// Package cli implements the vaultik command-line interface: cobra
// commands, fx application wiring, and process-level concerns such as
// signal handling and the PID lock.
package cli

import (
	"context"
	"errors"
	"fmt"
	"os"
	"os/signal"
	"path/filepath"
	"strings"
	"sync"
	"syscall"
	"time"

	"github.com/adrg/xdg"
	"github.com/spf13/cobra"
	"go.uber.org/fx"
	"sneak.berlin/go/vaultik/internal/config"
	"sneak.berlin/go/vaultik/internal/database"
	"sneak.berlin/go/vaultik/internal/globals"
	"sneak.berlin/go/vaultik/internal/log"
	"sneak.berlin/go/vaultik/internal/pidlock"
	"sneak.berlin/go/vaultik/internal/snapshot"
	"sneak.berlin/go/vaultik/internal/storage"
	"sneak.berlin/go/vaultik/internal/ui"
	"sneak.berlin/go/vaultik/internal/vaultik"
)

// shutdownTimeout bounds how long a signal-triggered graceful shutdown
// may take before we give up.
const shutdownTimeout = 30 * time.Second

// lockMode says whether a command mutates persistent state — the local
// index database or the remote store — and so must hold the process-wide
// PID lock, or only reads that state and may run alongside a mutator.
type lockMode int

const (
	// mutating commands (snapshot create, snapshot purge, snapshot remove,
	// prune, remote nuke) write the local index or the remote store. They
	// hold the PID lock so that at most one runs at a time.
	mutating lockMode = iota
	// readOnly commands (info, snapshot list, snapshot verify, remote info,
	// snapshot restore) do not write the local index or the remote store,
	// so they run without the lock and are never blocked by a running
	// mutator. restore writes only to the target directory it is given.
	readOnly
)

// AppOptions contains common options for creating and running the fx
// application: the configuration file path, logging options, additional fx
// modules and invocations, and whether the command mutates persistent
// state (which decides whether it takes the PID lock).
type AppOptions struct {
	ConfigPath string
	LogOptions log.Options
	Modules    []fx.Option
	Invokes    []fx.Option
	Mode       lockMode
}

// setupGlobals records the startup time and, when an output-suppression
// flag is active, marks the UI writer quiet so that Begin/Complete/
// Info/Notice/Detail/Progress are silenced. Warning and Error are NOT
// silenced — per the documented convention that --quiet suppresses
// non-error output only. The startup banner is printed by Entry
// before cobra parses arguments, gated by the same arg-level check.
//
// --json quiets the UI here too, because stdout then carries a JSON
// document and human narration would corrupt it. Unlike Quiet it does
// not lower the stderr log level (issue #112), so --verbose/--debug
// still surface diagnostics alongside the document.
func setupGlobals(
	lc fx.Lifecycle, g *globals.Globals, v *vaultik.Vaultik, opts log.Options,
) {
	lc.Append(fx.Hook{
		OnStart: func(_ context.Context) error {
			g.StartTime = time.Now().UTC()

			if opts.Cron || opts.Quiet || opts.JSON {
				v.UI.SetQuiet(true)
			}

			return nil
		},
	})
}

// writeStartupBanner prints the two-line application banner followed by a
// blank line. Used both from the fx hook (for subcommand invocations) and
// from the root cobra Run handler (for `vaultik` with no subcommand).
func writeStartupBanner(w *ui.Writer, startTime time.Time, shortCommit string) {
	w.Bannerf("%s %s by %s (commit %s, built on %s) starting up at %s.",
		globals.Appname, globals.Version, globals.Author,
		shortCommit, globals.CommitDate,
		startTime.Format(time.RFC3339))
	w.Bannerf("%s", globals.Homepage)
	w.Bannerf("")
}

// NewApp creates a new fx application with common modules.
// It sets up the base modules (config, database, logging, globals) and
// combines them with any additional modules specified in the options.
// The returned fx.App is ready to be started with RunApp.
func NewApp(opts AppOptions) *fx.App {
	baseModules := []fx.Option{
		fx.Supply(config.Path(opts.ConfigPath)),
		fx.Supply(opts.LogOptions),
		fx.Provide(globals.New),
		fx.Provide(log.New),
		config.Module,
		database.Module,
		log.Module,
		storage.Module,
		snapshot.Module,
		fx.Provide(vaultik.New),
		fx.Invoke(setupGlobals),
		fx.NopLogger,
	}

	capacity := len(baseModules) + len(opts.Modules) + len(opts.Invokes)
	allOptions := make([]fx.Option, 0, capacity)
	allOptions = append(allOptions, baseModules...)
	allOptions = append(allOptions, opts.Modules...)
	allOptions = append(allOptions, opts.Invokes...)

	return fx.New(allOptions...)
}

// startupError carries a startup failure message that has been cleaned
// of fx dependency-injection noise. A distinct type (rather than
// errors.New) keeps the dynamic message out of err113's sight while
// preserving the exact user-facing text.
type startupError struct {
	msg string
}

func (e *startupError) Error() string {
	return e.msg
}

// cleanStartupError strips fx's dependency-injection call-chain noise from
// startup errors. fx wraps the underlying error with messages like
//
//	could not build arguments for function "X" (file:line): failed to build T:
//	could not build arguments for function "Y" (file:line): failed to build U:
//	received non-nil error from function "Z" (file:line): <real error>
//
// Users care about the real error, not the DI plumbing. We strip everything
// up through the last "): " (which is always the close-paren of an fx
// function-location annotation followed by the wrapped error).
func cleanStartupError(err error) error {
	msg := err.Error()
	if idx := strings.LastIndex(msg, "): "); idx >= 0 {
		msg = msg[idx+3:]
	}

	return &startupError{msg: msg}
}

// RunApp starts and stops the fx application within the given context.
// It handles graceful shutdown on interrupt signals (SIGINT, SIGTERM) and
// ensures the application stops cleanly. The function blocks until the
// application completes or is interrupted. Returns an error if startup fails.
func RunApp(ctx context.Context, app *fx.App) error {
	// Set up signal handling for graceful shutdown
	sigChan := make(chan os.Signal, 1)
	signal.Notify(sigChan, os.Interrupt, syscall.SIGTERM)

	// Create a context that will be cancelled on signal
	ctx, cancel := context.WithCancel(ctx)
	defer cancel()

	// Start the app
	err := app.Start(ctx)
	if err != nil {
		return cleanStartupError(err)
	}

	// Handle shutdown
	shutdownComplete := make(chan struct{})

	go func() {
		defer close(shutdownComplete)

		<-sigChan
		log.Notice("Received interrupt signal, shutting down gracefully...")

		// Create a timeout context for shutdown. The parent ctx is being
		// cancelled, so detach from its cancellation but keep its values.
		shutdownCtx, shutdownCancel := context.WithTimeout(
			context.WithoutCancel(ctx), shutdownTimeout)
		defer shutdownCancel()

		err := app.Stop(shutdownCtx)
		if err != nil {
			log.Error("Error during shutdown", "error", err)
		}
	}()

	// Wait for the signal handler to complete shutdown or the app to
	// request shutdown.
	select {
	case <-shutdownComplete:
		// Shutdown completed via signal
		return nil
	case <-ctx.Done():
		// Context cancelled (shouldn't happen in normal operation)
		err := app.Stop(context.WithoutCancel(ctx))
		if err != nil {
			log.Error("Error stopping app", "error", err)
		}

		return ctx.Err()
	case <-app.Done():
		// App finished running (e.g., backup completed)
		return nil
	}
}

// errReported marks a failure the operation has already shown the user
// (and deliberately withheld under --json). Entry turns it into a
// non-zero exit status without printing anything further, so the error
// line is not doubled. It flows up from RunOperation through cobra to
// Entry.
var errReported = errors.New("operation failed")

// RunOperation runs op against the Vaultik instance inside the fx app
// and turns a failure into a returned error rather than an os.Exit from
// within the goroutine. An os.Exit there skipped main's deferred
// profile writers -- so profiling a failing command yielded a truncated
// profile (issue #75) -- and RunWithApp's PID-lock release, and denied
// the app any graceful shutdown; returning the error to the top runs
// all three.
//
// op runs in a goroutine so OnStart returns promptly and an interrupt
// can still cancel through OnStop; when it finishes, success or failure,
// it triggers shutdown, which is what lets RunWithApp return. report is
// called with a non-canceled failure so the caller can log it (and
// suppress it under --json) before it becomes errReported. A context
// cancellation is the interrupt path, not a failure: it is neither
// reported nor counted as one.
func RunOperation(
	ctx context.Context, opts AppOptions,
	op func(v *vaultik.Vaultik) error, report func(err error),
) error {
	var (
		mu     sync.Mutex
		failed bool
	)

	opts.Invokes = append(opts.Invokes,
		fx.Invoke(func(v *vaultik.Vaultik, lc fx.Lifecycle) {
			lc.Append(fx.Hook{
				OnStart: func(_ context.Context) error {
					go func() {
						err := op(v)
						if err != nil && !errors.Is(err, context.Canceled) {
							report(err)

							mu.Lock()
							failed = true
							mu.Unlock()
						}

						stopErr := v.Shutdowner.Shutdown()
						if stopErr != nil {
							log.Error("Failed to shutdown", "error", stopErr)
						}
					}()

					return nil
				},
				OnStop: func(_ context.Context) error {
					v.Cancel()

					return nil
				},
			})
		}))

	err := RunWithApp(ctx, opts)
	if err != nil {
		return err
	}

	// The goroutine sets failed before triggering the shutdown that lets
	// RunWithApp return, so the write is in place by the time we read it.
	mu.Lock()
	defer mu.Unlock()

	if failed {
		return errReported
	}

	return nil
}

// runVaultikApp runs the standard single-operation command lifecycle
// shared by the snapshot list/purge/remove and remote nuke subcommands:
// resolve the config, then run op against the Vaultik instance through
// RunOperation, reporting a failure prefixed with failMsg (suppressed
// while suppressErrors is true, e.g. under --json). mode says whether the
// command takes the PID lock. jsonOutput marks a command whose stdout is a
// JSON document: it quiets the UI but, unlike Quiet, leaves the stderr log
// level alone.
func runVaultikApp(
	cmd *cobra.Command, mode lockMode, jsonOutput, suppressErrors bool,
	failMsg string, op func(v *vaultik.Vaultik) error,
) error {
	configPath, err := ResolveConfigPath()
	if err != nil {
		return err
	}

	rootFlags := GetRootFlags()

	return RunOperation(cmd.Context(), AppOptions{
		ConfigPath: configPath,
		LogOptions: log.Options{
			Verbose: rootFlags.Verbose,
			Debug:   rootFlags.Debug,
			Quiet:   rootFlags.Quiet,
			JSON:    jsonOutput,
		},
		Mode: mode,
	}, op, func(err error) {
		if suppressErrors {
			return
		}

		log.Error(failMsg, "error", err)
		ReportErrorf("%s: %v", failMsg, err)
	})
}

// RunWithApp is a helper that creates and runs an fx app with the given options.
// It combines NewApp and RunApp into a single convenient function. This is the
// preferred way to run CLI commands that need the full application context.
// A mutating command takes the process-wide PID lock before starting so that
// only one runs at a time; a read-only command runs without it and is not
// blocked while a mutator holds the lock (opts.Mode).
func RunWithApp(ctx context.Context, opts AppOptions) error {
	release, err := acquireLockIfMutating(opts.Mode,
		filepath.Join(xdg.DataHome, "vaultik"))
	if err != nil {
		return err
	}

	defer release()

	app := NewApp(opts)

	return RunApp(ctx, app)
}

// acquireLockIfMutating takes the process-wide PID lock in lockDir for a
// mutating command and returns a function that releases it. A read-only
// command takes no lock, so it returns a no-op release and is never blocked
// while a mutator holds the lock. ErrAlreadyRunning (another mutator holds
// the lock) is surfaced as a "cannot start" error.
func acquireLockIfMutating(mode lockMode, lockDir string) (func(), error) {
	if mode != mutating {
		return func() {}, nil
	}

	lock, err := pidlock.Acquire(lockDir)
	if err != nil {
		if errors.Is(err, pidlock.ErrAlreadyRunning) {
			return nil, fmt.Errorf("cannot start: %w", err)
		}

		return nil, fmt.Errorf("failed to acquire lock: %w", err)
	}

	return func() {
		err := lock.Release()
		if err != nil {
			log.Warn("Failed to release PID lock", "error", err)
		}
	}, nil
}