package git

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

func snapshotPrefix(taskID string) string {
	return "refs/byre/tasks/" + taskID + "/snap/"
}

func SnapshotRef(taskID string, n int) string {
	return fmt.Sprintf("%s%d", snapshotPrefix(taskID), n)
}

func CommitSnapshot(dir, tree, ref, message string, env []string) (string, error) {
	head, err := Head(dir)
	if err != nil {
		return "", err
	}
	commit, err := runEnv(dir, env, "commit-tree", tree, "-p", head, "-m", message)
	if err != nil {
		return "", err
	}
	_, err = run(dir, "update-ref", ref, commit, "")
	if err != nil {
		return "", err
	}
	return commit, nil
}

func SnapshotRefs(repo, taskID string) ([]string, error) {
	out, err := run(repo, "for-each-ref", "--format=%(refname)", snapshotPrefix(taskID))
	if err != nil {
		return nil, err
	}
	if out == "" {
		return []string{}, nil
	}
	return strings.Split(out, "\n"), nil
}

func DeleteSnapshotRefs(repo, taskID string) error {
	refs, err := SnapshotRefs(repo, taskID)
	if err != nil {
		return err
	}
	if len(refs) == 0 {
		return nil
	}

	b := &strings.Builder{}
	for _, ref := range refs {
		fmt.Fprintf(b, "delete %s\n", ref)
	}
	cmd := exec.Command("git", "update-ref", "--stdin")
	cmd.Dir = repo
	cmd.Stdin = strings.NewReader(b.String())
	out, err := cmd.CombinedOutput()
	if err != nil {
		return fmt.Errorf("git update-ref --stdin: %w: %s", err, strings.TrimSpace(string(out)))
	}
	return nil
}