package opentelemetry

import (
	"fmt"
	"net/http"
	"time"

	"github.com/VictoriaMetrics/VictoriaMetrics/app/vminsert/common"
	"github.com/VictoriaMetrics/VictoriaMetrics/app/vminsert/relabel"
	"github.com/VictoriaMetrics/VictoriaMetrics/lib/httpserver"
	"github.com/VictoriaMetrics/VictoriaMetrics/lib/prompbmarshal"
	parserCommon "github.com/VictoriaMetrics/VictoriaMetrics/lib/protoparser/common"
	"github.com/VictoriaMetrics/VictoriaMetrics/lib/protoparser/opentelemetry/firehose"
	"github.com/VictoriaMetrics/VictoriaMetrics/lib/protoparser/opentelemetry/stream"
	"github.com/VictoriaMetrics/metrics"
)

var (
	rowsInserted  = metrics.NewCounter(`vm_rows_inserted_total{type="opentelemetry"}`)
	rowsPerInsert = metrics.NewHistogram(`vm_rows_per_insert{type="opentelemetry"}`)
)

// WriteResponseFn function to write HTTP response data
type WriteResponseFn func(http.ResponseWriter, time.Time, error)

// InsertHandler processes opentelemetry metrics.
func InsertHandler(req *http.Request) (WriteResponseFn, error) {
	isGzipped := req.Header.Get("Content-Encoding") == "gzip"
	var processBody func([]byte) ([]byte, error)
	writeResponse := func(w http.ResponseWriter, _ time.Time, err error) {
		if err == nil {
			w.WriteHeader(http.StatusOK)
		} else {
			httpserver.Errorf(w, req, "%s", err)
		}
	}
	if req.Header.Get("Content-Type") == "application/json" {
		if fhRequestID := req.Header.Get("X-Amz-Firehose-Request-Id"); fhRequestID != "" {
			processBody = firehose.ProcessRequestBody
			writeResponse = func(w http.ResponseWriter, t time.Time, err error) {
				firehose.ResponseWriter(w, t, fhRequestID, err)
			}
		} else {
			return writeResponse, fmt.Errorf("json encoding isn't supported for opentelemetry format. Use protobuf encoding")
		}
	}
	extraLabels, err := parserCommon.GetExtraLabels(req)
	if err != nil {
		return writeResponse, err
	}
	return writeResponse, stream.ParseStream(req.Body, isGzipped, processBody, func(tss []prompbmarshal.TimeSeries) error {
		return insertRows(tss, extraLabels)
	})
}

func insertRows(tss []prompbmarshal.TimeSeries, extraLabels []prompbmarshal.Label) error {
	ctx := common.GetInsertCtx()
	defer common.PutInsertCtx(ctx)

	rowsLen := 0
	for i := range tss {
		rowsLen += len(tss[i].Samples)
	}
	ctx.Reset(rowsLen)
	rowsTotal := 0
	hasRelabeling := relabel.HasRelabeling()
	for i := range tss {
		ts := &tss[i]
		rowsTotal += len(ts.Samples)
		ctx.Labels = ctx.Labels[:0]
		for _, label := range ts.Labels {
			ctx.AddLabel(label.Name, label.Value)
		}
		for _, label := range extraLabels {
			ctx.AddLabel(label.Name, label.Value)
		}
		if hasRelabeling {
			ctx.ApplyRelabeling()
		}
		if len(ctx.Labels) == 0 {
			// Skip metric without labels.
			continue
		}
		ctx.SortLabelsIfNeeded()
		var metricNameRaw []byte
		var err error
		samples := ts.Samples
		for i := range samples {
			r := &samples[i]
			metricNameRaw, err = ctx.WriteDataPointExt(metricNameRaw, ctx.Labels, r.Timestamp, r.Value)
			if err != nil {
				return err
			}
		}
	}
	rowsInserted.Add(rowsTotal)
	rowsPerInsert.Update(float64(rowsTotal))
	return ctx.FlushBufs()
}