// 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 elasticsearch

import (
	"encoding/json"
	"fmt"
	"net/url"
	"strings"
	"sync"
	"time"

	"github.com/elastic/beats/libbeat/common"
	"github.com/elastic/beats/metricbeat/helper"
	"github.com/elastic/beats/metricbeat/helper/elastic"
)

// CCRStatsAPIAvailableVersion is the version of Elasticsearch since when the CCR stats API is available
const CCRStatsAPIAvailableVersion = "6.5.0"

// Global clusterIdCache. Assumption is that the same node id never can belong to a different cluster id
var clusterIDCache = map[string]string{}

// ModuleName is the ame of this module
const ModuleName = "elasticsearch"

// Info construct contains the data from the Elasticsearch / endpoint
type Info struct {
	ClusterName string `json:"cluster_name"`
	ClusterID   string `json:"cluster_uuid"`
	Version     struct {
		Number string `json:"number"`
	} `json:"version"`
}

// NodeInfo struct cotains data about the node
type NodeInfo struct {
	Host             string `json:"host"`
	TransportAddress string `json:"transport_address"`
	IP               string `json:"ip"`
	Name             string `json:"name"`
	ID               string
}

// GetClusterID fetches cluster id for given nodeID
func GetClusterID(http *helper.HTTP, uri string, nodeID string) (string, error) {
	// Check if cluster id already cached. If yes, return it.
	if clusterID, ok := clusterIDCache[nodeID]; ok {
		return clusterID, nil
	}

	info, err := GetInfo(http, uri)
	if err != nil {
		return "", err
	}

	clusterIDCache[nodeID] = info.ClusterID
	return info.ClusterID, nil
}

// IsMaster checks if the given node host is a master node
//
// The detection of the master is done in two steps:
// * Fetch node name from /_nodes/_local/name
// * Fetch current master name from cluster state /_cluster/state/master_node
//
// The two names are compared
func IsMaster(http *helper.HTTP, uri string) (bool, error) {

	node, err := getNodeName(http, uri)
	if err != nil {
		return false, err
	}

	master, err := getMasterName(http, uri)
	if err != nil {
		return false, err
	}

	return master == node, nil
}

func getNodeName(http *helper.HTTP, uri string) (string, error) {
	content, err := fetchPath(http, uri, "/_nodes/_local/nodes")
	if err != nil {
		return "", err
	}

	nodesStruct := struct {
		Nodes map[string]interface{} `json:"nodes"`
	}{}

	json.Unmarshal(content, &nodesStruct)

	// _local will only fetch one node info. First entry is node name
	for k := range nodesStruct.Nodes {
		return k, nil
	}
	return "", fmt.Errorf("No local node found")
}

func getMasterName(http *helper.HTTP, uri string) (string, error) {
	// TODO: evaluate on why when run with ?local=true request does not contain master_node field
	content, err := fetchPath(http, uri, "_cluster/state/master_node")
	if err != nil {
		return "", err
	}

	clusterStruct := struct {
		MasterNode string `json:"master_node"`
	}{}

	json.Unmarshal(content, &clusterStruct)

	return clusterStruct.MasterNode, nil
}

// GetInfo returns the data for the Elasticsearch / endpoint
func GetInfo(http *helper.HTTP, uri string) (*Info, error) {

	content, err := fetchPath(http, uri, "/")
	if err != nil {
		return nil, err
	}

	info := &Info{}
	json.Unmarshal(content, info)

	return info, nil
}

func fetchPath(http *helper.HTTP, uri, path string) ([]byte, error) {
	defer http.SetURI(uri)

	// Parses the uri to replace the path
	u, _ := url.Parse(uri)
	u.Path = path
	u.RawQuery = ""

	// Http helper includes the HostData with username and password
	http.SetURI(u.String())
	return http.FetchContent()
}

// GetNodeInfo returns the node information
func GetNodeInfo(http *helper.HTTP, uri string, nodeID string) (*NodeInfo, error) {

	content, err := fetchPath(http, uri, "/_nodes/_local/nodes")
	if err != nil {
		return nil, err
	}

	nodesStruct := struct {
		Nodes map[string]*NodeInfo `json:"nodes"`
	}{}

	json.Unmarshal(content, &nodesStruct)

	// _local will only fetch one node info. First entry is node name
	for k, v := range nodesStruct.Nodes {
		// In case the nodeID is empty, first node info will be returned
		if k == nodeID || nodeID == "" {
			v.ID = k
			return v, nil
		}
	}
	return nil, fmt.Errorf("no node matched id %s", nodeID)
}

// GetLicense returns license information. Since we don't expect license information
// to change frequently, the information is cached for 1 minute to avoid
// hitting Elasticsearch frequently
func GetLicense(http *helper.HTTP, resetURI string) (common.MapStr, error) {
	// First, check the cache
	license := licenseCache.get()

	// Not cached, fetch license from Elasticsearch
	if license == nil {
		content, err := fetchPath(http, resetURI, "_xpack/license")
		if err != nil {
			return nil, err
		}

		var data common.MapStr
		err = json.Unmarshal(content, &data)
		if err != nil {
			return nil, err
		}

		l, err := data.GetValue("license")
		if err != nil {
			return nil, err
		}
		license, ok := l.(map[string]interface{})
		if !ok {
			return nil, elastic.MakeErrorForMissingField("license", elastic.Elasticsearch)
		}

		// Cache license for a minute
		licenseCache.set(license, time.Minute)
	}

	return licenseCache.get(), nil
}

// GetClusterState returns cluster state information
func GetClusterState(http *helper.HTTP, resetURI string, metrics []string) (common.MapStr, error) {
	clusterStateURI := "_cluster/state"
	if metrics != nil && len(metrics) > 0 {
		clusterStateURI += "/" + strings.Join(metrics, ",")
	}

	content, err := fetchPath(http, resetURI, clusterStateURI)
	if err != nil {
		return nil, err
	}

	var clusterState map[string]interface{}
	err = json.Unmarshal(content, &clusterState)
	return clusterState, err
}

// GetStackUsage returns stack usage information
func GetStackUsage(http *helper.HTTP, resetURI string) (common.MapStr, error) {
	content, err := fetchPath(http, resetURI, "_xpack/usage")
	if err != nil {
		return nil, err
	}

	var stackUsage map[string]interface{}
	err = json.Unmarshal(content, &stackUsage)
	return stackUsage, err
}

// PassThruField copies the field at the given path from the given source data object into
// the same path in the given target data object
func PassThruField(fieldPath string, sourceData, targetData common.MapStr) error {
	fieldValue, err := sourceData.GetValue(fieldPath)
	if err != nil {
		return elastic.MakeErrorForMissingField(fieldPath, elastic.Elasticsearch)
	}

	targetData.Put(fieldPath, fieldValue)
	return nil
}

// IsCCRStatsAPIAvailable returns whether the CCR stats API is available in the given version
// of Elasticsearch
func IsCCRStatsAPIAvailable(currentElasticsearchVersion string) (bool, error) {
	return elastic.IsFeatureAvailable(currentElasticsearchVersion, CCRStatsAPIAvailableVersion)
}

// Global cache for license information. Assumption is that license information changes infrequently
var licenseCache = &_licenseCache{}

type _licenseCache struct {
	sync.RWMutex
	license  common.MapStr
	cachedOn time.Time
	ttl      time.Duration
}

func (c *_licenseCache) get() common.MapStr {
	c.Lock()
	defer c.Unlock()

	if time.Since(c.cachedOn) > c.ttl {
		// We are past the TTL, so invalidate cache
		c.license = nil
	}

	return c.license
}

func (c *_licenseCache) set(license common.MapStr, ttl time.Duration) {
	c.Lock()
	defer c.Unlock()

	c.license = license
	c.ttl = ttl
	c.cachedOn = time.Now()
}