// Copyright 2023 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,
// 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 scheduler

import (
	"context"

	"github.com/pingcap/tidb/pkg/disttask/framework/proto"
	"github.com/pingcap/tidb/pkg/disttask/framework/scheduler/execute"
)

// TaskTable defines the interface to access task table.
type TaskTable interface {
	GetGlobalTasksInStates(ctx context.Context, states ...interface{}) (task []*proto.Task, err error)
	GetGlobalTaskByID(ctx context.Context, taskID int64) (task *proto.Task, err error)

	GetSubtasksInStates(ctx context.Context, tidbID string, taskID int64, step proto.Step, states ...interface{}) ([]*proto.Subtask, error)
	GetFirstSubtaskInStates(ctx context.Context, instanceID string, taskID int64, step proto.Step, states ...interface{}) (*proto.Subtask, error)
	StartManager(ctx context.Context, tidbID string, role string) error
	StartSubtask(ctx context.Context, subtaskID int64) error
	UpdateSubtaskStateAndError(ctx context.Context, tidbID string, subtaskID int64, state proto.TaskState, err error) error
	FinishSubtask(ctx context.Context, tidbID string, subtaskID int64, meta []byte) error

	HasSubtasksInStates(ctx context.Context, tidbID string, taskID int64, step proto.Step, states ...interface{}) (bool, error)
	UpdateErrorToSubtask(ctx context.Context, tidbID string, taskID int64, err error) error
	IsSchedulerCanceled(ctx context.Context, tidbID string, taskID int64) (bool, error)
	PauseSubtasks(ctx context.Context, tidbID string, taskID int64) error
}

// Pool defines the interface of a pool.
type Pool interface {
	Run(func()) error
	RunWithConcurrency(chan func(), uint32) error
	ReleaseAndWait()
}

// Scheduler is the subtask scheduler for a task.
// Each task type should implement this interface.
type Scheduler interface {
	Init(context.Context) error
	Run(context.Context, *proto.Task) error
	Rollback(context.Context, *proto.Task) error
	Pause(context.Context, *proto.Task) error
	Close()
}

// Extension extends the scheduler.
// each task type should implement this interface.
type Extension interface {
	// IsIdempotent returns whether the subtask is idempotent.
	// when tidb restart, the subtask might be left in the running state.
	// if it's idempotent, the scheduler can rerun the subtask, else
	// the scheduler will mark the subtask as failed.
	IsIdempotent(subtask *proto.Subtask) bool
	// GetSubtaskExecutor returns the subtask executor for the subtask.
	// Note: summary is the summary manager of all subtask of the same type now.
	GetSubtaskExecutor(ctx context.Context, task *proto.Task, summary *execute.Summary) (execute.SubtaskExecutor, error)
}

// EmptySubtaskExecutor is an empty scheduler.
// it can be used for the task that does not need to split into subtasks.
type EmptySubtaskExecutor struct {
}

var _ execute.SubtaskExecutor = &EmptySubtaskExecutor{}

// Init implements the SubtaskExecutor interface.
func (*EmptySubtaskExecutor) Init(context.Context) error {
	return nil
}

// RunSubtask implements the SubtaskExecutor interface.
func (*EmptySubtaskExecutor) RunSubtask(context.Context, *proto.Subtask) error {
	return nil
}

// Cleanup implements the SubtaskExecutor interface.
func (*EmptySubtaskExecutor) Cleanup(context.Context) error {
	return nil
}

// OnFinished implements the SubtaskExecutor interface.
func (*EmptySubtaskExecutor) OnFinished(_ context.Context, _ *proto.Subtask) error {
	return nil
}

// Rollback implements the SubtaskExecutor interface.
func (*EmptySubtaskExecutor) Rollback(context.Context) error {
	return nil
}