fairwind/commandline.go

package fairwind

import (
	"encoding/json"
	"fmt"
	"os"
	"reflect"
	"strings"
)

type CommandHandler func(Parameters) error

type Parameter struct {
	Kind     reflect.Kind
	Required bool
	Value    reflect.Value `json:"-"`
}

type Parameters map[string]*Parameter

type Command struct {
	Name          string
	Documentation string
	Parameters    Parameters
	Handler       CommandHandler `json:"-"`
	Commands      []Command
}

func (this *Command) Execute() {
	parts := os.Args[1:]

	if len(parts) == 0 {
		this.manual()
		return
	}

	currentCommand := this
	index := -1
	for i, part := range parts {
		if strings.Contains(part, "--") {
			index = i
			break
		}

		found := false
		for _, iteratedCommand := range currentCommand.Commands {
			if iteratedCommand.Name != part {
				continue
			}

			currentCommand = &iteratedCommand
			found = true
			break
		}

		if !found {
			fmt.Println("Command not found")
			os.Exit(1)
		}
	}

	parameters := Parameters{}
	fail := false

	if index >= 0 {
		for i := index; i < len(parts); i++ {
			part := parts[i]
			keyValue := strings.Split(part, "=")
			if len(keyValue) != 2 {
				fmt.Printf("Invalid argument: %s\n", part)
				os.Exit(1)
			}

			key := keyValue[0]
			value := keyValue[1]

			parameter, ok := currentCommand.Parameters[key]
			if !ok {
				fmt.Printf("Invalid argument: %s=%s\n", key, value)
				fail = true
				continue
			}

			switch parameter.Kind {
			case reflect.String:
				parameters[key[2:]] = &Parameter{
					Value: reflect.ValueOf(value),
				}
			}
		}
	}

	if fail {
		os.Exit(1)
	}

	for key, parameter := range currentCommand.Parameters {
		if !parameter.Required {
			continue
		}

		_, ok := parameters[key[2:]]
		if !ok {
			fmt.Printf("Argument required: %s\n", key)
			fail = true
		}
	}

	if fail {
		os.Exit(1)
	}

	if currentCommand.Handler == nil {
		fmt.Println("Handler for command not set")
		os.Exit(1)
	}

	err := currentCommand.Handler(parameters)
	if err != nil {
		fmt.Printf("Execution error: %v\n", err)
		os.Exit(1)
	}
}

func (this *Command) manual() {
	buffer, err := json.Marshal(this)
	if err != nil {
		fmt.Printf("Execution error: %v\n", err)
		os.Exit(1)
	}

	fmt.Println(string(buffer))
}