package s3_objectlock

import (
	"context"
	"errors"
	"fmt"
	"io"
	"strconv"
	"strings"
	"time"

	"github.com/seaweedfs/seaweedfs/weed/glog"
	"github.com/seaweedfs/seaweedfs/weed/pb/filer_pb"
	"github.com/seaweedfs/seaweedfs/weed/s3api/s3_constants"
)

// ====================================================================
// SHARED OBJECT LOCK CHECKING FUNCTIONS
// ====================================================================
// These functions are used by S3 API, Admin UI, and shell commands for
// checking Object Lock status before bucket deletion.

// EntryHasActiveLock checks if an entry has an active retention or legal hold
// This is a standalone function that can be used by any component
func EntryHasActiveLock(entry *filer_pb.Entry, currentTime time.Time) bool {
	if entry == nil || entry.Extended == nil {
		return false
	}

	// Check for active legal hold (case-insensitive, trimmed for defensive parsing)
	if legalHoldBytes, exists := entry.Extended[s3_constants.ExtLegalHoldKey]; exists {
		legalHold := strings.TrimSpace(strings.ToUpper(string(legalHoldBytes)))
		if legalHold == s3_constants.LegalHoldOn {
			return true
		}
	}

	// Check for active retention (case-insensitive, trimmed for defensive parsing)
	if modeBytes, exists := entry.Extended[s3_constants.ExtObjectLockModeKey]; exists {
		mode := strings.TrimSpace(strings.ToUpper(string(modeBytes)))
		if mode == s3_constants.RetentionModeCompliance || mode == s3_constants.RetentionModeGovernance {
			// Check if retention is still active
			if dateBytes, dateExists := entry.Extended[s3_constants.ExtRetentionUntilDateKey]; dateExists {
				dateStr := strings.TrimSpace(string(dateBytes))
				timestamp, err := strconv.ParseInt(dateStr, 10, 64)
				if err != nil {
					// Fail-safe: if we can't parse the retention date, assume the object is locked
					// to prevent accidental data loss
					glog.Warningf("Failed to parse retention date '%s' for entry, assuming locked: %v", dateStr, err)
					return true
				}
				retainUntil := time.Unix(timestamp, 0)
				if retainUntil.After(currentTime) {
					return true
				}
			}
		}
	}

	return false
}

// HasObjectsWithActiveLocks checks if any objects in the bucket have active retention or legal hold
// This function uses the filer gRPC client to scan the bucket directory
func HasObjectsWithActiveLocks(ctx context.Context, client filer_pb.SeaweedFilerClient, bucketPath string) (bool, error) {
	hasLocks := false
	currentTime := time.Now()

	err := recursivelyCheckLocksWithClient(ctx, client, bucketPath, &hasLocks, currentTime)
	if err != nil {
		return false, fmt.Errorf("error checking for locked objects: %w", err)
	}

	return hasLocks, nil
}

// paginateEntries is a generic helper that handles pagination logic for listing directory entries.
// The processEntry callback is called for each entry; returning stop=true stops iteration early.
func paginateEntries(ctx context.Context, client filer_pb.SeaweedFilerClient, dir string,
	processEntry func(entry *filer_pb.Entry) (stop bool, err error)) error {
	lastFileName := ""
	for {
		resp, err := client.ListEntries(ctx, &filer_pb.ListEntriesRequest{
			Directory:          dir,
			StartFromFileName:  lastFileName,
			InclusiveStartFrom: false,
			Limit:              10000,
		})
		if err != nil {
			return fmt.Errorf("failed to list directory %s: %w", dir, err)
		}

		entriesReceived := false
		for {
			entryResp, recvErr := resp.Recv()
			if recvErr != nil {
				if errors.Is(recvErr, io.EOF) {
					break // Normal end of stream
				}
				return fmt.Errorf("failed to receive entry from %s: %w", dir, recvErr)
			}
			entry := entryResp.Entry
			if entry == nil {
				continue
			}
			entriesReceived = true
			lastFileName = entry.Name

			// Skip invalid entry names to prevent path traversal
			if entry.Name == "" || entry.Name == "." || entry.Name == ".." ||
				strings.ContainsAny(entry.Name, "/\\") {
				glog.V(2).Infof("Skipping invalid entry name: %q in %s", entry.Name, dir)
				continue
			}

			stop, err := processEntry(entry)
			if err != nil {
				return err
			}
			if stop {
				return nil
			}
		}

		if !entriesReceived {
			break
		}
	}
	return nil
}

// recursivelyCheckLocksWithClient recursively checks all objects and versions for active locks
func recursivelyCheckLocksWithClient(ctx context.Context, client filer_pb.SeaweedFilerClient, dir string, hasLocks *bool, currentTime time.Time) error {
	if *hasLocks {
		return nil // Early exit if already found a locked object
	}

	return paginateEntries(ctx, client, dir, func(entry *filer_pb.Entry) (bool, error) {
		if *hasLocks {
			return true, nil // Stop iteration
		}

		// Skip special directories
		if entry.Name == s3_constants.MultipartUploadsFolder {
			return false, nil // Continue
		}

		if entry.IsDirectory {
			subDir := dir + "/" + entry.Name
			if entry.Name == s3_constants.VersionsFolder {
				// Check all version files (exact match for .versions folder)
				if err := checkVersionsForLocksWithClient(ctx, client, subDir, hasLocks, currentTime); err != nil {
					return false, err
				}
			} else {
				// A directory-marker object (key ending in "/") is stored as a
				// directory entry and can carry a lock, so check it before recursing.
				if EntryHasActiveLock(entry, currentTime) {
					*hasLocks = true
					glog.V(2).Infof("Found directory marker with active lock: %s/%s", dir, entry.Name)
					return true, nil
				}
				// Recursively check subdirectories
				if err := recursivelyCheckLocksWithClient(ctx, client, subDir, hasLocks, currentTime); err != nil {
					return false, err
				}
			}
		} else {
			// Check if this object has an active lock
			if EntryHasActiveLock(entry, currentTime) {
				*hasLocks = true
				glog.V(2).Infof("Found object with active lock: %s/%s", dir, entry.Name)
				return true, nil // Stop iteration
			}
		}
		return false, nil // Continue
	})
}

// checkVersionsForLocksWithClient checks all versions in a .versions directory for active locks
func checkVersionsForLocksWithClient(ctx context.Context, client filer_pb.SeaweedFilerClient, versionsDir string, hasLocks *bool, currentTime time.Time) error {
	return paginateEntries(ctx, client, versionsDir, func(entry *filer_pb.Entry) (bool, error) {
		if *hasLocks {
			return true, nil // Stop iteration
		}

		if EntryHasActiveLock(entry, currentTime) {
			*hasLocks = true
			glog.V(2).Infof("Found version with active lock: %s/%s", versionsDir, entry.Name)
			return true, nil // Stop iteration
		}
		return false, nil // Continue
	})
}

// IsObjectLockEnabled checks if Object Lock is enabled on a bucket entry
func IsObjectLockEnabled(entry *filer_pb.Entry) bool {
	if entry == nil || entry.Extended == nil {
		return false
	}

	enabledBytes, exists := entry.Extended[s3_constants.ExtObjectLockEnabledKey]
	if !exists {
		return false
	}

	enabled := string(enabledBytes)
	return enabled == s3_constants.ObjectLockEnabled || enabled == "true"
}

// CheckBucketForLockedObjects is a unified function that checks if a bucket has Object Lock enabled
// and if so, scans for objects with active locks. This combines the bucket lookup and lock check
// into a single operation used by S3 API, Admin UI, and shell commands.
// Returns an error if the bucket has locked objects or if the check fails.
func CheckBucketForLockedObjects(ctx context.Context, client filer_pb.SeaweedFilerClient, bucketsPath, bucketName string) error {
	// Look up the bucket entry
	lookupResp, err := client.LookupDirectoryEntry(ctx, &filer_pb.LookupDirectoryEntryRequest{
		Directory: bucketsPath,
		Name:      bucketName,
	})
	if err != nil {
		return fmt.Errorf("bucket not found: %w", err)
	}

	// Check if Object Lock is enabled
	if !IsObjectLockEnabled(lookupResp.Entry) {
		return nil // No Object Lock, nothing to check
	}

	// Check for objects with active locks
	bucketPath := bucketsPath + "/" + bucketName
	hasLockedObjects, checkErr := HasObjectsWithActiveLocks(ctx, client, bucketPath)
	if checkErr != nil {
		return fmt.Errorf("failed to check for locked objects: %w", checkErr)
	}
	if hasLockedObjects {
		return fmt.Errorf("bucket has objects with active Object Lock retention or legal hold")
	}

	return nil
}
