thanks/internal/zfs/zfs.go

package zfs

import (
	"bufio"
	"context"
	"fmt"
	"io"
	"log"
	"os/exec"
	"strconv"
	"strings"
	"time"

	"git.gentoo.party/sam/thanks/internal/executor"
	"git.gentoo.party/sam/thanks/internal/runner"
)

type Snapshot struct {
	SnapshotName string // Name sans dataset (the part after the '@')
	Name         string // Full dataset@snapname
	Dataset      string
	Creation     time.Time
	GUID         uint64
}

func Cmd(ctx context.Context, arg string, a ...any) ([]byte, error) {
	if len(a) > 0 {
		arg = fmt.Sprintf(arg, a...)
	}

	cmd := exec.CommandContext(ctx, "/bin/sh", "-c", arg)

	fmt.Printf("zfs: %+v\n", arg)
	out, err := cmd.CombinedOutput()
	if err != nil {
		return out, err
	}
	return out, err
}

func CreateSnapshot(ctx context.Context, e executor.Executor, dataset, name string) error {
	_, err := e.CombinedOutput(
		ctx,
		"zfs",
		"snapshot",
		fmt.Sprintf("%s@%s", dataset, name),
	)
	if err != nil {
		return fmt.Errorf("zfs-snapshot error: %w", err)
	}

	return nil
}

func ParseSnapshots(reader io.Reader) ([]Snapshot, error) {
	scanner := bufio.NewScanner(reader)

	snaps := make([]Snapshot, 0)
	for scanner.Scan() {
		line := scanner.Text()
		params := strings.Split(line, "\t") // "zroot@foo\tTIME" -> ["zroot@foo", "TIME"]
		if len(params) != 3 {
			continue
		}
		t, err := strconv.ParseInt(params[1], 10, 64)
		if err != nil {
			log.Fatalf("invalid time %s", params[1])
		}

		identifier := strings.Split(params[0], "@") // zroot@foo -> ["zroot", "foo"]

		GUID, err := strconv.ParseUint(params[2], 10, 64)
		if err != nil {
			log.Fatalf("invalid GUID: %s - %s", params[2], err.Error())
		}

		snaps = append(
			snaps,
			Snapshot{
				SnapshotName: identifier[1],
				Dataset:      identifier[0],
				Name:         params[0],
				Creation:     time.Unix(t, 0),
				GUID:         GUID,
			},
		)
	}

	if err := scanner.Err(); err != nil {
		return nil, fmt.Errorf("error parsing zfs-list output: %s", err.Error())
	}

	return snaps, nil
}

func Snapshots(ctx context.Context, e executor.Executor, target string) ([]Snapshot, error) {
	cmd := e.CommandContext(
		ctx,
		"zfs",
		"list",
		"-Hp",
		"-o",
		"name,creation,guid",
		"-t",
		"snapshot",
		"-s",
		"creation",
		target,
	)
	stdout, err := cmd.StdoutPipe()
	if err != nil {
		return nil, err
	}
	defer stdout.Close()

	err = cmd.Start()
	if err != nil {
		return nil, err
	}

	snaps, err := ParseSnapshots(stdout)
	if err != nil {
		return nil, err
	}

	err = cmd.Wait()
	if err != nil {
		return nil, err
	}

	return snaps, err
}

func FullSend(ctx context.Context, snap, sshTarget, target string) ([]byte, error) {
	return runner.Pipeline(
		exec.CommandContext(
			ctx,
			"zfs",
			"send",
			"-Lec",
			snap,
		),
		exec.CommandContext(
			ctx,
			"ssh",
			sshTarget,
			"zfs",
			"recv",
			"-Fu",
			target,
		),
	)
}

func IncrementalSend(ctx context.Context, prevSnapName, newSnapName, sshTarget, target string) ([]byte, error) {
	return runner.Pipeline(
		exec.CommandContext(
			ctx,
			"zfs",
			"send",
			fmt.Sprintf("-I@%s", prevSnapName),
			newSnapName,
		),
		exec.CommandContext(
			ctx,
			"ssh",
			sshTarget,
			"zfs",
			"recv",
			target,
		),
	)
}

func Destroy(ctx context.Context, e executor.Executor, target string) ([]byte, error) {
	return e.CombinedOutput(ctx, "zfs", target)
}