// Licensed to Elasticsearch B.V. under one or more contributor
// license agreements. See the NOTICE file distributed with
// this work for additional information regarding copyright
// ownership. Elasticsearch B.V. licenses this file to you 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 node

import (
	"time"

	"github.com/pkg/errors"

	"github.com/elastic/beats/libbeat/common"
	"github.com/elastic/beats/metricbeat/mb"
	"github.com/elastic/beats/metricbeat/module/munin"
)

// init registers the MetricSet with the central registry as soon as the program
// starts. The New function will be called later to instantiate an instance of
// the MetricSet for each host defined in the module's configuration. After the
// MetricSet has been created then Fetch will begin to be called periodically.
func init() {
	mb.Registry.MustAddMetricSet("munin", "node", New,
		mb.DefaultMetricSet(),
	)
}

// MetricSet holds any configuration or state information. It must implement
// the mb.MetricSet interface. And this is best achieved by embedding
// mb.BaseMetricSet because it implements all of the required mb.MetricSet
// interface methods except for Fetch.
type MetricSet struct {
	mb.BaseMetricSet
	serviceType string
	plugins     []string
	sanitize    bool
	timeout     time.Duration
}

// New creates a new instance of the MetricSet. New is responsible for unpacking
// any MetricSet specific configuration options if there are any.
func New(base mb.BaseMetricSet) (mb.MetricSet, error) {

	config := defaultConfig
	if err := base.Module().UnpackConfig(&config); err != nil {
		return nil, err
	}

	return &MetricSet{
		BaseMetricSet: base,
		plugins:       config.Plugins,
		sanitize:      config.Sanitize,
		timeout:       base.Module().Config().Timeout,
	}, nil
}

// Fetch method implements the data gathering
func (m *MetricSet) Fetch(r mb.ReporterV2) error {
	node, err := munin.Connect(m.Host(), m.timeout)
	if err != nil {
		return errors.Wrap(err, "error in Connect")
	}
	defer node.Close()

	plugins := m.plugins
	if len(plugins) == 0 {
		plugins, err = node.List()
		if err != nil {
			return errors.Wrap(err, "error getting plugin list")
		}
	}

	for _, plugin := range plugins {
		metrics, err := node.Fetch(plugin, m.sanitize)
		if err != nil {
			msg := errors.Wrap(err, "error fetching metrics")
			r.Error(err)
			m.Logger().Error(msg)
			continue
		}

		// Even if there was some error, keep sending succesfully collected metrics if any
		if len(metrics) == 0 {
			continue
		}
		event := mb.Event{
			Service: plugin,
			RootFields: common.MapStr{
				"munin": common.MapStr{
					"plugin": common.MapStr{
						"name": plugin,
					},
					"metrics": metrics,
				},
			},
		}
		if !r.Event(event) {
			return errors.New("metricset has closed")
		}
	}
	return nil
}
