feat: implement ping command (#31)

* build: use deepmap/oapi-codegen to generate an HTTP client
* feat: add global CLI options
* feat: load local config to find host and token
* feat: implement ping command
* test: add unit tests for ping command

cmd/influx/main.go

@@ -1,19 +1,103 @@
 package main
 
 import (
+	"context"
+	"crypto/tls"
 	"fmt"
+	"net/http"
 	"os"
+	"runtime"
 	"time"
 
+	"github.com/influxdata/influx-cli/v2/internal"
+	"github.com/influxdata/influx-cli/v2/internal/api"
+	"github.com/influxdata/influx-cli/v2/internal/config"
 	"github.com/urfave/cli/v2"
 )
 
+// Fields set via ldflags at build time.
 var (
 	version = "dev"
 	commit  = "none"
 	date    = ""
 )
 
+var (
+	tokenFlag      = "token"
+	hostFlag       = "host"
+	skipVerifyFlag = "skip-verify"
+	traceIdFlag    = "trace-debug-id"
+	configPathFlag = "config-path"
+	configNameFlag = "active-config"
+)
+
+// loadConfig reads CLI configs from disk, returning the config with the
+// name specified over the CLI (or default if no name was given).
+func loadConfig(ctx *cli.Context) (config.Config, error) {
+	configs := config.GetConfigsOrDefault(ctx.String(configPathFlag))
+	configName := ctx.String(configNameFlag)
+	if configName != "" {
+		if err := configs.Switch(configName); err != nil {
+			return config.Config{}, err
+		}
+	}
+	return configs.Active(), nil
+}
+
+// newApiClient returns an API client configured to communicate with a remote InfluxDB instance over HTTP.
+// Client parameters are pulled from the CLI context.
+func newApiClient(ctx *cli.Context, injectToken bool) (api.ClientWithResponsesInterface, error) {
+	cfg, err := loadConfig(ctx)
+	if err != nil {
+		return nil, err
+	}
+	if ctx.IsSet(tokenFlag) {
+		cfg.Token = ctx.String(tokenFlag)
+	}
+	if ctx.IsSet(hostFlag) {
+		cfg.Host = ctx.String(hostFlag)
+	}
+
+	clientTransport := http.DefaultTransport.(*http.Transport)
+	clientTransport.TLSClientConfig = &tls.Config{InsecureSkipVerify: ctx.Bool(skipVerifyFlag)}
+
+	client := &http.Client{Transport: clientTransport}
+	userAgent := fmt.Sprintf("influx/%s (%s) Sha/%s Date/%s", version, runtime.GOOS, commit, date)
+
+	opts := []api.ClientOption{
+		api.WithHTTPClient(client),
+		api.WithRequestEditorFn(func(_ context.Context, req *http.Request) error {
+			req.Header.Set("User-Agent", userAgent)
+			return nil
+		}),
+	}
+	if injectToken {
+		authHeader := fmt.Sprintf("Token %s", cfg.Token)
+		opts = append(opts, api.WithRequestEditorFn(func(_ context.Context, req *http.Request) error {
+			req.Header.Set("Authorization", authHeader)
+			return nil
+		}))
+	}
+
+	return api.NewClientWithResponses(cfg.Host, opts...)
+}
+
+// newCli builds a CLI core that reads from stdin, writes to stdout/stderr, and
+// optionally tracks a trace ID specified over the CLI.
+func newCli(ctx *cli.Context) *internal.CLI {
+	var traceId *api.TraceSpan
+	if ctx.IsSet(traceIdFlag) {
+		tid := api.TraceSpan(ctx.String(traceIdFlag))
+		traceId = &tid
+	}
+	return &internal.CLI{
+		Stdin:   ctx.App.Reader,
+		Stdout:  ctx.App.Writer,
+		Stderr:  ctx.App.ErrWriter,
+		TraceId: traceId,
+	}
+}
+
 func main() {
 	if len(date) == 0 {
 		date = time.Now().UTC().Format(time.RFC3339)
@@ -21,6 +105,46 @@ func main() {
 
 	cli.VersionFlag = nil
 
+	// NOTE: urfave/cli has dedicated support for global flags, but it only parses those flags
+	// if they're specified before any command names. This is incompatible with the old influx
+	// CLI, which repeatedly registered common flags on every "leaf" command, forcing the flags
+	// to be specified after _all_ command names were given.
+	//
+	// We replicate the pattern from the old CLI so existing scripts and docs stay valid.
+	commonFlags := []cli.Flag{
+		&cli.StringFlag{
+			Name:    tokenFlag,
+			Usage:   "Authentication token",
+			Aliases: []string{"t"},
+			EnvVars: []string{"INFLUX_TOKEN"},
+		},
+		&cli.StringFlag{
+			Name:    hostFlag,
+			Usage:   "HTTP address of InfluxDB",
+			EnvVars: []string{"INFLUX_HOST"},
+		},
+		&cli.BoolFlag{
+			Name:  skipVerifyFlag,
+			Usage: "Skip TLS certificate chain and host name verification",
+		},
+		&cli.StringFlag{
+			Name:    configPathFlag,
+			Usage:   "Path to the influx CLI configurations",
+			EnvVars: []string{"INFLUX_CLI_CONFIGS_PATH"},
+		},
+		&cli.StringFlag{
+			Name:    configNameFlag,
+			Usage:   "Config name to use for command",
+			Aliases: []string{"c"},
+			EnvVars: []string{"INFLUX_ACTIVE_CONFIG"},
+		},
+		&cli.StringFlag{
+			Name:    traceIdFlag,
+			Hidden:  true,
+			EnvVars: []string{"INFLUX_TRACE_DEBUG_ID"},
+		},
+	}
+
 	app := cli.App{
 		Name:      "influx",
 		Usage:     "Influx Client",
@@ -34,6 +158,18 @@ func main() {
 					return nil
 				},
 			},
+			{
+				Name:  "ping",
+				Usage: "Check the InfluxDB /health endpoint",
+				Flags: commonFlags,
+				Action: func(ctx *cli.Context) error {
+					client, err := newApiClient(ctx, false)
+					if err != nil {
+						return err
+					}
+					return newCli(ctx).Ping(ctx.Context, client)
+				},
+			},
 		},
 	}