/**
* Generates AdjacencyListGraph based on the values in the input file.
*
* @requires twitterStream is properly initialized
* @param twitterStream initialized input stream for reading twitter file
* @return generated graph based on input file
*/
private static Graph readTwitterFile(FileInputStream twitterStream) {
final int U1_INDEX = 0;
final int U2_INDEX = 1;
try {
Graph g = new AdjacencyListGraph();
BufferedReader twitterReader = new BufferedReader(new InputStreamReader(twitterStream));
String line;
while ((line = twitterReader.readLine()) != null) {
// eliminate any unnecessary whitespace
String[] columns = line.trim().replaceAll("\\s+", "").split("->");
// first column is user 1
// second column is user 2
Vertex u1 = new Vertex(columns[U1_INDEX]);
Vertex u2 = new Vertex(columns[U2_INDEX]);
// System.out.println(columns[0]+","+columns[1]);
g.addVertex(u1);
g.addVertex(u2);
g.addEdge(u1, u2);
// System.out.println(line);
}
twitterReader.close();
return g;
} catch (Exception e) { // if something somehow 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);
}
}