package pub_client

import (
	"context"
	"fmt"
	"github.com/seaweedfs/seaweedfs/weed/glog"
	"github.com/seaweedfs/seaweedfs/weed/pb"
	"github.com/seaweedfs/seaweedfs/weed/pb/mq_pb"
	"sort"
	"sync"
	"time"
)

type EachPartitionError struct {
	*mq_pb.BrokerPartitionAssignment
	Err error
	generation int
}

type EachPartitionPublishJob struct {
	*mq_pb.BrokerPartitionAssignment
	stopChan chan bool
	wg 	 sync.WaitGroup
	generation int
}
func (p *TopicPublisher) StartSchedulerThread(bootstrapBrokers []string) error {

	if err := p.doEnsureConfigureTopic(bootstrapBrokers); err != nil {
		return err
	}

	generation := 0
	var errChan chan EachPartitionError
	for {
		glog.V(0).Infof("lookup partitions gen %d topic %s/%s", generation, p.namespace, p.topic)
		if assignments, err := p.doLookupTopicPartitions(bootstrapBrokers); err == nil {
			generation++
			glog.V(0).Infof("start generation %d", generation)
			if errChan == nil {
				errChan = make(chan EachPartitionError, len(assignments))
			}
			p.onEachAssignments(generation, assignments, errChan)
		} else {
			glog.Errorf("lookup topic %s/%s: %v", p.namespace, p.topic, err)
			time.Sleep(5 * time.Second)
			continue
		}

		// wait for any error to happen. If so, consume all remaining errors, and retry
		for {
			select {
			case eachErr := <-errChan:
				glog.Errorf("gen %d publish to topic %s/%s partition %v: %v", eachErr.generation, p.namespace, p.topic, eachErr.Partition, eachErr.Err)
				if eachErr.generation < generation {
					continue
				}
				break
			}
		}
	}
}

func (p *TopicPublisher) onEachAssignments(generation int, assignments []*mq_pb.BrokerPartitionAssignment, errChan chan EachPartitionError) {
	// TODO assuming this is not re-configured so the partitions are fixed.
	sort.Slice(assignments, func(i, j int) bool {
		return assignments[i].Partition.RangeStart < assignments[j].Partition.RangeStart
	})
	var jobs []*EachPartitionPublishJob
	hasExistingJob := len(p.jobs) == len(assignments)
	for i, assignment := range assignments {
		if assignment.LeaderBroker == "" {
			continue
		}
		if hasExistingJob {
			var existingJob *EachPartitionPublishJob
			existingJob = p.jobs[i]
			if existingJob.BrokerPartitionAssignment.LeaderBroker == assignment.LeaderBroker {
				existingJob.generation = generation
				jobs = append(jobs, existingJob)
				continue
			} else {
				if existingJob.LeaderBroker != "" {
					close(existingJob.stopChan)
					existingJob.LeaderBroker = ""
					existingJob.wg.Wait()
				}
			}
		}

		// start a go routine to publish to this partition
		job := &EachPartitionPublishJob{
			BrokerPartitionAssignment: assignment,
			stopChan: make(chan bool, 1),
			generation: generation,
		}
		job.wg.Add(1)
		go func(job *EachPartitionPublishJob) {
			defer job.wg.Done()
			if err := p.doPublishToPartition(job); err != nil {
				errChan <- EachPartitionError{assignment, err, generation}
			}
		}(job)
		jobs = append(jobs, job)
	}
	p.jobs = jobs
}

func (p *TopicPublisher) doPublishToPartition(job *EachPartitionPublishJob) error {

	return nil
}

func (p *TopicPublisher) doEnsureConfigureTopic(bootstrapBrokers []string) (err error) {
	if len(bootstrapBrokers) == 0 {
		return fmt.Errorf("no bootstrap brokers")
	}
	var lastErr error
	for _, brokerAddress := range bootstrapBrokers {
		err = pb.WithBrokerGrpcClient(false,
			brokerAddress,
			p.grpcDialOption,
			func(client mq_pb.SeaweedMessagingClient) error {
				_, err := client.ConfigureTopic(context.Background(), &mq_pb.ConfigureTopicRequest{
					Topic: &mq_pb.Topic{
						Namespace: p.namespace,
						Name:      p.topic,
					},
					PartitionCount: p.config.CreateTopicPartitionCount,
				})
				return err
			})
		if err == nil {
			return nil
		} else {
			lastErr = err
		}
	}

	if lastErr != nil {
		return fmt.Errorf("configure topic %s/%s: %v", p.namespace, p.topic, err)
	}
	return nil
}

func (p *TopicPublisher) doLookupTopicPartitions(bootstrapBrokers []string) (assignments []*mq_pb.BrokerPartitionAssignment, err error) {
	if len(bootstrapBrokers) == 0 {
		return nil, fmt.Errorf("no bootstrap brokers")
	}
	var lastErr error
	for _, brokerAddress := range bootstrapBrokers {
		err := pb.WithBrokerGrpcClient(false,
			brokerAddress,
			p.grpcDialOption,
			func(client mq_pb.SeaweedMessagingClient) error {
				lookupResp, err := client.LookupTopicBrokers(context.Background(),
					&mq_pb.LookupTopicBrokersRequest{
						Topic: &mq_pb.Topic{
							Namespace: p.namespace,
							Name:      p.topic,
						},
					})
				glog.V(0).Infof("lookup topic %s/%s: %v", p.namespace, p.topic, lookupResp)

				if err != nil {
					return err
				}

				assignments = lookupResp.BrokerPartitionAssignments

				return nil
			})
		if err == nil {
			return assignments, nil
		} else {
			lastErr = err
		}
	}

	return nil, fmt.Errorf("lookup topic %s/%s: %v", p.namespace, p.topic, lastErr)

}