// Copyright 2019 The Gitea Authors. All rights reserved.
// Use of this source code is governed by a MIT-style
// license that can be found in the LICENSE file.

package queue

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"reflect"
	"strings"
	"time"

	"code.gitea.io/gitea/modules/log"

	"github.com/go-redis/redis"
)

// RedisQueueType is the type for redis queue
const RedisQueueType Type = "redis"

type redisClient interface {
	RPush(key string, args ...interface{}) *redis.IntCmd
	LPop(key string) *redis.StringCmd
	Ping() *redis.StatusCmd
	Close() error
}

// RedisQueue redis queue
type RedisQueue struct {
	pool      *WorkerPool
	client    redisClient
	queueName string
	closed    chan struct{}
	exemplar  interface{}
	workers   int
}

// RedisQueueConfiguration is the configuration for the redis queue
type RedisQueueConfiguration struct {
	Addresses    string
	Password     string
	DBIndex      int
	BatchLength  int
	QueueLength  int
	QueueName    string
	Workers      int
	BlockTimeout time.Duration
	BoostTimeout time.Duration
	BoostWorkers int
}

// NewRedisQueue creates single redis or cluster redis queue
func NewRedisQueue(handle HandlerFunc, cfg, exemplar interface{}) (Queue, error) {
	configInterface, err := toConfig(RedisQueueConfiguration{}, cfg)
	if err != nil {
		return nil, err
	}
	config := configInterface.(RedisQueueConfiguration)

	dbs := strings.Split(config.Addresses, ",")

	dataChan := make(chan Data, config.QueueLength)
	ctx, cancel := context.WithCancel(context.Background())

	var queue = RedisQueue{
		pool: &WorkerPool{
			baseCtx:      ctx,
			cancel:       cancel,
			batchLength:  config.BatchLength,
			handle:       handle,
			dataChan:     dataChan,
			blockTimeout: config.BlockTimeout,
			boostTimeout: config.BoostTimeout,
			boostWorkers: config.BoostWorkers,
		},
		queueName: config.QueueName,
		exemplar:  exemplar,
		closed:    make(chan struct{}),
		workers:   config.Workers,
	}
	if len(dbs) == 0 {
		return nil, errors.New("no redis host found")
	} else if len(dbs) == 1 {
		queue.client = redis.NewClient(&redis.Options{
			Addr:     strings.TrimSpace(dbs[0]), // use default Addr
			Password: config.Password,           // no password set
			DB:       config.DBIndex,            // use default DB
		})
	} else {
		queue.client = redis.NewClusterClient(&redis.ClusterOptions{
			Addrs: dbs,
		})
	}
	if err := queue.client.Ping().Err(); err != nil {
		return nil, err
	}
	return &queue, nil
}

// Run runs the redis queue
func (r *RedisQueue) Run(atShutdown, atTerminate func(context.Context, func())) {
	atShutdown(context.Background(), r.Shutdown)
	atTerminate(context.Background(), r.Terminate)

	go r.pool.addWorkers(r.pool.baseCtx, r.workers)

	go r.readToChan()

	<-r.closed
	r.pool.Wait()
	// FIXME: graceful: Needs HammerContext
	r.pool.CleanUp(context.TODO())
}

func (r *RedisQueue) readToChan() {
	for {
		select {
		case <-r.closed:
			// tell the pool to shutdown
			r.pool.cancel()
			return
		default:
			bs, err := r.client.LPop(r.queueName).Bytes()
			if err != nil && err != redis.Nil {
				log.Error("LPop failed: %v", err)
				time.Sleep(time.Millisecond * 100)
				continue
			}

			if len(bs) == 0 {
				time.Sleep(time.Millisecond * 100)
				continue
			}

			var data Data
			if r.exemplar != nil {
				t := reflect.TypeOf(r.exemplar)
				n := reflect.New(t)
				ne := n.Elem()
				err = json.Unmarshal(bs, ne.Addr().Interface())
				data = ne.Interface().(Data)
			} else {
				err = json.Unmarshal(bs, &data)
			}
			if err != nil {
				log.Error("Unmarshal: %v", err)
				time.Sleep(time.Millisecond * 100)
				continue
			}

			log.Trace("RedisQueue: task found: %#v", data)
			r.pool.Push(data)
			time.Sleep(time.Millisecond * 10)
		}
	}
}

// Push implements Queue
func (r *RedisQueue) Push(data Data) error {
	if r.exemplar != nil {
		// Assert data is of same type as r.exemplar
		value := reflect.ValueOf(data)
		t := value.Type()
		exemplarType := reflect.ValueOf(r.exemplar).Type()
		if !t.AssignableTo(exemplarType) || data == nil {
			return fmt.Errorf("Unable to assign data: %v to same type as exemplar: %v in %s", data, r.exemplar, r.name)
		}
	}
	bs, err := json.Marshal(data)
	if err != nil {
		return err
	}
	return r.client.RPush(r.queueName, bs).Err()
}

// Shutdown processing from this queue
func (r *RedisQueue) Shutdown() {
	select {
	case <-r.closed:
	default:
		close(r.closed)
	}
}

// Terminate this queue and close the queue
func (r *RedisQueue) Terminate() {
	r.Shutdown()
	if err := r.client.Close(); err != nil {
		log.Error("Error whilst closing internal redis client: %v", err)
	}
}

func init() {
	queuesMap[RedisQueueType] = NewRedisQueue
}