package es

import (
	"bytes"
	"context"
	"encoding/json"
	"fmt"
	"io/ioutil"
	"net/http"
	"net/url"
	"path"
	"strconv"
	"strings"
	"time"

	"github.com/Masterminds/semver"
	"github.com/grafana/grafana/pkg/components/simplejson"
	"github.com/grafana/grafana/pkg/infra/httpclient"
	"github.com/grafana/grafana/pkg/infra/log"
	"github.com/grafana/grafana/pkg/tsdb/interval"

	"github.com/grafana/grafana/pkg/models"
	"github.com/grafana/grafana/pkg/plugins"
	"golang.org/x/net/context/ctxhttp"
)

const loggerName = "tsdb.elasticsearch.client"

var (
	clientLog = log.New(loggerName)
)

var newDatasourceHttpClient = func(httpClientProvider httpclient.Provider, ds *models.DataSource) (*http.Client, error) {
	return ds.GetHTTPClient(httpClientProvider)
}

// Client represents a client which can interact with elasticsearch api
type Client interface {
	GetVersion() *semver.Version
	GetTimeField() string
	GetMinInterval(queryInterval string) (time.Duration, error)
	ExecuteMultisearch(r *MultiSearchRequest) (*MultiSearchResponse, error)
	MultiSearch() *MultiSearchRequestBuilder
	EnableDebug()
}

func coerceVersion(v *simplejson.Json) (*semver.Version, error) {
	versionString, err := v.String()

	if err != nil {
		versionNumber, err := v.Int()
		if err != nil {
			return nil, err
		}

		// Legacy version numbers (before Grafana 8)
		// valid values were 2,5,56,60,70
		switch versionNumber {
		case 2:
			return semver.NewVersion("2.0.0")
		case 5:
			return semver.NewVersion("5.0.0")
		case 56:
			return semver.NewVersion("5.6.0")
		case 60:
			return semver.NewVersion("6.0.0")
		case 70:
			return semver.NewVersion("7.0.0")
		default:
			return nil, fmt.Errorf("elasticsearch version=%d is not supported", versionNumber)
		}
	}

	return semver.NewVersion(versionString)
}

// NewClient creates a new elasticsearch client
var NewClient = func(ctx context.Context, httpClientProvider httpclient.Provider, ds *models.DataSource, timeRange plugins.DataTimeRange) (Client, error) {
	version, err := coerceVersion(ds.JsonData.Get("esVersion"))

	if err != nil {
		return nil, fmt.Errorf("elasticsearch version is required, err=%v", err)
	}

	timeField, err := ds.JsonData.Get("timeField").String()
	if err != nil {
		return nil, fmt.Errorf("elasticsearch time field name is required, err=%v", err)
	}

	indexInterval := ds.JsonData.Get("interval").MustString()
	ip, err := newIndexPattern(indexInterval, ds.Database)
	if err != nil {
		return nil, err
	}

	indices, err := ip.GetIndices(timeRange)
	if err != nil {
		return nil, err
	}

	clientLog.Info("Creating new client", "version", version.String(), "timeField", timeField, "indices", strings.Join(indices, ", "))

	return &baseClientImpl{
		ctx:                ctx,
		httpClientProvider: httpClientProvider,
		ds:                 ds,
		version:            version,
		timeField:          timeField,
		indices:            indices,
		timeRange:          timeRange,
	}, nil
}

type baseClientImpl struct {
	ctx                context.Context
	httpClientProvider httpclient.Provider
	ds                 *models.DataSource
	version            *semver.Version
	timeField          string
	indices            []string
	timeRange          plugins.DataTimeRange
	debugEnabled       bool
}

func (c *baseClientImpl) GetVersion() *semver.Version {
	return c.version
}

func (c *baseClientImpl) GetTimeField() string {
	return c.timeField
}

func (c *baseClientImpl) GetMinInterval(queryInterval string) (time.Duration, error) {
	return interval.GetIntervalFrom(c.ds, simplejson.NewFromAny(map[string]interface{}{
		"interval": queryInterval,
	}), 5*time.Second)
}

func (c *baseClientImpl) getSettings() *simplejson.Json {
	return c.ds.JsonData
}

type multiRequest struct {
	header   map[string]interface{}
	body     interface{}
	interval interval.Interval
}

func (c *baseClientImpl) executeBatchRequest(uriPath, uriQuery string, requests []*multiRequest) (*response, error) {
	bytes, err := c.encodeBatchRequests(requests)
	if err != nil {
		return nil, err
	}
	return c.executeRequest(http.MethodPost, uriPath, uriQuery, bytes)
}

func (c *baseClientImpl) encodeBatchRequests(requests []*multiRequest) ([]byte, error) {
	clientLog.Debug("Encoding batch requests to json", "batch requests", len(requests))
	start := time.Now()

	payload := bytes.Buffer{}
	for _, r := range requests {
		reqHeader, err := json.Marshal(r.header)
		if err != nil {
			return nil, err
		}
		payload.WriteString(string(reqHeader) + "\n")

		reqBody, err := json.Marshal(r.body)
		if err != nil {
			return nil, err
		}

		body := string(reqBody)
		body = strings.ReplaceAll(body, "$__interval_ms", strconv.FormatInt(r.interval.Milliseconds(), 10))
		body = strings.ReplaceAll(body, "$__interval", r.interval.Text)

		payload.WriteString(body + "\n")
	}

	elapsed := time.Since(start)
	clientLog.Debug("Encoded batch requests to json", "took", elapsed)

	return payload.Bytes(), nil
}

func (c *baseClientImpl) executeRequest(method, uriPath, uriQuery string, body []byte) (*response, error) {
	u, err := url.Parse(c.ds.Url)
	if err != nil {
		return nil, err
	}
	u.Path = path.Join(u.Path, uriPath)
	u.RawQuery = uriQuery

	var req *http.Request
	if method == http.MethodPost {
		req, err = http.NewRequest(http.MethodPost, u.String(), bytes.NewBuffer(body))
	} else {
		req, err = http.NewRequest(http.MethodGet, u.String(), nil)
	}
	if err != nil {
		return nil, err
	}

	clientLog.Debug("Executing request", "url", req.URL.String(), "method", method)

	var reqInfo *SearchRequestInfo
	if c.debugEnabled {
		reqInfo = &SearchRequestInfo{
			Method: req.Method,
			Url:    req.URL.String(),
			Data:   string(body),
		}
	}

	req.Header.Set("Content-Type", "application/x-ndjson")

	httpClient, err := newDatasourceHttpClient(c.httpClientProvider, c.ds)
	if err != nil {
		return nil, err
	}

	start := time.Now()
	defer func() {
		elapsed := time.Since(start)
		clientLog.Debug("Executed request", "took", elapsed)
	}()
	//nolint:bodyclose
	resp, err := ctxhttp.Do(c.ctx, httpClient, req)
	if err != nil {
		return nil, err
	}
	return &response{
		httpResponse: resp,
		reqInfo:      reqInfo,
	}, nil
}

func (c *baseClientImpl) ExecuteMultisearch(r *MultiSearchRequest) (*MultiSearchResponse, error) {
	clientLog.Debug("Executing multisearch", "search requests", len(r.Requests))

	multiRequests := c.createMultiSearchRequests(r.Requests)
	queryParams := c.getMultiSearchQueryParameters()
	clientRes, err := c.executeBatchRequest("_msearch", queryParams, multiRequests)
	if err != nil {
		return nil, err
	}
	res := clientRes.httpResponse
	defer func() {
		if err := res.Body.Close(); err != nil {
			clientLog.Warn("Failed to close response body", "err", err)
		}
	}()

	clientLog.Debug("Received multisearch response", "code", res.StatusCode, "status", res.Status, "content-length", res.ContentLength)

	start := time.Now()
	clientLog.Debug("Decoding multisearch json response")

	var bodyBytes []byte
	if c.debugEnabled {
		tmpBytes, err := ioutil.ReadAll(res.Body)
		if err != nil {
			clientLog.Error("failed to read http response bytes", "error", err)
		} else {
			bodyBytes = make([]byte, len(tmpBytes))
			copy(bodyBytes, tmpBytes)
			res.Body = ioutil.NopCloser(bytes.NewBuffer(tmpBytes))
		}
	}

	var msr MultiSearchResponse
	dec := json.NewDecoder(res.Body)
	err = dec.Decode(&msr)
	if err != nil {
		return nil, err
	}

	elapsed := time.Since(start)
	clientLog.Debug("Decoded multisearch json response", "took", elapsed)

	msr.Status = res.StatusCode

	if c.debugEnabled {
		bodyJSON, err := simplejson.NewFromReader(bytes.NewBuffer(bodyBytes))
		var data *simplejson.Json
		if err != nil {
			clientLog.Error("failed to decode http response into json", "error", err)
		} else {
			data = bodyJSON
		}

		msr.DebugInfo = &SearchDebugInfo{
			Request: clientRes.reqInfo,
			Response: &SearchResponseInfo{
				Status: res.StatusCode,
				Data:   data,
			},
		}
	}

	return &msr, nil
}

func (c *baseClientImpl) createMultiSearchRequests(searchRequests []*SearchRequest) []*multiRequest {
	multiRequests := []*multiRequest{}

	for _, searchReq := range searchRequests {
		mr := multiRequest{
			header: map[string]interface{}{
				"search_type":        "query_then_fetch",
				"ignore_unavailable": true,
				"index":              strings.Join(c.indices, ","),
			},
			body:     searchReq,
			interval: searchReq.Interval,
		}

		if c.version.Major() < 5 {
			mr.header["search_type"] = "count"
		} else {
			allowedVersionRange, _ := semver.NewConstraint(">=5.6.0, <7.0.0")

			if allowedVersionRange.Check(c.version) {
				maxConcurrentShardRequests := c.getSettings().Get("maxConcurrentShardRequests").MustInt(256)
				mr.header["max_concurrent_shard_requests"] = maxConcurrentShardRequests
			}
		}

		multiRequests = append(multiRequests, &mr)
	}

	return multiRequests
}

func (c *baseClientImpl) getMultiSearchQueryParameters() string {
	var qs []string

	if c.version.Major() >= 7 {
		maxConcurrentShardRequests := c.getSettings().Get("maxConcurrentShardRequests").MustInt(5)
		qs = append(qs, fmt.Sprintf("max_concurrent_shard_requests=%d", maxConcurrentShardRequests))
	}

	// Querying frozen indices was added in 6.6 with xpack
	includeFrozen := c.getSettings().Get("includeFrozen").MustBool(false)
	xpack := c.getSettings().Get("xpack").MustBool(false)
	allowedFrozenIndicesVersionRange, _ := semver.NewConstraint(">=6.6.0")

	if (allowedFrozenIndicesVersionRange.Check(c.version)) && includeFrozen && xpack {
		qs = append(qs, "ignore_throttled=false")
	}

	return strings.Join(qs, "&")
}

func (c *baseClientImpl) MultiSearch() *MultiSearchRequestBuilder {
	return NewMultiSearchRequestBuilder(c.GetVersion())
}

func (c *baseClientImpl) EnableDebug() {
	c.debugEnabled = true
}