// +build !nodiskstats

package collector

import (
	"errors"
	"fmt"

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

/*
#cgo LDFLAGS: -ldevstat -lkvm
#include <devstat.h>
#include <fcntl.h>
#include <libgeom.h>
#include <limits.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

typedef struct {
	uint64_t	read;
	uint64_t	write;
	uint64_t	free;
} Bytes;

typedef struct {
	uint64_t	other;
	uint64_t	read;
	uint64_t	write;
	uint64_t	free;
} Transfers;

typedef struct {
	double		other;
	double		read;
	double		write;
	double		free;
} Duration;

typedef struct {
	char		device[DEVSTAT_NAME_LEN];
	int		unit;
	Bytes		bytes;
	Transfers	transfers;
	Duration	duration;
	long		busyTime;
	uint64_t	blocks;
} Stats;

int _get_ndevs() {
	struct statinfo current;
	int num_devices;

	current.dinfo = (struct devinfo *)calloc(1, sizeof(struct devinfo));
	if (current.dinfo == NULL)
		return -2;

	devstat_checkversion(NULL);

	if (devstat_getdevs(NULL, &current) == -1)
		return -1;

	return current.dinfo->numdevs;
}

Stats _get_stats(int i) {
	struct statinfo current;
	int num_devices;

	current.dinfo = (struct devinfo *)calloc(1, sizeof(struct devinfo));
	devstat_getdevs(NULL, &current);

	num_devices = current.dinfo->numdevs;
	Stats stats;
	uint64_t bytes_read, bytes_write, bytes_free;
	uint64_t transfers_other, transfers_read, transfers_write, transfers_free;
	long double duration_other, duration_read, duration_write, duration_free;
	long double busy_time;
	uint64_t blocks;

	strcpy(stats.device, current.dinfo->devices[i].device_name);
	stats.unit = current.dinfo->devices[i].unit_number;
	devstat_compute_statistics(&current.dinfo->devices[i],
		NULL,
		1.0,
		DSM_TOTAL_BYTES_READ, &bytes_read,
		DSM_TOTAL_BYTES_WRITE, &bytes_write,
		DSM_TOTAL_BYTES_FREE, &bytes_free,
		DSM_TOTAL_TRANSFERS_OTHER, &transfers_other,
		DSM_TOTAL_TRANSFERS_READ, &transfers_read,
		DSM_TOTAL_TRANSFERS_WRITE, &transfers_write,
		DSM_TOTAL_TRANSFERS_FREE, &transfers_free,
		DSM_TOTAL_DURATION_OTHER, &duration_other,
		DSM_TOTAL_DURATION_READ, &duration_read,
		DSM_TOTAL_DURATION_WRITE, &duration_write,
		DSM_TOTAL_DURATION_FREE, &duration_free,
		DSM_TOTAL_BUSY_TIME, &busy_time,
		DSM_TOTAL_BLOCKS, &blocks,
		DSM_NONE);

	stats.bytes.read = bytes_read;
	stats.bytes.write = bytes_write;
	stats.bytes.free = bytes_free;
	stats.transfers.other = transfers_other;
	stats.transfers.read = transfers_read;
	stats.transfers.write = transfers_write;
	stats.transfers.free = transfers_free;
	stats.duration.other = duration_other;
	stats.duration.read = duration_read;
	stats.duration.write = duration_write;
	stats.duration.free = duration_free;
	stats.busyTime = busy_time;
	stats.blocks = blocks;

	return stats;
}
*/
import "C"

const (
	devstatSubsystem = "devstat"
)

type devstatCollector struct {
	bytes     *prometheus.GaugeVec
	transfers *prometheus.GaugeVec
	duration  *prometheus.GaugeVec
	busyTime  *prometheus.GaugeVec
	blocks    *prometheus.GaugeVec
}

func init() {
	Factories["devstat"] = NewDevstatCollector
}

// device stats.
func NewDevstatCollector() (Collector, error) {
	//var diskLabelNames = []string{"device"}
	//var ioType = []string{"type"}

	return &devstatCollector{
		// Docs from https://www.kernel.org/doc/Documentation/iostats.txt
		bytes: prometheus.NewGaugeVec(
			prometheus.GaugeOpts{
				Namespace: Namespace,
				Subsystem: devstatSubsystem,
				Name:      "bytes",
				Help:      "The total number of bytes transferred",
			},
			[]string{"device", "type"},
		),
		transfers: prometheus.NewGaugeVec(
			prometheus.GaugeOpts{
				Namespace: Namespace,
				Subsystem: devstatSubsystem,
				Name:      "transfers",
				Help:      "The total number of transactions",
			},
			[]string{"device", "type"},
		),
		duration: prometheus.NewGaugeVec(
			prometheus.GaugeOpts{
				Namespace: Namespace,
				Subsystem: devstatSubsystem,
				Name:      "duration",
				Help:      "The total duration of transactions",
			},
			[]string{"device", "type"},
		),
		busyTime: prometheus.NewGaugeVec(
			prometheus.GaugeOpts{
				Namespace: Namespace,
				Subsystem: devstatSubsystem,
				Name:      "busy_time",
				Help:      "Total time the device had one or more transactions outstanding",
			},
			[]string{"device"},
		),
		blocks: prometheus.NewGaugeVec(
			prometheus.GaugeOpts{
				Namespace: Namespace,
				Subsystem: devstatSubsystem,
				Name:      "blocks",
				Help:      "The total number of blocks transferred",
			},
			[]string{"device"},
		),
	}, nil
}

func (c *devstatCollector) Update(ch chan<- prometheus.Metric) (err error) {
	/*
		var busyTime [3]C.longlong
		var blocks [3]C.uint64_t
		var kbPerTransfer [3]C.longlong
		var transfersPerSecond [3]C.longlong
		var mbPerSecond [3]C.longlong
		var blocksPerSecond [3]C.longlong
		var msPerTransaction [3]C.longlong
		var busyPCT C.longlong
		var queueLength C.uint64_t

	*/
	count := C._get_ndevs()
	if count == -1 {
		return errors.New("devstat_getdevs() failed!")
	}
	if count == -2 {
		return errors.New("calloc() failed!")
	}

	for i := C.int(0); i < count; i++ {
		stats := C._get_stats(i)
		device := fmt.Sprintf("%s%d", C.GoString(&stats.device[0]), stats.unit)
		c.bytes.With(prometheus.Labels{"device": device, "type": "read"}).Set(float64(stats.bytes.read))
		c.bytes.With(prometheus.Labels{"device": device, "type": "write"}).Set(float64(stats.bytes.write))
		c.bytes.With(prometheus.Labels{"device": device, "type": "free"}).Set(float64(stats.bytes.free))
		c.transfers.With(prometheus.Labels{"device": device, "type": "other"}).Set(float64(stats.transfers.other))
		c.transfers.With(prometheus.Labels{"device": device, "type": "read"}).Set(float64(stats.transfers.read))
		c.transfers.With(prometheus.Labels{"device": device, "type": "write"}).Set(float64(stats.transfers.write))
		c.transfers.With(prometheus.Labels{"device": device, "type": "free"}).Set(float64(stats.transfers.free))
		c.duration.With(prometheus.Labels{"device": device, "type": "other"}).Set(float64(stats.duration.other))
		c.duration.With(prometheus.Labels{"device": device, "type": "read"}).Set(float64(stats.duration.read))
		c.duration.With(prometheus.Labels{"device": device, "type": "write"}).Set(float64(stats.duration.write))
		c.duration.With(prometheus.Labels{"device": device, "type": "free"}).Set(float64(stats.duration.free))
		c.busyTime.With(prometheus.Labels{"device": device}).Set(float64(stats.busyTime))
		c.blocks.With(prometheus.Labels{"device": device}).Set(float64(stats.blocks))
	}

	c.bytes.Collect(ch)
	c.transfers.Collect(ch)
	c.duration.Collect(ch)
	c.busyTime.Collect(ch)
	c.blocks.Collect(ch)

	return err
}