/*
   Copyright The containerd Authors.

   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at

       http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.
*/

package metadata

import (
	"context"
	"time"

	"github.com/boltdb/bolt"
	"github.com/containerd/containerd/errdefs"
	"github.com/containerd/containerd/leases"
	"github.com/containerd/containerd/metadata/boltutil"
	"github.com/containerd/containerd/namespaces"
	digest "github.com/opencontainers/go-digest"
	"github.com/pkg/errors"
)

// Lease retains resources to prevent garbage collection before
// the resources can be fully referenced.
type Lease struct {
	ID        string
	CreatedAt time.Time
	Labels    map[string]string

	Content   []string
	Snapshots map[string][]string
}

// LeaseManager manages the create/delete lifecyle of leases
// and also returns existing leases
type LeaseManager struct {
	tx *bolt.Tx
}

// NewLeaseManager creates a new lease manager for managing leases using
// the provided database transaction.
func NewLeaseManager(tx *bolt.Tx) *LeaseManager {
	return &LeaseManager{
		tx: tx,
	}
}

// Create creates a new lease using the provided lease
func (lm *LeaseManager) Create(ctx context.Context, lid string, labels map[string]string) (Lease, error) {
	namespace, err := namespaces.NamespaceRequired(ctx)
	if err != nil {
		return Lease{}, err
	}

	topbkt, err := createBucketIfNotExists(lm.tx, bucketKeyVersion, []byte(namespace), bucketKeyObjectLeases)
	if err != nil {
		return Lease{}, err
	}

	txbkt, err := topbkt.CreateBucket([]byte(lid))
	if err != nil {
		if err == bolt.ErrBucketExists {
			err = errdefs.ErrAlreadyExists
		}
		return Lease{}, errors.Wrapf(err, "lease %q", lid)
	}

	t := time.Now().UTC()
	createdAt, err := t.MarshalBinary()
	if err != nil {
		return Lease{}, err
	}
	if err := txbkt.Put(bucketKeyCreatedAt, createdAt); err != nil {
		return Lease{}, err
	}

	if labels != nil {
		if err := boltutil.WriteLabels(txbkt, labels); err != nil {
			return Lease{}, err
		}
	}

	return Lease{
		ID:        lid,
		CreatedAt: t,
		Labels:    labels,
	}, nil
}

// Delete delets the lease with the provided lease ID
func (lm *LeaseManager) Delete(ctx context.Context, lid string) error {
	namespace, err := namespaces.NamespaceRequired(ctx)
	if err != nil {
		return err
	}

	topbkt := getBucket(lm.tx, bucketKeyVersion, []byte(namespace), bucketKeyObjectLeases)
	if topbkt == nil {
		return nil
	}
	if err := topbkt.DeleteBucket([]byte(lid)); err != nil && err != bolt.ErrBucketNotFound {
		return err
	}
	return nil
}

// List lists all active leases
func (lm *LeaseManager) List(ctx context.Context, includeResources bool, filter ...string) ([]Lease, error) {
	namespace, err := namespaces.NamespaceRequired(ctx)
	if err != nil {
		return nil, err
	}

	var leases []Lease

	topbkt := getBucket(lm.tx, bucketKeyVersion, []byte(namespace), bucketKeyObjectLeases)
	if topbkt == nil {
		return leases, nil
	}

	if err := topbkt.ForEach(func(k, v []byte) error {
		if v != nil {
			return nil
		}
		txbkt := topbkt.Bucket(k)

		l := Lease{
			ID: string(k),
		}

		if v := txbkt.Get(bucketKeyCreatedAt); v != nil {
			t := &l.CreatedAt
			if err := t.UnmarshalBinary(v); err != nil {
				return err
			}
		}

		labels, err := boltutil.ReadLabels(txbkt)
		if err != nil {
			return err
		}
		l.Labels = labels

		// TODO: Read Snapshots
		// TODO: Read Content

		leases = append(leases, l)

		return nil
	}); err != nil {
		return nil, err
	}

	return leases, nil
}

func addSnapshotLease(ctx context.Context, tx *bolt.Tx, snapshotter, key string) error {
	lid, ok := leases.Lease(ctx)
	if !ok {
		return nil
	}

	namespace, ok := namespaces.Namespace(ctx)
	if !ok {
		panic("namespace must already be checked")
	}

	bkt := getBucket(tx, bucketKeyVersion, []byte(namespace), bucketKeyObjectLeases, []byte(lid))
	if bkt == nil {
		return errors.Wrap(errdefs.ErrNotFound, "lease does not exist")
	}

	bkt, err := bkt.CreateBucketIfNotExists(bucketKeyObjectSnapshots)
	if err != nil {
		return err
	}

	bkt, err = bkt.CreateBucketIfNotExists([]byte(snapshotter))
	if err != nil {
		return err
	}

	return bkt.Put([]byte(key), nil)
}

func removeSnapshotLease(ctx context.Context, tx *bolt.Tx, snapshotter, key string) error {
	lid, ok := leases.Lease(ctx)
	if !ok {
		return nil
	}

	namespace, ok := namespaces.Namespace(ctx)
	if !ok {
		panic("namespace must already be checked")
	}

	bkt := getBucket(tx, bucketKeyVersion, []byte(namespace), bucketKeyObjectLeases, []byte(lid), bucketKeyObjectSnapshots, []byte(snapshotter))
	if bkt == nil {
		// Key does not exist so we return nil
		return nil
	}

	return bkt.Delete([]byte(key))
}

func addContentLease(ctx context.Context, tx *bolt.Tx, dgst digest.Digest) error {
	lid, ok := leases.Lease(ctx)
	if !ok {
		return nil
	}

	namespace, ok := namespaces.Namespace(ctx)
	if !ok {
		panic("namespace must already be required")
	}

	bkt := getBucket(tx, bucketKeyVersion, []byte(namespace), bucketKeyObjectLeases, []byte(lid))
	if bkt == nil {
		return errors.Wrap(errdefs.ErrNotFound, "lease does not exist")
	}

	bkt, err := bkt.CreateBucketIfNotExists(bucketKeyObjectContent)
	if err != nil {
		return err
	}

	return bkt.Put([]byte(dgst.String()), nil)
}

func removeContentLease(ctx context.Context, tx *bolt.Tx, dgst digest.Digest) error {
	lid, ok := leases.Lease(ctx)
	if !ok {
		return nil
	}

	namespace, ok := namespaces.Namespace(ctx)
	if !ok {
		panic("namespace must already be checked")
	}

	bkt := getBucket(tx, bucketKeyVersion, []byte(namespace), bucketKeyObjectLeases, []byte(lid), bucketKeyObjectContent)
	if bkt == nil {
		// Key does not exist so we return nil
		return nil
	}

	return bkt.Delete([]byte(dgst.String()))
}