package git

import (
	"fmt"
	"os/exec"

	"github.com/sirupsen/logrus"
)

// getGitDiffArgs builds the `git diff` invocation args. It removes the usage
// of a pager and ensures that colours are specified even when Git might detect
// otherwise.
func getGitDiffArgs(repoPath string) []string {
	return []string{
		"-C",
		repoPath,
		"--no-pager",
		"-c",
		"color.diff=always",
		"diff",
	}
}

// DiffUnstaged shows a `git diff`. Due to limitations in the underlying go-git
// library, this implementation requires the /usr/bin/git binary. It gracefully
// skips if it cannot find the command on the system.
func DiffUnstaged(path string) error {
	if _, err := exec.LookPath("git"); err != nil {
		logrus.Warnf("unable to locate git command, cannot output diff")
		return nil
	}

	gitDiffArgs := getGitDiffArgs(path)
	diff, err := exec.Command("git", gitDiffArgs...).Output()
	if err != nil {
		return nil
	}

	fmt.Print(string(diff))

	return nil
}