Added exception handling to postback and implemented waiting properly.

services/git-bridge/src/uk/ac/ic/wlgitbridge/application/SnapshotPostExceptionBuilder.java

@@ -0,0 +1,35 @@
+package uk.ac.ic.wlgitbridge.application;
+
+import com.google.gson.JsonObject;
+import uk.ac.ic.wlgitbridge.writelatex.InvalidFilesException;
+import uk.ac.ic.wlgitbridge.writelatex.OutOfDateException;
+import uk.ac.ic.wlgitbridge.writelatex.SnapshotPostException;
+import uk.ac.ic.wlgitbridge.writelatex.UnexpectedErrorException;
+import uk.ac.ic.wlgitbridge.writelatex.api.request.getdoc.exception.InvalidProjectException;
+import uk.ac.ic.wlgitbridge.writelatex.api.request.push.UnexpectedPostbackException;
+
+/**
+ * Created by Winston on 17/11/14.
+ */
+public class SnapshotPostExceptionBuilder {
+
+    private static final String CODE_ERROR_OUT_OF_DATE = "outOfDate";
+    private static final String CODE_ERROR_INVALID_FILES = "invalidFiles";
+    private static final String CODE_ERROR_INVALID_PROJECT = "invalidProject";
+    private static final String CODE_ERROR_UNKNOWN = "error";
+
+    public SnapshotPostException build(String errorCode, JsonObject json) throws UnexpectedPostbackException {
+        if (errorCode.equals(CODE_ERROR_OUT_OF_DATE)) {
+            return new OutOfDateException(json);
+        } else if (errorCode.equals(CODE_ERROR_INVALID_FILES)) {
+            return new InvalidFilesException(json);
+        } else if (errorCode.equals(CODE_ERROR_INVALID_PROJECT)) {
+            return new InvalidProjectException(json);
+        } else if (errorCode.equals(CODE_ERROR_UNKNOWN)) {
+            return new UnexpectedErrorException(json);
+        } else {
+            throw new UnexpectedPostbackException();
+        }
+    }
+
+}

services/git-bridge/src/uk/ac/ic/wlgitbridge/application/SnapshotPushPostbackContents.java

@@ -0,0 +1,68 @@
+package uk.ac.ic.wlgitbridge.application;
+
+import com.google.gson.Gson;
+import com.google.gson.JsonElement;
+import com.google.gson.JsonObject;
+import uk.ac.ic.wlgitbridge.bridge.WriteLatexDataSource;
+import uk.ac.ic.wlgitbridge.writelatex.SnapshotPostException;
+import uk.ac.ic.wlgitbridge.writelatex.api.request.base.JSONSource;
+import uk.ac.ic.wlgitbridge.writelatex.api.request.push.UnexpectedPostbackException;
+
+/**
+ * Created by Winston on 17/11/14.
+ */
+public class SnapshotPushPostbackContents implements JSONSource {
+
+    private static final String CODE_SUCCESS = "upToDate";
+
+    private final WriteLatexDataSource writeLatexDataSource;
+    private final String projectName;
+
+    private final SnapshotPostExceptionBuilder snapshotPostExceptionBuilder;
+
+    private int versionID;
+    private SnapshotPostException exception;
+
+    public SnapshotPushPostbackContents(WriteLatexDataSource writeLatexDataSource, String projectName, String contents) {
+        this.projectName = projectName;
+        this.writeLatexDataSource = writeLatexDataSource;
+        snapshotPostExceptionBuilder = new SnapshotPostExceptionBuilder();
+        fromJSON(new Gson().fromJson(contents, JsonElement.class));
+    }
+
+    @Override
+    public void fromJSON(JsonElement json) {
+        JsonObject responseObject = json.getAsJsonObject();
+        String code = responseObject.get("code").getAsString();
+        setResult(responseObject, code);
+    }
+
+    public void sendPostback() throws UnexpectedPostbackException {
+        if (exception == null) {
+            writeLatexDataSource.postbackReceivedSuccessfully(projectName, versionID);
+        } else {
+            writeLatexDataSource.postbackReceivedWithException(projectName, exception);
+        }
+    }
+
+    private void setResult(JsonObject responseObject, String code) {
+        if (code.equals(CODE_SUCCESS)) {
+            setVersionID(responseObject);
+        } else {
+            setException(responseObject, code);
+        }
+    }
+
+    private void setVersionID(JsonObject responseObject) {
+        versionID = responseObject.get("latestVerId").getAsInt();
+    }
+
+    private void setException(JsonObject responseObject, String code) {
+        try {
+            exception = snapshotPostExceptionBuilder.build(code, responseObject);
+        } catch (UnexpectedPostbackException e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+}

services/git-bridge/src/uk/ac/ic/wlgitbridge/application/SnapshotPushPostbackHandler.java

@@ -1,10 +1,9 @@
 package uk.ac.ic.wlgitbridge.application;
 
-import com.google.gson.Gson;
-import com.google.gson.JsonObject;
 import org.eclipse.jetty.server.Request;
 import org.eclipse.jetty.server.handler.AbstractHandler;
 import uk.ac.ic.wlgitbridge.bridge.WriteLatexDataSource;
+import uk.ac.ic.wlgitbridge.writelatex.api.request.push.UnexpectedPostbackException;
 
 import javax.servlet.ServletException;
 import javax.servlet.http.HttpServletRequest;
@@ -30,17 +29,24 @@ public class SnapshotPushPostbackHandler extends AbstractHandler {
 //                response.setContentType("text/html;charset=utf-8");
 //                response.setStatus(HttpServletResponse.SC_OK);
         if (request.getMethod().equals("POST") && request.getPathInfo().endsWith("postback")) {
-            BufferedReader reader = request.getReader();
+            String contents = getContentsOfReader(request.getReader());
-            StringBuilder sb = new StringBuilder();
+            String projectName = request.getRequestURI().split("/")[1];
-            for (String line; (line = reader.readLine()) != null; ) {
+            SnapshotPushPostbackContents postbackContents = new SnapshotPushPostbackContents(writeLatexDataSource, projectName, contents);
-                sb.append(line);
+            try {
+                postbackContents.sendPostback();
+            } catch (UnexpectedPostbackException e) {
+                throw new ServletException();
             }
-            String data = sb.toString();
-            JsonObject dataObj = new Gson().fromJson(data, JsonObject.class);
-            System.out.println(request.getRequestURI());
-            writeLatexDataSource.postbackReceivedSuccessfully(request.getRequestURI().split("/")[1]);
             baseRequest.setHandled(true);
         }
     }
 
+    private static String getContentsOfReader(BufferedReader reader) throws IOException {
+        StringBuilder sb = new StringBuilder();
+        for (String line; (line = reader.readLine()) != null; ) {
+            sb.append(line);
+        }
+        return sb.toString();
+    }
+
 }

services/git-bridge/src/uk/ac/ic/wlgitbridge/bridge/WriteLatexDataSource.java

@@ -3,6 +3,7 @@ package uk.ac.ic.wlgitbridge.bridge;
 import uk.ac.ic.wlgitbridge.writelatex.api.request.exception.FailedConnectionException;
 import uk.ac.ic.wlgitbridge.writelatex.api.request.getdoc.exception.InvalidProjectException;
 import uk.ac.ic.wlgitbridge.writelatex.SnapshotPostException;
+import uk.ac.ic.wlgitbridge.writelatex.api.request.push.UnexpectedPostbackException;
 
 import java.io.IOException;
 import java.util.List;
@@ -16,10 +17,9 @@ public interface WriteLatexDataSource {
     public boolean repositoryExists(String projectName) throws FailedConnectionException;
     public List<WritableRepositoryContents> getWritableRepositories(String projectName) throws FailedConnectionException, InvalidProjectException;
     public void putDirectoryContentsToProjectWithName(String projectName, RawDirectoryContents directoryContents, String hostname) throws SnapshotPostException, IOException, FailedConnectionException;
-    public void expectPostback(String projectName);
 
     /* Called by postback thread. */
-    public void postbackReceivedSuccessfully(String projectName);
+    public void postbackReceivedSuccessfully(String projectName, int versionID) throws UnexpectedPostbackException;
-    public void postbackReceivedWithException(String projectName, SnapshotPostException exception);
+    public void postbackReceivedWithException(String projectName, SnapshotPostException exception) throws UnexpectedPostbackException;
 
 }

services/git-bridge/src/uk/ac/ic/wlgitbridge/git/handler/hook/WriteLatexPutHook.java

@@ -51,6 +51,7 @@ public class WriteLatexPutHook implements PreReceiveHook {
                 receiveCommand.setResult(Result.REJECTED_OTHER_REASON, message);
             }
         }
+        System.out.println("success");
     }
 
     private void handleReceiveCommand(Repository repository, ReceiveCommand receiveCommand) throws IOException, SnapshotPostException, FailedConnectionException {

services/git-bridge/src/uk/ac/ic/wlgitbridge/git/handler/hook/exception/ForcedPushException.java

@@ -1,5 +1,6 @@
 package uk.ac.ic.wlgitbridge.git.handler.hook.exception;
 
+import com.google.gson.JsonElement;
 import uk.ac.ic.wlgitbridge.writelatex.SnapshotPostException;
 
 import java.util.Arrays;
@@ -26,4 +27,8 @@ public class ForcedPushException extends SnapshotPostException {
         return Arrays.asList(DESCRIPTION_LINES);
     }
 
+    @Override
+    public void fromJSON(JsonElement json) {
+
+    }
 }

services/git-bridge/src/uk/ac/ic/wlgitbridge/writelatex/InvalidFilesException.java

@@ -1,5 +1,8 @@
 package uk.ac.ic.wlgitbridge.writelatex;
 
+import com.google.gson.JsonElement;
+import com.google.gson.JsonObject;
+
 import java.util.List;
 
 /**
@@ -7,6 +10,10 @@ import java.util.List;
  */
 public class InvalidFilesException extends SnapshotPostException {
 
+    public InvalidFilesException(JsonObject json) {
+        super(json);
+    }
+
     @Override
     public String getMessage() {
         return null;
@@ -17,4 +24,9 @@ public class InvalidFilesException extends SnapshotPostException {
         return null;
     }
 
+    @Override
+    public void fromJSON(JsonElement json) {
+
+    }
+
 }

services/git-bridge/src/uk/ac/ic/wlgitbridge/writelatex/InvalidProjectException.java

@@ -1,5 +1,7 @@
 package uk.ac.ic.wlgitbridge.writelatex;
 
+import com.google.gson.JsonElement;
+
 import java.util.List;
 
 /**
@@ -7,6 +9,10 @@ import java.util.List;
  */
 public class InvalidProjectException extends SnapshotPostException {
 
+    public InvalidProjectException(JsonElement jsonElement) {
+        super(jsonElement);
+    }
+
     @Override
     public String getMessage() {
         return null;
@@ -17,4 +23,9 @@ public class InvalidProjectException extends SnapshotPostException {
         return null;
     }
 
+    @Override
+    public void fromJSON(JsonElement json) {
+
+    }
+
 }

services/git-bridge/src/uk/ac/ic/wlgitbridge/writelatex/OutOfDateException.java

@@ -1,5 +1,8 @@
 package uk.ac.ic.wlgitbridge.writelatex;
 
+import com.google.gson.JsonElement;
+import com.google.gson.JsonObject;
+
 import java.util.List;
 
 /**
@@ -7,6 +10,10 @@ import java.util.List;
  */
 public class OutOfDateException extends SnapshotPostException {
 
+    public OutOfDateException(JsonObject json) {
+        super(json);
+    }
+
     @Override
     public String getMessage() {
         return null;
@@ -17,4 +24,9 @@ public class OutOfDateException extends SnapshotPostException {
         return null;
     }
 
+    @Override
+    public void fromJSON(JsonElement json) {
+
+    }
+
 }

services/git-bridge/src/uk/ac/ic/wlgitbridge/writelatex/SnapshotPostException.java

@@ -1,11 +1,22 @@
 package uk.ac.ic.wlgitbridge.writelatex;
 
+import com.google.gson.JsonElement;
+import uk.ac.ic.wlgitbridge.writelatex.api.request.base.JSONSource;
+
 import java.util.List;
 
 /**
  * Created by Winston on 16/11/14.
  */
-public abstract class SnapshotPostException extends Exception {
+public abstract class SnapshotPostException extends Exception implements JSONSource {
+
+    public SnapshotPostException() {
+
+    }
+
+    public SnapshotPostException(JsonElement jsonElement) {
+        fromJSON(jsonElement);
+    }
 
     public abstract String getMessage();
     public abstract List<String> getDescriptionLines();

services/git-bridge/src/uk/ac/ic/wlgitbridge/writelatex/UnexpectedErrorException.java

@@ -1,5 +1,8 @@
 package uk.ac.ic.wlgitbridge.writelatex;
 
+import com.google.gson.JsonElement;
+import com.google.gson.JsonObject;
+
 import java.util.List;
 
 /**
@@ -7,6 +10,10 @@ import java.util.List;
  */
 public class UnexpectedErrorException extends SnapshotPostException {
 
+    public UnexpectedErrorException(JsonObject json) {
+        super(json);
+    }
+
     @Override
     public String getMessage() {
         return null;
@@ -17,4 +24,9 @@ public class UnexpectedErrorException extends SnapshotPostException {
         return null;
     }
 
+    @Override
+    public void fromJSON(JsonElement json) {
+
+    }
+
 }

services/git-bridge/src/uk/ac/ic/wlgitbridge/writelatex/WriteLatexAPI.java

@@ -7,7 +7,9 @@ import uk.ac.ic.wlgitbridge.bridge.WriteLatexDataSource;
 import uk.ac.ic.wlgitbridge.writelatex.api.request.exception.FailedConnectionException;
 import uk.ac.ic.wlgitbridge.writelatex.api.request.getdoc.SnapshotGetDocRequest;
 import uk.ac.ic.wlgitbridge.writelatex.api.request.getdoc.exception.InvalidProjectException;
+import uk.ac.ic.wlgitbridge.writelatex.api.request.push.PostbackManager;
 import uk.ac.ic.wlgitbridge.writelatex.api.request.push.SnapshotPushRequest;
+import uk.ac.ic.wlgitbridge.writelatex.api.request.push.UnexpectedPostbackException;
 import uk.ac.ic.wlgitbridge.writelatex.model.WLDataModel;
 
 import java.io.IOException;
@@ -21,13 +23,13 @@ import java.util.Map;
 public class WriteLatexAPI implements WriteLatexDataSource {
 
     private final WLDataModel dataModel;
-    private final Map<String, Object> postbackConds;
+    private final PostbackManager postbackManager;
 
     boolean cond = false;
 
     public WriteLatexAPI(WLDataModel dataModel) {
         this.dataModel = dataModel;
-        postbackConds = new HashMap<String, Object>();
+        postbackManager = new PostbackManager();
     }
 
     @Override
@@ -51,37 +53,18 @@ public class WriteLatexAPI implements WriteLatexDataSource {
     public void putDirectoryContentsToProjectWithName(String projectName, RawDirectoryContents directoryContents, String hostname) throws SnapshotPostException, IOException, FailedConnectionException {
         CandidateSnapshot candidate = dataModel.createCandidateSnapshotFromProjectWithContents(projectName, directoryContents, hostname);
         new SnapshotPushRequest(candidate).request();
-        expectPostback(projectName);
+        candidate.approveWithVersionID(postbackManager.getVersionID(projectName));
-        candidate.approveWithVersionID(100);
-    }
-
-    @Override
-    public void expectPostback(String projectName) {
-        Object value = new Object();
-        postbackConds.put(projectName, value);
-        cond = false;
-        System.out.println("sleeping");
-        try {
-            while (!cond) {
-                wait();
-            }
-        } catch (InterruptedException e) {
-            e.printStackTrace();
-        }
-        System.out.println("finished sleep");
     }
 
     /* Called by postback thread. */
     @Override
-    public void postbackReceivedSuccessfully(String projectName) {
+    public void postbackReceivedSuccessfully(String projectName, int versionID) throws UnexpectedPostbackException {
-        System.out.println("successfully received postback for " + projectName);
+        postbackManager.postVersionIDForProject(projectName, versionID);
-        cond = true;
-        notifyAll();
     }
 
     @Override
-    public void postbackReceivedWithException(String projectName, SnapshotPostException exception) {
+    public void postbackReceivedWithException(String projectName, SnapshotPostException exception) throws UnexpectedPostbackException {
-        postbackReceivedSuccessfully(projectName);
+        postbackManager.postExceptionForProject(projectName, exception);
     }
 
 }

services/git-bridge/src/uk/ac/ic/wlgitbridge/writelatex/api/request/base/JSONSource.java

@@ -1,13 +1,12 @@
 package uk.ac.ic.wlgitbridge.writelatex.api.request.base;
 
 import com.google.gson.JsonElement;
-import uk.ac.ic.wlgitbridge.writelatex.api.request.exception.FailedConnectionException;
 
 /**
  * Created by Winston on 06/11/14.
  */
 public interface JSONSource {
 
-    public abstract void fromJSON(JsonElement json) throws FailedConnectionException;
+    public abstract void fromJSON(JsonElement json);
 
 }

services/git-bridge/src/uk/ac/ic/wlgitbridge/writelatex/api/request/base/Result.java

@@ -1,7 +1,6 @@
 package uk.ac.ic.wlgitbridge.writelatex.api.request.base;
 
 import com.google.gson.JsonElement;
-import uk.ac.ic.wlgitbridge.writelatex.api.request.exception.FailedConnectionException;
 
 /**
  * Created by Winston on 06/11/14.
@@ -11,7 +10,7 @@ public abstract class Result implements JSONSource {
     private JsonElement json;
     private final Request request;
 
-    public Result(Request request, JsonElement json) throws FailedConnectionException {
+    public Result(Request request, JsonElement json) {
         this.request = request;
         this.json = json;
         fromJSON(json);

services/git-bridge/src/uk/ac/ic/wlgitbridge/writelatex/api/request/getdoc/exception/InvalidProjectException.java

@@ -1,7 +1,36 @@
 package uk.ac.ic.wlgitbridge.writelatex.api.request.getdoc.exception;
 
+import com.google.gson.JsonElement;
+import com.google.gson.JsonObject;
+import uk.ac.ic.wlgitbridge.writelatex.SnapshotPostException;
+
+import java.util.List;
+
 /**
  * Created by Winston on 08/11/14.
  */
-public class InvalidProjectException extends Exception {
+public class InvalidProjectException extends SnapshotPostException {
+
+    public InvalidProjectException(JsonObject json) {
+        super(json);
+    }
+
+    public InvalidProjectException() {
+        super();
+    }
+
+    @Override
+    public String getMessage() {
+        return null;
+    }
+
+    @Override
+    public List<String> getDescriptionLines() {
+        return null;
+    }
+
+    @Override
+    public void fromJSON(JsonElement json) {
+
+    }
 }

services/git-bridge/src/uk/ac/ic/wlgitbridge/writelatex/api/request/getforversion/SnapshotAttachment.java

@@ -10,7 +10,6 @@ import uk.ac.ic.wlgitbridge.writelatex.api.request.exception.FailedConnectionExc
 
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
-import java.util.concurrent.ExecutionException;
 import java.util.concurrent.Future;
 
 /**
@@ -21,7 +20,7 @@ public class SnapshotAttachment extends SnapshotFile {
     private Future<byte[]> future;
     private String url;
 
-    public SnapshotAttachment(JsonElement json) throws FailedConnectionException {
+    public SnapshotAttachment(JsonElement json) {
         super(json);
     }
 
@@ -38,7 +37,7 @@ public class SnapshotAttachment extends SnapshotFile {
     }
 
     @Override
-    protected void getContentsFromJSON(JsonArray jsonArray) throws FailedConnectionException {
+    protected void getContentsFromJSON(JsonArray jsonArray) {
         url = jsonArray.get(0).getAsString();
 //        fetchContents(jsonArray.get(0).getAsString());
     }

services/git-bridge/src/uk/ac/ic/wlgitbridge/writelatex/api/request/getforversion/SnapshotData.java

@@ -3,7 +3,6 @@ package uk.ac.ic.wlgitbridge.writelatex.api.request.getforversion;
 import com.google.gson.JsonArray;
 import com.google.gson.JsonElement;
 import uk.ac.ic.wlgitbridge.writelatex.api.request.base.JSONSource;
-import uk.ac.ic.wlgitbridge.writelatex.api.request.exception.FailedConnectionException;
 
 import java.util.LinkedList;
 import java.util.List;
@@ -19,25 +18,25 @@ public class SnapshotData implements JSONSource {
     private List<SnapshotFile> srcs;
     private List<SnapshotAttachment> atts;
 
-    public SnapshotData(JsonElement json) throws FailedConnectionException {
+    public SnapshotData(JsonElement json) {
         srcs = new LinkedList<SnapshotFile>();
         atts = new LinkedList<SnapshotAttachment>();
         fromJSON(json);
     }
 
     @Override
-    public void fromJSON(JsonElement json) throws FailedConnectionException {
+    public void fromJSON(JsonElement json) {
         populateSrcs(json.getAsJsonObject().get(JSON_KEY_SRCS).getAsJsonArray());
         populateAtts(json.getAsJsonObject().get(JSON_KEY_ATTS).getAsJsonArray());
     }
 
-    private void populateSrcs(JsonArray jsonArray) throws FailedConnectionException {
+    private void populateSrcs(JsonArray jsonArray) {
         for (JsonElement json : jsonArray) {
             srcs.add(new SnapshotFile(json));
         }
     }
 
-    private void populateAtts(JsonArray jsonArray) throws FailedConnectionException {
+    private void populateAtts(JsonArray jsonArray) {
         for (JsonElement json : jsonArray) {
             atts.add(new SnapshotAttachment(json));
         }

services/git-bridge/src/uk/ac/ic/wlgitbridge/writelatex/api/request/getforversion/SnapshotFile.java

@@ -4,7 +4,6 @@ import com.google.gson.JsonArray;
 import com.google.gson.JsonElement;
 import uk.ac.ic.wlgitbridge.bridge.RawFile;
 import uk.ac.ic.wlgitbridge.writelatex.api.request.base.JSONSource;
-import uk.ac.ic.wlgitbridge.writelatex.api.request.exception.FailedConnectionException;
 
 /**
  * Created by Winston on 06/11/14.
@@ -14,7 +13,7 @@ public class SnapshotFile implements JSONSource, RawFile {
     protected byte[] contents;
     private String path;
 
-    public SnapshotFile(JsonElement json) throws FailedConnectionException {
+    public SnapshotFile(JsonElement json) {
         fromJSON(json);
     }
 
@@ -29,13 +28,13 @@ public class SnapshotFile implements JSONSource, RawFile {
     }
 
     @Override
-    public void fromJSON(JsonElement json) throws FailedConnectionException {
+    public void fromJSON(JsonElement json) {
         JsonArray jsonArray = json.getAsJsonArray();
         getContentsFromJSON(jsonArray);
         getPathFromJSON(jsonArray);
     }
 
-    protected void getContentsFromJSON(JsonArray jsonArray) throws FailedConnectionException {
+    protected void getContentsFromJSON(JsonArray jsonArray) {
         contents = jsonArray.get(0).getAsString().getBytes();
     }
 

services/git-bridge/src/uk/ac/ic/wlgitbridge/writelatex/api/request/getforversion/SnapshotGetForVersionResult.java

@@ -12,12 +12,12 @@ public class SnapshotGetForVersionResult extends Result {
 
     private SnapshotData snapshotData;
 
-    public SnapshotGetForVersionResult(Request request, JsonElement json) throws FailedConnectionException {
+    public SnapshotGetForVersionResult(Request request, JsonElement json) {
         super(request, json);
     }
 
     @Override
-    public void fromJSON(JsonElement json) throws FailedConnectionException {
+    public void fromJSON(JsonElement json) {
         snapshotData = new SnapshotData(json);
     }
 

services/git-bridge/src/uk/ac/ic/wlgitbridge/writelatex/api/request/push/PostbackContents.java

@@ -0,0 +1,44 @@
+package uk.ac.ic.wlgitbridge.writelatex.api.request.push;
+
+import uk.ac.ic.wlgitbridge.writelatex.SnapshotPostException;
+
+/**
+ * Created by Winston on 17/11/14.
+ */
+public class PostbackContents {
+
+    private boolean received;
+    private int versionID;
+    private SnapshotPostException exception;
+
+    public PostbackContents() {
+        received = false;
+    }
+
+    public synchronized int waitForPostback() throws SnapshotPostException {
+        while (!received) {
+            try {
+                wait();
+            } catch (InterruptedException e) {
+                e.printStackTrace();
+            }
+        }
+        if (exception != null) {
+            throw exception;
+        }
+        return versionID;
+    }
+
+    public synchronized void receivedVersionID(int versionID) {
+        this.versionID = versionID;
+        received = true;
+        notifyAll();
+    }
+
+    public synchronized void receivedException(SnapshotPostException exception) {
+        this.exception = exception;
+        received = true;
+        notifyAll();
+    }
+
+}

services/git-bridge/src/uk/ac/ic/wlgitbridge/writelatex/api/request/push/PostbackManager.java

@@ -0,0 +1,43 @@
+package uk.ac.ic.wlgitbridge.writelatex.api.request.push;
+
+import uk.ac.ic.wlgitbridge.writelatex.SnapshotPostException;
+
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * Created by Winston on 17/11/14.
+ */
+public class PostbackManager {
+
+    private final Map<String, PostbackContents> postbackContentsTable;
+
+    public PostbackManager() {
+        postbackContentsTable = new HashMap<String, PostbackContents>();
+    }
+
+    public int getVersionID(String projectName) throws SnapshotPostException {
+        PostbackContents contents = new PostbackContents();
+        postbackContentsTable.put(projectName, contents);
+        int versionID = contents.waitForPostback();
+        postbackContentsTable.remove(projectName);
+        return versionID;
+    }
+
+    public void postVersionIDForProject(String projectName, int versionID) throws UnexpectedPostbackException {
+        getPostbackForProject(projectName).receivedVersionID(versionID);
+    }
+
+    public void postExceptionForProject(String projectName, SnapshotPostException exception) throws UnexpectedPostbackException {
+        getPostbackForProject(projectName).receivedException(exception);
+    }
+
+    private PostbackContents getPostbackForProject(String projectName) throws UnexpectedPostbackException {
+        PostbackContents contents = postbackContentsTable.get(projectName);
+        if (contents == null) {
+            throw new UnexpectedPostbackException();
+        }
+        return contents;
+    }
+
+}

services/git-bridge/src/uk/ac/ic/wlgitbridge/writelatex/api/request/push/SnapshotPushRequestResult.java

@@ -15,7 +15,7 @@ public class SnapshotPushRequestResult extends Result {
     }
 
     @Override
-    public void fromJSON(JsonElement json) throws FailedConnectionException {
+    public void fromJSON(JsonElement json) {
 
     }
 

services/git-bridge/src/uk/ac/ic/wlgitbridge/writelatex/api/request/push/UnexpectedPostbackException.java

@@ -0,0 +1,7 @@
+package uk.ac.ic.wlgitbridge.writelatex.api.request.push;
+
+/**
+ * Created by Winston on 17/11/14.
+ */
+public class UnexpectedPostbackException extends Throwable {
+}

services/git-bridge/src/uk/ac/ic/wlgitbridge/writelatex/filestore/store/WLFileStore.java

@@ -60,7 +60,7 @@ public class WLFileStore {
         return getDirectoryNodeForProjectName(project.getName()).createFromRawDirectoryContents(directoryContents, attDirectory);
     }
 
-    public void approveCandidateSnapshot(int versionID, CandidateSnapshot candidateSnapshot) {
+    public void approveCandidateSnapshot(CandidateSnapshot candidateSnapshot) {
         fileStore.put(candidateSnapshot.getProjectName(), candidateSnapshot.getDirectoryNode());
     }
 

services/git-bridge/src/uk/ac/ic/wlgitbridge/writelatex/model/WLDataModel.java

@@ -54,7 +54,7 @@ public class WLDataModel implements CandidateSnapshotCallback {
     @Override
     public void approveSnapshot(int versionID, CandidateSnapshot candidateSnapshot) {
         getProjectWithName(candidateSnapshot.getProjectName()).putLatestSnapshot(versionID);
-        fileStore.approveCandidateSnapshot(versionID, candidateSnapshot);
+        fileStore.approveCandidateSnapshot(candidateSnapshot);
     }
 
 }