codecrafters-shell-go/app/runnable/runnable.go

package runnable

import "os/exec"
import "fmt"

import "github.com/codecrafters-io/shell-starter-go/app/core"
import "github.com/codecrafters-io/shell-starter-go/app/tokenize"
import "github.com/codecrafters-io/shell-starter-go/app/builtin"

type Runnable interface {
	Run(ctx *core.Context) core.ExitStatus
}

type ExternalCommand struct {
	Args     []string
	ExecPath string
	Name     string
}

func (self ExternalCommand) Run(ctx *core.Context) core.ExitStatus {
	cmd := exec.Command(self.ExecPath, self.Args...)
	cmd.Args[0] = self.Name
	cmd.Stdout = ctx.Stdout
	cmd.Stderr = ctx.Stderr
	cmd.Stdin = ctx.Stdin
	err := cmd.Run()
	if err != nil {
		if exiterr, ok := err.(*exec.ExitError); ok {
			return core.ExitStatus(exiterr.ExitCode())
			// fmt.Printf("Handle():exiterr=%#v\n", exiterr.ExitCode())
		} else {
			fmt.Printf("Handle():err=%#v\n", err)
			return core.ExitStatus(65535)
		}
	}
	return 0
}

type ParseError struct {
	code  ParseErrorCode
	value string
}
type ParseErrorCode int

const (
	ParseErrorCodeNothing ParseErrorCode = iota
	ParseErrorCodeNotFound
)

func (e ParseError) Error() string {
	switch e.code {
	case ParseErrorCodeNotFound:
		return fmt.Sprintf("%s: not found", e.value)
	case ParseErrorCodeNothing:
		return ""
	default:
		return fmt.Sprintf("unknown ParseErrorCode code: %d .value=%q", e.code, e.value)
	}

}

func Parse(ctx *core.Context, command_line string) (Runnable, error) {
	tokens := tokenize.Tokenize(command_line)
	if len(tokens) == 0 { // ie. empty or whitespace-only input
		return nil, ParseError{
			code: ParseErrorCodeNothing,
		}
	}
	bltn, err := builtin.Parse(ctx, tokens[0], tokens[1:])
	if err == nil { // it was a builtin
		return bltn, nil
	}
	if e, ok := err.(builtin.ParseError); ok {
		switch e.Code {
		case builtin.ParseErrorCodeUsage:
			return nil, err
		case builtin.ParseErrorCodeUnknownBuiltin:
			exec_path, err := exec.LookPath(tokens[0])
			if err != nil { // command not found
				return nil, ParseError{
					code:  ParseErrorCodeNotFound,
					value: tokens[0],
				}
			}
			return ExternalCommand{
				ExecPath: exec_path,
				Name:     tokens[0],
				Args:     tokens[1:],
			}, nil
		}
	}
	panic("unexpected builtin.Parse(); only builtin.ParseError is expected")
}