/*
 * MinIO Cloud Storage, (C) 2018 MinIO, 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 target

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"net/url"
	"os"
	"path/filepath"
	"strings"
	"time"

	"github.com/gomodule/redigo/redis"
	"github.com/minio/minio/cmd/logger"
	"github.com/minio/minio/pkg/event"
	xnet "github.com/minio/minio/pkg/net"
)

// RedisArgs - Redis target arguments.
type RedisArgs struct {
	Enable     bool      `json:"enable"`
	Format     string    `json:"format"`
	Addr       xnet.Host `json:"address"`
	Password   string    `json:"password"`
	Key        string    `json:"key"`
	QueueDir   string    `json:"queueDir"`
	QueueLimit uint64    `json:"queueLimit"`
}

// Validate RedisArgs fields
func (r RedisArgs) Validate() error {
	if !r.Enable {
		return nil
	}

	if r.Format != "" {
		f := strings.ToLower(r.Format)
		if f != event.NamespaceFormat && f != event.AccessFormat {
			return fmt.Errorf("unrecognized format")
		}
	}

	if r.Key == "" {
		return fmt.Errorf("empty key")
	}

	if r.QueueDir != "" {
		if !filepath.IsAbs(r.QueueDir) {
			return errors.New("queueDir path should be absolute")
		}
	}
	if r.QueueLimit > 10000 {
		return errors.New("queueLimit should not exceed 10000")
	}

	return nil
}

func (r RedisArgs) validateFormat(c redis.Conn) error {
	typeAvailable, err := redis.String(c.Do("TYPE", r.Key))
	if err != nil {
		return err
	}

	if typeAvailable != "none" {
		expectedType := "hash"
		if r.Format == event.AccessFormat {
			expectedType = "list"
		}

		if typeAvailable != expectedType {
			return fmt.Errorf("expected type %v does not match with available type %v", expectedType, typeAvailable)
		}
	}

	return nil
}

// RedisTarget - Redis target.
type RedisTarget struct {
	id        event.TargetID
	args      RedisArgs
	pool      *redis.Pool
	store     Store
	firstPing bool
}

// ID - returns target ID.
func (target *RedisTarget) ID() event.TargetID {
	return target.id
}

// Save - saves the events to the store if questore is configured, which will be replayed when the redis connection is active.
func (target *RedisTarget) Save(eventData event.Event) error {
	if target.store != nil {
		return target.store.Put(eventData)
	}
	conn := target.pool.Get()
	defer func() {
		cErr := conn.Close()
		logger.LogOnceIf(context.Background(), cErr, target.ID())
	}()
	_, pingErr := conn.Do("PING")
	if pingErr != nil {
		if IsConnRefusedErr(pingErr) {
			return errNotConnected
		}
		return pingErr
	}
	return target.send(eventData)
}

// send - sends an event to the redis.
func (target *RedisTarget) send(eventData event.Event) error {
	conn := target.pool.Get()
	defer func() {
		cErr := conn.Close()
		logger.LogOnceIf(context.Background(), cErr, target.ID())
	}()

	if target.args.Format == event.NamespaceFormat {
		objectName, err := url.QueryUnescape(eventData.S3.Object.Key)
		if err != nil {
			return err
		}
		key := eventData.S3.Bucket.Name + "/" + objectName

		if eventData.EventName == event.ObjectRemovedDelete {
			_, err = conn.Do("HDEL", target.args.Key, key)
		} else {
			var data []byte
			if data, err = json.Marshal(struct{ Records []event.Event }{[]event.Event{eventData}}); err != nil {
				return err
			}

			_, err = conn.Do("HSET", target.args.Key, key, data)
		}
		if err != nil {
			return err
		}
	}

	if target.args.Format == event.AccessFormat {
		data, err := json.Marshal([]interface{}{eventData.EventTime, []event.Event{eventData}})
		if err != nil {
			return err
		}
		if _, err := conn.Do("RPUSH", target.args.Key, data); err != nil {
			return err
		}
	}

	return nil
}

// Send - reads an event from store and sends it to redis.
func (target *RedisTarget) Send(eventKey string) error {
	conn := target.pool.Get()
	defer func() {
		cErr := conn.Close()
		logger.LogOnceIf(context.Background(), cErr, target.ID())
	}()
	_, pingErr := conn.Do("PING")
	if pingErr != nil {
		if IsConnRefusedErr(pingErr) {
			return errNotConnected
		}
		return pingErr
	}

	if !target.firstPing {
		if err := target.args.validateFormat(conn); err != nil {
			if IsConnRefusedErr(err) {
				return errNotConnected
			}
			return err
		}
		target.firstPing = true
	}

	eventData, eErr := target.store.Get(eventKey)
	if eErr != nil {
		// The last event key in a successful batch will be sent in the channel atmost once by the replayEvents()
		// Such events will not exist and would've been already been sent successfully.
		if os.IsNotExist(eErr) {
			return nil
		}
		return eErr
	}

	if err := target.send(eventData); err != nil {
		if IsConnRefusedErr(err) {
			return errNotConnected
		}
		return err
	}

	// Delete the event from store.
	return target.store.Del(eventKey)
}

// Close - does nothing and available for interface compatibility.
func (target *RedisTarget) Close() error {
	return nil
}

// NewRedisTarget - creates new Redis target.
func NewRedisTarget(id string, args RedisArgs, doneCh <-chan struct{}) (*RedisTarget, error) {
	pool := &redis.Pool{
		MaxIdle:     3,
		IdleTimeout: 2 * 60 * time.Second,
		Dial: func() (redis.Conn, error) {
			conn, err := redis.Dial("tcp", args.Addr.String())
			if err != nil {
				return nil, err
			}

			if args.Password == "" {
				return conn, nil
			}

			if _, err = conn.Do("AUTH", args.Password); err != nil {
				cErr := conn.Close()
				targetID := event.TargetID{ID: id, Name: "redis"}
				logger.LogOnceIf(context.Background(), cErr, targetID.String())
				return nil, err
			}

			return conn, nil
		},
		TestOnBorrow: func(c redis.Conn, t time.Time) error {
			_, err := c.Do("PING")
			return err
		},
	}

	var store Store

	if args.QueueDir != "" {
		queueDir := filepath.Join(args.QueueDir, storePrefix+"-redis-"+id)
		store = NewQueueStore(queueDir, args.QueueLimit)
		if oErr := store.Open(); oErr != nil {
			return nil, oErr
		}
	}

	target := &RedisTarget{
		id:    event.TargetID{ID: id, Name: "redis"},
		args:  args,
		pool:  pool,
		store: store,
	}

	conn := target.pool.Get()
	defer func() {
		cErr := conn.Close()
		logger.LogOnceIf(context.Background(), cErr, target.ID())
	}()

	_, pingErr := conn.Do("PING")
	if pingErr != nil {
		if target.store == nil || !(IsConnRefusedErr(pingErr) || IsConnResetErr(pingErr)) {
			return nil, pingErr
		}
	} else {
		if err := target.args.validateFormat(conn); err != nil {
			return nil, err
		}
		target.firstPing = true
	}

	if target.store != nil {
		// Replays the events from the store.
		eventKeyCh := replayEvents(target.store, doneCh)
		// Start replaying events from the store.
		go sendEvents(target, eventKeyCh, doneCh)
	}

	return target, nil
}