package main

import (
	"context"
	"errors"
	"fmt"
	"log"
	"os"
	"path/filepath"
	"sort"
	"strings"
	"time"

	"github.com/nats-io/nats.go"
	"github.com/nats-io/nats.go/jetstream"
	"github.com/spf13/cobra"
	"github.com/spf13/pflag"
	"github.com/spf13/viper"
	"golang.org/x/mod/semver"
)

type Config struct {
	NatsURL     string `mapstructure:"nats"`
	BucketName  string `mapstructure:"bucket"`
	Directory   string `mapstructure:"dir"`
	Prefix      string `mapstructure:"prefix"`
	BinaryName  string `mapstructure:"binary"`
	NotifyTopic string `mapstructure:"notify"`
	SkipNotify  bool   `mapstructure:"skip-notify"`
	Cleanup     int    `mapstructure:"cleanup"`
	CleanupAll  bool   `mapstructure:"cleanup-all"`
}

var rootCmd = &cobra.Command{
	Use:   "nats-upload",
	Short: "Upload binaries to NATS object store and cleanup old versions",
	RunE: func(cmd *cobra.Command, args []string) error {
		var cfg Config
		if err := viper.Unmarshal(&cfg); err != nil {
			return fmt.Errorf("failed to unmarshal config: %w", err)
		}
		if cfg.Directory == "" && cfg.Cleanup == 0 {
			return errors.New("directory path is required or cleanup must be enabled")
		}
		return runUploadAndCleanup(cmd.Context(), &cfg)
	},
}

var cleanCmd = &cobra.Command{
	Use:   "clean",
	Short: "Cleanup old versions in NATS object store",
	RunE: func(cmd *cobra.Command, args []string) error {
		var cfg Config
		if err := viper.Unmarshal(&cfg); err != nil {
			return fmt.Errorf("failed to unmarshal config: %w", err)
		}
		if cfg.Cleanup == 0 {
			return errors.New("cleanup count must be greater than 0")
		}
		return runCleanupOnly(cmd.Context(), &cfg)
	},
}

func init() {
	cobra.OnInitialize(initConfig)

	rootCmd.PersistentFlags().String("nats", "nats://localhost:4222", "NATS server URL")
	rootCmd.PersistentFlags().String("bucket", "binaries", "Object store bucket name")
	rootCmd.PersistentFlags().String("binary", "", "Binary name (defaults to first binary found)")
	rootCmd.PersistentFlags().Int("cleanup", 2, "Keep only N most recent versions (0 disables cleanup)")
	rootCmd.PersistentFlags().Bool("cleanup-all", false, "Cleanup all binaries, not just current one")
	rootCmd.PersistentFlags().Bool("clean-all", false, "Alias for --cleanup-all")

	rootCmd.Flags().String("dir", "upload", "Directory containing binaries to upload")
	rootCmd.Flags().String("prefix", "", "Prefix to strip from paths (like 'upload/')")
	rootCmd.Flags().String("notify", "binaries.update", "NATS topic to publish update notification")
	rootCmd.Flags().Bool("skip-notify", false, "Skip publishing update notification")
}

func bindPFlag(fs *pflag.FlagSet, key string, flagNames ...string) {
	name := key
	if len(flagNames) > 0 {
		name = flagNames[0]
	}
	if err := viper.BindPFlag(key, fs.Lookup(name)); err != nil {
		log.Fatalf("error binding %s flag: %v", key, err)
	}
}

func init() {
	rootPersistentFlags := rootCmd.PersistentFlags()
	for _, name := range []string{"nats", "bucket", "binary", "cleanup", "cleanup-all"} {
		bindPFlag(rootPersistentFlags, name)
	}

	rootFlags := rootCmd.Flags()
	for _, name := range []string{"dir", "prefix", "notify", "skip-notify"} {
		bindPFlag(rootFlags, name)
	}

	rootCmd.AddCommand(cleanCmd)
}

func initConfig() {
	viper.SetEnvPrefix("INPUT")
	viper.AutomaticEnv()

	viper.RegisterAlias("nats_url", "nats")
	viper.RegisterAlias("source", "dir")
	viper.RegisterAlias("strip_prefix", "prefix")
	viper.RegisterAlias("notify_topic", "notify")
	viper.RegisterAlias("clean_all", "cleanup-all")
}

type NATSClient struct {
	Conn  *nats.Conn
	JS    jetstream.JetStream
	Store jetstream.ObjectStore
}

func getNATSConnection(ctx context.Context, cfg *Config) (*NATSClient, error) {
	nc, err := nats.Connect(cfg.NatsURL)
	if err != nil {
		return nil, fmt.Errorf("failed to connect to NATS: %w", err)
	}

	js, err := jetstream.New(nc)
	if err != nil {
		nc.Close()
		return nil, fmt.Errorf("failed to create JetStream context: %w", err)
	}

	store, err := js.ObjectStore(ctx, cfg.BucketName)
	if err != nil {
		store, err = js.CreateObjectStore(ctx, jetstream.ObjectStoreConfig{
			Bucket:      cfg.BucketName,
			Description: "Binary storage for self-update",
		})
		if err != nil {
			nc.Close()
			return nil, fmt.Errorf("failed to get/create object store: %w", err)
		}
		log.Printf("Created object store: %s", cfg.BucketName)
	}

	return &NATSClient{
		Conn:  nc,
		JS:    js,
		Store: store,
	}, nil
}

func runUploadAndCleanup(ctx context.Context, cfg *Config) error {
	client, err := getNATSConnection(ctx, cfg)
	if err != nil {
		return err
	}
	defer client.Conn.Close()

	if cfg.Directory != "" {
		err := filepath.Walk(cfg.Directory, func(path string, info os.FileInfo, err error) error {
			if err != nil {
				return err
			}

			if info.IsDir() {
				return nil
			}

			data, err := os.ReadFile(path)
			if err != nil {
				return fmt.Errorf("failed to read %s: %w", path, err)
			}

			relPath, err := filepath.Rel(cfg.Directory, path)
			if err != nil {
				return fmt.Errorf("failed to get relative path: %w", err)
			}

			objectKey := relPath
			if cfg.Prefix != "" {
				objectKey = strings.TrimPrefix(relPath, cfg.Prefix)
			}

			objectKey = filepath.ToSlash(objectKey)

			if cfg.BinaryName == "" {
				parts := strings.Split(objectKey, "/")
				if len(parts) >= 2 {
					cfg.BinaryName = parts[0]
				}
			}

			log.Printf("Uploading %s as %s (%d bytes)", path, objectKey, len(data))

			_, err = client.Store.PutBytes(ctx, objectKey, data)
			if err != nil {
				return fmt.Errorf("failed to upload %s: %w", path, err)
			}

			log.Printf("✓ Uploaded %s", objectKey)
			return nil
		})

		if err != nil {
			return fmt.Errorf("failed to upload files: %w", err)
		}

		log.Printf("Successfully uploaded all files from %s to NATS object store '%s'", cfg.Directory, cfg.BucketName)
	}

	if cfg.Cleanup > 0 {
		log.Printf("Cleaning up old versions, keeping %d most recent", cfg.Cleanup)
		err := cleanupOldVersions(ctx, client.Store, cfg.BinaryName, cfg.Cleanup, cfg.CleanupAll)
		if err != nil {
			return fmt.Errorf("failed to cleanup old versions: %w", err)
		}
	}

	if !cfg.SkipNotify && cfg.NotifyTopic != "" {
		log.Printf("Publishing update notification to topic: %s", cfg.NotifyTopic)

		message := fmt.Sprintf("binaries updated in %s", cfg.BucketName)
		err := client.Conn.Publish(cfg.NotifyTopic, []byte(message))
		if err != nil {
			return fmt.Errorf("failed to publish notification: %w", err)
		}

		// Flush to ensure message is sent
		err = client.Conn.Flush()
		if err != nil {
			return fmt.Errorf("failed to flush notification: %w", err)
		}

		log.Printf("✓ Published update notification")
	}
	return nil
}

func runCleanupOnly(ctx context.Context, cfg *Config) error {
	client, err := getNATSConnection(ctx, cfg)
	if err != nil {
		return err
	}
	defer client.Conn.Close()

	log.Printf("Cleaning up old versions, keeping %d most recent", cfg.Cleanup)
	err = cleanupOldVersions(ctx, client.Store, cfg.BinaryName, cfg.Cleanup, cfg.CleanupAll)
	if err != nil {
		return fmt.Errorf("failed to cleanup old versions: %w", err)
	}
	return nil
}

func cleanupOldVersions(ctx context.Context, store jetstream.ObjectStore, currentBinary string, keepCount int, cleanAll bool) error {
	objects, err := store.List(ctx)
	if err != nil {
		return fmt.Errorf("failed to list objects: %w", err)
	}

	// Group objects by binary/architecture path
	// Expected structure: binary/arch/version
	versionsByPath := make(map[string][]*jetstream.ObjectInfo)

	for _, obj := range objects {
		parts := strings.Split(obj.Name, "/")
		if len(parts) < 3 {
			// Not a version path, skip
			continue
		}

		binName := parts[0]
		arch := parts[1]
		pathKey := binName + "/" + arch

		// If not cleaning all and this isn't the current binary, skip
		if !cleanAll && currentBinary != "" && binName != currentBinary {
			continue
		}

		versionsByPath[pathKey] = append(versionsByPath[pathKey], obj)
	}

	// For each binary/arch combination, keep only the most recent N versions
	for pathKey, versions := range versionsByPath {
		if len(versions) <= keepCount {
			log.Printf("Path %s has %d versions, keeping all", pathKey, len(versions))
			continue
		}

		// Sort by semantic version (newest first)
		sort.Slice(versions, func(i, j int) bool {
			// Extract version from path: binary/arch/version
			versionI := filepath.Base(versions[i].Name)
			versionJ := filepath.Base(versions[j].Name)

			// Ensure versions start with 'v' for semver.Compare
			if !strings.HasPrefix(versionI, "v") {
				versionI = "v" + versionI
			}
			if !strings.HasPrefix(versionJ, "v") {
				versionJ = "v" + versionJ
			}

			// semver.Compare returns -1, 0, or 1
			// We want newest first, so reverse the comparison
			return semver.Compare(versionI, versionJ) > 0
		})

		// Delete old versions (everything after keepCount)
		toDelete := versions[keepCount:]
		log.Printf("Path %s has %d versions, deleting %d old versions", pathKey, len(versions), len(toDelete))

		for _, obj := range toDelete {
			version := filepath.Base(obj.Name)
			log.Printf("Deleting old version: %s (version: %s)", obj.Name, version)
			err := store.Delete(ctx, obj.Name)
			if err != nil && !errors.Is(err, jetstream.ErrObjectNotFound) {
				return fmt.Errorf("failed to delete %s: %w", obj.Name, err)
			}
			log.Printf("✓ Deleted %s", obj.Name)
		}
	}

	return nil
}

func main() {
	ctx, cancel := context.WithTimeout(context.Background(), 15*time.Minute)
	defer cancel()

	if err := rootCmd.ExecuteContext(ctx); err != nil {
		_, _ = fmt.Fprintln(os.Stderr, err)
		os.Exit(1)
	}
}