package cli

import (
	"context"
	"errors"
	"fmt"
	"io"
	"net/http"
	"os"
	"os/exec"
	"path/filepath"
	"strings"
	"time"

	"banger/internal/api"
	"banger/internal/buildinfo"
	"banger/internal/installmeta"
	"banger/internal/paths"
	"banger/internal/rpc"
	"banger/internal/updater"

	"github.com/spf13/cobra"
)

// stagingTarballName is what the staged release tarball is saved as
// inside the staging dir. Doesn't really matter (the path is internal
// and ephemeral) but a stable name makes it easy to find for
// debugging a stuck update.
const stagingTarballName = "release.tar.gz"

func (d *deps) newUpdateCommand() *cobra.Command {
	var (
		checkOnly bool
		dryRun    bool
		force     bool
		toVersion string
	)
	cmd := &cobra.Command{
		Use:   "update",
		Short: "Download and install a newer banger release",
		Long: strings.TrimSpace(`
Replace the running banger install with a newer release published
to ` + updater.ManifestURL() + `.

Flow:
  1. Fetch the release manifest.
  2. Refuse if any banger operation is in flight (use --force to skip).
  3. Download tarball + SHA256SUMS, verify hashes.
  4. Sanity-run the staged binaries; refuse if --check-migrations
     reports the new bangerd can't open this host's state DB.
  5. Atomically swap binaries; restart bangerd-root + bangerd.
  6. Run banger doctor; auto-roll back on failure.
  7. Update install metadata with the new version triple.

Steps 1-4 are non-destructive — failures abort with the install
untouched. Step 5+ is the cutover; auto-rollback in step 6 covers
the half-failed-update case.

Requires root: the swap writes /usr/local/bin and the restart
talks to systemd. Run with sudo.
`),
		Example: strings.TrimSpace(`
  banger update --check
  sudo banger update
  sudo banger update --to v0.1.1
  sudo banger update --dry-run
`),
		Args: noArgsUsage("usage: banger update [--check] [--dry-run] [--force] [--to vX.Y.Z]"),
		RunE: func(cmd *cobra.Command, args []string) error {
			return d.runUpdate(cmd, runUpdateOpts{
				checkOnly: checkOnly,
				dryRun:    dryRun,
				force:     force,
				toVersion: toVersion,
			})
		},
	}
	cmd.Flags().BoolVar(&checkOnly, "check", false, "report whether a newer release is available, then exit")
	cmd.Flags().BoolVar(&dryRun, "dry-run", false, "fetch and verify, but do not swap or restart anything")
	cmd.Flags().BoolVar(&force, "force", false, "skip in-flight-op refusal and post-restart doctor verification")
	cmd.Flags().StringVar(&toVersion, "to", "", "specific release version to install (default: latest_stable from manifest)")
	return cmd
}

type runUpdateOpts struct {
	checkOnly bool
	dryRun    bool
	force     bool
	toVersion string
}

func (d *deps) runUpdate(cmd *cobra.Command, opts runUpdateOpts) error {
	ctx := cmd.Context()
	out := cmd.OutOrStdout()

	// Discover.
	client := &http.Client{Timeout: 30 * time.Second}
	manifest, err := updater.FetchManifest(ctx, client)
	if err != nil {
		return fmt.Errorf("discover: %w", err)
	}
	var target updater.Release
	if strings.TrimSpace(opts.toVersion) != "" {
		target, err = manifest.LookupRelease(opts.toVersion)
	} else {
		target, err = manifest.Latest()
	}
	if err != nil {
		return fmt.Errorf("resolve target release: %w", err)
	}

	currentVersion := buildinfo.Current().Version
	if opts.checkOnly {
		return reportCheckResult(out, currentVersion, target.Version)
	}
	if currentVersion == target.Version {
		fmt.Fprintf(out, "already on %s\n", target.Version)
		return nil
	}

	// Past this point we're going to mutate the host. Require root.
	if err := requireRoot(); err != nil {
		return err
	}
	socketPath := paths.ResolveSystem().SocketPath

	// Refuse if anything is in flight.
	if !opts.force {
		if err := refuseIfInFlight(ctx, socketPath); err != nil {
			return err
		}
	}

	// Stage the download.
	stagingDir := updater.DefaultStagingDir(paths.ResolveSystem().CacheDir)
	if err := updater.PrepareCleanStaging(stagingDir); err != nil {
		return fmt.Errorf("staging: %w", err)
	}
	tarballPath := filepath.Join(stagingDir, stagingTarballName)
	fmt.Fprintf(out, "downloading %s …\n", target.TarballURL)
	sumsBody, err := updater.DownloadRelease(ctx, client, target, tarballPath)
	if err != nil {
		return fmt.Errorf("download: %w", err)
	}
	if err := updater.FetchAndVerifySignature(ctx, client, target, sumsBody); err != nil {
		// Don't leave the staged tarball around — it failed
		// signature verification and shouldn't be re-runnable.
		_ = os.Remove(tarballPath)
		return fmt.Errorf("signature: %w", err)
	}
	stagedDir := filepath.Join(stagingDir, "staged")
	if err := os.RemoveAll(stagedDir); err != nil && !os.IsNotExist(err) {
		return err
	}
	staged, err := updater.StageTarball(tarballPath, stagedDir)
	if err != nil {
		return fmt.Errorf("stage: %w", err)
	}

	// Sanity-run the staged binaries.
	if err := sanityRunStaged(ctx, staged, target.Version); err != nil {
		return fmt.Errorf("sanity check: %w", err)
	}

	if opts.dryRun {
		fmt.Fprintf(out, "dry-run: would install %s → %s, restart services, run doctor\n", currentVersion, target.Version)
		return nil
	}

	// Swap.
	targets := updater.DefaultInstallTargets()
	swap, err := updater.Swap(staged, targets)
	if err != nil {
		// Best-effort rollback of any partial swap that did land
		// before failure. If rollback also fails we surface both.
		if rbErr := updater.Rollback(swap); rbErr != nil {
			return fmt.Errorf("swap: %w (rollback also failed: %v)", err, rbErr)
		}
		return fmt.Errorf("swap: %w (rolled back)", err)
	}

	// Restart services + wait for the new daemon.
	if err := d.runSystemctl(ctx, "restart", installmeta.DefaultRootHelperService); err != nil {
		return rollbackAndWrap(swap, "restart helper", err)
	}
	if err := d.runSystemctl(ctx, "restart", installmeta.DefaultService); err != nil {
		return rollbackAndWrap(swap, "restart daemon", err)
	}
	if err := d.waitForDaemonReady(ctx, socketPath); err != nil {
		return rollbackAndWrap(swap, "wait daemon ready", err)
	}

	// Verify with doctor unless --force says otherwise.
	if !opts.force {
		if err := runPostUpdateDoctor(ctx, d, cmd); err != nil {
			return rollbackAndRestart(ctx, d, swap, "post-update doctor", err)
		}
	}

	// Finalise: refresh install metadata, drop backups, clean staging.
	info := buildinfo.Current()
	// We just installed `target.Version` — info.Version still reflects
	// the OLD running binary (we're it). The new bangerd encodes its
	// own version; for install.toml we record what we INSTALLED.
	if err := installmeta.UpdateBuildInfo(installmeta.DefaultPath, target.Version, info.Commit, info.BuiltAt); err != nil {
		// Don't fail the update for this — the install is healthy;
		// install.toml drift is a doctor warning, not a broken host.
		fmt.Fprintf(out, "warning: update install metadata: %v\n", err)
	}
	if err := updater.CleanupBackups(swap); err != nil {
		fmt.Fprintf(out, "warning: cleanup backups: %v\n", err)
	}
	_ = os.RemoveAll(stagingDir)

	fmt.Fprintf(out, "updated %s → %s\n", currentVersion, target.Version)
	return nil
}

func reportCheckResult(out io.Writer, current, latest string) error {
	if current == latest {
		fmt.Fprintf(out, "up to date (%s)\n", current)
		return nil
	}
	fmt.Fprintf(out, "update available: %s → %s\n", current, latest)
	return nil
}

// refuseIfInFlight asks the running daemon for in-flight operations
// and refuses the update if any are not Done. Per the v0.1.0 plan:
// no wait, no drain — the operator runs `banger update` on an idle
// host or passes --force.
func refuseIfInFlight(ctx context.Context, socketPath string) error {
	res, err := rpc.Call[api.OperationsListResult](ctx, socketPath, "daemon.operations.list", nil)
	if err != nil {
		// A daemon that's down or unreachable is itself a reason to
		// refuse — we'd be unable to verify anything. Surface that
		// clearly rather than blindly proceeding.
		return fmt.Errorf("contact daemon: %w (use --force to override)", err)
	}
	pending := []string{}
	for _, op := range res.Operations {
		if op.Done {
			continue
		}
		pending = append(pending, fmt.Sprintf("%s/%s (stage=%s)", op.Kind, op.ID, op.Stage))
	}
	if len(pending) > 0 {
		return fmt.Errorf("refusing update: %d in-flight operation(s): %s", len(pending), strings.Join(pending, ", "))
	}
	return nil
}

// sanityRunStaged executes the staged banger and bangerd to confirm
// they can at least print their own version + report schema state.
// Catches obvious-broken binaries (wrong arch, missing libs,
// embedded panics) before we swap them into place.
func sanityRunStaged(ctx context.Context, staged updater.StagedRelease, expectedVersion string) error {
	// banger --version: must succeed and mention the expected version
	// somewhere (the format is "banger vX.Y.Z (commit ..., built ...)").
	out, err := exec.CommandContext(ctx, staged.BangerPath, "--version").CombinedOutput()
	if err != nil {
		return fmt.Errorf("staged banger --version: %w (%s)", err, strings.TrimSpace(string(out)))
	}
	if !strings.Contains(string(out), expectedVersion) {
		return fmt.Errorf("staged banger --version reported %q, expected to mention %s", strings.TrimSpace(string(out)), expectedVersion)
	}

	// bangerd --check-migrations against the configured DB. Exit 2
	// means incompatible — we refuse to swap. Exit 0 (compatible) and
	// exit 1 (migrations needed; will auto-apply on first Open) are
	// both acceptable.
	out, err = exec.CommandContext(ctx, staged.BangerdPath, "--check-migrations", "--system").CombinedOutput()
	if err != nil {
		var exitErr *exec.ExitError
		if errors.As(err, &exitErr) && exitErr.ExitCode() == 1 {
			return nil // migrations-needed; safe to proceed
		}
		if errors.As(err, &exitErr) && exitErr.ExitCode() == 2 {
			return fmt.Errorf("staged bangerd would not open this host's state DB: %s", strings.TrimSpace(string(out)))
		}
		return fmt.Errorf("staged bangerd --check-migrations: %w (%s)", err, strings.TrimSpace(string(out)))
	}
	return nil
}

// runPostUpdateDoctor invokes `banger doctor` on the JUST-INSTALLED
// CLI (not d.doctor — that's the in-process implementation; we want
// to exercise the new binary end-to-end).
func runPostUpdateDoctor(ctx context.Context, d *deps, cmd *cobra.Command) error {
	out, err := exec.CommandContext(ctx, "/usr/local/bin/banger", "doctor").CombinedOutput()
	if err != nil {
		return fmt.Errorf("doctor: %w\n%s", err, string(out))
	}
	// banger doctor prints to stdout regardless of pass/fail; print
	// it through so the operator can see the new install's check
	// result. (Doctor's exit code is what we trust; printing is
	// just operator UX.)
	fmt.Fprintln(cmd.OutOrStdout(), strings.TrimSpace(string(out)))
	return nil
}

// rollbackAndWrap is for failures BEFORE we restarted services. The
// previous binaries are still on disk under .previous; restoring them
// is an atomic-rename, no service involvement needed (the OLD daemon
// is still running because the restart never happened).
func rollbackAndWrap(swap updater.SwapResult, stage string, err error) error {
	if rbErr := updater.Rollback(swap); rbErr != nil {
		return fmt.Errorf("%s failed: %w (rollback also failed: %v; install is broken)", stage, err, rbErr)
	}
	return fmt.Errorf("%s failed: %w (rolled back to previous install)", stage, err)
}

// rollbackAndRestart is for failures AFTER the service restart. We
// roll back binaries AND re-restart so the OLD versions take over
// again. If even that fails, the install is broken; surface
// everything we know.
func rollbackAndRestart(ctx context.Context, d *deps, swap updater.SwapResult, stage string, err error) error {
	if rbErr := updater.Rollback(swap); rbErr != nil {
		return fmt.Errorf("%s failed: %w (rollback also failed: %v; install is broken)", stage, err, rbErr)
	}
	if rsErr := d.runSystemctl(ctx, "restart", installmeta.DefaultRootHelperService); rsErr != nil {
		return fmt.Errorf("%s failed: %w (restored binaries but failed to restart helper: %v)", stage, err, rsErr)
	}
	if rsErr := d.runSystemctl(ctx, "restart", installmeta.DefaultService); rsErr != nil {
		return fmt.Errorf("%s failed: %w (restored binaries but failed to restart daemon: %v)", stage, err, rsErr)
	}
	return fmt.Errorf("%s failed: %w (rolled back to previous install)", stage, err)
}