/**
* Reads query file and parses the queries.
*
* @requires querystream, outstream, are successfully initialized
* @requires g to be already generated
* @param queryStream file input stream of query file
* @param outStream file output stream of output file
* @param g
* @effects writes results to output file
*/
private static void parseQuery(FileInputStream queryStream, FileOutputStream outStream, Graph g) {
try {
BufferedWriter output = new BufferedWriter(new OutputStreamWriter(outStream));
BufferedReader queryReader = new BufferedReader(new InputStreamReader(queryStream));
final int COMMAND_INDEX = 0;
final int U1_INDEX = 1;
final int U2_INDEX = 2;
final String QUERY_ENDING = " ?";
Set<Set<String>> queries = new LinkedHashSet<Set<String>>();
String line;
while ((line = queryReader.readLine()) != null) {
// each query set contains two user id strings and a command
// this also handles duplicate user ids with different commands
Set<String> query = new LinkedHashSet<String>();
// a bit overkill, but eliminate any unnecessary whitespace if needed and replaces with
// single space
String[] columns = line.trim().replaceAll("\\s+", " ").split(" ");
// first column is query
// second column is user 1
// third column is user 2
String command = columns[COMMAND_INDEX];
String id1 = columns[U1_INDEX];
String id2 = columns[U2_INDEX];
query.add(id1);
query.add(id2);
query.add(command);
// check if query ends with question mark (with leading space) and query is unique
if (line.endsWith(QUERY_ENDING) && !queries.contains(query)) {
queries.add(query);
Vertex u1 = new Vertex(id1);
Vertex u2 = new Vertex(id2);
printResults(output, g, u1, u2, command);
}
}
queryReader.close();
output.close();
// return new LinkedHashMap<List<Vertex>, String>(queries);
} catch (Exception e) { // if something goes wrong
throw new RuntimeException(e);
}
}
/**
* Helper method for parseQuery. Writes the results of the queries to the output file.
*
* @param output initialized BufferedWriter for the output file
* @param g initialized graph of edges and vertices
* @param u1 one vertex used in commands
* @param u2 another vertex used in commands
* @param command command to execute
*/
private static void printResults(
BufferedWriter output, Graph g, Vertex u1, Vertex u2, String command) {
final String commonInfluencers = "commonInfluencers";
final String numRetweets = "numRetweets";
final String VERTEX_NOT_FOUND_ERROR =
"ERROR: One or more vertices does not exist in the graph.";
final String INVALID_COMMAND_ERROR = "\tError: invalid command ";
final String PATH_NOT_FOUND_ERROR = "\tPath not found.";
List<Vertex> allVertices = new ArrayList<Vertex>(g.getVertices());
try {
output.write("query: " + command + " " + u1.toString() + " " + u2.toString());
output.newLine();
output.write("<result>");
output.newLine();
// check if vertices exist in graph
if (!allVertices.contains(u1) || !allVertices.contains(u2)) {
output.write(VERTEX_NOT_FOUND_ERROR);
output.newLine();
output.write("</result>");
output.newLine();
output.newLine();
return;
}
// if query is commonInfluencers
if (command.equals(commonInfluencers)) {
List<Vertex> commonFollowers =
new LinkedList<Vertex>(Algorithms.commonDownstreamVertices(g, u1, u2));
for (Vertex v : commonFollowers) {
output.write("\t" + v.toString());
output.newLine();
}
}
// if query is numRetweets
else if (command.equals(numRetweets)) {
// note switch in u1 and u2; this is because tweets go upstream
int distance = Algorithms.shortestDistance(g, u2, u1);
if (distance == -1) {
output.write(PATH_NOT_FOUND_ERROR);
} else {
// implicitly convert distance to string as printing out ints somehow didn't work
output.write("" + distance);
// System.out.println(distance);
}
output.newLine();
} else {
output.write(INVALID_COMMAND_ERROR + command);
output.newLine();
}
output.write("</result>");
output.newLine();
output.newLine();
} catch (Exception e) {
throw new RuntimeException(e);
}
}