Add HTA-side implementation of sync-interrupted scenario (HT-508). Also replace deprecated AsyncTask.

[wmergenthal]

Formerly HT sent HTA "sync_success" regardless of whether 'mergeCompleted' was True. Now the False case leads to HTA receiving sync status "sync_interrupted". HTA parses the HttpRequest from HT to extract the status, then informs the user. One new string is added to HTA for the interrupt-or-cancelled case.
Also, deprecated class 'AsyncTask' is replaced with 'Executors' and 'Handlers'.

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This change is 

[tombogle]

@tombogle reviewed 3 of 3 files at r1, all commit messages.
Reviewable status: all files reviewed, 4 unresolved discussions (waiting on @wmergenthal)

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app/src/main/java/org/sil/hearthis/AcceptNotificationHandler.java line 43 at r1 (raw file):

        //
        // NOTE: like several things in HearThisAndroid, HttpRequest is deprecated. It will be
        // replaced with something more appropriate, hopefully soon.

Options:

• Use HttpURLConnection (built-in JDK/Android)
  → Standard replacement for most simple request/response work.

  • Pros: No external dependency.

  • Cons: Verbose API; no built-in high-level features.

• Use OkHttp (square.github.io/okhttp)
  → De facto standard for Android networking.

  • Pros: Clean API, better performance, supports HTTP/2, widely adopted.

  • Cons: Adds dependency, but well worth it in most apps.

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app/src/main/java/org/sil/hearthis/AcceptNotificationHandler.java line 49 at r1 (raw file):

        String s2 = s1.substring(s1.indexOf(' ') + 1, s1.lastIndexOf(' '));
        String status = s2.substring(s2.indexOf('=') + 1);

This logic could be done in a less cryptic way:
String s1 = request.getRequestLine().getUri(); // avoid toString() if possible
URI uri = new URI(s1);
String query = uri.getQuery(); // e.g., "status=123&foo=bar"

String status = null;
for (String param : query.split("&")) {
String[] pair = param.split("=");
if (pair.length == 2 && pair[0].equals("status")) {
status = pair[1];
break;
}
}

Alternatively, it could be done very simply with a regular expression. But using URI is probably safer and makes the intent clear.

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app/src/main/java/org/sil/hearthis/SyncActivity.java line 166 at r1 (raw file):

                                                              socket.send(packet);
                                                          } catch (UnknownHostException e) {
                                                              e.printStackTrace();

In the case of an exception, is there anything else we need to do to give feedback to the user and/or prevent the HTA app from getting stuck in a bad state?

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app/src/main/java/org/sil/hearthis/SyncActivity.java line 280 at r1 (raw file):

            setProgress(getString(R.string.sync_interrupted));
        } else {
            // Should never happen. Not sure what to do here, if anything...

For the sake of future proofing, we should probably handle any unexpected message by letting the use know that they are probably using a version of HTA that is not fully compatible with HT desktop. Then probably we should treat it similar to the "interrupted" case, since we probably can't safely assume it was completed successfully.

[wmergenthal]

Re comment 1: thanks for suggesting some options. OkHttp certainly looks compelling.
Re comment 2: addressed in 3727d83.
Re comment 3: currently working on this one.
Re comment 4: addressed in 399e532.

[tombogle]

I wonder if we should display a different message in the case where we get an unexpected status message. I assume the processing should be the same (since we can't possibly know how else to interpret the unexpected message), but if this ever happens, we could give the user some indication that we got an unexpected message and suggest they check for an update. We could even include in the query (from HT) an indication of the minimum version of HTA known to handle the particular status message. Then if we ever get an unexpected status and it includes a version number as well, we could tell the user the minimum version of HTA that is compatible with the version of HT they are using. The HTA code would then look something like this:

String status = null;
String minHtaVersion = null;
try {
    String s1 = request.getRequestLine().getUri();
    URI uri = new URI(s1);
    String query = uri.getQuery();
    if (query != null) {
        for (String param : query.split("&")) {
            String[] pair = param.split("=", 2); // limit=2 in case value contains '='
            if (pair.length == 2) {
                if (pair[0].equals("message")) {
                    status = pair[1];
                } else if (pair[0].equals("minHtaVersion")) {
                    minHtaVersion = pair[1];
                }
            }
        }
    }
} catch (Exception e) {
    e.printStackTrace();
}

if (status == null || isUnexpectedStatus(status)) {
    if (minHtaVersion != null) {
        showError("Unexpected sync status received. This version of HearThis for Android appears to be incompatible with your version of HearThis. Please update HearThis for Android to at least version " + minHtaVersion + ".");
    } else {
        showError("Unexpected sync status received. Please check for updates.");
    }
    status = "sync_interrupted"; // Or possibly a distinct status
}