// Copyright 2018 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.

// Scrape `information_schema.INNODB_CMP`.

package collector

import (
	"context"
	"database/sql"

	"github.com/go-kit/log"
	"github.com/prometheus/client_golang/prometheus"
)

const innodbCmpQuery = `
		SELECT
		  page_size, compress_ops, compress_ops_ok, compress_time, uncompress_ops, uncompress_time
		  FROM information_schema.innodb_cmp
		`

// Metric descriptors.
var (
	infoSchemaInnodbCmpCompressOps = prometheus.NewDesc(
		prometheus.BuildFQName(namespace, informationSchema, "innodb_cmp_compress_ops_total"),
		"Number of times a B-tree page of the size PAGE_SIZE has been compressed.",
		[]string{"page_size"}, nil,
	)
	infoSchemaInnodbCmpCompressOpsOk = prometheus.NewDesc(
		prometheus.BuildFQName(namespace, informationSchema, "innodb_cmp_compress_ops_ok_total"),
		"Number of times a B-tree page of the size PAGE_SIZE has been successfully compressed.",
		[]string{"page_size"}, nil,
	)
	infoSchemaInnodbCmpCompressTime = prometheus.NewDesc(
		prometheus.BuildFQName(namespace, informationSchema, "innodb_cmp_compress_time_seconds_total"),
		"Total time in seconds spent in attempts to compress B-tree pages.",
		[]string{"page_size"}, nil,
	)
	infoSchemaInnodbCmpUncompressOps = prometheus.NewDesc(
		prometheus.BuildFQName(namespace, informationSchema, "innodb_cmp_uncompress_ops_total"),
		"Number of times a B-tree page of the size PAGE_SIZE has been uncompressed.",
		[]string{"page_size"}, nil,
	)
	infoSchemaInnodbCmpUncompressTime = prometheus.NewDesc(
		prometheus.BuildFQName(namespace, informationSchema, "innodb_cmp_uncompress_time_seconds_total"),
		"Total time in seconds spent in uncompressing B-tree pages.",
		[]string{"page_size"}, nil,
	)
)

// ScrapeInnodbCmp collects from `information_schema.innodb_cmp`.
type ScrapeInnodbCmp struct{}

// Name of the Scraper. Should be unique.
func (ScrapeInnodbCmp) Name() string {
	return informationSchema + ".innodb_cmp"
}

// Help describes the role of the Scraper.
func (ScrapeInnodbCmp) Help() string {
	return "Collect metrics from information_schema.innodb_cmp"
}

// Version of MySQL from which scraper is available.
func (ScrapeInnodbCmp) Version() float64 {
	return 5.5
}

// Scrape collects data from database connection and sends it over channel as prometheus metric.
func (ScrapeInnodbCmp) Scrape(ctx context.Context, db *sql.DB, ch chan<- prometheus.Metric, logger log.Logger) error {
	informationSchemaInnodbCmpRows, err := db.QueryContext(ctx, innodbCmpQuery)
	if err != nil {
		return err
	}
	defer informationSchemaInnodbCmpRows.Close()

	var (
		page_size                                                                     string
		compress_ops, compress_ops_ok, compress_time, uncompress_ops, uncompress_time float64
	)

	for informationSchemaInnodbCmpRows.Next() {
		if err := informationSchemaInnodbCmpRows.Scan(
			&page_size, &compress_ops, &compress_ops_ok, &compress_time, &uncompress_ops, &uncompress_time,
		); err != nil {
			return err
		}

		ch <- prometheus.MustNewConstMetric(infoSchemaInnodbCmpCompressOps, prometheus.CounterValue, compress_ops, page_size)
		ch <- prometheus.MustNewConstMetric(infoSchemaInnodbCmpCompressOpsOk, prometheus.CounterValue, compress_ops_ok, page_size)
		ch <- prometheus.MustNewConstMetric(infoSchemaInnodbCmpCompressTime, prometheus.CounterValue, compress_time, page_size)
		ch <- prometheus.MustNewConstMetric(infoSchemaInnodbCmpUncompressOps, prometheus.CounterValue, uncompress_ops, page_size)
		ch <- prometheus.MustNewConstMetric(infoSchemaInnodbCmpUncompressTime, prometheus.CounterValue, uncompress_time, page_size)
	}

	return nil
}

// check interface
var _ Scraper = ScrapeInnodbCmp{}
