package vaultik

import (
	"encoding/json"
	"fmt"
	"strings"

	"github.com/dustin/go-humanize"
	"sneak.berlin/go/vaultik/internal/log"
)

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

// PruneBlobsResult contains the result of a blob prune operation
type PruneBlobsResult struct {
	BlobsFound   int   `json:"blobs_found"`
	BlobsDeleted int   `json:"blobs_deleted"`
	BlobsFailed  int   `json:"blobs_failed,omitempty"`
	BytesFreed   int64 `json:"bytes_freed"`
}

// PruneBlobs removes unreferenced blobs from storage
func (v *Vaultik) PruneBlobs(opts *PruneOptions) error {
	log.Info("Starting prune operation")

	allBlobsReferenced, err := v.collectReferencedBlobs()
	if err != nil {
		return err
	}

	allBlobs, err := v.listAllRemoteBlobs()
	if err != nil {
		return err
	}

	unreferencedBlobs, totalSize := v.findUnreferencedBlobs(allBlobs, allBlobsReferenced)

	result := &PruneBlobsResult{BlobsFound: len(unreferencedBlobs)}

	if len(unreferencedBlobs) == 0 {
		log.Info("No unreferenced blobs found")
		if opts.JSON {
			return v.outputPruneBlobsJSON(result)
		}
		v.printlnStdout("No unreferenced blobs to remove.")
		return nil
	}

	log.Info("Found unreferenced blobs", "count", len(unreferencedBlobs), "total_size", humanize.Bytes(uint64(totalSize)))
	if !opts.JSON {
		v.printfStdout("Found %d unreferenced blob(s) totaling %s\n", len(unreferencedBlobs), humanize.Bytes(uint64(totalSize)))
	}

	if !opts.Force && !opts.JSON {
		v.printfStdout("\nDelete %d unreferenced blob(s)? [y/N] ", len(unreferencedBlobs))
		var confirm string
		if _, err := v.scanStdin(&confirm); err != nil {
			v.printlnStdout("Cancelled")
			return nil
		}
		if strings.ToLower(confirm) != "y" {
			v.printlnStdout("Cancelled")
			return nil
		}
	}

	v.deleteUnreferencedBlobs(unreferencedBlobs, allBlobs, result)

	if opts.JSON {
		return v.outputPruneBlobsJSON(result)
	}

	v.printfStdout("\nDeleted %d blob(s) totaling %s\n", result.BlobsDeleted, humanize.Bytes(uint64(result.BytesFreed)))
	if result.BlobsFailed > 0 {
		v.printfStdout("Failed to delete %d blob(s)\n", result.BlobsFailed)
	}

	return nil
}

// collectReferencedBlobs downloads all manifests and returns the set of referenced blob hashes
func (v *Vaultik) collectReferencedBlobs() (map[string]bool, error) {
	log.Info("Listing remote snapshots")
	snapshotIDs, err := v.listUniqueSnapshotIDs()
	if err != nil {
		return nil, fmt.Errorf("listing snapshot IDs: %w", err)
	}
	log.Info("Found manifests in remote storage", "count", len(snapshotIDs))

	allBlobsReferenced := make(map[string]bool)
	manifestCount := 0

	for _, snapshotID := range snapshotIDs {
		log.Debug("Processing manifest", "snapshot_id", snapshotID)
		manifest, err := v.downloadManifest(snapshotID)
		if err != nil {
			log.Error("Failed to download manifest", "snapshot_id", snapshotID, "error", err)
			continue
		}
		for _, blob := range manifest.Blobs {
			allBlobsReferenced[blob.Hash] = true
		}
		manifestCount++
	}

	log.Info("Processed manifests", "count", manifestCount, "unique_blobs_referenced", len(allBlobsReferenced))
	return allBlobsReferenced, nil
}

// listUniqueSnapshotIDs returns deduplicated snapshot IDs from remote metadata
func (v *Vaultik) listUniqueSnapshotIDs() ([]string, error) {
	objectCh := v.Storage.ListStream(v.ctx, "metadata/")
	seen := make(map[string]bool)
	var snapshotIDs []string

	for object := range objectCh {
		if object.Err != nil {
			return nil, fmt.Errorf("listing metadata objects: %w", object.Err)
		}
		parts := strings.Split(object.Key, "/")
		if len(parts) >= 2 && parts[0] == "metadata" && parts[1] != "" {
			if strings.HasSuffix(object.Key, "/") || strings.Contains(object.Key, "/manifest.json.zst") {
				snapshotID := parts[1]
				if !seen[snapshotID] {
					seen[snapshotID] = true
					snapshotIDs = append(snapshotIDs, snapshotID)
				}
			}
		}
	}
	return snapshotIDs, nil
}

// listAllRemoteBlobs returns a map of all blob hashes to their sizes in remote storage
func (v *Vaultik) listAllRemoteBlobs() (map[string]int64, error) {
	log.Info("Listing all blobs in storage")
	allBlobs := make(map[string]int64)
	blobObjectCh := v.Storage.ListStream(v.ctx, "blobs/")

	for object := range blobObjectCh {
		if object.Err != nil {
			return nil, fmt.Errorf("listing blobs: %w", object.Err)
		}
		parts := strings.Split(object.Key, "/")
		if len(parts) == 4 && parts[0] == "blobs" {
			allBlobs[parts[3]] = object.Size
		}
	}

	log.Info("Found blobs in storage", "count", len(allBlobs))
	return allBlobs, nil
}

// findUnreferencedBlobs returns blob hashes not referenced by any manifest and their total size
func (v *Vaultik) findUnreferencedBlobs(allBlobs map[string]int64, referenced map[string]bool) ([]string, int64) {
	var unreferenced []string
	var totalSize int64
	for hash, size := range allBlobs {
		if !referenced[hash] {
			unreferenced = append(unreferenced, hash)
			totalSize += size
		}
	}
	return unreferenced, totalSize
}

// deleteUnreferencedBlobs deletes the given blobs from storage and populates the result
func (v *Vaultik) deleteUnreferencedBlobs(unreferencedBlobs []string, allBlobs map[string]int64, result *PruneBlobsResult) {
	log.Info("Deleting unreferenced blobs")

	for i, hash := range unreferencedBlobs {
		blobPath := fmt.Sprintf("blobs/%s/%s/%s", hash[:2], hash[2:4], hash)

		if err := v.Storage.Delete(v.ctx, blobPath); err != nil {
			log.Error("Failed to delete blob", "hash", hash, "error", err)
			continue
		}

		result.BlobsDeleted++
		result.BytesFreed += allBlobs[hash]

		if (i+1)%100 == 0 || i == len(unreferencedBlobs)-1 {
			log.Info("Deletion progress",
				"deleted", i+1,
				"total", len(unreferencedBlobs),
				"percent", fmt.Sprintf("%.1f%%", float64(i+1)/float64(len(unreferencedBlobs))*100),
			)
		}
	}

	result.BlobsFailed = len(unreferencedBlobs) - result.BlobsDeleted

	log.Info("Prune complete",
		"deleted_count", result.BlobsDeleted,
		"deleted_size", humanize.Bytes(uint64(result.BytesFreed)),
		"failed", result.BlobsFailed,
	)
}

// outputPruneBlobsJSON outputs the prune result as JSON
func (v *Vaultik) outputPruneBlobsJSON(result *PruneBlobsResult) error {
	encoder := json.NewEncoder(v.Stdout)
	encoder.SetIndent("", "  ")
	return encoder.Encode(result)
}