open-hardware-monitor-client/lib/app/app.go

package app

import (
	"fmt"
	"io"
	"log"
	"net/http"
	"net/url"
	"os"

	"git.buddy.wtf/buddy/open-hardware-monitor-client/lib/client"
	"git.buddy.wtf/buddy/open-hardware-monitor-client/lib/metrics"
	"github.com/prometheus/client_golang/prometheus"
	"github.com/prometheus/client_golang/prometheus/promhttp"
	"github.com/urfave/cli/v2"
)

// App context
type App struct {
	cli    *cli.App
	Client *client.Client
	Out    io.Writer
}

// FlagHost flag for host
var FlagHost = &cli.StringFlag{
	Name:    "host",
	EnvVars: []string{"OHWM_HOST"},
	Value:   "127.0.0.1",
	Usage:   "open hardware monitor host [OSHW_HOST]",
}

// FlagPort flag for host
var FlagPort = &cli.IntFlag{
	Name:    "port",
	EnvVars: []string{"OHWM_PORT"},
	Value:   8085,
	Usage:   "open hardware port [OSHW_PORT]",
}

// FlagScheme flag for host
var FlagScheme = &cli.StringFlag{
	Name:    "scheme",
	EnvVars: []string{"OHWM_SCHEME"},
	Value:   "http",
	Usage:   "open hardware monitor scheme (http/https)",
}

// FlagPath flag for path url
var FlagPath = &cli.StringFlag{
	Name:    "path",
	EnvVars: []string{"OHWM_PATH"},
	Value:   "/data.json",
	Usage:   "open hardware monitor path (ie /data.json)",
}

// FlagInterface flag for host
var FlagInterface = &cli.StringFlag{
	Name:    "http",
	EnvVars: []string{"OHWM_HTTP"},
	Value:   ":9200",
	Usage:   "interface to serve http requests",
}

// New returns instance of an app
func New() *App {
	cliapp := cli.NewApp()
	app := &App{
		Out: os.Stdout,
		cli: cliapp,
	}

	app.cli.Name = "ohwm-client"
	app.cli.Description = "Open Hardware Manager Client"
	app.cli.UsageText = "ohwm-client [flags] <command> [flags]"
	app.cli.HideVersion = true

	app.cli.Flags = []cli.Flag{
		FlagHost,
		FlagPort,
		FlagScheme,
		FlagPath,
	}

	app.cli.Commands = []*cli.Command{
		&cli.Command{
			Name:   "print",
			Usage:  "pretty prints api result",
			Action: app.ActionPrint,
		},
		&cli.Command{
			Name:   "export",
			Usage:  "runs http exporter for prometheus",
			Action: app.ActionMetrics,
			Flags: []cli.Flag{
				FlagInterface,
			},
		},
	}

	app.cli.Before = app.Before
	return app
}

// Run runs cli action
func (a *App) Run(args []string) error {
	return a.cli.Run(args)
}

// Before sets up app
func (a *App) Before(ctx *cli.Context) error {
	host := fmt.Sprintf("%s:%d", ctx.String("host"), ctx.Int("port"))
	a.Client = &client.Client{
		URL: url.URL{
			Scheme: ctx.String("scheme"),
			Host:   host,
			Path:   ctx.String("path"),
		},
	}
	return nil
}

// ActionPrint prints api result
func (a *App) ActionPrint(_ *cli.Context) error {
	node, err := a.Client.Fetch()
	if err != nil {
		return err
	}
	fmt.Fprint(a.Out, node.Stringify())
	return nil
}

// ActionMetrics serves http
func (a *App) ActionMetrics(ctx *cli.Context) error {
	addr := ctx.String("http")
	http.HandleFunc("/metrics", a.HandleMetrics)
	log.Println("listen on: " + addr)
	return http.ListenAndServe(addr, nil)
}

// HandleMetrics handler
func (a *App) HandleMetrics(resp http.ResponseWriter, req *http.Request) {
	root, err := a.Client.Fetch()
	if err != nil {
		http.Error(resp, err.Error(), http.StatusInternalServerError)
		return
	}
	vals, err := root.Values()
	if err != nil {
		http.Error(resp, err.Error(), http.StatusInternalServerError)
		return
	}

	collection := metrics.FromVals(vals)
	registry := prometheus.NewRegistry()
	if err := registry.Register(collection); err != nil {
		http.Error(resp, err.Error(), http.StatusInternalServerError)
		return
	}

	handler := promhttp.HandlerFor(registry, promhttp.HandlerOpts{
		Registry: registry,
	})

	handler.ServeHTTP(resp, req)
	registry.Unregister(collection)
}