package native

import (
	"net/http"
	"sync"

	"github.com/VictoriaMetrics/VictoriaMetrics/app/vminsert/common"
	"github.com/VictoriaMetrics/VictoriaMetrics/app/vminsert/relabel"
	"github.com/VictoriaMetrics/VictoriaMetrics/lib/cgroup"
	"github.com/VictoriaMetrics/VictoriaMetrics/lib/logger"
	"github.com/VictoriaMetrics/VictoriaMetrics/lib/prompbmarshal"
	parserCommon "github.com/VictoriaMetrics/VictoriaMetrics/lib/protoparser/common"
	parser "github.com/VictoriaMetrics/VictoriaMetrics/lib/protoparser/native"
	"github.com/VictoriaMetrics/VictoriaMetrics/lib/storage"
	"github.com/VictoriaMetrics/VictoriaMetrics/lib/writeconcurrencylimiter"
	"github.com/VictoriaMetrics/metrics"
)

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

// InsertHandler processes `/api/v1/import/native` request.
func InsertHandler(req *http.Request) error {
	extraLabels, err := parserCommon.GetExtraLabels(req)
	if err != nil {
		return err
	}
	return writeconcurrencylimiter.Do(func() error {
		return parser.ParseStream(req, func(block *parser.Block) error {
			return insertRows(block, extraLabels)
		})
	})
}

func insertRows(block *parser.Block, extraLabels []prompbmarshal.Label) error {
	ctx := getPushCtx()
	defer putPushCtx(ctx)

	// Update rowsInserted and rowsPerInsert before actual inserting,
	// since relabeling can prevent from inserting the rows.
	rowsLen := len(block.Values)
	rowsInserted.Add(rowsLen)
	rowsPerInsert.Update(float64(rowsLen))

	ic := &ctx.Common
	ic.Reset(rowsLen)
	hasRelabeling := relabel.HasRelabeling()
	mn := &block.MetricName
	ic.Labels = ic.Labels[:0]
	ic.AddLabelBytes(nil, mn.MetricGroup)
	for j := range mn.Tags {
		tag := &mn.Tags[j]
		ic.AddLabelBytes(tag.Key, tag.Value)
	}
	for j := range extraLabels {
		label := &extraLabels[j]
		ic.AddLabel(label.Name, label.Value)
	}
	if hasRelabeling {
		ic.ApplyRelabeling()
	}
	if len(ic.Labels) == 0 {
		// Skip metric without labels.
		return nil
	}
	ctx.metricNameBuf = storage.MarshalMetricNameRaw(ctx.metricNameBuf[:0], ic.Labels)
	values := block.Values
	timestamps := block.Timestamps
	if len(timestamps) != len(values) {
		logger.Panicf("BUG: len(timestamps)=%d must match len(values)=%d", len(timestamps), len(values))
	}
	for j, value := range values {
		timestamp := timestamps[j]
		if err := ic.WriteDataPoint(ctx.metricNameBuf, nil, timestamp, value); err != nil {
			return err
		}
	}
	return ic.FlushBufs()
}

type pushCtx struct {
	Common        common.InsertCtx
	metricNameBuf []byte
}

func (ctx *pushCtx) reset() {
	ctx.Common.Reset(0)
	ctx.metricNameBuf = ctx.metricNameBuf[:0]
}

func getPushCtx() *pushCtx {
	select {
	case ctx := <-pushCtxPoolCh:
		return ctx
	default:
		if v := pushCtxPool.Get(); v != nil {
			return v.(*pushCtx)
		}
		return &pushCtx{}
	}
}

func putPushCtx(ctx *pushCtx) {
	ctx.reset()
	select {
	case pushCtxPoolCh <- ctx:
	default:
		pushCtxPool.Put(ctx)
	}
}

var pushCtxPool sync.Pool
var pushCtxPoolCh = make(chan *pushCtx, cgroup.AvailableCPUs())