/
cli.go
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/
cli.go
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package cli
// cli provides a rails-like system for running command-line interface
// web-services without requiring repetitive boilerplate.
import (
"fmt"
"io"
"os"
"os/signal"
"github.com/gigawattio/upstart"
"github.com/gigawattio/web/interfaces"
cliv2 "gopkg.in/urfave/cli.v2"
)
var (
DefaultBindAddr = "127.0.0.1:8080"
DefaultServiceUser = os.Getenv("USER")
)
// Options provider for Cli struct.
type Options struct {
AppName string
Usage string
Version string
Flags []cliv2.Flag
Stdout io.Writer
Stderr io.Writer
WebServiceProvider interfaces.WebServiceProvider
Args []string
ExitOnError bool // Exit on non-nil error during invocation of `Main()`.
}
// Cli provides a command-line-interface in-a-box for web-services.
type Cli struct {
App *cliv2.App
WebServiceProvider interfaces.WebServiceProvider
Args []string
Install bool // NB: Flag variable.
Uninstall bool // NB: Flag variable.
ServiceUser string // NB: Flag variable.
BindAddr string // NB: Flag variable.
ExitOnError bool // true triggers os.exit upon error from Main().
initialized bool
}
func New(options Options) (*Cli, error) {
cli := &Cli{
App: &cliv2.App{
Name: options.AppName,
Version: options.Version,
Usage: options.Usage,
Flags: options.Flags,
Writer: options.Stdout,
ErrWriter: options.Stderr,
},
WebServiceProvider: options.WebServiceProvider,
Args: options.Args,
ExitOnError: options.ExitOnError,
}
if err := cli.Init(); err != nil {
return nil, err
}
return cli, nil
}
// Init performs validation and when possible auto-populates absent fields with
// the `os` package equivalent (e.g. if `cli.App.Writer == nil` then it is set to
// `os.Stderr`) or other default value.
func (cli *Cli) Init() error {
if len(cli.App.Name) == 0 {
return AppNameRequiredError
}
if cli.WebServiceProvider == nil {
return WebServiceProviderRequiredError
}
// Don't change or check anything if already initialized.
if cli.initialized {
return nil
}
// Replace empty fields with default values where possible.
if len(cli.ServiceUser) == 0 {
cli.ServiceUser = DefaultServiceUser
}
if len(cli.BindAddr) == 0 {
cli.BindAddr = DefaultBindAddr
}
// Auto-populate empty fields with os.* equivalents.
if cli.Args == nil {
cli.Args = os.Args
}
if cli.App.ErrWriter == nil {
cli.App.Writer = os.Stdout
}
if cli.App.ErrWriter == nil {
cli.App.ErrWriter = os.Stderr
}
// App flags and action.
if cli.App.Flags == nil {
cli.App.Flags = []cliv2.Flag{}
}
cli.App.Flags = append(
cli.App.Flags,
[]cliv2.Flag{
&cliv2.BoolFlag{
Name: "install",
Usage: fmt.Sprintf("Install %s as a system service", cli.App.Name),
Destination: &cli.Install,
},
&cliv2.BoolFlag{
Name: "uninstall",
Usage: fmt.Sprintf("Uninstall %s as a system service", cli.App.Name),
Destination: &cli.Uninstall,
},
&cliv2.StringFlag{
Name: "user",
Aliases: []string{"u"},
Usage: fmt.Sprintf("Specifies the user to run the %s system service as", cli.App.Name),
Value: cli.ServiceUser,
Destination: &cli.ServiceUser,
},
&cliv2.StringFlag{
Name: "bind",
Aliases: []string{"b"},
Usage: "Set the web-server bind-address and (optionally) port",
Value: cli.BindAddr,
Destination: &cli.BindAddr,
},
}...,
)
// Setup default action
cli.App.Action = cli.DefaultAction
cli.initialized = true // Mark as initialized.
return nil
}
// DefaultAction can be overriden by setting cli.App.Action after invoking
// `Init()`.
func (cli *Cli) DefaultAction(ctx *cliv2.Context) error {
if err := cli.ServiceManagementHandler(); err != nil {
return err
}
if err := cli.RunWeb(ctx); err != nil {
return err
}
return nil
}
// ServiceManagementHandler performs system service management updates.
func (cli *Cli) ServiceManagementHandler() error {
if cli.Uninstall || cli.Install {
if cli.Uninstall {
config := upstart.DefaultConfig(cli.App.Name)
if err := upstart.UninstallService(config); err != nil {
return err
}
}
if cli.Install {
config := upstart.DefaultConfig(cli.App.Name)
config.User = cli.ServiceUser
if err := upstart.InstallService(config); err != nil {
return err
}
}
}
return nil
}
func (cli *Cli) RunWeb(ctx *cliv2.Context) error {
if cli.WebServiceProvider == nil {
return WebServiceProviderRequiredError
}
webService, err := cli.WebServiceProvider(ctx)
if err != nil {
return err
}
if webService == nil {
return NilWebServiceError
}
if err := webService.Start(); err != nil {
return err
}
fmt.Fprintf(cli.App.Writer, "Successfully started web service on addr=%v\n", webService.Addr())
sig := make(chan os.Signal, 1)
signal.Notify(sig, os.Interrupt)
<-sig // Wait for ^C signal.
fmt.Fprintln(cli.App.ErrWriter, "\nInterrupt signal detected, shutting down..")
if err := webService.Stop(); err != nil {
return err
}
return nil
}
func (cli *Cli) Main() error {
// Temporarily disable cliv2 os exiter and redirect ErrWriter to the one for
// this app.
var (
backupOsExiter = cliv2.OsExiter
backupErrWriter = cliv2.ErrWriter
)
cliv2.OsExiter = func(_ int) {}
cliv2.ErrWriter = cli.App.ErrWriter
defer func() {
// Restore backed up values.
cliv2.OsExiter = backupOsExiter
cliv2.ErrWriter = backupErrWriter
}()
if err := cli.App.Run(cli.Args); err != nil {
if cli.ExitOnError {
ErrorExit(cli.App.ErrWriter, err, 1)
} else {
fmt.Fprintln(cli.App.ErrWriter, err.Error())
return err
}
}
return nil
}
func ErrorExit(w io.Writer, err error, statusCode int) {
fmt.Fprintf(w, "error: %s\n", err)
fmt.Fprintf(w, "exiting with status-code=%v\n", statusCode)
os.Exit(statusCode)
}