Refactor AFC

[dmissmann]

The current implementation has a lot of repeated code. Every method that communicates with the afc service on the device has it's own logic for building the package and maintaining the package identifiers.

This is now done in a single place that abstracts away of this logic that was repeated over and over before.

Also, file I/O works now similar to "regular" filesystems. When we open a file using the afc service, we get back a io.ReadWriteCloser, which allows us to use functions like io.Copy on those files.

[iSevenDays]

Suggested change

	copy(p, resp.Payload)
	if err != nil {
	return 0, fmt.Errorf("error reading data: %w", err)
	}
	copy(p, resp.Payload)

[iSevenDays]

@dmissmann AFC directories may contain "." and "..". It may cause infinite recursion or traversing outside the subtree that was requested

[dmissmann]

That was changed as you also did in the comment #627 (comment) the List method doesn't show those entries now and WalkDir won't see them when traversing the direcotry

[iSevenDays]

Suggested change

	if len(s) == 0 {
	if len(s) <= 1 {

[dmissmann]

There's now a local variable that cuts off the NULL-terminator and we can check again for 0 (like in the example you posted below 😄 )

[iSevenDays]

Suggested change

	list = append(list, s[:len(s)-1])
	entry := s[:len(s)-1])
	if entry == "." || entry == ".." {
	continue
	}
	list = append(list, s[:len(s)-1])

[iSevenDays]

do I understand correctly that fsync --pull and --push only operate on single files now?
maybe in main.go:1136 we could use smth like

    _, err = io.Copy(local, remote)
    if dp == "" {
        dp = "."
}
err = afcService.Pull(sp, dp)

instead of

local, err := os.Create(path.Join(dp, filepath.Base(sp)))
exitIfError("failed to open local file", err)
defer local.Close()
remote, err := afcService.Open(sp, afc.READ_ONLY)

I think the pulling/pushing of directories may fail with AFC

[iSevenDays]

shouldn't it be "VendContainer"? I'm not sure renaming changes here anything, just to confirm :)

[dmissmann]

do I understand correctly that fsync --pull and --push only operate on single files now? maybe in main.go:1136 we could use smth like

    _, err = io.Copy(local, remote)
    if dp == "" {
        dp = "."
}
err = afcService.Pull(sp, dp)

instead of

local, err := os.Create(path.Join(dp, filepath.Base(sp)))
exitIfError("failed to open local file", err)
defer local.Close()
remote, err := afcService.Open(sp, afc.READ_ONLY)

I think the pulling/pushing of directories may fail with AFC

I reverted the changes in main.go now and it works as before. And that was pulling works with directories as well, but pushing was always file-only

[iSevenDays]

@dmissmann maybe we should return an error here?

return fmt.Errorf("unknown AFC error code: %d", errorCode)

[dmissmann]

yep, thanks :)