package shell

import (
	"path/filepath"
	"strings"
	"syscall"
)

type Executor struct {
	cwd string        // 当前目录
	pg  *processGroup // --进程组
}

func NewExecutor() *Executor {
	return &Executor{cwd: "/"}
}

func (e *Executor) Exec(p ExecuteParams) (*ExecuteResult, error) {
	if isCD(p.Cmd) {
		dir, err := resolveCD(e.cwd, p.Cmd)
		if err != nil {
			return &ExecuteResult{
				Stderr:   err.Error() + "\n",
				ExitCode: 1,
			}, nil
		}
		e.cwd = dir
		return &ExecuteResult{ExitCode: 0}, nil
	}

	if strings.TrimSpace(p.Cmd) == "pwd" {
		return &ExecuteResult{
			Stdout:   e.cwd + "\n",
			ExitCode: 0,
		}, nil
	}

	p.Dir = e.cwd

	defer func() {
		e.pg = nil // 命令结束
	}()

	result, err := executeInternal(p, func(pg *processGroup) { e.pg = pg })
	if result != nil {
		result.Cwd = e.cwd
	}

	return result, err
}

func isCD(cmd string) bool {
	s := strings.TrimSpace(cmd)
	return s == "cd" || strings.HasPrefix(s, "cd ")
}

func resolveCD(cwd, cmd string) (string, error) {
	fields := strings.Fields(cmd)
	if len(fields) == 1 { // 只有"cd", 没有参数
		return "/", nil
	}

	path := fields[1]
	if filepath.IsAbs(path) { // 绝对路径
		return filepath.Clean(path), nil
	}

	return filepath.Clean(filepath.Join(cwd, path)), nil // 相对路径
}

func (e *Executor) Interrupt() error {
	if e.pg == nil {
		return nil
	}

	return syscall.Kill(-e.pg.pgid, syscall.SIGINT) // 等价于 Ctrl+C
}