package exec

import (
	"fmt"
	"io"
	"os"
	"os/exec"
	"strings"

	"golang.org/x/sys/execabs"
)

// Cmd represents a command to be executed, with options to control its behavior.
// The Cmd struct embeds the standard library's exec.Cmd, adding additional fields
// to control the command's output and tracing.
type Cmd struct {
	*exec.Cmd
	Trace       bool      // Print composed command before execution.
	TraceWriter io.Writer // Where to write the trace output.
}

// Run runs the command and waits for it to complete.
// If there is an error starting the command, it is returned.
// Otherwise, the command is waited for and its exit status is returned.
func (c *Cmd) Run() error {
	if c.Trace {
		fmt.Fprintf(c.TraceWriter, "+ %s\n", strings.Join(c.Args, " "))
	}

	if err := c.Start(); err != nil {
		return err
	}

	return c.Wait()
}

// Command creates a new Cmd struct with the given name and arguments. It looks up the
// absolute path of the executable using execabs.LookPath, and sets up the Cmd with
// the necessary environment and output streams. The Cmd is configured to trace
// the command execution by setting Trace to true and TraceWriter to os.Stdout.
func Command(name string, arg ...string) (*Cmd, error) {
	abs, err := execabs.LookPath(name)
	if err != nil {
		return nil, fmt.Errorf("could not find executable %q: %w", name, err)
	}

	cmd := &Cmd{
		Cmd:         execabs.Command(abs, arg...),
		Trace:       true,
		TraceWriter: os.Stdout,
	}

	cmd.Env = os.Environ()

	return cmd, nil
}