func (p *ListParam) New() Param {
	return &ListParam{p.paramCommon, p.el, nil}
}
New clones this parameter
package schema
import (
	"encoding/json"
	"fmt"
	"go/ast"
	"go/parser"
	"io"
	"strconv"
	"strings"
	"github.com/gravitational/configure/cstrings"
	"github.com/gravitational/trace"
	"gopkg.in/alecthomas/kingpin.v2"
)
func ParseJSON(r io.Reader) (*Config, error) {
	var c *configV1
	if err := json.NewDecoder(r).Decode(&c); err != nil {
		return nil, trace.Wrap(err)
	}
	return newParser().parse(*c)
}
func ParseVariablesJSON(r io.Reader) (*Config, error) {
	var variables []paramSpec
	if err := json.NewDecoder(r).Decode(&variables); err != nil {
		return nil, trace.Wrap(err)
	}
	return newParser().parse(configV1{Params: variables})
}
type Config struct {
	Params []Param
}
func (c *Config) Vars() map[string]string {
	vars := make(map[string]string, len(c.Params))
	for _, p := range c.Params {
		k, v := p.Vars()
		vars[k] = v
	}
	return vars
}
func (c *Config) EnvVars() map[string]string {
	vars := make(map[string]string, len(c.Params))
	for _, p := range c.Params {
		k, v := p.EnvVars()
		vars[k] = v
	}
	return vars
}
func (c *Config) Args() []string {
	args := []string{}
	for _, p := range c.Params {
		args = append(args, p.Args()...)
	}
	return args
}
func (c *Config) ParseArgs(args []string) error {
	app := cliApp(c, false)
	_, err := app.Parse(args)
	return err
}
func (c *Config) ParseEnv() error {
	app := cliApp(c, true)
	_, err := app.Parse([]string{})
	return err
}
func (c *Config) ParseVars(vars map[string]string) error {
	for _, p := range c.Params {
		val, ok := vars[p.Name()]
		if !ok {
			if p.Required() {
				return trace.Errorf("missing value for required variable: %v", p.Name())
			} else {
				val = p.Default()
			}
		}
		if err := p.Set(val); err != nil {
			return trace.Wrap(err)
		}
	}
	return nil
}
func cliApp(c *Config, useEnv bool) *kingpin.Application {
	app := kingpin.New("app", "Orbit package configuration tool")
	for _, p := range c.Params {
		cliFlag(app, p, useEnv)
	}
	return app
}
func cliFlag(app *kingpin.Application, p Param, useEnv bool) {
	name := p.CLIName()
	f := app.Flag(name, p.Description())
	if p.Required() {
		f = f.Required()
	}
	if p.Default() != "" {
		f = f.Default(p.Default())
	}
	if useEnv {
		f.OverrideDefaultFromEnvar(p.EnvName())
	}
	SetParam(p, f)
}
func SetParam(p Param, s kingpin.Settings) {
	s.SetValue(p)
}
type Param interface {
	Name() string
	CLIName() string
	Description() string
	Check() string
	Required() bool
	Default() string
	New() Param
	Set(string) error
	String() string
	Args() []string
	EnvVars() (string, string)
	Vars() (string, string)
	EnvName() string
}
func newParser() *cparser {
	return &cparser{
		params: []Param{},
	}
}
type cparser struct {
	params []Param
}
func (p *cparser) parse(c configV1) (*Config, error) {
	cfg := &Config{
		Params: make([]Param, len(c.Params)),
	}
	if len(c.Params) != 0 {
		for i, ts := range c.Params {
			pr, err := p.parseParam(ts, false)
			if err != nil {
				return nil, err
			}
			cfg.Params[i] = pr
		}
	}
	return cfg, nil
}
func (p *cparser) parseParam(s paramSpec, scalar bool) (Param, error) {
	if s.Name == "" {
		return nil, trace.Errorf("set a type name")
	}
	if err := p.checkName(s.Name); err != nil {
		return nil, err
	}
	if s.Type == "" {
		return nil, trace.Errorf("set a type for '%v'", s.Name)
	}
	switch s.Type {
	case "String":
		pr := &StringParam{}
		pr.paramCommon = s.common()
		return pr, nil
	case "Path":
		pr := &PathParam{}
		pr.paramCommon = s.common()
		return pr, nil
	case "Int":
		pr := &IntParam{}
		pr.paramCommon = s.common()
		return pr, nil
	case "Bool":
		pr := &BoolParam{}
		pr.paramCommon = s.common()
		return pr, nil
	case "KeyVal":
		return p.parseKeyVal(s)
	case "Enum":
		return p.parseEnum(s)
	case "List":
		if scalar {
			return nil, trace.Errorf(
				"scalar values are not allowed here: '%v'", s.Type)
		}
		return p.parseList(s)
	}
	return nil, trace.Errorf("unrecognized type: '%v'", s.Type)
}
func (p *cparser) parseList(s paramSpec) (Param, error) {
	var ps *paramSpec
	if err := json.Unmarshal(s.S, &ps); err != nil {
		return nil, trace.Wrap(err, "failed to parse: '%v'", string(s.S))
	}
	el, err := p.parseParam(*ps, false)
	if err != nil {
		return nil, err
	}
	l := &ListParam{el: el}
	l.paramCommon = s.common()
	return l, nil
}
func (p *cparser) parseEnum(s paramSpec) (Param, error) {
	var e *enumSpec
	if err := json.Unmarshal(s.S, &e); err != nil {
		return nil, trace.Wrap(
			err, fmt.Sprintf("failed to parse: '%v'", string(s.S)))
	}
	if len(e.Values) == 0 {
		return nil, trace.Errorf("provide at least one value for '%v'", s.Name)
	}
	values := make([]string, len(e.Values))
	seen := make(map[string]bool, len(e.Values))
	for i, v := range e.Values {
		if v == "" {
			return nil, trace.Errorf("value can not be an empty string")
		}
		if seen[v] {
			return nil, trace.Errorf("duplicate value: '%v'", v)
		}
		values[i] = v
	}
	ep := &EnumParam{values: values}
	ep.paramCommon = s.common()
	return ep, nil
}
func (p *cparser) parseKeyVal(s paramSpec) (Param, error) {
	var k *kvSpec
	if err := json.Unmarshal(s.S, &k); err != nil {
		return nil, trace.Wrap(
			err, fmt.Sprintf("failed to parse: '%v'", string(s.S)))
	}
	if len(k.Keys) == 0 {
		return nil, trace.Errorf("provide at least one key for '%v'", s.Name)
	}
	keys := make([]Param, len(k.Keys))
	for i, ks := range k.Keys {
		k, err := p.parseParam(ks, true)
		if err != nil {
			return nil, err
		}
		keys[i] = k
	}
	if err := checkSameNames(keys); err != nil {
		return nil, err
	}
	kv := &KVParam{keys: keys, separator: k.Separator}
	kv.paramCommon = s.common()
	return kv, nil
}
func (p *cparser) checkName(n string) error {
	for _, pr := range p.params {
		if pr.Name() == n {
			return trace.Errorf("parameter '%v' is already defined", n)
		}
	}
	e, err := parser.ParseExpr(n)
	if err != nil {
		return trace.Wrap(
			err, fmt.Sprintf("failed to parse name: '%v'", n))
	}
	if _, ok := e.(*ast.Ident); !ok {
		return trace.Wrap(
			err, fmt.Sprintf("name should be a valid identifier: '%v'", n))
	}
	return nil
}
func checkSameNames(ps []Param) error {
	n := map[string]bool{}
	for _, p := range ps {
		if n[p.Name()] {
			return trace.Errorf("parameter '%v' is already defined", n)
		}
		n[p.Name()] = true
	}
	return nil
}
type PathParam struct {
	paramCommon
	val *string
}
func (p *PathParam) New() Param {
	return &PathParam{p.paramCommon, nil}
}
func (p *PathParam) Args() []string {
	return []string{fmt.Sprintf("--%v", p.CLIName()), p.String()}
}
func (p *PathParam) EnvVars() (string, string) {
	return p.EnvName(), p.String()
}
func (p *PathParam) Vars() (string, string) {
	return p.Name(), p.String()
}
func (p *PathParam) Set(s string) error {
	p.val = &s
	return nil
}
func (p *PathParam) String() string {
	if p.val == nil {
		return p.Default()
	}
	return *p.val
}
type StringParam struct {
	paramCommon
	val *string
}
func (p *StringParam) New() Param {
	return &StringParam{p.paramCommon, nil}
}
func (p *StringParam) Set(s string) error {
	p.val = &s
	return nil
}
func (p *StringParam) String() string {
	if p.val == nil {
		return p.Default()
	}
	return *p.val
}
func (p *StringParam) Args() []string {
	return []string{fmt.Sprintf("--%v", p.CLIName()), p.String()}
}
func (p *StringParam) EnvVars() (string, string) {
	return p.EnvName(), p.String()
}
func (p *StringParam) Vars() (string, string) {
	return p.Name(), p.String()
}
type BoolParam struct {
	paramCommon
	val *bool
}
func (p *BoolParam) New() Param {
	return &BoolParam{p.paramCommon, nil}
}
func (p *BoolParam) Vars() (string, string) {
	return p.Name(), p.String()
}
func (p *BoolParam) Set(s string) error {
	v, err := strconv.ParseBool(s)
	if err != nil {
		return err
	}
	p.val = &v
	return nil
}
func (p *BoolParam) String() string {
	if p.val == nil {
		return "false"
	}
	return fmt.Sprintf("%v", *p.val)
}
func (p *BoolParam) Args() []string {
	return []string{fmt.Sprintf("--%v", p.CLIName()), p.String()}
}
func (p *BoolParam) EnvVars() (string, string) {
	return p.EnvName(), p.String()
}
type IntParam struct {
	paramCommon
	val *int64
}
func (p *IntParam) Set(s string) error {
	v, err := strconv.ParseInt(s, 0, 64)
	if err != nil {
		return err
	}
	p.val = &v
	return nil
}
func (p *IntParam) String() string {
	if p.val == nil {
		return p.Default()
	}
	return fmt.Sprintf("%v", *p.val)
}
func (p *IntParam) New() Param {
	return &IntParam{p.paramCommon, nil}
}
func (p *IntParam) Args() []string {
	return []string{fmt.Sprintf("--%v", p.CLIName()), p.String()}
}
func (p *IntParam) EnvVars() (string, string) {
	return p.EnvName(), p.String()
}
func (p *IntParam) Vars() (string, string) {
	return p.Name(), p.String()
}
type ListParam struct {
	paramCommon
	el     Param
	values []Param
}
func (p *ListParam) CLIName() string {
	return p.el.CLIName()
}
func (p *ListParam) EnvName() string {
	return p.el.EnvName()
}
func (p *ListParam) Set(s string) error {
	values := cstrings.Split(',', '\\', s)
	for _, v := range values {
		el := p.el.New()
		if err := el.Set(v); err != nil {
			return err
		}
		p.values = append(p.values, el)
	}
	return nil
}