package cli

import (
	"context"
	"fmt"
	"strings"

	"git.eeqj.de/sneak/vaultik/internal/config"
	"git.eeqj.de/sneak/vaultik/internal/database"
	"git.eeqj.de/sneak/vaultik/internal/globals"
	"git.eeqj.de/sneak/vaultik/internal/log"
	"git.eeqj.de/sneak/vaultik/internal/s3"
	"git.eeqj.de/sneak/vaultik/internal/snapshot"
	"github.com/dustin/go-humanize"
	"github.com/spf13/cobra"
	"go.uber.org/fx"
)

// PruneOptions contains options for the prune command
type PruneOptions struct {
	DryRun bool
}

// PruneApp contains all dependencies needed for pruning
type PruneApp struct {
	Globals      *globals.Globals
	Config       *config.Config
	Repositories *database.Repositories
	S3Client     *s3.Client
	DB           *database.DB
	Shutdowner   fx.Shutdowner
}

// NewPruneCommand creates the prune command
func NewPruneCommand() *cobra.Command {
	opts := &PruneOptions{}

	cmd := &cobra.Command{
		Use:   "prune",
		Short: "Remove unreferenced blobs",
		Long: `Delete blobs that are no longer referenced by any snapshot.

This command will:
1. Download the manifest from the last successful snapshot
2. List all blobs in S3
3. Delete any blobs not referenced in the manifest

Config is located at /etc/vaultik/config.yml by default, but can be overridden by 
specifying a path using --config or by setting VAULTIK_CONFIG to a path.`,
		Args: cobra.NoArgs,
		RunE: func(cmd *cobra.Command, args []string) error {
			// Use unified config resolution
			configPath, err := ResolveConfigPath()
			if err != nil {
				return err
			}

			// Use the app framework like other commands
			rootFlags := GetRootFlags()
			return RunWithApp(cmd.Context(), AppOptions{
				ConfigPath: configPath,
				LogOptions: log.LogOptions{
					Verbose: rootFlags.Verbose,
					Debug:   rootFlags.Debug,
				},
				Modules: []fx.Option{
					snapshot.Module,
					s3.Module,
					fx.Provide(fx.Annotate(
						func(g *globals.Globals, cfg *config.Config, repos *database.Repositories,
							s3Client *s3.Client, db *database.DB, shutdowner fx.Shutdowner) *PruneApp {
							return &PruneApp{
								Globals:      g,
								Config:       cfg,
								Repositories: repos,
								S3Client:     s3Client,
								DB:           db,
								Shutdowner:   shutdowner,
							}
						},
					)),
				},
				Invokes: []fx.Option{
					fx.Invoke(func(app *PruneApp, lc fx.Lifecycle) {
						lc.Append(fx.Hook{
							OnStart: func(ctx context.Context) error {
								// Start the prune operation in a goroutine
								go func() {
									// Run the prune operation
									if err := app.runPrune(ctx, opts); err != nil {
										if err != context.Canceled {
											log.Error("Prune operation failed", "error", err)
										}
									}

									// Shutdown the app when prune completes
									if err := app.Shutdowner.Shutdown(); err != nil {
										log.Error("Failed to shutdown", "error", err)
									}
								}()
								return nil
							},
							OnStop: func(ctx context.Context) error {
								log.Debug("Stopping prune operation")
								return nil
							},
						})
					}),
				},
			})
		},
	}

	cmd.Flags().BoolVar(&opts.DryRun, "dry-run", false, "Show what would be deleted without actually deleting")

	return cmd
}

// runPrune executes the prune operation
func (app *PruneApp) runPrune(ctx context.Context, opts *PruneOptions) error {
	log.Info("Starting prune operation",
		"bucket", app.Config.S3.Bucket,
		"prefix", app.Config.S3.Prefix,
		"dry_run", opts.DryRun,
	)

	// Step 1: Get the latest complete snapshot from the database
	log.Info("Getting latest snapshot from database")
	snapshots, err := app.Repositories.Snapshots.ListRecent(ctx, 1)
	if err != nil {
		return fmt.Errorf("listing snapshots: %w", err)
	}

	if len(snapshots) == 0 {
		return fmt.Errorf("no snapshots found in database")
	}

	latestSnapshot := snapshots[0]
	if latestSnapshot.CompletedAt == nil {
		return fmt.Errorf("latest snapshot %s is incomplete", latestSnapshot.ID)
	}

	log.Info("Found latest snapshot",
		"id", latestSnapshot.ID,
		"completed_at", latestSnapshot.CompletedAt.Format("2006-01-02 15:04:05"))

	// Step 2: Find and download the manifest from the last successful snapshot in S3
	log.Info("Finding last successful snapshot in S3")
	metadataPrefix := "metadata/"

	// List all snapshots in S3
	var s3Snapshots []string
	objectCh := app.S3Client.ListObjectsStream(ctx, metadataPrefix, false)
	for obj := range objectCh {
		if obj.Err != nil {
			return fmt.Errorf("listing metadata objects: %w", obj.Err)
		}
		// Extract snapshot ID from path like "metadata/hostname-20240115-143052Z/manifest.json.zst"
		parts := strings.Split(obj.Key, "/")
		if len(parts) >= 2 && strings.HasSuffix(obj.Key, "/manifest.json.zst") {
			s3Snapshots = append(s3Snapshots, parts[1])
		}
	}

	if len(s3Snapshots) == 0 {
		return fmt.Errorf("no snapshot manifests found in S3")
	}

	// Find the most recent snapshot (they're named with timestamps)
	var lastS3Snapshot string
	for _, snap := range s3Snapshots {
		if lastS3Snapshot == "" || snap > lastS3Snapshot {
			lastS3Snapshot = snap
		}
	}

	log.Info("Found last S3 snapshot", "id", lastS3Snapshot)

	// Step 3: Verify the last S3 snapshot matches the latest DB snapshot
	if lastS3Snapshot != latestSnapshot.ID {
		return fmt.Errorf("latest snapshot in database (%s) does not match last successful snapshot in S3 (%s)",
			latestSnapshot.ID, lastS3Snapshot)
	}

	// Step 4: Download and parse the manifest
	log.Info("Downloading manifest", "snapshot_id", lastS3Snapshot)
	manifest, err := app.downloadManifest(ctx, lastS3Snapshot)
	if err != nil {
		return fmt.Errorf("downloading manifest: %w", err)
	}

	log.Info("Manifest loaded", "blob_count", len(manifest.Blobs))

	// Step 5: Build set of referenced blobs
	referencedBlobs := make(map[string]bool)
	for _, blob := range manifest.Blobs {
		referencedBlobs[blob.Hash] = true
	}

	// Step 6: List all blobs in S3
	log.Info("Listing all blobs in S3")
	blobPrefix := "blobs/"
	var totalBlobs int
	var unreferencedBlobs []s3.ObjectInfo
	var unreferencedSize int64

	objectCh = app.S3Client.ListObjectsStream(ctx, blobPrefix, true)
	for obj := range objectCh {
		if obj.Err != nil {
			return fmt.Errorf("listing blobs: %w", obj.Err)
		}

		totalBlobs++

		// Extract blob hash from path like "blobs/ca/fe/cafebabe..."
		parts := strings.Split(obj.Key, "/")
		if len(parts) == 4 {
			blobHash := parts[3]
			if !referencedBlobs[blobHash] {
				unreferencedBlobs = append(unreferencedBlobs, obj)
				unreferencedSize += obj.Size
			}
		}
	}

	log.Info("Blob scan complete",
		"total_blobs", totalBlobs,
		"referenced_blobs", len(referencedBlobs),
		"unreferenced_blobs", len(unreferencedBlobs),
		"unreferenced_size", humanize.Bytes(uint64(unreferencedSize)))

	// Step 7: Delete or report unreferenced blobs
	if opts.DryRun {
		fmt.Printf("\nDry run mode - would delete %d unreferenced blobs\n", len(unreferencedBlobs))
		fmt.Printf("Total size of blobs to delete: %s\n", humanize.Bytes(uint64(unreferencedSize)))

		if len(unreferencedBlobs) > 0 {
			log.Debug("Unreferenced blobs found", "count", len(unreferencedBlobs))
			for _, obj := range unreferencedBlobs {
				log.Debug("Would delete blob", "key", obj.Key, "size", humanize.Bytes(uint64(obj.Size)))
			}
		}
	} else {
		if len(unreferencedBlobs) == 0 {
			fmt.Println("No unreferenced blobs to delete")
			return nil
		}

		fmt.Printf("\nDeleting %d unreferenced blobs (%s)...\n",
			len(unreferencedBlobs), humanize.Bytes(uint64(unreferencedSize)))

		deletedCount := 0
		deletedSize := int64(0)

		for _, obj := range unreferencedBlobs {
			if err := app.S3Client.RemoveObject(ctx, obj.Key); err != nil {
				log.Error("Failed to delete blob", "key", obj.Key, "error", err)
				continue
			}
			deletedCount++
			deletedSize += obj.Size

			// Show progress every 100 blobs
			if deletedCount%100 == 0 {
				fmt.Printf("  Deleted %d/%d blobs (%s)...\n",
					deletedCount, len(unreferencedBlobs),
					humanize.Bytes(uint64(deletedSize)))
			}
		}

		fmt.Printf("\nDeleted %d blobs (%s)\n", deletedCount, humanize.Bytes(uint64(deletedSize)))
	}

	log.Info("Prune operation completed successfully")
	return nil
}

// downloadManifest downloads and decompresses a snapshot manifest
func (app *PruneApp) downloadManifest(ctx context.Context, snapshotID string) (*snapshot.Manifest, error) {
	manifestPath := fmt.Sprintf("metadata/%s/manifest.json.zst", snapshotID)

	// Download the compressed manifest
	reader, err := app.S3Client.GetObject(ctx, manifestPath)
	if err != nil {
		return nil, fmt.Errorf("downloading manifest: %w", err)
	}
	defer func() { _ = reader.Close() }()

	// Decode manifest
	manifest, err := snapshot.DecodeManifest(reader)
	if err != nil {
		return nil, fmt.Errorf("decoding manifest: %w", err)
	}

	return manifest, nil
}