hecate shutdown --config /etc/hecate/hecate.yaml --execute --reason "manual-maintenance"
  hecate etcd-restore --config /etc/hecate/hecate.yaml --execute
  hecate daemon --config /etc/hecate/hecate.yaml
  hecate status --config /etc/hecate/hecate.yaml
  hecate intent --config /etc/hecate/hecate.yaml --set normal --reason "manual-clear" --execute
`)
}

func tryPeerBootstrapHandoff(ctx context.Context, cfg config.Config, logger *log.Logger) (bool, error) {
	coordinator := strings.TrimSpace(cfg.Coordination.ForwardShutdownHost)
	if coordinator == "" {
		return false, fmt.Errorf("coordination.forward_shutdown_host is empty for peer role")
	}
	user := strings.TrimSpace(cfg.Coordination.ForwardShutdownUser)
	if user == "" {
		if override, ok := cfg.SSHNodeUsers[coordinator]; ok && strings.TrimSpace(override) != "" {
			user = strings.TrimSpace(override)
		} else {
			user = strings.TrimSpace(cfg.SSHUser)
		}
	}

	host := coordinator
	if mapped, ok := cfg.SSHNodeHosts[coordinator]; ok && strings.TrimSpace(mapped) != "" {
		host = strings.TrimSpace(mapped)
	}
	target := host
	if user != "" {
		target = user + "@" + host
	}

	args := buildSSHBaseArgs(cfg)

	remote := "sudo -n systemctl start hecate-bootstrap.service"
	attempt := 1
	for {
		cmdArgs := append(append([]string{}, args...), target, remote)
		cmd := exec.CommandContext(ctx, "ssh", cmdArgs...)
		out, err := cmd.CombinedOutput()
		if err == nil {
			logger.Printf("peer bootstrap handoff succeeded on %s (attempt=%d)", coordinator, attempt)
			return true, nil
		}
		trimmed := strings.TrimSpace(string(out))
		if trimmed == "" {
			logger.Printf("peer bootstrap handoff attempt %d failed for %s: %v", attempt, coordinator, err)
		} else {
			logger.Printf("peer bootstrap handoff attempt %d failed for %s: %v: %s", attempt, coordinator, err, trimmed)
		}

		select {
		case <-ctx.Done():
			return false, fmt.Errorf("coordinator handoff timeout for %s: %w", coordinator, ctx.Err())
		case <-time.After(5 * time.Second):
			attempt++
		}
	}
}

func coordinatorAllowsPeerFallbackStartup(ctx context.Context, cfg config.Config, logger *log.Logger) (bool, string, error) {
	coordinator := strings.TrimSpace(cfg.Coordination.ForwardShutdownHost)
	if coordinator == "" {
		return true, "no coordinator configured", nil
	}
	user := strings.TrimSpace(cfg.Coordination.ForwardShutdownUser)
	if user == "" {
		if override, ok := cfg.SSHNodeUsers[coordinator]; ok && strings.TrimSpace(override) != "" {
			user = strings.TrimSpace(override)
		} else {
			user = strings.TrimSpace(cfg.SSHUser)
		}
	}
	host := coordinator
	if mapped, ok := cfg.SSHNodeHosts[coordinator]; ok && strings.TrimSpace(mapped) != "" {
		host = strings.TrimSpace(mapped)
	}
	target := host
	if user != "" {
		target = user + "@" + host
	}
	remoteCmd := "sudo -n sh -lc 'if systemctl is-active --quiet hecate-bootstrap.service; then echo __HECATE_BOOTSTRAP_ACTIVE__; else echo __HECATE_BOOTSTRAP_IDLE__; fi; if [ -s /var/lib/hecate/intent.json ]; then cat /var/lib/hecate/intent.json; else echo \"{}\"; fi'"
	args := append(buildSSHBaseArgs(cfg), target, remoteCmd)
	cmd := exec.CommandContext(ctx, "ssh", args...)
	out, err := cmd.CombinedOutput()
	if err != nil {
		trimmed := strings.TrimSpace(string(out))
		if trimmed == "" {
			logger.Printf("warning: coordinator guard check unavailable on %s: %v; allowing peer fallback startup", coordinator, err)
		} else {
			logger.Printf("warning: coordinator guard check unavailable on %s: %v: %s; allowing peer fallback startup", coordinator, err, trimmed)
		}
		return true, "coordinator unreachable", nil
	}
	trimmed := strings.TrimSpace(string(out))
	if strings.Contains(trimmed, "__HECATE_BOOTSTRAP_ACTIVE__") {
		return false, "coordinator bootstrap service is active", nil
	}
	start := strings.Index(trimmed, "{")
	end := strings.LastIndex(trimmed, "}")
	if start < 0 || end < start {
		return false, "coordinator intent payload missing", nil
	}
	rawIntent := trimmed[start : end+1]
	var remoteIntent state.Intent
	if err := json.Unmarshal([]byte(rawIntent), &remoteIntent); err != nil {
		return false, "", fmt.Errorf("decode coordinator intent: %w", err)
	}
	if remoteIntent.State == "" || remoteIntent.State == state.IntentNormal {
		return true, "coordinator intent is normal", nil
	}
	guardAge := time.Duration(maxInt(cfg.Coordination.StartupGuardMaxAgeSec, 60)) * time.Second
	intentAge := time.Duration(0)
	if !remoteIntent.UpdatedAt.IsZero() {
		intentAge = time.Since(remoteIntent.UpdatedAt)
	}
	switch remoteIntent.State {
	case state.IntentShuttingDown:
		if remoteIntent.UpdatedAt.IsZero() || intentAge <= guardAge {
			return false, fmt.Sprintf("coordinator intent=%s age=%s reason=%q", remoteIntent.State, intentAge.Round(time.Second), remoteIntent.Reason), nil
		}
		logger.Printf("warning: coordinator shutdown intent appears stale (age=%s > guard=%s); allowing peer fallback startup", intentAge.Round(time.Second), guardAge)
		return true, "coordinator shutdown intent stale", nil
	case state.IntentStartupInProgress:
		if remoteIntent.UpdatedAt.IsZero() || intentAge <= guardAge {
			return false, fmt.Sprintf("coordinator intent=%s age=%s reason=%q", remoteIntent.State, intentAge.Round(time.Second), remoteIntent.Reason), nil
		}
		logger.Printf("warning: coordinator startup intent appears stale (age=%s > guard=%s); allowing peer fallback startup", intentAge.Round(time.Second), guardAge)
		return true, "coordinator startup intent stale", nil
	case state.IntentShutdownComplete:
		if remoteIntent.UpdatedAt.IsZero() {
			return false, "coordinator reported shutdown_complete with unknown age", nil
		}
		if intentAge <= 45*time.Second {
			return false, fmt.Sprintf("coordinator recently completed shutdown (%s ago)", intentAge.Round(time.Second)), nil
		}
		return true, "coordinator shutdown_complete is old enough", nil
	default:
		return false, fmt.Sprintf("coordinator intent state %q is unknown", remoteIntent.State), nil
	}
}

func buildSSHBaseArgs(cfg config.Config) []string {
	args := []string{
		"-o", "BatchMode=yes",
		"-o", "ConnectTimeout=8",
		"-o", "StrictHostKeyChecking=accept-new",
	}
	if cfgPath := resolveSSHConfigFile(cfg); cfgPath != "" {
		args = append(args, "-F", cfgPath)
	}
	if idPath := resolveSSHIdentityFile(cfg); idPath != "" {
		args = append(args, "-i", idPath)
	}
	if cfg.SSHPort > 0 {
		args = append(args, "-p", strconv.Itoa(cfg.SSHPort))
	}
	if cfg.SSHJumpHost != "" {
		jump := cfg.SSHJumpHost
		if cfg.SSHJumpUser != "" {
			jump = cfg.SSHJumpUser + "@" + jump
		}
		if cfg.SSHPort > 0 && !strings.Contains(jump, ":") {
			jump = fmt.Sprintf("%s:%d", jump, cfg.SSHPort)
		}
		args = append(args, "-J", jump)
	}
	return args
}

func resolveSSHConfigFile(cfg config.Config) string {
	if strings.TrimSpace(cfg.SSHConfigFile) != "" {
		return strings.TrimSpace(cfg.SSHConfigFile)
	}
	candidates := []string{
		"/home/atlas/.ssh/config",
		"/home/tethys/.ssh/config",
	}
	for _, p := range candidates {
		if stat, err := os.Stat(p); err == nil && !stat.IsDir() {
			return p
		}
	}
	return ""
}

func resolveSSHIdentityFile(cfg config.Config) string {
	if strings.TrimSpace(cfg.SSHIdentityFile) != "" {
		return strings.TrimSpace(cfg.SSHIdentityFile)
	}
	candidates := []string{
		"/home/atlas/.ssh/id_ed25519",
		"/home/tethys/.ssh/id_ed25519",
	}
	for _, p := range candidates {
		if stat, err := os.Stat(p); err == nil && !stat.IsDir() {
			return p
		}
	}
	return ""
}

func maxInt(a, b int) int {
	if a > b {
		return a
	}
	return b
}