iot_server/internal/pkg/flags/flags.go

/*******************************************************************************
 * Copyright 2020 Intel Corp.
 *
 * 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.
 *******************************************************************************/

package flags

import (
	"flag"
	"fmt"
	"os"
	"regexp"
)

const (
	DefaultConfigProvider = "consul.http://localhost:8500"
	DefaultConfigFile     = "configuration.toml"
)

// Common is an interface that defines AP for the common command-line flags used by most EdgeX services
type Common interface {
	OverwriteConfig() bool
	UseRegistry() bool
	ConfigProviderUrl() string
	Profile() string
	ConfigDirectory() string
	ConfigFileName() string
	Parse([]string)
	Help()
}

// Default is the Default implementation of Common used by most EdgeX services
type Default struct {
	FlagSet           *flag.FlagSet
	additionalUsage   string
	overwriteConfig   bool
	useRegistry       bool
	configProviderUrl string
	profile           string
	configDir         string
	configFileName    string
}

// NewWithUsage returns a Default struct.
func NewWithUsage(additionalUsage string) *Default {
	return &Default{
		FlagSet:         flag.NewFlagSet("", flag.ExitOnError),
		additionalUsage: additionalUsage,
	}
}

// New returns a Default struct with an empty additional usage string.
func New() *Default {
	return NewWithUsage("")
}

// Parse parses the passed in command-lie arguments looking to the default set of common flags
func (d *Default) Parse(arguments []string) {
	// The flags package doesn't allow for String flags to be specified without a value, so to support
	// -cp/-configProvider without value to indicate using default host value we must detect use of this option with
	// out value and insert the default value before parsing the command line options.
	configProviderRE, _ := regexp.Compile("^--?(cp|configProvider)=?")

	for index, option := range arguments {
		if loc := configProviderRE.FindStringIndex(option); loc != nil {
			if option[loc[1]-1] != '=' {
				arguments[index] = "-cp=" + DefaultConfigProvider
			}

			continue
		}
	}

	// Usage is provided by caller, so leaving individual usage blank here so not confusing where if comes from.
	d.FlagSet.StringVar(&d.configProviderUrl, "configProvider", "", "")
	d.FlagSet.StringVar(&d.configProviderUrl, "cp", "", "")
	d.FlagSet.BoolVar(&d.overwriteConfig, "overwrite", false, "")
	d.FlagSet.BoolVar(&d.overwriteConfig, "o", false, "")
	d.FlagSet.StringVar(&d.configFileName, "f", DefaultConfigFile, "")
	d.FlagSet.StringVar(&d.configFileName, "file", DefaultConfigFile, "")
	d.FlagSet.StringVar(&d.profile, "profile", "", "")
	d.FlagSet.StringVar(&d.profile, "p", "", ".")
	d.FlagSet.StringVar(&d.configDir, "confdir", "", "")
	d.FlagSet.StringVar(&d.configDir, "c", "", "")
	d.FlagSet.BoolVar(&d.useRegistry, "registry", false, "")
	d.FlagSet.BoolVar(&d.useRegistry, "r", false, "")

	d.FlagSet.Usage = d.helpCallback

	err := d.FlagSet.Parse(arguments)
	if err != nil {
		fmt.Println(err)
		os.Exit(0)
	}
}

// OverwriteConfig returns whether the local configuration should be pushed (overwrite) into the Configuration provider
func (d *Default) OverwriteConfig() bool {
	return d.overwriteConfig
}

// UseRegistry returns whether the Registry should be used or not
func (d *Default) UseRegistry() bool {
	return d.useRegistry
}

// ConfigProviderUrl returns the url for the Configuration Provider, if one was specified.
func (d *Default) ConfigProviderUrl() string {
	return d.configProviderUrl
}

// Profile returns the profile name to use, if one was specified
func (d *Default) Profile() string {
	return d.profile
}

// ConfigDirectory returns the directory where the config file(s) are located, if it was specified.
func (d *Default) ConfigDirectory() string {
	return d.configDir
}

// ConfigFileName returns the name of the local configuration file
func (d *Default) ConfigFileName() string {
	return d.configFileName
}

// Help displays the usage help message and exit.
func (d *Default) Help() {
	d.helpCallback()
}

// commonHelpCallback displays the help usage message and exits
func (d *Default) helpCallback() {
	fmt.Printf(
		"Usage: %s [options]\n"+
			"Server Options:\n"+
			"    -cp, --configProvider           Indicates to use Configuration Provider service at specified URL.\n"+
			"                                    URL Format: {type}.{protocol}://{host}:{port} ex: consul.http://localhost:8500\n"+
			"    -o, --overwrite                 Overwrite configuration in provider with local configuration\n"+
			"                                    *** Use with cation *** Use will clobber existing settings in provider,\n"+
			"                                    problematic if those settings were edited by hand intentionally\n"+
			"    -f, --file <name>               Indicates name of the local configuration file. Defaults to configuration.toml\n"+
			"    -p, --profile <name>            Indicate configuration profile other than default\n"+
			"    -c, --confdir                   Specify local configuration directory\n"+
			"    -r, --registry                  Indicates service should use Registry.\n"+
			"%s\n"+
			"Common Options:\n"+
			"	-h, --help                      Show this message\n",
		os.Args[0], d.additionalUsage,
	)
	os.Exit(0)
}