/*
 * 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"
	"net"
	"net/url"
	"os"
	"path/filepath"
	"sync"

	"github.com/minio/minio/cmd/logger"
	"github.com/minio/minio/pkg/event"
	xnet "github.com/minio/minio/pkg/net"
	"github.com/streadway/amqp"
)

// AMQPArgs - AMQP target arguments.
type AMQPArgs struct {
	Enable       bool     `json:"enable"`
	URL          xnet.URL `json:"url"`
	Exchange     string   `json:"exchange"`
	RoutingKey   string   `json:"routingKey"`
	ExchangeType string   `json:"exchangeType"`
	DeliveryMode uint8    `json:"deliveryMode"`
	Mandatory    bool     `json:"mandatory"`
	Immediate    bool     `json:"immediate"`
	Durable      bool     `json:"durable"`
	Internal     bool     `json:"internal"`
	NoWait       bool     `json:"noWait"`
	AutoDeleted  bool     `json:"autoDeleted"`
	QueueDir     string   `json:"queueDir"`
	QueueLimit   uint64   `json:"queueLimit"`
}

// Validate AMQP arguments
func (a *AMQPArgs) Validate() error {
	if !a.Enable {
		return nil
	}
	if _, err := amqp.ParseURI(a.URL.String()); err != nil {
		return err
	}
	if a.QueueDir != "" {
		if !filepath.IsAbs(a.QueueDir) {
			return errors.New("queueDir path should be absolute")
		}
	}
	if a.QueueLimit > 10000 {
		return errors.New("queueLimit should not exceed 10000")
	}

	return nil
}

// AMQPTarget - AMQP target
type AMQPTarget struct {
	id        event.TargetID
	args      AMQPArgs
	conn      *amqp.Connection
	connMutex sync.Mutex
	store     Store
}

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

func (target *AMQPTarget) channel() (*amqp.Channel, error) {
	var err error
	var conn *amqp.Connection
	var ch *amqp.Channel

	isAMQPClosedErr := func(err error) bool {
		if err == amqp.ErrClosed {
			return true
		}

		if nerr, ok := err.(*net.OpError); ok {
			return (nerr.Err.Error() == "use of closed network connection")
		}

		return false
	}

	target.connMutex.Lock()
	defer target.connMutex.Unlock()

	if target.conn != nil {
		ch, err = target.conn.Channel()
		if err == nil {
			return ch, nil
		}

		if !isAMQPClosedErr(err) {
			return nil, err
		}
	}

	conn, err = amqp.Dial(target.args.URL.String())
	if err != nil {
		if IsConnRefusedErr(err) {
			return nil, errNotConnected
		}
		return nil, err
	}

	ch, err = conn.Channel()
	if err != nil {
		return nil, err
	}

	target.conn = conn

	return ch, nil
}

// send - sends an event to the AMQP.
func (target *AMQPTarget) send(eventData event.Event, ch *amqp.Channel) error {
	objectName, err := url.QueryUnescape(eventData.S3.Object.Key)
	if err != nil {
		return err
	}
	key := eventData.S3.Bucket.Name + "/" + objectName

	data, err := json.Marshal(event.Log{EventName: eventData.EventName, Key: key, Records: []event.Event{eventData}})
	if err != nil {
		return err
	}

	if err = ch.ExchangeDeclare(target.args.Exchange, target.args.ExchangeType, target.args.Durable,
		target.args.AutoDeleted, target.args.Internal, target.args.NoWait, nil); err != nil {
		return err
	}

	if err := ch.Publish(target.args.Exchange, target.args.RoutingKey, target.args.Mandatory,
		target.args.Immediate, amqp.Publishing{
			ContentType:  "application/json",
			DeliveryMode: target.args.DeliveryMode,
			Body:         data,
		}); err != nil {
		return err
	}

	return nil
}

// Save - saves the events to the store which will be replayed when the amqp connection is active.
func (target *AMQPTarget) Save(eventData event.Event) error {
	if target.store != nil {
		return target.store.Put(eventData)
	}
	ch, err := target.channel()
	if err != nil {
		return err
	}
	defer func() {
		cErr := ch.Close()
		logger.LogOnceIf(context.Background(), cErr, target.ID())
	}()

	return target.send(eventData, ch)
}

// Send - sends event to AMQP.
func (target *AMQPTarget) Send(eventKey string) error {
	ch, err := target.channel()
	if err != nil {
		return err
	}
	defer func() {
		cErr := ch.Close()
		logger.LogOnceIf(context.Background(), cErr, target.ID())
	}()

	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 wouldve been already been sent successfully.
		if os.IsNotExist(eErr) {
			return nil
		}
		return eErr
	}

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

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

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

// NewAMQPTarget - creates new AMQP target.
func NewAMQPTarget(id string, args AMQPArgs, doneCh <-chan struct{}) (*AMQPTarget, error) {
	var conn *amqp.Connection
	var err error

	var store Store

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

	conn, err = amqp.Dial(args.URL.String())
	if err != nil {
		if store == nil || !IsConnRefusedErr(err) {
			return nil, err
		}
	}

	target := &AMQPTarget{
		id:    event.TargetID{ID: id, Name: "amqp"},
		args:  args,
		conn:  conn,
		store: store,
	}

	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
}