// Copyright 2019 The Prometheus Authors
// Licensed 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.

//go:build !nosoftnet
// +build !nosoftnet

package collector

import (
	"fmt"
	"log/slog"
	"strconv"

	"github.com/prometheus/client_golang/prometheus"
	"github.com/prometheus/procfs"
)

type softnetCollector struct {
	fs                procfs.FS
	processed         *prometheus.Desc
	dropped           *prometheus.Desc
	timeSqueezed      *prometheus.Desc
	cpuCollision      *prometheus.Desc
	receivedRps       *prometheus.Desc
	flowLimitCount    *prometheus.Desc
	softnetBacklogLen *prometheus.Desc
	logger            *slog.Logger
}

const (
	softnetSubsystem = "softnet"
)

func init() {
	registerCollector("softnet", defaultEnabled, NewSoftnetCollector)
}

// NewSoftnetCollector returns a new Collector exposing softnet metrics.
func NewSoftnetCollector(logger *slog.Logger) (Collector, error) {
	fs, err := procfs.NewFS(*procPath)
	if err != nil {
		return nil, fmt.Errorf("failed to open procfs: %w", err)
	}

	return &softnetCollector{
		fs: fs,
		processed: prometheus.NewDesc(
			prometheus.BuildFQName(namespace, softnetSubsystem, "processed_total"),
			"Number of processed packets",
			[]string{"cpu"}, nil,
		),
		dropped: prometheus.NewDesc(
			prometheus.BuildFQName(namespace, softnetSubsystem, "dropped_total"),
			"Number of dropped packets",
			[]string{"cpu"}, nil,
		),
		timeSqueezed: prometheus.NewDesc(
			prometheus.BuildFQName(namespace, softnetSubsystem, "times_squeezed_total"),
			"Number of times processing packets ran out of quota",
			[]string{"cpu"}, nil,
		),
		cpuCollision: prometheus.NewDesc(
			prometheus.BuildFQName(namespace, softnetSubsystem, "cpu_collision_total"),
			"Number of collision occur while obtaining device lock while transmitting",
			[]string{"cpu"}, nil,
		),
		receivedRps: prometheus.NewDesc(
			prometheus.BuildFQName(namespace, softnetSubsystem, "received_rps_total"),
			"Number of times cpu woken up received_rps",
			[]string{"cpu"}, nil,
		),
		flowLimitCount: prometheus.NewDesc(
			prometheus.BuildFQName(namespace, softnetSubsystem, "flow_limit_count_total"),
			"Number of times flow limit has been reached",
			[]string{"cpu"}, nil,
		),
		softnetBacklogLen: prometheus.NewDesc(
			prometheus.BuildFQName(namespace, softnetSubsystem, "backlog_len"),
			"Softnet backlog status",
			[]string{"cpu"}, nil,
		),
		logger: logger,
	}, nil
}

// Update gets parsed softnet statistics using procfs.
func (c *softnetCollector) Update(ch chan<- prometheus.Metric) error {
	var cpu string

	stats, err := c.fs.NetSoftnetStat()
	if err != nil {
		return fmt.Errorf("could not get softnet statistics: %w", err)
	}

	for _, cpuStats := range stats {
		cpu = strconv.FormatUint(uint64(cpuStats.Index), 10)

		ch <- prometheus.MustNewConstMetric(
			c.processed,
			prometheus.CounterValue,
			float64(cpuStats.Processed),
			cpu,
		)
		ch <- prometheus.MustNewConstMetric(
			c.dropped,
			prometheus.CounterValue,
			float64(cpuStats.Dropped),
			cpu,
		)
		ch <- prometheus.MustNewConstMetric(
			c.timeSqueezed,
			prometheus.CounterValue,
			float64(cpuStats.TimeSqueezed),
			cpu,
		)
		ch <- prometheus.MustNewConstMetric(
			c.cpuCollision,
			prometheus.CounterValue,
			float64(cpuStats.CPUCollision),
			cpu,
		)
		ch <- prometheus.MustNewConstMetric(
			c.receivedRps,
			prometheus.CounterValue,
			float64(cpuStats.ReceivedRps),
			cpu,
		)
		ch <- prometheus.MustNewConstMetric(
			c.flowLimitCount,
			prometheus.CounterValue,
			float64(cpuStats.FlowLimitCount),
			cpu,
		)
		ch <- prometheus.MustNewConstMetric(
			c.softnetBacklogLen,
			prometheus.GaugeValue,
			float64(cpuStats.SoftnetBacklogLen),
			cpu,
		)
	}

	return nil
}