// Copyright 2017 Google LLC. All Rights Reserved.
//
// 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 memory

import (
	"context"
	"fmt"
	"sync"
	"time"

	"github.com/google/trillian"
	"github.com/google/trillian/storage"
	"google.golang.org/protobuf/proto"
	"google.golang.org/protobuf/types/known/timestamppb"
	"k8s.io/klog/v2"
)

// NewAdminStorage returns a storage.AdminStorage implementation backed by
// TreeStorage.
func NewAdminStorage(ms *TreeStorage) storage.AdminStorage {
	return &memoryAdminStorage{ms}
}

// memoryAdminStorage implements storage.AdminStorage
type memoryAdminStorage struct {
	ms *TreeStorage
}

func (s *memoryAdminStorage) Snapshot(ctx context.Context) (storage.ReadOnlyAdminTX, error) {
	return &adminTX{ms: s.ms}, nil
}

func (s *memoryAdminStorage) ReadWriteTransaction(ctx context.Context, f storage.AdminTXFunc) error {
	tx := &adminTX{ms: s.ms}
	defer func() {
		if err := tx.Close(); err != nil {
			klog.Errorf("tx.Close(): %v", err)
		}
	}()
	if err := f(ctx, tx); err != nil {
		return err
	}
	return tx.Commit()
}

func (s *memoryAdminStorage) CheckDatabaseAccessible(ctx context.Context) error {
	return nil
}

type adminTX struct {
	ms *TreeStorage

	// mu guards reads/writes on closed, which happen on Commit/Close methods.
	//
	// We don't check closed on methods apart from the ones above, as we trust tx
	// to keep tabs on its state, and hence fail to do queries after closed.
	mu     sync.RWMutex
	closed bool
}

func (t *adminTX) Commit() error {
	// TODO(al): The admin implementation isn't transactional.
	return t.Close()
}

func (t *adminTX) Close() error {
	// TODO(al): The admin implementation isn't transactional.
	t.mu.Lock()
	defer t.mu.Unlock()
	t.closed = true
	return nil
}

func (t *adminTX) GetTree(ctx context.Context, treeID int64) (*trillian.Tree, error) {
	tree := t.ms.getTree(treeID)
	if tree == nil {
		return nil, fmt.Errorf("no such treeID %d", treeID)
	}
	tree.RLock()
	defer tree.RUnlock()

	return tree.meta, nil
}

func (t *adminTX) ListTrees(ctx context.Context, includeDeleted bool) ([]*trillian.Tree, error) {
	t.ms.mu.RLock()
	defer t.ms.mu.RUnlock()

	var ret []*trillian.Tree
	for _, v := range t.ms.trees {
		ret = append(ret, v.meta)
	}
	return ret, nil
}

func (t *adminTX) CreateTree(ctx context.Context, tr *trillian.Tree) (*trillian.Tree, error) {
	if err := storage.ValidateTreeForCreation(ctx, tr); err != nil {
		return nil, err
	}
	if err := validateStorageSettings(tr); err != nil {
		return nil, err
	}

	id, err := storage.NewTreeID()
	if err != nil {
		return nil, err
	}

	now := time.Now()

	meta := proto.Clone(tr).(*trillian.Tree)
	meta.TreeId = id
	meta.CreateTime = timestamppb.New(now)
	if err := meta.CreateTime.CheckValid(); err != nil {
		return nil, err
	}
	meta.UpdateTime = timestamppb.New(now)
	if err := meta.UpdateTime.CheckValid(); err != nil {
		return nil, err
	}

	t.ms.mu.Lock()
	defer t.ms.mu.Unlock()
	t.ms.trees[id] = newTree(meta)

	klog.V(1).Infof("trees: %v", t.ms.trees)

	return meta, nil
}

func (t *adminTX) UpdateTree(ctx context.Context, treeID int64, updateFunc func(*trillian.Tree)) (*trillian.Tree, error) {
	mTree := t.ms.getTree(treeID)
	mTree.mu.Lock()
	defer mTree.mu.Unlock()

	tree := mTree.meta
	beforeUpdate := proto.Clone(tree).(*trillian.Tree)
	updateFunc(tree)
	if err := storage.ValidateTreeForUpdate(ctx, beforeUpdate, tree); err != nil {
		return nil, err
	}
	if err := validateStorageSettings(tree); err != nil {
		return nil, err
	}

	tree.UpdateTime = timestamppb.New(time.Now())
	if err := tree.UpdateTime.CheckValid(); err != nil {
		return nil, err
	}
	return tree, nil
}

func (t *adminTX) SoftDeleteTree(ctx context.Context, treeID int64) (*trillian.Tree, error) {
	return nil, fmt.Errorf("method not supported: SoftDeleteTree")
}

func (t *adminTX) HardDeleteTree(ctx context.Context, treeID int64) error {
	return fmt.Errorf("method not supported: HardDeleteTree")
}

func (t *adminTX) UndeleteTree(ctx context.Context, treeID int64) (*trillian.Tree, error) {
	return nil, fmt.Errorf("method not supported: UndeleteTree")
}

func validateStorageSettings(tree *trillian.Tree) error {
	if tree.StorageSettings != nil {
		return fmt.Errorf("storage_settings not supported, but got %v", tree.StorageSettings)
	}
	return nil
}