plugins.go

/*
Copyright 2017 The Kubernetes Authors.

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 plugins

import (
	"fmt"
	"strings"
	"unicode"
)

var (
	// ErrIncompletePlugin indicates plugin is incomplete.
	ErrIncompletePlugin = fmt.Errorf("incomplete plugin descriptor: name, shortDesc and command fields are required")
	// ErrInvalidPluginName indicates plugin name is invalid.
	ErrInvalidPluginName = fmt.Errorf("plugin name can't contain spaces")
	// ErrIncompleteFlag indicates flag is incomplete.
	ErrIncompleteFlag = fmt.Errorf("incomplete flag descriptor: name and desc fields are required")
	// ErrInvalidFlagName indicates flag name is invalid.
	ErrInvalidFlagName = fmt.Errorf("flag name can't contain spaces")
	// ErrInvalidFlagShorthand indicates flag shorthand is invalid.
	ErrInvalidFlagShorthand = fmt.Errorf("flag shorthand must be only one letter")
)

// Plugin is the representation of a CLI extension (plugin).
type Plugin struct {
	Description
	Source
	Context RunningContext `json:"-"`
}

// Description holds everything needed to register a
// plugin as a command. Usually comes from a descriptor file.
type Description struct {
	Name      string  `json:"name"`
	ShortDesc string  `json:"shortDesc"`
	LongDesc  string  `json:"longDesc,omitempty"`
	Example   string  `json:"example,omitempty"`
	Command   string  `json:"command"`
	Flags     []Flag  `json:"flags,omitempty"`
	Tree      Plugins `json:"tree,omitempty"`
}

// Source holds the location of a given plugin in the filesystem.
type Source struct {
	Dir            string `json:"-"`
	DescriptorName string `json:"-"`
}

// Validate validates plugin data.
func (p Plugin) Validate() error {
	if len(p.Name) == 0 || len(p.ShortDesc) == 0 || (len(p.Command) == 0 && len(p.Tree) == 0) {
		return ErrIncompletePlugin
	}
	if strings.Contains(p.Name, " ") {
		return ErrInvalidPluginName
	}
	for _, flag := range p.Flags {
		if err := flag.Validate(); err != nil {
			return err
		}
	}
	for _, child := range p.Tree {
		if err := child.Validate(); err != nil {
			return err
		}
	}
	return nil
}

// IsValid returns true if plugin data is valid.
func (p Plugin) IsValid() bool {
	return p.Validate() == nil
}

// Plugins is a list of plugins.
type Plugins []*Plugin

// Flag describes a single flag supported by a given plugin.
type Flag struct {
	Name      string `json:"name"`
	Shorthand string `json:"shorthand,omitempty"`
	Desc      string `json:"desc"`
	DefValue  string `json:"defValue,omitempty"`
}

// Validate validates flag data.
func (f Flag) Validate() error {
	if len(f.Name) == 0 || len(f.Desc) == 0 {
		return ErrIncompleteFlag
	}
	if strings.Contains(f.Name, " ") {
		return ErrInvalidFlagName
	}
	return f.ValidateShorthand()
}

// ValidateShorthand validates flag shorthand data.
func (f Flag) ValidateShorthand() error {
	length := len(f.Shorthand)
	if length == 0 || (length == 1 && unicode.IsLetter(rune(f.Shorthand[0]))) {
		return nil
	}
	return ErrInvalidFlagShorthand
}

// Shorthanded returns true if flag shorthand data is valid.
func (f Flag) Shorthanded() bool {
	return f.ValidateShorthand() == nil
}