// Copyright 2022 PingCAP, Inc.
//
// 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,
// See the License for the specific language governing permissions and
// limitations under the License.

package partition

import (
	"sync"

	"github.com/pingcap/tiflow/cdc/model"
	"github.com/pingcap/tiflow/pkg/hash"
)

// TableDispatcher is a partition dispatcher which dispatches events
// based on the schema and table name.
type TableDispatcher struct {
	hasher *hash.PositionInertia
	lock   sync.Mutex
}

// NewTableDispatcher creates a TableDispatcher.
func NewTableDispatcher() *TableDispatcher {
	return &TableDispatcher{
		hasher: hash.NewPositionInertia(),
	}
}

// DispatchRowChangedEvent returns the target partition to which
// a row changed event should be dispatched.
func (t *TableDispatcher) DispatchRowChangedEvent(row *model.RowChangedEvent, partitionNum int32) (int32, string, error) {
	t.lock.Lock()
	defer t.lock.Unlock()
	t.hasher.Reset()
	// distribute partition by table
	t.hasher.Write([]byte(row.TableInfo.GetSchemaName()), []byte(row.TableInfo.GetTableName()))
	return int32(t.hasher.Sum32() % uint32(partitionNum)), row.TableInfo.TableName.String(), nil
}