// 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_stats

import (
	"net/url"

	"github.com/elastic/beats/v7/metricbeat/mb"
	"github.com/elastic/beats/v7/metricbeat/mb/parse"
	"github.com/elastic/beats/v7/metricbeat/module/logstash"
)

// init registers the MetricSet with the central registry.
// The New method will be called after the setup of the module and before starting to fetch data
func init() {
	mb.Registry.MustAddMetricSet(logstash.ModuleName, "node_stats", New,
		mb.WithHostParser(hostParser),
		mb.WithNamespace("logstash.node.stats"),
		mb.DefaultMetricSet(),
	)
}

const (
	nodeStatsPath = "/_node/stats"
)

var (
	hostParser = parse.URLHostParserBuilder{
		DefaultScheme: "http",
		PathConfigKey: "path",
		DefaultPath:   nodeStatsPath,
	}.Build()
)

// MetricSet type defines all fields of the MetricSet
type MetricSet struct {
	*logstash.MetricSet
}

// New create a new instance of the MetricSet
func New(base mb.BaseMetricSet) (mb.MetricSet, error) {
	ms, err := logstash.NewMetricSet(base)
	if err != nil {
		return nil, err
	}

	return &MetricSet{
		MetricSet: ms,
	}, nil
}

// Fetch methods implements the data gathering and data conversion to the right format
// It returns the event which is then forward to the output. In case of an error, a
// descriptive error must be returned.
func (m *MetricSet) Fetch(r mb.ReporterV2) error {
	if err := m.updateServiceURI(); err != nil {
		if m.XPack {
			m.Logger().Error(err)
			return nil
		}
		return err
	}

	content, err := m.HTTP.FetchContent()
	if err != nil {
		if m.XPack {
			m.Logger().Error(err)
			return nil
		}
		return err
	}

	if !m.XPack {
		return eventMapping(r, content)
	}

	err = eventMappingXPack(r, m, content)
	if err != nil {
		m.Logger().Error(err)
	}

	return nil
}

func (m *MetricSet) updateServiceURI() error {
	u, err := getServiceURI(m.GetURI(), m.XPack, m.CheckPipelineGraphAPIsAvailable)
	if err != nil {
		return err
	}

	m.HTTP.SetURI(u)
	return nil

}

func getServiceURI(currURI string, xpackEnabled bool, graphAPIsAvailable func() error) (string, error) {
	if !xpackEnabled {
		// No need to request pipeline vertices from service API
		return currURI, nil
	}

	if err := graphAPIsAvailable(); err != nil {
		return "", err
	}

	u, err := url.Parse(currURI)
	if err != nil {
		return "", err
	}

	q := u.Query()
	if q.Get("vertices") == "" {
		q.Set("vertices", "true")
	}

	u.RawQuery = q.Encode()
	return u.String(), nil
}
