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"
)

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

var (
	// FlagHost flag for host
	FlagHost = cli.StringFlag{
		Name:   "host",
		EnvVar: "OHWM_HOST",
		Value:  "127.0.0.1:8085",
		Usage:  "open hardware monitor host [OSHW_HOST]",
	}

	// FlagScheme flag for host
	FlagScheme = cli.StringFlag{
		Name:   "scheme",
		EnvVar: "OHWM_SCHEME",
		Value:  "http",
		Usage:  "open hardware monitor scheme (http/https)",
	}

	// FlagPath flag for path url
	FlagPath = cli.StringFlag{
		Name:   "path",
		EnvVar: "OHWM_PATH",
		Value:  "/data.json",
		Usage:  "open hardware monitor path (ie /data.json)",
	}

	// FlagInterface flag for host
	FlagInterface = cli.StringFlag{
		Name:   "http",
		EnvVar: "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,
		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 {
	a.Client = &client.Client{
		URL: url.URL{
			Scheme: ctx.String("scheme"),
			Host:   ctx.String("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.Print(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(a.Out, "listen on: "+addr)
	return http.ListenAndServe(addr, nil)
}

// HandleMetrics handler
func (a *App) HandleMetrics(resp http.ResponseWriter, req *http.Request) {
	log.Println("GET /metrics")
	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)
}